Merge audit chain (Batches 6-15) into main

Reconciles two lines of history that both descended from the same
feat/tray-background-clipboard branch (background running, clipboard-link
detection, updater auth): main picked it up as a single squash commit
(PR #7, d112bc4), while the audit chain (p1-docs..batch-15) branched off
that feature branch's pre-squash tip and continued with its own granular
history, including the H1 decomposition of DownloadBar.tsx/SettingsView.tsx.

12 files conflicted, all resolved by verifying the audit chain already
carries PR #7's functionality (confirmed per-file against the original
d112bc4 diff) and keeping the chain's newer/relocated version:
- shared/ipc.ts, main/settings.ts: DEFAULT_SETTINGS single-sourced (C1)
- main/download.ts, main/tray.ts: trivial, chain is a superset
- main/index.ts: ipcMain.handle wiring extracted to main/ipc.ts (L2);
  removed a silent duplicate notifyBackgroundOnce that 3-way merge
  produced with no conflict markers
- renderer/main.tsx, store/settings.ts: mock/fallback settings
  single-sourced (C1/mockApi.ts)
- LibraryView.tsx: old inline clipboard-suggestion banner replaced by
  the shared LinkSuggestion primitive (Batch 9/UI19); removed dead
  icon imports + styles left behind by the auto-merge
- DownloadBar.tsx, SettingsView.tsx: taken wholesale from the chain
  (H1-decomposed shells) after confirming their extracted hook/cards
  already contain PR #7's additions (useClipboardLink.offer(),
  launchAtStartup, updateToken)
- useClipboardLink.ts, test/clipboardLink.test.ts (add/add): chain's
  version is a strict refinement of the same code (L40/L138/L145)

Verified post-merge: typecheck (node+web), 279 tests, eslint, and the
production build all pass; touched files are prettier-clean.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.gitignore

@@ -10,3 +10,6 @@ dist
 
 # Secrets — never commit
 .gitea-token
+
+# VS Code user settings (workspace settings/.vscode/launch.json are committed)
+.vscode/settings.json

.prettierrc

@@ -0,0 +1,6 @@
+{
+  "semi": false,
+  "singleQuote": true,
+  "printWidth": 100,
+  "trailingComma": "none"
+}

ROADMAP-PINCHFLAT.md

@@ -109,19 +109,26 @@ yet. This is the prerequisite for every later phase.
         channel?: string
         addedAt: number
         lastIndexedAt?: number
+        itemCount: number      // cached MediaItem count for list display
+        watched?: boolean      // included in scheduled / startup sync (Phase J)
+        feedUrl?: string       // YouTube RSS feed for cheap "anything new?" checks
       }
       interface MediaItem {
-        id: string            // yt-dlp video id — the dedup key
+        id: string             // globally unique, `${sourceId}:${videoId}`
         sourceId: string
+        videoId: string        // yt-dlp video id — the dedup key within a source
         title: string
-        playlistTitle?: string // for the folder path; 'Uploads' fallback
+        url: string
-        playlistIndex?: number // 1-based, for NNN numbering
+        playlistTitle: string  // for the folder path; 'Uploads' fallback
+        playlistIndex: number  // 1-based, for NNN numbering
         durationLabel?: string
         downloaded: boolean
         downloadedAt?: number
         filePath?: string
       }
       ```
+      *(This block reflects the shipped `src/shared/ipc.ts` shape; the original sketch
+      predated the `videoId`/`itemCount`/`watched`/`feedUrl` fields.)*
 - [x] **Dedup on index.** A video appearing in multiple playlists collapses to one `MediaItem`
       (keyed by video id); first playlist seen wins the folder assignment (surface this choice
       in the UI so the user can reassign). The "Uploads" synthetic playlist catches anything in

ROADMAP.md

@@ -32,9 +32,10 @@ filename template · yt-dlp version check · NSIS installer + portable build.
 
 A shared `DownloadOptions` model (`src/shared/ipc.ts`) carries the post-processing
 choices end-to-end. Persisted defaults are editable in **Settings → Format &
-post-processing** via a reusable `DownloadOptionsForm` component, which the download
+post-processing** via a reusable `DownloadOptionsForm` component. (The per-download
-bar also hosts in a collapsible per-download **Options** panel. The main process emits
+**Options** panel in the download bar is plumbed end-to-end — `StartDownloadOptions.options`/
-the flags in `buildArgs` (`src/main/download.ts`). All items verified in the UI preview
+`extraArgs` — but not yet surfaced in the bar UI; see audit UX1/M5.) The main process emits
+the flags in `buildArgs` (`src/main/buildArgs.ts`). All items verified in the UI preview
 (typecheck clean). **Real-download smoke test ✅ (2026-06-23):** crop-to-square cover,
 audio re-encode (opus), video container + codec preference (mkv + vp9 merge), subtitle
 embed (→ mov_text), chapter embed, and SponsorBlock-remove (output duration shrinks by the
@@ -55,7 +56,7 @@ found and fixed a real shipping bug — the bundled `ffprobe.exe` was missing (s
 - [x] **Video container + codec preference.** Container choice (mp4/mkv/webm) +
       preferred codec (`-S res,fps,vcodec:…`) to nudge toward av1 / vp9 / h264 without
       overriding the requested resolution.
-- [x] **Embed chapters.** `--embed-chapters` toggle. (`--split-chapters` still TODO.)
+- [x] **Embed chapters.** `--embed-chapters` toggle. (`--split-chapters` shipped in Phase L.)
 - [x] **Embed thumbnail crop-to-square** for audio (Seal's "crop artwork") via thumbnail
       post-processor args. *Smoke-tested ✅: the embedded cover comes out a perfect square
       (360×360) — the `--ppa` crop recipe survives yt-dlp's shlex split + ffmpeg's filtergraph.*
@@ -126,10 +127,12 @@ extraArgs ordering). **Smoke-tested ✅ (2026-06-23):** `parseExtraArgs('--write
       the Custom commands card). The **"run custom command" mode** is
       `Settings.customCommandEnabled`, applied to every new download unless overridden
       per-download in the download bar's Custom command panel.
-- [x] **Command preview.** `IpcChannels.commandPreview` → `previewCommand()`
+- [ ] **Command preview (plumbed, not surfaced).** `IpcChannels.commandPreview` →
-      (`src/main/download.ts`) builds the exact argv via the same `buildCommand()` path
+      `previewCommand()` (`src/main/download.ts`) builds the exact argv via the same
-      a real download would take, then renders it with `formatCommandLine`. Surfaced as
+      `buildCommand()` path a real download would take, then renders it with
-      a **Preview command** button in the download bar, with a Copy button.
+      `formatCommandLine`. The **Preview command** button is NOT yet in the download bar —
+      only the main/preload/buildArgs chain exists. Wire it into the per-download Options
+      panel or remove the chain (audit M5/UX1).
 - [x] **In-app yt-dlp updater.** `updateYtdlp(channel)` (`src/main/ytdlp.ts`) runs
       yt-dlp's own `--update-to stable|nightly`. Surfaced in **Settings → About**, right
       next to the existing version check, with a channel picker + result output.
@@ -154,9 +157,12 @@ parallel storage. All items verified in the UI preview (typecheck + `npm run tes
 - [x] **Native OS notifications** on completion / failure (Electron `Notification`,
       `src/main/download.ts`). Gated by a new **Notify when downloads finish** switch
       (`Settings.notifyOnComplete`, default on); clicking a notification refocuses the window.
-- [x] **Private / incognito mode** — a download bar toggle (`DownloadBar.tsx`, sticky like an
+- [ ] **Private / incognito mode (plumbed, not surfaced).** `DownloadItem.incognito` flows
-      incognito tab) sets `DownloadItem.incognito`, which `store/downloads.ts` checks before
+      through `buildItem` → history-skip → the QueueItem "Private" badge, and
-      ever calling `useHistory().add(...)`. Queue items show an eye-off badge when private.
+      `store/downloads.ts` checks it before ever calling `useHistory().add(...)`. But no UI
+      control sets `incognito: true` yet — the download-bar toggle is not wired (audit M6/UX1).
+      Note `download.ts` would still log a failure / show a completion title for a private item,
+      so the "private" promise currently covers history only (audit L136).
 - [x] **Backup / restore** settings + templates (export / import JSON). New
       `src/main/backup.ts` writes/reads `{ settings, templates }` via a save/open dialog;
       `replaceTemplates()` (`src/main/templates.ts`) does a full restore rather than a
@@ -171,9 +177,9 @@ parallel storage. All items verified in the UI preview (typecheck + `npm run tes
 Some items are Android-specific in Seal and adapted to Windows here.
 
 - [x] **Theme presets + "follow system" and high-contrast.** Settings → Appearance has a
-      Theme select (Light / Dark / **Follow system**) and four accent presets — Toffee
+      Theme select (Light / Dark / **Follow system**) and four accent presets — Rose,
-      (original), Slate, Evergreen, Lavender — each a 16-stop `BrandVariants` ramp sharing
+      Coral, Amber, Teal ("Sunset-to-sea", default Teal) — each a 16-stop `BrandVariants`
-      toffee's lightness curve at a different hue (`src/renderer/src/theme.ts`). "Follow
+      ramp sharing one lightness curve at a different hue (`src/renderer/src/theme.ts`). "Follow
       system" reads Electron's `nativeTheme.shouldUseDarkColors` in the main process
       (`src/main/index.ts`'s `resolveBackgroundMode`/`registerSystemThemeBridge`, pushed to
       the renderer over a new `system-theme:update` channel into
@@ -184,8 +190,8 @@ Some items are Android-specific in Seal and adapted to Windows here.
       Chromium's native `forced-colors` handling since nothing in the app sets
       `forced-color-adjust: none`. The sidebar's quick toggle still works under "system" — it
       sets an explicit light/dark away from whatever's currently resolved, breaking out of
-      auto. Verified in the UI preview (typecheck + `npm run test` clean): default Toffee,
+      auto. Verified in the UI preview (typecheck + `npm run test` clean): default Teal,
-      switching to Slate/Evergreen/Lavender, Light/Dark/Follow-system, and the sidebar
+      switching to Rose/Coral/Amber, Light/Dark/Follow-system, and the sidebar
       toggle's break-out-of-system behavior all checked visually.
 - [x] **Windows "open with" / share integration.** Both mechanisms named above, since a Win32
       (non-MSIX) app can't register as an actual Share Target:
@@ -285,14 +291,11 @@ YTDLnis's signature differentiator. The keyframe plumbing already exists in Aero
       keeps the full file and writes per-chapter files via its default `chapter:` template.
       *Implemented + unit-tested (`buildArgs.test.ts`, typecheck + test green); live smoke test
       still pending.*
-- [ ] **Metadata editing before download.** Change title / author / artist pre-download
+- [x] **Metadata editing before download.** Change title / author / artist pre-download
-      (YTDLnis: "modify metadata such as title and author"). → `--parse-metadata` /
+      (YTDLnis: "modify metadata such as title and author"). Uses `--replace-in-metadata FIELD ^.*$ VALUE`
-      `--replace-in-metadata`; fits the audio path. Good for building a clean music library
+      (not `--parse-metadata FROM:TO` which splits on colons). Only backslashes need escaping in the
-      where the source title is messy. *Held: the exact set-a-literal recipe is fragile
+      replacement string. Title, Artist, Album inputs in `DownloadOptionsForm.tsx`; setting any override
-      (`--parse-metadata FROM:TO` splits on a colon that titles often contain;
+      implicitly enables `--embed-metadata`. Unit-tested in `buildArgs.test.ts`.
-      `--replace-in-metadata FIELD REGEX REPLACE` has empty-field + regex-replacement edge
-      cases) — confirm against a live yt-dlp run before wiring it, rather than guessing the
-      flag.*
 
 ## Phase M — Queue & daily-use UX ✅ COMPLETE
 
@@ -339,8 +342,10 @@ Today `src/renderer/src/store/downloads.ts` has cancel + retry only.
       `datetime-local` input in `DownloadBar.tsx` (future time parks the new download as
       scheduled), plus per-row **Save for later** / **Add to queue** actions in `QueueItem.tsx`;
       saved items survive "Clear finished". Distinct from the Phase J `--sync` schedule (which is
-      for *sources*). **Limitation: the queue isn't persisted, so a schedule only fires while
+      for *sources*). The queue is now persisted across restarts (audit M4 — `queue.json` via
-      AeroFetch is running** — noted in the UI hint and the code.*
+      `src/main/queue.ts`), so a parked/scheduled item survives a quit and its schedule fires on the
+      next launch once due. (The app must still be running at the scheduled moment for an immediate
+      fire; a schedule that came due while closed fires at the next launch.)*
 
 ## Phase N — Power-user surface ✅ COMPLETE
 
@@ -384,9 +389,10 @@ All in the main process. typecheck + test + `npm run build` clean.
 - [x] **Jump list.** *Done: `app.setUserTasks` adds an "Open AeroFetch" task (focuses the
       single instance). **Thumbnail toolbar buttons deferred** — they need per-button `NativeImage`
       assets this repo doesn't have tooling to generate here.*
-- [ ] **Taskbar overlay badge** (`win.setOverlayIcon`) showing active-download count / error state.
+- [x] **Taskbar overlay badge** (`win.setOverlayIcon`) showing active-download count / error state.
-      *Deferred: a numeric/status badge needs a drawn `NativeImage` (no canvas in main); the
+      Green dot when downloading, red dot on error, cleared when idle. Pure-JS PNG generator in
-      taskbar progress bar's `error` mode already signals failures.*
+      `src/main/badge.ts` (Buffer + zlib, no new deps); badgeCount threaded through the existing
+      `taskbarProgress` IPC channel from `summarizeQueue`.
 - [x] **Settings discoverability.** *Done: a search box atop `SettingsView` filters the ~11 cards
       live by matching each card's text (DOM `display` toggle keyed off the root's children — no
       per-card refactor), with a "no settings match" hint.*
@@ -400,17 +406,21 @@ build clean); the parts that inherently need a human or a paid cert are delivere
       `youtubePoToken` → one `--extractor-args "youtube:player_client=…;po_token=…"` group
       (`accessArgs` in `buildArgs.ts`, unit-tested), with "advanced" fields in Settings → Network.
       Lets a power user switch extraction client (`web_safari`/`tv`/`mweb`) or paste a token.*
-      **Deferred: automatic WebView token minting** (the YTDLnis headline) — the hard part;
+      **Automatic WebView token minting shipped:** `src/main/poToken.ts` opens a YouTube video
-      this is the argv plumbing it would feed. Cookies remain the easier bot-check fix.
+      page in a hardened BrowserWindow (shared login session), injects an async poll for
+      `ytInitialPlayerResponse.serviceIntegrityDimensions.poToken`, saves the result encrypted
+      via `safeStorage`. "Fetch" button in Settings → Network triggers it via `youtube:po-token-mint`
+      IPC. Falls back gracefully (null) if YouTube's page structure changes.
 - [x] **Verify the shipped-but-untested OS wiring.** *Can't be executed here (no real install).
       Delivered as a release-gate checklist — [docs/SMOKE-TEST.md](docs/SMOKE-TEST.md) —
       enumerating every untested path (cookies window, `aerofetch://` + Send-to, scheduled
       `--sync` + RSS, aria2c, proxy, plus the new tray/taskbar/pause-resume/terminal) with exact
       steps + expected results. **Still needs a human to run it.**
-- [x] **Code signing.** *Build is signing-ready: electron-builder picks the cert up from
+- [x] **Code signing — non-goal.** *Decision: no certificate will be purchased, so builds ship
-      `CSC_LINK` / `CSC_KEY_PASSWORD` with no yml change (unset = unsigned, as today). Documented
+      unsigned and the SmartScreen first-run prompt is accepted. The build stays signing-ready —
-      in [docs/SIGNING.md](docs/SIGNING.md) (OV vs EV, local + CI, HSM/EV hook, signature
+      electron-builder picks the cert up from `CSC_LINK` / `CSC_KEY_PASSWORD` with no yml change
-      verification). **Actual signing needs a purchased certificate.***
+      (unset = unsigned, as today), documented in [docs/SIGNING.md](docs/SIGNING.md) (OV vs EV,
+      local + CI, HSM/EV hook, signature verification) — if that decision is ever reversed.*
 - [ ] **i18n / language setting.** Still deferred — deliberately not faked. Shipping a language
       picker that doesn't change anything would be misleading; doing it properly means wiring an
       i18n library + extracting every string, with translations arriving incrementally. Tracked,

build/icon.svg

@@ -1,12 +1,26 @@
 <svg width="256" height="256" viewBox="0 0 256 256" xmlns="http://www.w3.org/2000/svg">
-  <!-- Placeholder app icon (audit M3). Mirrors the in-app brand mark in
+  <!-- AeroFetch app icon (audit W14). A white download glyph — shaft + chevron over
-       Onboarding.tsx: a white download arrow on a rounded square in the default
+       a landing shelf — on the teal brand square, with a top-lit vertical gradient
-       "teal" accent (theme.ts teal[80] = colorBrandBackground in light mode).
+       drawn from the teal accent ramp (theme.ts teal 50→90, centred on teal[80]
-       Replace with a designed asset before v1.0; regenerate icon.ico from this. -->
+       #148185, the light-mode colorBrandBackground) and a soft upper sheen for depth.
-  <rect x="0" y="0" width="256" height="256" rx="52" ry="52" fill="#148185"/>
+       The bold rounded strokes stay legible down to 16px. Regenerate the multi-size
-  <g fill="#ffffff">
+       .ico after any edit:
-    <rect x="112" y="46" width="32" height="88" rx="12" ry="12"/>
+         magick -background none build/icon.svg -define icon:auto-resize=256,128,64,48,32,16 build/icon.ico -->
-    <polygon points="82,114 174,114 128,176"/>
+  <defs>
-    <rect x="66" y="190" width="124" height="20" rx="10" ry="10"/>
+    <linearGradient id="bg" x1="0" y1="0" x2="0" y2="1">
+      <stop offset="0" stop-color="#1aa6ab"/>
+      <stop offset="1" stop-color="#0d595c"/>
+    </linearGradient>
+    <linearGradient id="sheen" x1="0" y1="0" x2="0" y2="1">
+      <stop offset="0" stop-color="#ffffff" stop-opacity="0.16"/>
+      <stop offset="0.45" stop-color="#ffffff" stop-opacity="0"/>
+    </linearGradient>
+  </defs>
+  <rect x="0" y="0" width="256" height="256" rx="56" ry="56" fill="url(#bg)"/>
+  <rect x="0" y="0" width="256" height="256" rx="56" ry="56" fill="url(#sheen)"/>
+  <g fill="none" stroke="#ffffff" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M128 56 L128 150" stroke-width="30"/>
+    <path d="M84 116 L128 160 L172 116" stroke-width="30"/>
+    <path d="M80 200 L176 200" stroke-width="26"/>
   </g>
 </svg>

electron-builder.yml

@@ -1,6 +1,6 @@
 appId: com.aerofetch.app
 productName: AeroFetch
-copyright: yt-dlp frontend
+copyright: Copyright © 2026 AeroFetch
 
 # Lets a browser/another app hand AeroFetch a link via aerofetch://download?url=<encoded>
 # (src/main/deeplink.ts) — the closest Windows analog to Android's share-to-app intent.
@@ -15,13 +15,18 @@ directories:
   buildResources: build
   output: dist
 
+# Generate a <installer>.exe.sha256 next to every built .exe (H8). The updater
+# hard-requires this checksum asset or it refuses to install the update.
+afterAllArtifactBuild: ./scripts/generate-checksums.cjs
+
 files:
   - '!**/.vscode/*'
   - '!src/*'
   - '!electron.vite.config.{js,ts,mjs,cjs}'
-  - '!{.eslintignore,.eslintrc.cjs,.eslintrc.js,.prettierignore,.prettierrc.yaml,dev-app-update.yml,CHANGELOG.md,README.md}'
+  - '!{eslint.config.js,.prettierrc,dev-app-update.yml,CHANGELOG.md,README.md}'
   - '!{.env,.env.*,.npmrc,pnpm-lock.yaml,package-lock.json}'
-  - '!{tsconfig.json,tsconfig.node.json,tsconfig.web.json,tsconfig.tsbuildinfo}'
+  - '!{tsconfig.json,tsconfig.node.json,tsconfig.web.json}'
+  - '!*.tsbuildinfo'
 
 # yt-dlp.exe + ffmpeg.exe ship outside the asar archive so they can be spawned
 # directly. They land in <install>/resources/bin, reachable via process.resourcesPath.
@@ -46,9 +51,9 @@ win:
     - portable
   # Never request admin elevation.
   requestedExecutionLevel: asInvoker
-  # Placeholder icon (audit M3): white download glyph on the teal brand square,
+  # App icon (audit W14): white download glyph on the teal brand square with a
-  # mirroring the in-app brand mark. Generated from build/icon.svg as a multi-size
+  # top-lit gradient. Generated from build/icon.svg as a multi-size .ico
-  # .ico (256/128/64/48/32/16). Replace with a designed asset before v1.0 — re-run
+  # (256/128/64/48/32/16). After editing the SVG, regenerate with:
   #   magick -background none build/icon.svg -define icon:auto-resize=256,128,64,48,32,16 build/icon.ico
   icon: build/icon.ico
 
@@ -63,4 +68,7 @@ nsis:
   perMachine: false
   allowToChangeInstallationDirectory: true
   deleteAppDataOnUninstall: false
+  # The custom updater (src/main/updater.ts) does a full download and never consumes
+  # the differential .blockmap, so don't emit it (audit L83 — dead build artifact).
+  differentialPackage: false
   # Flip perMachine to true for an all-users install to Program Files (requires admin).

electron.vite.config.ts

@@ -9,7 +9,11 @@ export default defineConfig({
       alias: {
         '@shared': resolve('src/shared')
       }
-    }
+    },
+    // Hidden source maps: emit .map files so a field crash stack (the logger writes
+    // raw stacks, CC8) can be symbolicated offline, without referencing/exposing them
+    // in the shipped bundle (L170).
+    build: { sourcemap: 'hidden' }
   },
   preload: {
     plugins: [externalizeDepsPlugin()],
@@ -21,6 +25,7 @@ export default defineConfig({
     // Emit CommonJS (.cjs): sandboxed preload scripts must be CJS, and enabling
     // the sandbox (webPreferences.sandbox) is part of the security hardening.
     build: {
+      sourcemap: 'hidden',
       rollupOptions: {
         output: {
           format: 'cjs',
@@ -36,6 +41,7 @@ export default defineConfig({
         '@shared': resolve('src/shared')
       }
     },
-    plugins: [react()]
+    plugins: [react()],
+    build: { sourcemap: 'hidden' }
   }
 })

eslint.config.js

@@ -0,0 +1,43 @@
+import js from '@eslint/js'
+import tseslint from 'typescript-eslint'
+import globals from 'globals'
+import prettier from 'eslint-config-prettier'
+
+// Flat config (ESLint 9 + typescript-eslint 8). Codifies the existing house style
+// (CC2): typescript-eslint's recommended logic/type rules, with formatting left
+// entirely to Prettier (eslint-config-prettier turns off any stylistic rules).
+// Run with `npm run lint`; `npm run format` applies Prettier.
+export default tseslint.config(
+  { ignores: ['out/**', 'dist/**', 'node_modules/**', '**/*.cjs'] },
+  js.configs.recommended,
+  ...tseslint.configs.recommended,
+  {
+    languageOptions: {
+      globals: { ...globals.node, ...globals.browser }
+    },
+    rules: {
+      // Empty catch blocks are a deliberate best-effort pattern across the app.
+      'no-empty': ['error', { allowEmptyCatch: true }],
+      // Allow a documented @ts-ignore. The preload's window fallback needs one
+      // whose necessity is incremental-build-state-dependent, so @ts-expect-error
+      // (which errors when momentarily unused) is the wrong tool there.
+      '@typescript-eslint/ban-ts-comment': [
+        'error',
+        { 'ts-ignore': 'allow-with-description', minimumDescriptionLength: 3 }
+      ],
+      // Allow intentionally-unused names prefixed with `_` (e.g. IPC event args).
+      '@typescript-eslint/no-unused-vars': [
+        'error',
+        { argsIgnorePattern: '^_', varsIgnorePattern: '^_' }
+      ]
+    }
+  },
+  {
+    // TypeScript already resolves identifiers/types, so core no-undef only
+    // false-positives on globals and type-only references here.
+    files: ['**/*.{ts,tsx}'],
+    rules: { 'no-undef': 'off' }
+  },
+  // Keep Prettier last so it wins over any formatting-related rule.
+  prettier
+)

package.json

@@ -4,7 +4,12 @@
   "description": "A yt-dlp frontend for Windows",
   "main": "./out/main/index.js",
   "author": "AeroFetch",
-  "homepage": "https://github.com/yt-dlp/yt-dlp",
+  "license": "UNLICENSED",
+  "homepage": "https://gitea.netbird.zimspace.uk:5938/debont80/AeroFetch",
+  "repository": {
+    "type": "git",
+    "url": "https://gitea.netbird.zimspace.uk:5938/debont80/AeroFetch.git"
+  },
   "private": true,
   "type": "module",
   "scripts": {
@@ -14,12 +19,18 @@
     "ui:build": "vite build",
     "ui:preview": "vite preview",
     "build": "electron-vite build",
-    "build:win": "electron-vite build && electron-builder --win",
+    "clean:dist": "node -e \"require('fs').rmSync('dist',{recursive:true,force:true})\"",
+    "build:win": "npm run clean:dist && electron-vite build && electron-builder --win",
     "start": "electron-vite preview",
     "typecheck:node": "tsc --noEmit -p tsconfig.node.json --composite false",
     "typecheck:web": "tsc --noEmit -p tsconfig.web.json --composite false",
     "typecheck": "npm run typecheck:node && npm run typecheck:web",
-    "test": "vitest run"
+    "lint": "eslint .",
+    "lint:fix": "eslint . --fix",
+    "format": "prettier --write \"src/**/*.{ts,tsx}\" \"test/**/*.ts\"",
+    "format:check": "prettier --check \"src/**/*.{ts,tsx}\" \"test/**/*.ts\"",
+    "test": "vitest run",
+    "test:integration": "set AEROFETCH_REAL_DOWNLOAD=1&& vitest run test/real-download.integration.test.ts"
   },
   "dependencies": {
     "@electron-toolkit/utils": "^4.0.0",
@@ -33,6 +44,7 @@
   },
   "devDependencies": {
     "@electron-toolkit/tsconfig": "^2.0.0",
+    "@eslint/js": "^9.39.4",
     "@types/node": "^26.0.0",
     "@types/react": "^19.2.17",
     "@types/react-dom": "^19.2.3",
@@ -40,7 +52,12 @@
     "electron": "^42.4.1",
     "electron-builder": "^26.15.3",
     "electron-vite": "^5.0.0",
+    "eslint": "^9.39.4",
+    "eslint-config-prettier": "^10.1.8",
+    "globals": "^15.15.0",
+    "prettier": "^3.9.3",
     "typescript": "^6.0.3",
+    "typescript-eslint": "^8.62.1",
     "vite": "^7.3.5",
     "vitest": "^4.1.9"
   }

scripts/generate-checksums.cjs

@@ -0,0 +1,36 @@
+// electron-builder `afterAllArtifactBuild` hook (H8).
+//
+// The in-app updater (src/main/updater.ts) sets REQUIRE_CHECKSUM = true and
+// refuses any release whose installer lacks a sibling `<installer>.exe.sha256`
+// asset — so a release published without one makes EVERY client's in-app update
+// fail. `build:win` never generated these, so they had to be made by hand (and
+// the 0.5.0 build shipped without any). This hook writes one next to every built
+// `.exe`, in `sha256sum` format (`<lowercase-hex>  <filename>`), which the
+// updater's extractSha256 parses (it just needs a standalone 64-char hex token).
+//
+// Returning the paths tells electron-builder to also upload them as release
+// assets when publishing.
+
+const { createHash } = require('crypto')
+const { readFileSync, writeFileSync } = require('fs')
+const { basename } = require('path')
+
+/** The `sha256sum`-format line for a file: "<lowercase-hex>  <basename>". */
+function checksumLine(filePath) {
+  const hex = createHash('sha256').update(readFileSync(filePath)).digest('hex')
+  return `${hex}  ${basename(filePath)}`
+}
+
+exports.default = function generateChecksums(context) {
+  const written = []
+  for (const file of context.artifactPaths) {
+    if (!/\.exe$/i.test(file)) continue
+    const out = `${file}.sha256`
+    writeFileSync(out, checksumLine(file) + '\n')
+    written.push(out)
+  }
+  return written
+}
+
+// Exported for unit testing the hashing/format without running electron-builder.
+exports.checksumLine = checksumLine

src/main/backup.ts

@@ -1,14 +1,9 @@
 import { dialog, type BrowserWindow } from 'electron'
 import { readFileSync, writeFileSync } from 'fs'
-import { getSettings, setSettings } from './settings'
+import { getSettings, setSettings, SECRET_KEYS } from './settings'
 import { listTemplates, replaceTemplates } from './templates'
 import { isTemplateLike } from './validation'
-import type {
+import type { BackupExportResult, BackupImportResult, Settings, CommandTemplate } from '@shared/ipc'
-  BackupExportResult,
-  BackupImportResult,
-  Settings,
-  CommandTemplate
-} from '@shared/ipc'
 
 interface BackupFile {
   version: 1
@@ -17,12 +12,18 @@ interface BackupFile {
 }
 
 export async function exportBackup(win: BrowserWindow | undefined): Promise<BackupExportResult> {
-  const res = await dialog.showSaveDialog(win!, {
+  const opts = {
     defaultPath: 'aerofetch-backup.json',
     filters: [{ name: 'JSON', extensions: ['json'] }]
-  })
+  }
+  const res = await (win ? dialog.showSaveDialog(win, opts) : dialog.showSaveDialog(opts))
   if (res.canceled || !res.filePath) return { ok: false }
-  const payload: BackupFile = { version: 1, settings: getSettings(), templates: listTemplates() }
+  // Strip credentials (proxy creds, API tokens) so a backup file shared or synced
+  // to the cloud doesn't leak secrets in plaintext (M22). The user re-enters them
+  // after import. Shares SECRET_KEYS with settings.ts so the lists can't drift.
+  const settings = { ...getSettings() }
+  for (const key of SECRET_KEYS) (settings as Record<string, unknown>)[key] = ''
+  const payload: BackupFile = { version: 1, settings, templates: listTemplates() }
   try {
     writeFileSync(res.filePath, JSON.stringify(payload, null, 2))
     return { ok: true, path: res.filePath }
@@ -32,10 +33,11 @@ export async function exportBackup(win: BrowserWindow | undefined): Promise<Back
 }
 
 export async function importBackup(win: BrowserWindow | undefined): Promise<BackupImportResult> {
-  const res = await dialog.showOpenDialog(win!, {
+  const openOpts = {
-    properties: ['openFile'],
+    properties: ['openFile' as const],
     filters: [{ name: 'JSON', extensions: ['json'] }]
-  })
+  }
+  const res = await (win ? dialog.showOpenDialog(win, openOpts) : dialog.showOpenDialog(openOpts))
   if (res.canceled || !res.filePaths[0]) return { ok: false }
 
   let parsed: unknown
@@ -85,10 +87,9 @@ export async function importBackup(win: BrowserWindow | undefined): Promise<Back
         return `• ${name}: ${args}`
       })
       .join('\n')
-    const more =
+    const more = commandTemplates.length > 10 ? `\n…and ${commandTemplates.length - 10} more.` : ''
-      commandTemplates.length > 10 ? `\n…and ${commandTemplates.length - 10} more.` : ''
+    const msgOpts = {
-    const choice = await dialog.showMessageBox(win!, {
+      type: 'warning' as const,
-      type: 'warning',
       buttons: ['Enable custom commands', 'Import without enabling', 'Cancel'],
       defaultId: 1,
       cancelId: 2,
@@ -100,17 +101,26 @@ export async function importBackup(win: BrowserWindow | undefined): Promise<Back
         'Custom commands run extra yt-dlp flags on every download. Only enable them if you trust this backup file.\n\n' +
         preview +
         more
-    })
+    }
+    const choice = await (win
+      ? dialog.showMessageBox(win, msgOpts)
+      : dialog.showMessageBox(msgOpts))
     if (choice.response === 2) return { ok: false } // Cancel — change nothing
     applyCustomCommands = choice.response === 0
   }
 
   if (incomingSettings) {
+    // Never restore credential fields from a backup. Exports strip them (M22), so an
+    // imported '' would otherwise wipe a proxy/token already configured on this
+    // machine; honoring a hand-edited one would reintroduce the leak vector. Either
+    // way, import leaves the user's existing secrets untouched — they re-enter as needed.
+    const restored: Partial<Settings> = { ...incomingSettings }
+    for (const key of SECRET_KEYS) delete restored[key]
     // When the user declined to enable custom commands (or there were none to
     // enable), force the toggle off so an imported defaultTemplateId can't auto-run.
     const safeSettings = applyCustomCommands
-      ? incomingSettings
+      ? restored
-      : { ...incomingSettings, customCommandEnabled: false }
+      : { ...restored, customCommandEnabled: false }
     setSettings(safeSettings)
   }
   if (incomingTemplates.length > 0 || Array.isArray(file.templates)) {

src/main/badge.ts

@@ -0,0 +1,87 @@
+import { deflateSync } from 'zlib'
+import { nativeImage, type NativeImage } from 'electron'
+
+// CRC32 table polynomial used by PNG.
+function crc32(buf: Buffer): number {
+  let crc = 0xffffffff
+  for (const b of buf) {
+    crc ^= b
+    for (let i = 0; i < 8; i++) crc = crc & 1 ? (crc >>> 1) ^ 0xedb88320 : crc >>> 1
+  }
+  return (crc ^ 0xffffffff) >>> 0
+}
+
+function pngChunk(type: string, data: Buffer): Buffer {
+  const t = Buffer.from(type, 'ascii')
+  const len = Buffer.alloc(4)
+  len.writeUInt32BE(data.length)
+  const crc = Buffer.alloc(4)
+  crc.writeUInt32BE(crc32(Buffer.concat([t, data])))
+  return Buffer.concat([len, t, data, crc])
+}
+
+/**
+ * Build a 16×16 RGBA PNG containing a solid-colour filled circle. Used for the
+ * Windows taskbar overlay badge. No external deps — pure Node.js (Buffer + zlib).
+ */
+function makeDotPng(r: number, g: number, b: number): NativeImage {
+  const W = 16,
+    H = 16
+  const px = Buffer.alloc(W * H * 4, 0) // transparent bg
+  const cx = W / 2,
+    cy = H / 2,
+    rad = W / 2 - 1.5
+
+  for (let y = 0; y < H; y++) {
+    for (let x = 0; x < W; x++) {
+      const dx = x + 0.5 - cx,
+        dy = y + 0.5 - cy
+      if (dx * dx + dy * dy <= rad * rad) {
+        const i = (y * W + x) * 4
+        px[i] = r
+        px[i + 1] = g
+        px[i + 2] = b
+        px[i + 3] = 255
+      }
+    }
+  }
+
+  // PNG: IHDR (8-bit RGBA, no interlace), filter-0 rows, deflated IDAT, IEND.
+  const ihdr = Buffer.alloc(13)
+  ihdr.writeUInt32BE(W, 0)
+  ihdr.writeUInt32BE(H, 4)
+  ihdr[8] = 8 // bit depth
+  ihdr[9] = 6 // colour type: RGBA
+
+  const rows = Buffer.alloc(H * (1 + W * 4))
+  for (let y = 0; y < H; y++) {
+    rows[y * (1 + W * 4)] = 0 // filter type: None
+    px.copy(rows, y * (1 + W * 4) + 1, y * W * 4, (y + 1) * W * 4)
+  }
+
+  const sig = Buffer.from([137, 80, 78, 71, 13, 10, 26, 10])
+  const png = Buffer.concat([
+    sig,
+    pngChunk('IHDR', ihdr),
+    pngChunk('IDAT', deflateSync(rows)),
+    pngChunk('IEND', Buffer.alloc(0))
+  ])
+  return nativeImage.createFromBuffer(png)
+}
+
+// Lazy-initialised singletons — created on first use so this module is safe to
+// import before the app is ready (nativeImage.createFromBuffer is fine post-ready).
+let activeBadge: NativeImage | null = null
+let errorBadge: NativeImage | null = null
+
+/** Green dot badge for the taskbar overlay — shown when downloads are active. */
+export function getActiveBadge(): NativeImage {
+  if (!activeBadge) activeBadge = makeDotPng(58, 185, 108) // #3ab96c
+  return activeBadge
+}
+
+/** Red dot badge for the taskbar overlay — shown when a download has errored. */
+export function getErrorBadge(): NativeImage {
+  if (!errorBadge) errorBadge = makeDotPng(217, 48, 37) // #d93025
+  return errorBadge
+}

src/main/binaries.ts

@@ -1,4 +1,4 @@
-import { app } from 'electron'
+import { app, nativeImage, type NativeImage } from 'electron'
 import { join } from 'path'
 import { is } from '@electron-toolkit/utils'
 
@@ -24,6 +24,23 @@ export function getAppIconPath(): string {
     : join(process.resourcesPath, 'icon.ico')
 }
 
+let appIconImage: NativeImage | null = null
+/**
+ * The app icon as a cached NativeImage, for OS notifications (W13/L127). Loaded
+ * once from getAppIconPath(); a missing icon yields an empty image, which
+ * Notification treats as "no icon" (the OS default) rather than erroring. This
+ * gives completion/background toasts the real brand glyph — notably on the
+ * portable build, which has no installed AUMID shortcut icon for Windows to use.
+ */
+export function getAppIconImage(): NativeImage {
+  // Cache only a valid image so a transient read miss isn't latched forever; a
+  // genuinely-missing icon just re-reads (cheap — notifications are infrequent).
+  if (!appIconImage || appIconImage.isEmpty()) {
+    appIconImage = nativeImage.createFromPath(getAppIconPath())
+  }
+  return appIconImage
+}
+
 /**
  * AeroFetch keeps its OWN writable copy of yt-dlp.exe under userData, separate
  * from the read-only bundled seed in resources/bin. The managed copy is what
@@ -35,7 +52,7 @@ export function getAppIconPath(): string {
  * ffmpeg/ffprobe/aria2c stay in getBinDir(): they're not self-updating and
  * yt-dlp finds them via `--ffmpeg-location <binDir>`.
  */
-export function getManagedBinDir(): string {
+function getManagedBinDir(): string {
   return join(app.getPath('userData'), 'bin')
 }
 
@@ -63,6 +80,10 @@ export function getFfprobePath(): string {
   return join(getBinDir(), 'ffprobe.exe')
 }
 
+/** User-facing error shown by download/probe/index/update when yt-dlp.exe is missing. */
+export const YTDLP_MISSING_MSG =
+  'yt-dlp.exe is missing. Open Settings → Software update to re-download it.'
+
 /** Optional bundled external downloader; absent unless dropped into resources/bin. */
 export function getAria2cPath(): string {
   return join(getBinDir(), 'aria2c.exe')

src/main/buildArgs.ts

@@ -42,9 +42,7 @@ function videoFormat(quality: string): string {
  */
 function videoSelector(opts: StartDownloadOptions): string {
   if (opts.formatId && opts.formatId !== BEST_FORMAT_ID) {
-    return opts.formatHasAudio
+    return opts.formatHasAudio ? opts.formatId : `${opts.formatId}+bestaudio/${opts.formatId}`
-      ? opts.formatId
-      : `${opts.formatId}+bestaudio/${opts.formatId}`
   }
   return videoFormat(opts.quality)
 }
@@ -57,18 +55,27 @@ function audioQuality(quality: string): string {
       return '192K'
     case '128 kbps':
       return '128K'
+    case 'Best':
+      return '0'
     default:
-      return '0' // Best
+      // Unrecognised label — fall back to best (0) so the download still works.
+      return '0'
   }
 }
 
+// Stdout line markers, shared by the emit side (the --print templates here) and
+// the parse side (download.ts). Defined once so changing a marker can't silently
+// break the parser that splits on it (CL1).
+export const PROGRESS_MARKER = 'prog|'
+export const FILEPATH_MARKER = 'path|'
+
 // The progress line yt-dlp emits (one per --newline tick). Note the leading
 // `download:` is the progress-template TYPE selector and is consumed by yt-dlp
-// (it does NOT appear in the output). The literal `prog|` that follows is our
+// (it does NOT appear in the output). The PROGRESS_MARKER that follows is our
 // own marker, so we can tell progress lines apart from the after-move filepath
 // print on the same stdout stream.
-export const PROGRESS_TEMPLATE =
+const PROGRESS_TEMPLATE =
-  'download:prog|%(progress.status)s|%(progress.downloaded_bytes)s|' +
+  `download:${PROGRESS_MARKER}%(progress.status)s|%(progress.downloaded_bytes)s|` +
   '%(progress.total_bytes)s|%(progress.total_bytes_estimate)s|' +
   '%(progress.speed)s|%(progress.eta)s'
 
@@ -77,8 +84,7 @@ export const PROGRESS_TEMPLATE =
 // double quotes and leaving ffmpeg single-quoted crop expressions whose commas are
 // protected from ffmpeg's filtergraph separator. Side = min(width, height).
 export const CROP_SQUARE_PPA =
-  'EmbedThumbnail+ffmpeg_o:-c:v mjpeg -vf ' +
+  'EmbedThumbnail+ffmpeg_o:-c:v mjpeg -vf ' + "crop=\"'if(gt(ih,iw),iw,ih)':'if(gt(iw,ih),ih,iw)'\""
-  'crop="\'if(gt(ih,iw),iw,ih)\':\'if(gt(iw,ih),ih,iw)\'"'
 
 /**
  * Phase B "Access & networking" settings — not per-download options, always
@@ -127,7 +133,9 @@ export function parseExtraArgs(raw: string): string[] {
   const re = /"([^"]*)"|'([^']*)'|(\S+)/g
   let m: RegExpExecArray | null
   while ((m = re.exec(raw)) !== null) {
-    args.push(m[1] ?? m[2] ?? m[3])
+    // Exactly one of the three alternation groups matches; the '' fallback only
+    // satisfies the type checker (noUncheckedIndexedAccess) and never fires.
+    args.push(m[1] ?? m[2] ?? m[3] ?? '')
   }
   return args
 }
@@ -197,7 +205,10 @@ export function matchesUrl(pattern: string, url: string): boolean {
  */
 export function parseTrimSections(raw: string | undefined): string[] {
   if (!raw) return []
-  const TIME = String.raw`\d+(?::\d{1,2})*(?:\.\d+)?`
+  // A time is SS, M:SS, or H:MM:SS — at most two colon-separated groups. The old
+  // `*` quantifier accepted nonsense like `1:2:3:4`, which then failed inside
+  // yt-dlp's --download-sections rather than being rejected up front (L146).
+  const TIME = String.raw`\d+(?::\d{1,2}){0,2}(?:\.\d+)?`
   const RANGE = new RegExp(`^${TIME}-${TIME}$`)
   const out: string[] = []
   for (const piece of raw.split(/[,\n]/)) {
@@ -244,7 +255,11 @@ export function sanitizeDirSegment(name: string): string {
   // byte ever appears in this source file.
   let s = Array.from(name ?? '', (ch) => (ch.charCodeAt(0) < 0x20 ? ' ' : ch)).join('')
   s = s.replace(/[<>:"/\\|?*]/g, ' ')
-  s = s.replace(/\s+/g, ' ').trim().replace(/[. ]+$/, '').replace(/^[. ]+/, '')
+  s = s
+    .replace(/\s+/g, ' ')
+    .trim()
+    .replace(/[. ]+$/, '')
+    .replace(/^[. ]+/, '')
   // Reserved device names are reserved even WITH an extension ('CON.txt' is still
   // the CON device), so match an optional trailing '.<ext>' too (audit T3).
   if (/^(con|prn|aux|nul|com[1-9]|lpt[1-9])(\..*)?$/i.test(s)) s = `_${s}`
@@ -328,7 +343,23 @@ function postProcessArgs(opts: StartDownloadOptions, o: DownloadOptions): string
   // Split into one file per chapter. yt-dlp also keeps the full file; the
   // per-chapter files use yt-dlp's default `chapter:` output template.
   if (o.splitChapters) args.push('--split-chapters')
-  if (o.embedMetadata) args.push('--embed-metadata')
+
+  // Metadata embedding + optional per-field overrides.
+  // --replace-in-metadata FIELD REGEX REPLACE is used instead of --parse-metadata
+  // FROM:TO because the replacement arg is a separate element (no colon-splitting
+  // on values like "Foo: Bar"). ^.*$ matches any string including empty. The only
+  // escaping Python's re.sub needs in the replacement string is backslash.
+  const metaOverrides: [string, string | undefined][] = [
+    ['title', o.metadataTitle],
+    ['artist', o.metadataArtist],
+    ['album', o.metadataAlbum]
+  ]
+  const hasOverrides = metaOverrides.some(([, v]) => v?.trim())
+  if (o.embedMetadata || hasOverrides) args.push('--embed-metadata')
+  const escRepl = (s: string): string => s.replace(/\\/g, '\\\\')
+  for (const [field, val] of metaOverrides) {
+    if (val?.trim()) args.push('--replace-in-metadata', field, '^.*$', escRepl(val.trim()))
+  }
 
   // Media-server sidecar files (Phase K) — written next to the output file so
   // Jellyfin/Plex/Kodi can ingest metadata, poster art, and the description.
@@ -339,18 +370,39 @@ function postProcessArgs(opts: StartDownloadOptions, o: DownloadOptions): string
   return args
 }
 
-export function buildArgs(
+/**
-  opts: StartDownloadOptions,
+ * Everything buildArgs needs to construct a yt-dlp argv. A single options object
-  outputTemplate: string,
+ * (rather than six positional params) so callers can't transpose `opts`/`options`
-  o: DownloadOptions,
+ * or the two path-like strings, and new inputs can be added without churning every
-  binDir: string,
+ * call site (CL2).
-  access: AccessOptions,
+ */
-  extraArgs: string[] = []
+export interface BuildArgsInput {
-): string[] {
+  /** The per-download request (url, kind, quality, chosen format, trim, …). */
+  opts: StartDownloadOptions
+  /** The resolved `-o` output template (flat filename or collection folder tree). */
+  outputTemplate: string
+  /** The post-processing options group (per-download override or the persisted default). */
+  options: DownloadOptions
+  /** ffmpeg/yt-dlp bin dir, passed in so this module stays free of path resolution. */
+  binDir: string
+  /** Global access/networking settings (proxy, cookies, rate limit, …). */
+  access: AccessOptions
+  /** Custom-command extra args, already consent-gated by the caller. */
+  extraArgs?: string[]
+}
+
+export function buildArgs(input: BuildArgsInput): string[] {
+  const { opts, outputTemplate, options: o, binDir, access, extraArgs = [] } = input
   const args = [
     '--newline',
     '--no-color',
     '--no-playlist',
+    // Bound a dead/hung connection so yt-dlp aborts (and retries, then exits) a
+    // stalled socket instead of hanging forever and pinning a concurrency slot
+    // with no recovery. The app-side idle watchdog in download.ts is the backstop
+    // for a fully-wedged process. (B1)
+    '--socket-timeout',
+    '30',
     // --print (below) implies --quiet, which would suppress progress; --progress
     // forces the progress template to emit anyway.
     '--progress',
@@ -362,7 +414,7 @@ export function buildArgs(
     PROGRESS_TEMPLATE,
     // Print the final path after post-processing/move so we can open it later.
     '--print',
-    'after_move:path|%(filepath)s',
+    `after_move:${FILEPATH_MARKER}%(filepath)s`,
     '--no-simulate'
   ]
 
@@ -370,7 +422,11 @@ export function buildArgs(
   args.push(...postProcessArgs(opts, o))
 
   if (opts.kind === 'audio') {
-    args.push('-x', '--audio-format', o.audioFormat, '--audio-quality', audioQuality(opts.quality))
+    // --audio-quality is a bitrate selector meaningful only for lossy re-encodes.
+    // For lossless formats (flac/wav) it is silently ignored by yt-dlp (M21).
+    const lossless = o.audioFormat === 'flac' || o.audioFormat === 'wav'
+    args.push('-x', '--audio-format', o.audioFormat)
+    if (!lossless) args.push('--audio-quality', audioQuality(opts.quality))
     if (o.embedThumbnail) {
       args.push('--embed-thumbnail')
       if (o.cropThumbnail) args.push('--ppa', CROP_SQUARE_PPA)

src/main/constants.ts

@@ -0,0 +1,67 @@
+/**
+ * Central home for the main-process timeouts, buffer sizes, and store caps that
+ * were previously scattered as bare literals across the spawn/probe/index/store
+ * modules (L10). Collecting them here makes the operational envelope reviewable
+ * in one place and stops the same "how long / how big" decision drifting between
+ * modules. Values that are already single-sourced in the shared contract
+ * (e.g. HISTORY_MAX_ENTRIES) stay there; this file is for the main-only ones.
+ */
+
+// --- Child-process timeouts (ms) --------------------------------------------
+
+/** `<binary> -version` probes (yt-dlp, ffmpeg, ffprobe) — a quick liveness call. */
+export const VERSION_TIMEOUT_MS = 15_000
+/** yt-dlp self-update run — can pull a fresh binary, so a touch longer. */
+export const YTDLP_UPDATE_TIMEOUT_MS = 60_000
+/** Best-effort metadata --print alongside a download (title/uploader/duration). */
+export const META_PROBE_TIMEOUT_MS = 30_000
+/** Full format/metadata probe (`-J`) for the download bar. */
+export const PROBE_TIMEOUT_MS = 60_000
+/** Channel/playlist indexing walk — a big channel legitimately takes minutes. */
+export const INDEX_TIMEOUT_MS = 180_000
+/** RSS feed fetch for a watched source's new-item check. */
+export const FEED_FETCH_TIMEOUT_MS = 15_000
+
+/**
+ * Idle watchdog for a running download: if a spawned yt-dlp emits no stdout or
+ * stderr for this long, treat it as wedged and kill it so the concurrency slot
+ * frees (B1). Generous on purpose so a long, output-less post-processing step
+ * (e.g. a large ffmpeg merge) isn't mistaken for a stall.
+ */
+export const STALL_TIMEOUT_MS = 5 * 60_000
+
+// --- execFile maxBuffer sizes (bytes) ---------------------------------------
+// yt-dlp JSON for a big channel/format list is large; cap generously so a valid
+// response is never truncated (which would look like a parse failure).
+
+/** Metadata --print output (three short fields). */
+export const META_MAX_BUFFER = 4 * 1024 * 1024
+/** Single-video `-J` probe JSON. */
+export const PROBE_MAX_BUFFER = 64 * 1024 * 1024
+/** Whole-channel index JSON. */
+export const INDEX_MAX_BUFFER = 256 * 1024 * 1024
+
+// --- Misc ------------------------------------------------------------------
+
+/** How much of a failed download's stderr to retain for the error message. */
+export const STDERR_TAIL_BYTES = 4000
+
+/**
+ * Size cap for the diagnostic log file (logger.ts, CC8). Once the live
+ * `aerofetch.log` passes this, it's rotated to `aerofetch.log.1` (one generation
+ * kept) so app logging can't fill the disk.
+ */
+export const LOG_MAX_BYTES = 1024 * 1024
+
+// --- JSON-store row caps ----------------------------------------------------
+// Each hand-rolled JSON store trims to its cap on write so a store file can't
+// grow without bound.
+
+/** Diagnostics error log (errorlog.json). */
+export const ERRORLOG_MAX_ENTRIES = 200
+/** Saved custom-command templates (templates.json). */
+export const TEMPLATES_MAX = 100
+/** Indexed media items across all sources (media-items.json). */
+export const MEDIA_ITEMS_MAX = 20_000
+/** Persisted download-queue rows (queue.json, M4) — generous; a whole channel can be queued. */
+export const QUEUE_MAX = 10_000

src/main/contextMenu.ts

@@ -0,0 +1,45 @@
+import { Menu, type WebContents, type MenuItemConstructorOptions } from 'electron'
+
+/**
+ * Give editable fields (and any selected text) the standard Windows Cut / Copy /
+ * Paste / Select All right-click menu that Electron does not provide by default
+ * (W4) — plus spellcheck suggestions for text areas. The menu items use built-in
+ * roles, so the editing works directly in the sandboxed, context-isolated
+ * renderer without any extra IPC. Wired onto the main window only; the untrusted
+ * cookie sign-in window deliberately keeps its minimal chrome.
+ */
+export function attachEditContextMenu(wc: WebContents): void {
+  wc.on('context-menu', (_e, params) => {
+    const { isEditable, editFlags, selectionText, dictionarySuggestions } = params
+    // Only worth a menu over an editable field or a real text selection.
+    if (!isEditable && !selectionText.trim()) return
+
+    const template: MenuItemConstructorOptions[] = []
+
+    // Spellcheck suggestions first, when the caret sits on a misspelling.
+    if (isEditable && dictionarySuggestions.length > 0) {
+      for (const suggestion of dictionarySuggestions) {
+        template.push({ label: suggestion, click: () => wc.replaceMisspelling(suggestion) })
+      }
+      template.push({ type: 'separator' })
+    }
+
+    if (isEditable) {
+      template.push(
+        { role: 'cut', enabled: editFlags.canCut },
+        { role: 'copy', enabled: editFlags.canCopy },
+        { role: 'paste', enabled: editFlags.canPaste },
+        { type: 'separator' },
+        { role: 'selectAll', enabled: editFlags.canSelectAll }
+      )
+    } else {
+      // Read-only text with a selection: offer Copy (and Select All).
+      template.push(
+        { role: 'copy', enabled: editFlags.canCopy },
+        { role: 'selectAll', enabled: editFlags.canSelectAll }
+      )
+    }
+
+    Menu.buildFromTemplate(template).popup()
+  })
+}

src/main/cookies.ts

@@ -1,15 +1,17 @@
-import { app, session, BrowserWindow, type Cookie, type WebContents } from 'electron'
+import { app, safeStorage, session, BrowserWindow, type Cookie, type WebContents } from 'electron'
-import { existsSync, statSync, unlinkSync, writeFileSync } from 'fs'
+import { existsSync, statSync, unlinkSync, writeFileSync, readFileSync } from 'fs'
 import { join } from 'path'
 import { assertHttpUrl } from './url'
+import { logger } from './logger'
 import type { CookiesStatus, CookiesLoginResult } from '@shared/ipc'
 
 /**
  * Persisted session AeroFetch's built-in sign-in window uses. Kept separate
  * from the main window's (default) session so a logged-in site can't see or
- * touch anything the app itself loads.
+ * touch anything the app itself loads. Exported so the PO-token window can
+ * share the same session (and thus the user's YouTube sign-in state).
  */
-const PARTITION = 'persist:aerofetch-login'
+export const LOGIN_PARTITION = 'persist:aerofetch-login'
 
 /**
  * The sign-in window renders untrusted remote content, so every navigation and
@@ -43,7 +45,7 @@ function hardenLoginWebContents(wc: WebContents): void {
       overrideBrowserWindowOptions: {
         autoHideMenuBar: true,
         webPreferences: {
-          partition: PARTITION,
+          partition: LOGIN_PARTITION,
           sandbox: true,
           contextIsolation: true,
           nodeIntegration: false
@@ -60,20 +62,99 @@ function hardenLoginWebContents(wc: WebContents): void {
   wc.on('did-create-window', (child) => hardenLoginWebContents(child.webContents))
 }
 
-export function getCookiesFilePath(): string {
+// The persisted cookie jar is encrypted at rest (H7). yt-dlp's `--cookies` needs
+// a plaintext file, so the stored form is encrypted via Electron safeStorage
+// (DPAPI on Windows — the same protection settings secrets get) and only ever
+// decrypted to a short-lived temp file for the duration of a download. This
+// matters for the portable build, where userData sits next to the exe (USB /
+// shared Downloads folder) and a plaintext jar would hand over a logged-in session.
+function cookieStorePath(): string {
+  return join(app.getPath('userData'), 'cookies.dat')
+}
+
+function legacyCookiePath(): string {
   return join(app.getPath('userData'), 'cookies.txt')
 }
 
+// Marks ciphertext so a read can tell it from legacy/fallback plaintext (written
+// before encryption, or where safeStorage was unavailable). Mirrors settings.ts.
+const ENC_PREFIX = 'enc:v1:'
+
+/** Persist the Netscape cookie text, encrypted where safeStorage is available. */
+function storeCookies(netscape: string): void {
+  let out = netscape
+  try {
+    if (safeStorage.isEncryptionAvailable()) {
+      out = ENC_PREFIX + safeStorage.encryptString(netscape).toString('base64')
+    }
+  } catch {
+    /* fall through — store plaintext, as it was before encryption existed */
+  }
+  writeFileSync(cookieStorePath(), out)
+}
+
+/** Decrypt the persisted cookie text, or null if none / undecryptable here. */
+function loadCookies(): string | null {
+  const p = cookieStorePath()
+  if (!existsSync(p)) return null
+  const stored = readFileSync(p, 'utf8')
+  if (!stored.startsWith(ENC_PREFIX)) return stored // legacy / fallback plaintext
+  try {
+    return safeStorage.decryptString(Buffer.from(stored.slice(ENC_PREFIX.length), 'base64'))
+  } catch {
+    // A different Windows user/machine (portable jar copied elsewhere) or a
+    // corrupt blob — unusable; treat as no cookies rather than feed ciphertext.
+    return null
+  }
+}
+
+/**
+ * One-time migration of a pre-encryption plaintext `cookies.txt` into the
+ * encrypted store, deleting the plaintext so a logged-in session no longer sits
+ * in the open after an update (H7). Best-effort; safe to call on every launch.
+ */
+export function migrateLegacyCookies(): void {
+  const legacy = legacyCookiePath()
+  try {
+    if (!existsSync(legacy)) return
+    if (!existsSync(cookieStorePath())) storeCookies(readFileSync(legacy, 'utf8'))
+    unlinkSync(legacy)
+  } catch {
+    /* best-effort */
+  }
+}
+
+/** Whether a stored cookie jar exists (regardless of decryptability here). */
+export function hasStoredCookies(): boolean {
+  return existsSync(cookieStorePath())
+}
+
+/**
+ * Decrypt the jar to a plaintext file at `dest` for yt-dlp's `--cookies`. Returns
+ * false when there's nothing usable to write. The caller deletes `dest` once the
+ * download settles, keeping the plaintext window as short as possible.
+ */
+export function materializeCookies(dest: string): boolean {
+  const text = loadCookies()
+  if (text == null) return false
+  try {
+    writeFileSync(dest, text)
+    return true
+  } catch {
+    return false
+  }
+}
+
 export function getCookiesStatus(): CookiesStatus {
-  const p = getCookiesFilePath()
+  const p = cookieStorePath()
   if (!existsSync(p)) return { exists: false }
   return { exists: true, savedAt: statSync(p).mtimeMs }
 }
 
 export async function clearCookies(): Promise<void> {
-  const p = getCookiesFilePath()
+  const p = cookieStorePath()
   if (existsSync(p)) unlinkSync(p)
-  await session.fromPartition(PARTITION).clearStorageData()
+  await session.fromPartition(LOGIN_PARTITION).clearStorageData()
 }
 
 /**
@@ -89,9 +170,15 @@ function toNetscapeCookieFile(cookies: Cookie[]): string {
     const includeSubdomains = domain.startsWith('.') ? 'TRUE' : 'FALSE'
     const expiry = c.session || !c.expirationDate ? 0 : Math.round(c.expirationDate)
     lines.push(
-      [domain, includeSubdomains, c.path || '/', c.secure ? 'TRUE' : 'FALSE', expiry, c.name, c.value].join(
+      [
-        '\t'
+        domain,
-      )
+        includeSubdomains,
+        c.path || '/',
+        c.secure ? 'TRUE' : 'FALSE',
+        expiry,
+        c.name,
+        c.value
+      ].join('\t')
     )
   }
   return lines.join('\n') + '\n'
@@ -102,10 +189,13 @@ let pendingResolvers: Array<(r: CookiesLoginResult) => void> = []
 
 function exportAndResolve(): void {
   session
-    .fromPartition(PARTITION)
+    .fromPartition(LOGIN_PARTITION)
     .cookies.get({})
     .then((cookies) => {
-      writeFileSync(getCookiesFilePath(), toNetscapeCookieFile(cookies))
+      // Don't persist an empty jar: closing the window without signing in would
+      // otherwise leave a useless "saved" cookie file behind (L50). The renderer
+      // turns cookieCount === 0 into a "did you sign in?" hint.
+      if (cookies.length > 0) storeCookies(toNetscapeCookieFile(cookies))
       const result: CookiesLoginResult = { ok: true, cookieCount: cookies.length }
       pendingResolvers.forEach((resolve) => resolve(result))
     })
@@ -124,7 +214,10 @@ function exportAndResolve(): void {
  * window — cookies are exported to a Netscape-format file at that point,
  * ready for yt-dlp's `--cookies`. Mirrors Seal's "log in via WebView" feature.
  */
-export function openCookieLoginWindow(url: string): Promise<CookiesLoginResult> {
+export function openCookieLoginWindow(
+  url: string,
+  parent?: BrowserWindow
+): Promise<CookiesLoginResult> {
   return new Promise((resolve) => {
     let validUrl: string
     try {
@@ -136,7 +229,7 @@ export function openCookieLoginWindow(url: string): Promise<CookiesLoginResult>
 
     if (loginWindow && !loginWindow.isDestroyed()) {
       pendingResolvers.push(resolve)
-      loginWindow.loadURL(validUrl).catch(() => {})
+      loginWindow.loadURL(validUrl).catch((e) => logger.error('cookie login loadURL failed', e))
       loginWindow.focus()
       return
     }
@@ -149,8 +242,11 @@ export function openCookieLoginWindow(url: string): Promise<CookiesLoginResult>
         height: 720,
         title: 'Sign in — AeroFetch',
         autoHideMenuBar: true,
+        // Group under the app window instead of taking its own taskbar button
+        // (W6); a child window stays above its parent without a modal block.
+        parent: parent && !parent.isDestroyed() ? parent : undefined,
         webPreferences: {
-          partition: PARTITION,
+          partition: LOGIN_PARTITION,
           sandbox: true,
           contextIsolation: true,
           nodeIntegration: false
@@ -170,13 +266,26 @@ export function openCookieLoginWindow(url: string): Promise<CookiesLoginResult>
     hardenLoginWebContents(win.webContents)
     win.webContents.session.setPermissionRequestHandler((_wc, _permission, cb) => cb(false))
 
+    // 'close' fires on a normal user close; a programmatic destroy() fires only
+    // 'closed'. Latch whichever runs first so the partition is exported exactly
+    // once and the promise can never hang (B7) — without this, a destroy()
+    // without a preceding 'close' would leave pendingResolvers pending forever.
+    let exportStarted = false
+    const exportOnce = (): void => {
+      if (exportStarted) return
+      exportStarted = true
+      exportAndResolve()
+    }
     win.on('closed', () => {
       loginWindow = null
+      // Fallback for destroy()/closed-without-close: the partition outlives the
+      // window, so a late export still captures whatever cookies were collected.
+      exportOnce()
     })
     // Closing the window IS "I'm done" — export whatever the partition
     // collected. The partition itself outlives the window, so this is safe
     // even though cookies.get() resolves after 'close' has already fired.
-    win.on('close', exportAndResolve)
+    win.on('close', exportOnce)
 
     win.loadURL(validUrl).catch(() => {
       /* navigation errors surface as Chromium's own error page */

src/main/deeplink.ts

@@ -2,6 +2,7 @@ import { app, shell, type BrowserWindow } from 'electron'
 import { existsSync, openSync, readSync, closeSync } from 'fs'
 import { join } from 'path'
 import { assertHttpUrl } from './url'
+import { parseUrlShortcutContent } from '@shared/ipc'
 
 /** Only ever forward http(s) targets into the app — same restriction the
  *  external-link window-open handler in index.ts applies to in-page links.
@@ -29,8 +30,8 @@ function readUrlShortcut(path: string): string | null {
     fd = openSync(path, 'r')
     const buf = Buffer.alloc(MAX_URL_FILE_BYTES)
     const bytes = readSync(fd, buf, 0, buf.length, 0)
-    const match = /^URL=(.+)$/im.exec(buf.toString('utf8', 0, bytes))
+    const url = parseUrlShortcutContent(buf.toString('utf8', 0, bytes))
-    return match ? asHttpUrl(match[1].trim()) : null
+    return url ? asHttpUrl(url) : null
   } catch {
     return null
   } finally {

src/main/download.ts

@@ -1,5 +1,6 @@
 import { spawn, execFile, type ChildProcess } from 'child_process'
-import { existsSync } from 'fs'
+import { existsSync, unlinkSync } from 'fs'
+import { tmpdir } from 'os'
 import { join } from 'path'
 import { BrowserWindow, Notification, type WebContents } from 'electron'
 import {
@@ -8,11 +9,16 @@ import {
   getAria2cPath,
   getFfmpegPath,
   getFfprobePath,
-  getSystem32Path
+  getSystem32Path,
+  getAppIconImage,
+  YTDLP_MISSING_MSG
 } from './binaries'
-import { getSettings, getDownloadArchivePath, getDefaultMediaDir } from './settings'
+import { getSettings } from './settings'
+import { execFileAsync } from './lib/exec'
+import { createLineBuffer } from './lib/lineBuffer'
+import { getDownloadArchivePath, getDefaultMediaDir } from './paths'
 import { ensureManagedYtdlp } from './ytdlp'
-import { getCookiesFilePath } from './cookies'
+import { materializeCookies, hasStoredCookies } from './cookies'
 import { listTemplates } from './templates'
 import { assertHttpUrl } from './url'
 import { isSafeOutputDir } from './validation'
@@ -20,10 +26,18 @@ import {
   buildArgs,
   selectExtraArgs,
   formatCommandLine,
-  collectionOutputTemplate
+  collectionOutputTemplate,
+  PROGRESS_MARKER,
+  FILEPATH_MARKER
 } from './buildArgs'
 import { cleanError } from './log'
 import { addErrorLog } from './errorlog'
+import {
+  STALL_TIMEOUT_MS,
+  META_PROBE_TIMEOUT_MS,
+  META_MAX_BUFFER,
+  STDERR_TAIL_BYTES
+} from './constants'
 import {
   IpcChannels,
   type StartDownloadOptions,
@@ -31,7 +45,6 @@ import {
   type CommandPreviewResult,
   type DownloadEvent,
   type DownloadMeta,
-  type DownloadProgress,
   type Settings
 } from '@shared/ipc'
 
@@ -43,6 +56,21 @@ interface ActiveDownload {
 
 const active = new Map<string, ActiveDownload>()
 
+// Per-spawn sequence, so a retry/resume that reuses the item id still gets a
+// unique transient cookie file (below) — otherwise a superseded download's
+// teardown could unlink the new spawn's jar mid-read.
+let spawnSeq = 0
+
+// Remove an item from the active map, but only if THIS rec still owns the slot.
+// cancel/pause release the slot synchronously (so the renderer's just-promoted
+// next item isn't rejected by the maxConcurrent guard while the killed tree is
+// still tearing down); the doomed child's later 'close'/'error' then runs this as
+// a no-op. The identity check matters because a retry/resume reuses the item id,
+// so a stale teardown must not evict the newer same-id spawn. (L140/L148)
+function releaseActive(id: string, rec: ActiveDownload): void {
+  if (active.get(id) === rec) active.delete(id)
+}
+
 /**
  * Whether any yt-dlp download is currently running. Used by the window's close
  * handler to keep the app alive in the tray (instead of quitting and killing the
@@ -53,63 +81,22 @@ export function hasActiveDownloads(): boolean {
 }
 
 // --- Formatting helpers (raw yt-dlp numbers → human strings) ----------------
-
+// parseProgress lives in lib/formatters.ts (no electron import chain) so it can
-function num(s?: string): number | undefined {
+// be unit-tested in isolation (L37). Byte/ETA formatters live in @shared/format.
-  if (!s || s === 'NA') return undefined
+export { parseProgress } from './lib/formatters'
-  const n = Number(s)
+import { parseProgress } from './lib/formatters'
-  return Number.isFinite(n) ? n : undefined
-}
-
-export function fmtBytes(bytes: number): string {
-  if (bytes < 1024) return `${bytes} B`
-  const units = ['KB', 'MB', 'GB', 'TB']
-  let v = bytes / 1024
-  let i = 0
-  while (v >= 1024 && i < units.length - 1) {
-    v /= 1024
-    i++
-  }
-  return `${v.toFixed(v >= 100 ? 0 : 1)} ${units[i]}`
-}
-
-function fmtSpeed(bytesPerSec?: number): string | undefined {
-  if (bytesPerSec == null) return undefined
-  return `${fmtBytes(bytesPerSec)}/s`
-}
-
-function fmtEta(seconds?: number): string | undefined {
-  if (seconds == null) return undefined
-  const s = Math.max(0, Math.round(seconds))
-  const m = Math.floor(s / 60)
-  const r = s % 60
-  return `${m}:${String(r).padStart(2, '0')}`
-}
-
-function parseProgress(rest: string): DownloadProgress | null {
-  const parts = rest.split('|')
-  if (parts.length < 6) return null
-  const [status, dl, total, totalEst, speed, eta] = parts
-  const downloaded = num(dl)
-  const totalBytes = num(total) ?? num(totalEst)
-  let progress = 0
-  if (totalBytes && downloaded != null) progress = Math.min(1, downloaded / totalBytes)
-  return {
-    status: status || 'downloading',
-    progress,
-    speed: fmtSpeed(num(speed)),
-    eta: fmtEta(num(eta)),
-    sizeLabel: totalBytes ? fmtBytes(totalBytes) : undefined
-  }
-}
 
 function send(wc: WebContents, ev: DownloadEvent): void {
   if (!wc.isDestroyed()) wc.send(IpcChannels.downloadEvent, ev)
 }
 
 /** Native OS notification on completion/failure, gated by Settings.notifyOnComplete. */
-function notify(wc: WebContents, title: string, body: string): void {
+function notify(wc: WebContents, title: string, body: string, incognito = false): void {
   if (!getSettings().notifyOnComplete || !Notification.isSupported()) return
-  const n = new Notification({ title, body })
+  // L136: an incognito ("private") download must not leak its title/URL into an OS
+  // toast (it persists in the Windows Action Center). Callers pass a generic outcome
+  // title for the private case; here we additionally drop the detail body.
+  const n = new Notification({ title, body: incognito ? '' : body, icon: getAppIconImage() })
   n.on('click', () => {
     if (wc.isDestroyed()) return
     const win = BrowserWindow.fromWebContents(wc)
@@ -120,9 +107,17 @@ function notify(wc: WebContents, title: string, body: string): void {
     }
   })
   n.show()
+  // W10: flash the taskbar button for attention when the event happened in the
+  // background (window unfocused/minimized/hidden). Windows stops the flash on its
+  // own once the window gets focus, so there's no explicit stop to manage.
+  const flashWin = BrowserWindow.fromWebContents(wc)
+  if (flashWin && !flashWin.isDestroyed() && !flashWin.isFocused()) flashWin.flashFrame(true)
 }
 
 function logFailure(opts: StartDownloadOptions, title: string | undefined, error: string): void {
+  // L136: incognito downloads are never recorded — not even a failure entry, which
+  // would persist the title + URL in the user-facing diagnostics log.
+  if (opts.incognito) return
   addErrorLog({
     id: opts.id,
     title,
@@ -135,37 +130,34 @@ function logFailure(opts: StartDownloadOptions, title: string | undefined, error
 
 // --- Best-effort metadata probe (runs alongside the download) ---------------
 
-function probeMeta(ytdlp: string, url: string): Promise<DownloadMeta | null> {
+// Unit Separator (0x1F): a control char that can't appear in a title/uploader,
-  return new Promise((resolve) => {
+// so it safely delimits the three fields in ONE --print template. Splitting on
-    execFile(
+// newlines instead (B4) would mis-assign channel/duration whenever a title
+// itself contains a newline, since each --print field is emitted on its own line.
+const META_SEP = '\u001f'
+
+async function probeMeta(ytdlp: string, url: string): Promise<DownloadMeta | null> {
+  const r = await execFileAsync(
     ytdlp,
     [
       '--no-playlist',
       '--no-warnings',
       '--skip-download',
       '--print',
-        'title',
+      `%(title)s${META_SEP}%(uploader)s${META_SEP}%(duration_string)s`,
-        '--print',
-        'uploader',
-        '--print',
-        'duration_string',
       '--',
       url
     ],
-      { windowsHide: true, maxBuffer: 4 * 1024 * 1024, timeout: 30_000 },
+    { maxBuffer: META_MAX_BUFFER, timeout: META_PROBE_TIMEOUT_MS }
-      (err, stdout) => {
+  )
-        if (err) return resolve(null)
+  if (!r.ok) return null
-        const [title, uploader, duration] = stdout.split('\n').map((l) => l.trim())
+  const [title, uploader, duration] = r.stdout.split(META_SEP).map((l) => l.trim())
-        const clean = (v?: string): string | undefined =>
+  const clean = (v?: string): string | undefined => (v && v !== 'NA' ? v : undefined)
-          v && v !== 'NA' ? v : undefined
+  return {
-        resolve({
     title: clean(title),
     channel: clean(uploader),
     durationLabel: clean(duration)
-        })
   }
-    )
-  })
 }
 
 // --- Argv construction (shared by startDownload and the command preview) ---
@@ -175,6 +167,9 @@ function probeMeta(ytdlp: string, url: string): Promise<DownloadMeta | null> {
 // (see selectExtraArgs / audit F2). The gate is enforced here in main, not just
 // in the renderer UI, so the renderer can't be trusted to apply it.
 function resolveExtraArgs(opts: StartDownloadOptions, settings: Settings): string[] {
+  // Gate the file read: listTemplates() parses templates.json on every call, so
+  // skip it entirely when the feature is off (PERF2).
+  if (!settings.customCommandEnabled) return []
   return selectExtraArgs({
     customCommandEnabled: settings.customCommandEnabled,
     perDownloadExtraArgs: opts.extraArgs,
@@ -184,8 +179,10 @@ function resolveExtraArgs(opts: StartDownloadOptions, settings: Settings): strin
   })
 }
 
-/** Resolve settings + per-download overrides into the full yt-dlp argv. */
+/** Resolve settings + per-download overrides into the full yt-dlp argv.
-export function buildCommand(opts: StartDownloadOptions): string[] {
+ *  `cookiesFile` is the transient decrypted jar the caller materialises for the
+ *  'login' cookie source (H7); the 'browser' source uses --cookies-from-browser. */
+export function buildCommand(opts: StartDownloadOptions, cookiesFile?: string): string[] {
   const settings = getSettings()
   // Output dir resolution: a per-download override wins, then the user's explicit
   // per-kind folder (Settings → Video/Audio folder), and finally — when that's
@@ -210,17 +207,13 @@ export function buildCommand(opts: StartDownloadOptions): string[] {
   // Silently fall back to yt-dlp's own downloader if aria2c.exe wasn't dropped
   // into resources/bin — the toggle shouldn't turn into a hard error.
   const aria2cPath = settings.useAria2c && existsSync(getAria2cPath()) ? getAria2cPath() : undefined
-  // Same idea: 'login' cookies only apply once the sign-in window has actually
-  // exported a file; otherwise the download proceeds cookie-less rather than failing.
-  const cookiesFile =
-    settings.cookieSource === 'login' && existsSync(getCookiesFilePath())
-      ? getCookiesFilePath()
-      : undefined
   const access = {
     proxy: settings.proxy,
     rateLimit: settings.rateLimit,
     aria2cPath,
-    cookiesFromBrowser: settings.cookieSource === 'browser' ? settings.cookiesBrowser : undefined,
+    // L136/M6: incognito attaches no cookies from the browser either.
+    cookiesFromBrowser:
+      !opts.incognito && settings.cookieSource === 'browser' ? settings.cookiesBrowser : undefined,
     cookiesFile,
     restrictFilenames: settings.restrictFilenames,
     downloadArchivePath: settings.downloadArchive ? getDownloadArchivePath() : undefined,
@@ -228,7 +221,7 @@ export function buildCommand(opts: StartDownloadOptions): string[] {
     youtubePoToken: settings.youtubePoToken
   }
   const extraArgs = resolveExtraArgs(opts, settings)
-  return buildArgs(opts, outputTemplate, options, getBinDir(), access, extraArgs)
+  return buildArgs({ opts, outputTemplate, options, binDir: getBinDir(), access, extraArgs })
 }
 
 /** Build the exact command line for the current form state, without running it. */
@@ -250,10 +243,7 @@ export function previewCommand(opts: StartDownloadOptions): CommandPreviewResult
 
 // --- Public API -------------------------------------------------------------
 
-export function startDownload(
+export function startDownload(wc: WebContents, opts: StartDownloadOptions): StartDownloadResult {
-  wc: WebContents,
-  opts: StartDownloadOptions
-): StartDownloadResult {
   // Self-heal the managed copy from the bundled seed before spawning, so a
   // never-seeded or deleted yt-dlp.exe doesn't fail an otherwise-fine download.
   ensureManagedYtdlp()
@@ -261,7 +251,7 @@ export function startDownload(
   if (!existsSync(ytdlp)) {
     return {
       ok: false,
-      error: `yt-dlp.exe is missing and couldn't be restored from the bundle.\nReinstall AeroFetch, or drop yt-dlp.exe into resources/bin/ (see the README there).`
+      error: YTDLP_MISSING_MSG
     }
   }
   // ffmpeg is used by nearly every download (merge, audio extract, thumbnail/
@@ -275,9 +265,7 @@ export function startDownload(
   if (missingBins.length > 0) {
     return {
       ok: false,
-      error:
+      error: `${missingBins.join(' and ')} not found in ${getBinDir()}. Add the ffmpeg build's binaries to resources/bin/ (see the README there).`
-        `${missingBins.join(' and ')} not found in ${getBinDir()}\n` +
-        `Add the ffmpeg build's binaries to resources/bin/ (see the README there).`
     }
   }
   // Reject anything that isn't an http(s) URL before it reaches yt-dlp's argv,
@@ -301,10 +289,34 @@ export function startDownload(
     return { ok: false, error: 'Max concurrent downloads reached. Wait for a slot to free up.' }
   }
 
+  // Decrypt the stored cookie jar to a short-lived per-download temp file (H7).
+  // yt-dlp reads --cookies once at startup; we delete it the moment the download
+  // settles, so the plaintext never lingers at rest.
+  let cookiesFile: string | undefined
+  // L136/M6: an incognito download attaches no saved login cookies (the UI promises
+  // "no cookies"), so it can't be tied to the user's signed-in identity.
+  if (!opts.incognito && getSettings().cookieSource === 'login' && hasStoredCookies()) {
+    // Unique per spawn (not just per id): a retry/resume reuses opts.id, and the
+    // superseded download's cleanupCookies() must not unlink the new spawn's jar.
+    const tmp = join(tmpdir(), `aerofetch-cookies-${opts.id}-${++spawnSeq}.txt`)
+    if (materializeCookies(tmp)) cookiesFile = tmp
+  }
+  function cleanupCookies(): void {
+    if (cookiesFile) {
+      try {
+        unlinkSync(cookiesFile)
+      } catch {
+        /* best-effort */
+      }
+      cookiesFile = undefined
+    }
+  }
+
   let child: ChildProcess
   try {
-    child = spawn(ytdlp, buildCommand(opts), { windowsHide: true })
+    child = spawn(ytdlp, buildCommand(opts, cookiesFile), { windowsHide: true })
   } catch (e) {
+    cleanupCookies()
     return { ok: false, error: (e as Error).message }
   }
 
@@ -324,66 +336,162 @@ export function startDownload(
     // it in parallel so the card fills in quickly.
     probeMeta(ytdlp, opts.url).then((meta) => {
       if (meta?.title) resolvedTitle = meta.title
-      if (meta && active.has(opts.id)) send(wc, { type: 'meta', id: opts.id, meta })
+      if (active.has(opts.id)) {
+        // Always emit a meta event: on success it fills in title/channel/duration;
+        // on failure (null from timeout/error) the renderer clears the
+        // "Resolving…" placeholder via applyEvent('meta') (SR6 / L47).
+        send(wc, { type: 'meta', id: opts.id, meta: meta ?? {} })
+      }
     })
   }
 
-  let stdoutBuf = ''
+  // Wire the child's streams + teardown (CL3). resolvedTitle is passed as a getter
+  // because the parallel probeMeta above may fill it in after this returns.
+  wireChildProcess({ wc, opts, rec, cleanup: cleanupCookies, getTitle: () => resolvedTitle })
+
+  return { ok: true }
+}
+
+// --- Child-process wiring ---------------------------------------------------
+
+/**
+ * Wire a spawned yt-dlp child's stdout/stderr/close/error to download events, and
+ * run the B1 idle watchdog. Extracted from startDownload so that function reads as
+ * a linear spawn + pre-flight and this owns the streaming/teardown lifecycle (CL3).
+ *
+ * `getTitle` is read lazily on each event: the completion/error paths need the
+ * best title known *at settle time*, which the parallel metadata probe may only
+ * fill in after wiring is set up.
+ */
+function wireChildProcess(params: {
+  wc: WebContents
+  opts: StartDownloadOptions
+  rec: ActiveDownload
+  cleanup: () => void
+  getTitle: () => string | undefined
+}): void {
+  const { wc, opts, rec, cleanup, getTitle } = params
+  const child = rec.child
+
   let stderrTail = ''
   let filePath: string | undefined
+  // Latched once the first download stream reports 'finished'; flags later
+  // progress as the merge/post-processing "finishing" phase (SR7).
+  let finishing = false
   // 'error' and 'close' can both fire for one process; only act on the first.
   let settled = false
 
+  // Idle watchdog (B1): reset on any output; if it ever fires, the child has been
+  // silent for STALL_TIMEOUT_MS, so kill + error it and free the slot.
+  let stallTimer: ReturnType<typeof setTimeout> | null = null
+  function clearWatchdog(): void {
+    if (stallTimer) {
+      clearTimeout(stallTimer)
+      stallTimer = null
+    }
+  }
+  function bumpWatchdog(): void {
+    clearWatchdog()
+    stallTimer = setTimeout(() => {
+      // A cancel/pause races the timer: it already released the slot and the
+      // child's close stays silent, so don't fire a spurious stall error (mirrors
+      // the canceled/paused guards on the close handler below).
+      if (settled || rec.canceled || rec.paused) return
+      settled = true
+      clearWatchdog()
+      cleanup()
+      releaseActive(opts.id, rec)
+      killTree(rec)
+      const msg = `Download stalled — no activity for ${Math.round(STALL_TIMEOUT_MS / 60_000)} min. Stopped; retry to resume.`
+      send(wc, { type: 'error', id: opts.id, error: msg })
+      logFailure(opts, getTitle(), msg)
+      notify(
+        wc,
+        opts.incognito ? 'Download stopped' : (getTitle() ?? 'Download failed'),
+        msg,
+        opts.incognito
+      )
+    }, STALL_TIMEOUT_MS)
+  }
+  bumpWatchdog()
+
+  // Split stdout into lines (shared helper, CC3/CC4) and parse our --print markers.
+  // No flush on close: yt-dlp's progress/path template lines are always
+  // newline-terminated, so a trailing partial is never a real marker.
+  const stdoutLines = createLineBuffer((line) => {
+    if (line.startsWith(PROGRESS_MARKER)) {
+      const p = parseProgress(line.slice(PROGRESS_MARKER.length))
+      if (p) {
+        // SR7: yt-dlp reports a 'finished' status when each download stream
+        // completes. A video+audio download has two streams, so the bar would
+        // otherwise fill 0→100% twice. Latch on the first 'finished' and flag
+        // every later tick as "finishing" so the renderer shows an indeterminate
+        // merge state instead of a visible restart.
+        if (p.status === 'finished') finishing = true
+        send(wc, { type: 'progress', id: opts.id, progress: { ...p, finishing } })
+      }
+    } else if (line.startsWith(FILEPATH_MARKER)) {
+      filePath = line.slice(FILEPATH_MARKER.length).trim()
+    }
+  })
   child.stdout?.on('data', (chunk: Buffer) => {
-    stdoutBuf += chunk.toString()
+    bumpWatchdog()
-    let nl: number
+    stdoutLines.push(chunk.toString())
-    while ((nl = stdoutBuf.indexOf('\n')) >= 0) {
-      const line = stdoutBuf.slice(0, nl).replace(/\r$/, '')
-      stdoutBuf = stdoutBuf.slice(nl + 1)
-      if (line.startsWith('prog|')) {
-        const p = parseProgress(line.slice('prog|'.length))
-        if (p) send(wc, { type: 'progress', id: opts.id, progress: p })
-      } else if (line.startsWith('path|')) {
-        filePath = line.slice('path|'.length).trim()
-      }
-    }
   })
 
   child.stderr?.on('data', (chunk: Buffer) => {
-    stderrTail = (stderrTail + chunk.toString()).slice(-4000)
+    bumpWatchdog()
+    stderrTail = (stderrTail + chunk.toString()).slice(-STDERR_TAIL_BYTES)
   })
 
   child.on('error', (err) => {
     if (settled) return
     settled = true
-    active.delete(opts.id)
+    clearWatchdog()
+    cleanup()
+    releaseActive(opts.id, rec)
     // A paused download was killed on purpose — stay silent, like a cancel.
     if (!rec.canceled && !rec.paused) {
       send(wc, { type: 'error', id: opts.id, error: err.message })
-      logFailure(opts, resolvedTitle, err.message)
+      logFailure(opts, getTitle(), err.message)
-      notify(wc, resolvedTitle ?? 'Download failed', err.message)
+      notify(
+        wc,
+        opts.incognito ? 'Download failed' : (getTitle() ?? 'Download failed'),
+        err.message,
+        opts.incognito
+      )
     }
   })
 
   child.on('close', (code) => {
     if (settled) return
     settled = true
-    active.delete(opts.id)
+    clearWatchdog()
+    cleanup()
+    releaseActive(opts.id, rec)
     // Canceled: renderer already showed 'canceled'. Paused: renderer showed
     // 'paused' and keeps the .part for a later resume. Either way, no event.
     if (rec.canceled || rec.paused) return
     if (code === 0) {
       send(wc, { type: 'done', id: opts.id, filePath })
-      notify(wc, resolvedTitle ?? 'Download complete', 'Finished downloading.')
+      notify(
+        wc,
+        opts.incognito ? 'Download complete' : (getTitle() ?? 'Download complete'),
+        'Finished downloading.',
+        opts.incognito
+      )
     } else {
       const msg = cleanError(stderrTail) || `yt-dlp exited with code ${code}`
       send(wc, { type: 'error', id: opts.id, error: msg })
-      logFailure(opts, resolvedTitle, msg)
+      logFailure(opts, getTitle(), msg)
-      notify(wc, resolvedTitle ?? 'Download failed', msg)
+      notify(
+        wc,
+        opts.incognito ? 'Download failed' : (getTitle() ?? 'Download failed'),
+        msg,
+        opts.incognito
+      )
     }
   })
-
-  return { ok: true }
 }
 
 // Kill the whole process tree (/T) so the spawned ffmpeg child dies too. Resolve
@@ -407,6 +515,11 @@ export function cancelDownload(id: string): void {
   const rec = active.get(id)
   if (!rec) return
   rec.canceled = true
+  // Free the slot now (not on the async 'close') so the renderer's just-promoted
+  // next item isn't rejected by the maxConcurrent guard — or run briefly over the
+  // cap — while taskkill tears down this tree. The child's later 'close' stays
+  // silent (rec.canceled) and releaseActive() no-ops. (L148)
+  active.delete(id)
   killTree(rec)
 }
 
@@ -421,5 +534,9 @@ export function pauseDownload(id: string): void {
   const rec = active.get(id)
   if (!rec) return
   rec.paused = true
+  // Free the slot now (see cancelDownload / L148). The partial .part stays on disk
+  // for a later resume, which reuses this id — releaseActive()'s identity check
+  // keeps the doomed child's 'close' from evicting that fresh spawn. (L140)
+  active.delete(id)
   killTree(rec)
 }

src/main/errorlog.ts

@@ -1,45 +1,23 @@
-import { app } from 'electron'
-import { join } from 'path'
-import { readFileSync, writeFileSync, existsSync } from 'fs'
 import type { ErrorLogEntry } from '@shared/ipc'
 import { isValidErrorLogEntry } from './validation'
+import { createJsonStore } from './jsonStore'
+import { ERRORLOG_MAX_ENTRIES } from './constants'
 
 // Plain JSON in userData, same shape as history.ts. Persisted so a failure
-// report survives the queue item being cleared (Seal's "debug report").
+// report survives the queue item being cleared (Seal's "debug report"). Atomic
-const MAX_ENTRIES = 200
+// writes / corruption backup / caching come from the shared jsonStore (R1–R3).
+// Per-entry validation (isValidErrorLogEntry) so a hand-edited or corrupted
+// errorlog.json can't feed the UI entries with the wrong shape. (audit S5)
+const store = createJsonStore('errorlog.json', isValidErrorLogEntry, ERRORLOG_MAX_ENTRIES)
 
-function errorLogFile(): string {
-  return join(app.getPath('userData'), 'errorlog.json')
-}
-
-// Per-entry validation (isValidErrorLogEntry, in validation.ts) so a hand-edited
-// or corrupted errorlog.json can't feed the UI entries with the wrong shape —
-// invalid rows are dropped. (audit S5)
 export function listErrorLog(): ErrorLogEntry[] {
-  try {
+  return store.read()
-    if (!existsSync(errorLogFile())) return []
-    const data = JSON.parse(readFileSync(errorLogFile(), 'utf8'))
-    return Array.isArray(data) ? data.filter(isValidErrorLogEntry) : []
-  } catch {
-    return []
-  }
-}
-
-function save(entries: ErrorLogEntry[]): void {
-  try {
-    writeFileSync(errorLogFile(), JSON.stringify(entries.slice(0, MAX_ENTRIES), null, 2))
-  } catch {
-    /* best-effort; a read-only data dir just means no persisted error log */
-  }
 }
 
 export function addErrorLog(entry: ErrorLogEntry): ErrorLogEntry[] {
-  const entries = [entry, ...listErrorLog()]
+  return store.write([entry, ...listErrorLog()])
-  save(entries)
-  return entries
 }
 
 export function clearErrorLog(): ErrorLogEntry[] {
-  save([])
+  return store.write([])
-  return []
 }

src/main/ffmpeg.ts

@@ -1,6 +1,7 @@
-import { execFile } from 'child_process'
 import { existsSync } from 'fs'
 import { getFfmpegPath, getFfprobePath } from './binaries'
+import { execFileAsync } from './lib/exec'
+import { VERSION_TIMEOUT_MS } from './constants'
 import type { FfmpegVersionResult } from '@shared/ipc'
 
 /**
@@ -11,19 +12,13 @@ import type { FfmpegVersionResult } from '@shared/ipc'
  * out, or the line doesn't parse — Settings then shows "not found" instead of
  * failing. Unlike yt-dlp these are never self-updated, so there's no update path.
  */
-function readToolVersion(path: string): Promise<string | null> {
+async function readToolVersion(path: string): Promise<string | null> {
-  if (!existsSync(path)) return Promise.resolve(null)
+  if (!existsSync(path)) return null
-  return new Promise((resolve) => {
+  const r = await execFileAsync(path, ['-version'], { timeout: VERSION_TIMEOUT_MS })
-    execFile(path, ['-version'], { windowsHide: true, timeout: 15_000 }, (err, stdout) => {
+  if (!r.ok) return null
-      if (err) {
+  const firstLine = r.stdout.split('\n', 1)[0] ?? ''
-        resolve(null)
-        return
-      }
-      const firstLine = stdout.split('\n', 1)[0] ?? ''
   const m = firstLine.match(/version\s+(\S+)/i)
-      resolve(m ? m[1] : null)
+  return m?.[1] ?? null
-    })
-  })
 }
 
 /** Versions of the bundled ffmpeg + ffprobe, read in parallel for the Settings panel. */

src/main/history.ts

@@ -1,59 +1,39 @@
-import { app } from 'electron'
+import { HISTORY_MAX_ENTRIES, type HistoryEntry } from '@shared/ipc'
-import { join } from 'path'
-import { readFileSync, writeFileSync, existsSync } from 'fs'
-import type { HistoryEntry } from '@shared/ipc'
 import { isValidHistoryEntry } from './validation'
+import { createJsonStore } from './jsonStore'
 
 // Plain JSON in userData (portable build redirects userData next to the exe).
-// Kept simple per the build plan; can migrate to better-sqlite3 later.
+// Kept simple per the build plan; can migrate to better-sqlite3 later. Atomic
-const MAX_ENTRIES = 500
+// writes, corruption backup, and caching come from the shared jsonStore (R1–R3).
+// The row cap (HISTORY_MAX_ENTRIES) is shared with the renderer's optimistic list.
+//
+// Per-entry validation (isValidHistoryEntry) so a hand-edited or corrupted
+// history.json can't feed the UI (or openPath) entries with the wrong shape —
+// invalid rows are dropped rather than trusted. (audit S5)
+const store = createJsonStore('history.json', isValidHistoryEntry, HISTORY_MAX_ENTRIES)
 
-function historyFile(): string {
-  return join(app.getPath('userData'), 'history.json')
-}
-
-// Per-entry validation (isValidHistoryEntry, in validation.ts) so a hand-edited
-// or corrupted history.json can't feed the UI (or openPath) entries with the
-// wrong shape — invalid rows are dropped rather than trusted. (audit S5)
 export function listHistory(): HistoryEntry[] {
-  try {
+  return store.read()
-    if (!existsSync(historyFile())) return []
-    const data = JSON.parse(readFileSync(historyFile(), 'utf8'))
-    return Array.isArray(data) ? data.filter(isValidHistoryEntry) : []
-  } catch {
-    return []
-  }
-}
-
-function save(entries: HistoryEntry[]): void {
-  try {
-    writeFileSync(historyFile(), JSON.stringify(entries.slice(0, MAX_ENTRIES), null, 2))
-  } catch {
-    /* best-effort; a read-only data dir just means no persisted history */
-  }
 }
 
 export function addHistory(entry: HistoryEntry): HistoryEntry[] {
-  // De-dupe by id (a retry of the same item replaces its prior entry).
+  // De-dupe by id AND url (M35): a History re-download re-queues via addFromUrl,
-  const entries = [entry, ...listHistory().filter((e) => e.id !== entry.id)]
+  // which mints a NEW id, so id-only de-dup would let the same video accumulate a
-  save(entries)
+  // fresh row on every re-download. Dropping any prior entry with the same url
-  return entries
+  // keeps one row per video, refreshed to the top.
+  const prior = listHistory().filter((e) => e.id !== entry.id && e.url !== entry.url)
+  return store.write([entry, ...prior])
 }
 
 export function removeHistory(id: string): HistoryEntry[] {
-  const entries = listHistory().filter((e) => e.id !== id)
+  return store.write(listHistory().filter((e) => e.id !== id))
-  save(entries)
-  return entries
 }
 
 export function removeManyHistory(ids: string[]): HistoryEntry[] {
   const remove = new Set(ids)
-  const entries = listHistory().filter((e) => !remove.has(e.id))
+  return store.write(listHistory().filter((e) => !remove.has(e.id)))
-  save(entries)
-  return entries
 }
 
 export function clearHistory(): HistoryEntry[] {
-  save([])
+  return store.write([])
-  return []
 }

src/main/index.ts

@@ -1,55 +1,28 @@
-import { app, shell, BrowserWindow, ipcMain, dialog, clipboard, nativeTheme, Notification } from 'electron'
+import { app, shell, BrowserWindow, nativeTheme, Notification, Menu } from 'electron'
 import { join, resolve } from 'path'
 import { electronApp, optimizer, is } from '@electron-toolkit/utils'
+import { IpcChannels } from '@shared/ipc'
+import { PAGE_BACKGROUND } from '@shared/theme'
 import {
-  IpcChannels,
+  registerIpcHandlers,
-  type StartDownloadOptions,
+  resolveBackgroundMode,
-  type Settings,
+  applyNativeTheme,
-  type HistoryEntry,
+  getSystemThemeInfo
-  type CommandTemplate,
+} from './ipc'
-  type YtdlpUpdateChannel,
+import { runStartupYtdlpAutoUpdate } from './ytdlp'
-  type SystemThemeInfo,
+import { getAppIconImage } from './binaries'
-  type TaskbarProgress
+import { hasActiveDownloads } from './download'
-} from '@shared/ipc'
+import { getSettings, applyLaunchAtStartup, migrateSecretsAtRest } from './settings'
-import { getYtdlpVersion, updateYtdlp, runStartupYtdlpAutoUpdate } from './ytdlp'
+import { ensureMediaDirs } from './paths'
-import { getFfmpegVersions } from './ffmpeg'
-import { checkForAppUpdate, downloadAppUpdate, runAppUpdate } from './updater'
-import { probeMedia } from './probe'
-import {
-  startDownload,
-  cancelDownload,
-  pauseDownload,
-  previewCommand,
-  hasActiveDownloads
-} from './download'
-import { runTerminal, cancelTerminal } from './terminal'
-import {
-  getSettings,
-  setSettings,
-  ensureMediaDirs,
-  applyLaunchAtStartup,
-  migrateSecretsAtRest
-} from './settings'
-import { listHistory, addHistory, removeHistory, removeManyHistory, clearHistory } from './history'
-import { listTemplates, saveTemplate, removeTemplate } from './templates'
 import { setupPortableData } from './portable'
-import { safeOpenPath, safeShowInFolder } from './reveal'
+import { migrateLegacyCookies } from './cookies'
-import { openCookieLoginWindow, getCookiesStatus, clearCookies } from './cookies'
+import { attachEditContextMenu } from './contextMenu'
-import { listErrorLog, addErrorLog, clearErrorLog } from './errorlog'
+import { flushAllStores } from './jsonStore'
-import { exportBackup, importBackup } from './backup'
 import { extractIncomingUrl, registerSendToShortcut, focusWindow } from './deeplink'
-import {
+import { isSyncLaunch } from './schedule'
-  listSources,
-  getSource,
-  removeSource,
-  listMediaItems,
-  setMediaItemDownloaded,
-  setSourceWatched
-} from './sources'
-import { indexSource } from './indexer'
-import { syncWatchedSources } from './sync'
-import { getScheduledSync, setScheduledSync, isSyncLaunch } from './schedule'
 import { createTray, markQuitting, isQuitting } from './tray'
+import { logger } from './logger'
+import { initialWindowState, saveWindowState } from './windowState'
 
 // Only one instance ever runs. A second launch — e.g. the OS invoking us again
 // for an aerofetch:// link or a "Send to AeroFetch" file — hands its argv to
@@ -79,34 +52,15 @@ setupPortableData()
 // installer also declares this scheme (electron-builder.yml's `protocols`)
 // so it's registered even before first launch; this call additionally covers
 // the portable build and dev, which have no installer step to do it for us.
-if (is.dev && process.argv.length >= 2) {
+const devScript = process.argv[1]
-  app.setAsDefaultProtocolClient('aerofetch', process.execPath, [resolve(process.argv[1])])
+if (is.dev && devScript) {
+  app.setAsDefaultProtocolClient('aerofetch', process.execPath, [resolve(devScript)])
 } else {
   app.setAsDefaultProtocolClient('aerofetch')
 }
 
 let mainWindow: BrowserWindow | null = null
 
-// Page background per theme — keep in sync with `pageBackground` in
-// src/renderer/src/theme.ts. Set as the window's NATIVE background so the
-// one-frame compositor repaint (when a tooltip/dropdown overlay first paints on
-// Windows) shows the app's current color instead of a mismatched white flash.
-const THEME_BACKGROUND = { light: '#f7f7f8', dark: '#161618' } as const
-
-// 'system' isn't a real background — resolve it against the OS's current
-// preference (nativeTheme.themeSource defaults to 'system', so this tracks it
-// without AeroFetch ever touching themeSource itself).
-function resolveBackgroundMode(theme: Settings['theme']): 'light' | 'dark' {
-  return theme === 'system' ? (nativeTheme.shouldUseDarkColors ? 'dark' : 'light') : theme
-}
-
-function getSystemThemeInfo(): SystemThemeInfo {
-  return {
-    shouldUseDarkColors: nativeTheme.shouldUseDarkColors,
-    shouldUseHighContrastColors: nativeTheme.shouldUseHighContrastColors
-  }
-}
-
 // Tell the user (once per run) that closing the window left AeroFetch running so
 // an in-progress download could finish — shown only when they haven't already
 // opted into tray mode, so a window that "won't close" doesn't read as a bug.
@@ -116,7 +70,8 @@ function notifyBackgroundOnce(): void {
   notifiedBackground = true
   new Notification({
     title: 'AeroFetch is still running',
-    body: 'Your download is finishing in the background. Use the tray icon to reopen or quit.'
+    body: 'Your download is finishing in the background. Use the tray icon to reopen or quit.',
+    icon: getAppIconImage()
   }).show()
 }
 
@@ -140,11 +95,22 @@ const DENIED_PERMISSIONS = new Set([
 ])
 
 function createWindow(): void {
+  // Reopen where the user left off (size / position / maximized), falling back to the
+  // default size when there's no usable saved state — first run, or the saved monitor
+  // is no longer connected (W2 / UX19).
+  const ws = initialWindowState()
   const win = new BrowserWindow({
-    width: 920,
+    title: 'AeroFetch',
-    height: 700,
+    width: ws.width,
+    height: ws.height,
+    x: ws.x,
+    y: ws.y,
+    // Below this the 212px sidebar + content layout breaks; pin a sensible
+    // floor so the window can't be dragged down to unusable widths (W1).
+    minWidth: 640,
+    minHeight: 480,
     show: false,
-    backgroundColor: THEME_BACKGROUND[resolveBackgroundMode(getSettings().theme)],
+    backgroundColor: PAGE_BACKGROUND[resolveBackgroundMode(getSettings().theme)],
     autoHideMenuBar: true,
     webPreferences: {
       preload: join(__dirname, '../preload/index.cjs'),
@@ -155,6 +121,22 @@ function createWindow(): void {
   })
   mainWindow = win
 
+  if (ws.maximized) win.maximize()
+
+  // Persist size/position/maximized so the next launch restores them (W2). Debounced
+  // so a drag-resize writes once when it settles; also saved on close (which may only
+  // hide to tray) to capture the final state.
+  let saveTimer: ReturnType<typeof setTimeout> | null = null
+  const scheduleSave = (): void => {
+    if (saveTimer) clearTimeout(saveTimer)
+    saveTimer = setTimeout(() => saveWindowState(win), 500)
+  }
+  win.on('resize', scheduleSave)
+  win.on('move', scheduleSave)
+
+  // Standard Cut/Copy/Paste/Select All right-click menu on editable fields (W4).
+  attachEditContextMenu(win.webContents)
+
   win.on('ready-to-show', () => {
     // A scheduled `--sync` launch starts unobtrusively (shown but not focused) so
     // the daily background sync doesn't steal focus; a normal launch shows + focuses.
@@ -167,6 +149,8 @@ function createWindow(): void {
   // kill the spawned yt-dlp processes and lose the download. A real quit (tray
   // menu / before-quit) sets isQuitting() so this lets the close through.
   win.on('close', (e) => {
+    // Capture the final bounds even when the close only hides to tray (W2).
+    saveWindowState(win)
     if (isQuitting()) return
     const downloadsRunning = hasActiveDownloads()
     if (getSettings().minimizeToTray || downloadsRunning) {
@@ -183,6 +167,13 @@ function createWindow(): void {
     if (mainWindow === win) mainWindow = null
   })
 
+  // When the user re-opens the window (via tray, second-instance, or deeplink)
+  // reset the background-notify latch so they're informed again if they close
+  // while a download is still running (L68).
+  win.on('show', () => {
+    notifiedBackground = false
+  })
+
   // The OS may have launched us with an aerofetch:// link or a "Send to" .url
   // file on the command line — hand it to DownloadBar's link-suggestion banner
   // once the page (and its IPC listener) is actually ready to receive it.
@@ -225,161 +216,12 @@ function createWindow(): void {
   }
 }
 
-function registerIpcHandlers(): void {
-  ipcMain.handle(IpcChannels.appVersion, () => app.getVersion())
-
-  ipcMain.handle(IpcChannels.appUpdateCheck, () => checkForAppUpdate())
-  ipcMain.handle(IpcChannels.appUpdateDownload, (e, url: string) =>
-    downloadAppUpdate(url, e.sender)
-  )
-  ipcMain.handle(IpcChannels.appUpdateRun, (_e, filePath: string) => runAppUpdate(filePath))
-
-  ipcMain.handle(IpcChannels.ytdlpVersion, () => getYtdlpVersion())
-
-  ipcMain.handle(IpcChannels.ffmpegVersion, () => getFfmpegVersions())
-
-  ipcMain.handle(IpcChannels.probe, (_e, url: string) => probeMedia(url))
-
-  ipcMain.handle(IpcChannels.downloadStart, (e, opts: StartDownloadOptions) => {
-    const result = startDownload(e.sender, opts)
-    // Pre-spawn failures (missing yt-dlp.exe, bad URL, duplicate id) never reach
-    // download.ts's own close/error handlers, so log them here instead.
-    if (!result.ok) {
-      addErrorLog({
-        id: opts.id,
-        url: opts.url,
-        kind: opts.kind,
-        error: result.error ?? 'Unknown error',
-        occurredAt: Date.now()
-      })
-    }
-    return result
-  })
-  ipcMain.handle(IpcChannels.downloadCancel, (_e, id: string) => cancelDownload(id))
-  ipcMain.handle(IpcChannels.downloadPause, (_e, id: string) => pauseDownload(id))
-  ipcMain.handle(IpcChannels.terminalRun, (e, id: string, args: string) =>
-    runTerminal(e.sender, id, args)
-  )
-  ipcMain.handle(IpcChannels.terminalCancel, (_e, id: string) => cancelTerminal(id))
-
-  ipcMain.handle(IpcChannels.defaultFolder, () => app.getPath('downloads'))
-
-  ipcMain.handle(IpcChannels.chooseFolder, async (e) => {
-    const win = BrowserWindow.fromWebContents(e.sender) ?? undefined
-    const res = await dialog.showOpenDialog(win!, {
-      properties: ['openDirectory', 'createDirectory']
-    })
-    return res.canceled || !res.filePaths[0] ? null : res.filePaths[0]
-  })
-
-  ipcMain.handle(IpcChannels.openPath, (_e, p: string) => safeOpenPath(p))
-  ipcMain.handle(IpcChannels.showInFolder, (_e, p: string) => safeShowInFolder(p))
-
-  ipcMain.handle(IpcChannels.clipboardRead, () => clipboard.readText())
-
-  ipcMain.handle(IpcChannels.settingsGet, () => getSettings())
-  ipcMain.handle(IpcChannels.settingsSet, (e, partial: Partial<Settings>) => {
-    const result = setSettings(partial)
-    // Keep the window's native background in sync with the theme so a compositor
-    // repaint never flashes a mismatched color behind an overlay. Use the
-    // validated result, not the raw partial (which may hold a bogus value).
-    if (partial.theme) {
-      BrowserWindow.fromWebContents(e.sender)?.setBackgroundColor(
-        THEME_BACKGROUND[resolveBackgroundMode(result.theme)]
-      )
-    }
-    return result
-  })
-
-  ipcMain.handle(IpcChannels.systemThemeGet, () => getSystemThemeInfo())
-
-  ipcMain.handle(IpcChannels.openHighContrastSettings, () =>
-    shell.openExternal('ms-settings:easeofaccess-highcontrast')
-  )
-
-  ipcMain.handle(IpcChannels.historyList, () => listHistory())
-  ipcMain.handle(IpcChannels.historyAdd, (_e, entry: HistoryEntry) => addHistory(entry))
-  ipcMain.handle(IpcChannels.historyRemove, (_e, id: string) => removeHistory(id))
-  ipcMain.handle(IpcChannels.historyRemoveMany, (_e, ids: string[]) => removeManyHistory(ids))
-  ipcMain.handle(IpcChannels.historyClear, () => clearHistory())
-
-  ipcMain.handle(IpcChannels.cookiesLogin, (_e, url: string) => openCookieLoginWindow(url))
-  ipcMain.handle(IpcChannels.cookiesStatus, () => getCookiesStatus())
-  ipcMain.handle(IpcChannels.cookiesClear, () => clearCookies())
-
-  ipcMain.handle(IpcChannels.templatesList, () => listTemplates())
-  ipcMain.handle(IpcChannels.templatesSave, (_e, template: CommandTemplate) => saveTemplate(template))
-  ipcMain.handle(IpcChannels.templatesRemove, (_e, id: string) => removeTemplate(id))
-
-  ipcMain.handle(IpcChannels.commandPreview, (_e, opts: StartDownloadOptions) =>
-    previewCommand(opts)
-  )
-
-  ipcMain.handle(IpcChannels.ytdlpUpdate, (_e, channel: YtdlpUpdateChannel) => updateYtdlp(channel))
-
-  ipcMain.handle(IpcChannels.errorLogList, () => listErrorLog())
-  ipcMain.handle(IpcChannels.errorLogClear, () => clearErrorLog())
-
-  ipcMain.handle(IpcChannels.backupExport, (e) =>
-    exportBackup(BrowserWindow.fromWebContents(e.sender) ?? undefined)
-  )
-  ipcMain.handle(IpcChannels.backupImport, async (e) => {
-    const win = BrowserWindow.fromWebContents(e.sender) ?? undefined
-    const result = await importBackup(win)
-    // A restored backup may have changed the theme; keep the native window
-    // background in sync the same way settingsSet does.
-    if (result.ok) {
-      win?.setBackgroundColor(THEME_BACKGROUND[resolveBackgroundMode(getSettings().theme)])
-    }
-    return result
-  })
-
-  // --- Media-manager sources (Pinchflat-style index; see ROADMAP-PINCHFLAT.md) ---
-  ipcMain.handle(IpcChannels.sourcesList, () => listSources())
-  ipcMain.handle(IpcChannels.sourceItems, (_e, sourceId: string) => listMediaItems(sourceId))
-  ipcMain.handle(IpcChannels.sourceRemove, (_e, id: string) => removeSource(id))
-  ipcMain.handle(IpcChannels.sourceItemDownloaded, (_e, id: string, filePath?: string) =>
-    setMediaItemDownloaded(id, filePath)
-  )
-  // Indexing pushes live progress to the requesting renderer over `indexProgress`
-  // and resolves with the final result.
-  ipcMain.handle(IpcChannels.sourceIndex, (e, url: string) =>
-    indexSource(url, (p) => {
-      if (!e.sender.isDestroyed()) e.sender.send(IpcChannels.indexProgress, p)
-    })
-  )
-  ipcMain.handle(IpcChannels.sourceReindex, (e, id: string) => {
-    const src = getSource(id)
-    if (!src) return { ok: false, error: 'Source not found.' }
-    return indexSource(src.url, (p) => {
-      if (!e.sender.isDestroyed()) e.sender.send(IpcChannels.indexProgress, p)
-    })
-  })
-  ipcMain.handle(IpcChannels.sourceSetWatched, (_e, id: string, watched: boolean) =>
-    setSourceWatched(id, watched)
-  )
-  ipcMain.handle(IpcChannels.sourcesSync, (e) =>
-    syncWatchedSources((p) => {
-      if (!e.sender.isDestroyed()) e.sender.send(IpcChannels.indexProgress, p)
-    })
-  )
-  ipcMain.handle(IpcChannels.scheduledSyncGet, () => getScheduledSync())
-  ipcMain.handle(IpcChannels.scheduledSyncSet, (_e, enabled: boolean) => setScheduledSync(enabled))
-
-  // Reflect overall queue progress on the Windows taskbar (fire-and-forget).
-  ipcMain.on(IpcChannels.taskbarProgress, (_e, p: TaskbarProgress) => {
-    if (!mainWindow || mainWindow.isDestroyed()) return
-    if (p.mode === 'none') mainWindow.setProgressBar(-1)
-    else mainWindow.setProgressBar(Math.max(0, Math.min(1, p.fraction)), { mode: p.mode })
-  })
-}
-
 // Push OS theme/contrast changes to every window, and keep the native
 // background in sync for windows currently following 'system'.
 function registerSystemThemeBridge(): void {
   nativeTheme.on('updated', () => {
     const info = getSystemThemeInfo()
-    const bg = THEME_BACKGROUND[resolveBackgroundMode(getSettings().theme)]
+    const bg = PAGE_BACKGROUND[resolveBackgroundMode(getSettings().theme)]
     for (const win of BrowserWindow.getAllWindows()) {
       win.webContents.send(IpcChannels.systemThemeUpdate, info)
       if (getSettings().theme === 'system') win.setBackgroundColor(bg)
@@ -400,6 +242,10 @@ if (isPrimaryInstance) {
   app.whenReady().then(() => {
     electronApp.setAppUserModelId('com.aerofetch.app')
 
+    // M31: suppress the default Electron menu (which exposes DevTools/Reload via
+    // Alt) in production builds. In dev the menu is kept so DevTools are accessible.
+    if (!is.dev) Menu.setApplicationMenu(null)
+
     // Create the default Documents\Video and Documents\Audio destinations so they
     // exist from first launch (downloads are routed into them by kind).
     ensureMediaDirs()
@@ -407,6 +253,9 @@ if (isPrimaryInstance) {
     // Encrypt any credential still stored as legacy plaintext (from before at-rest
     // encryption), once safeStorage is available post-ready.
     migrateSecretsAtRest()
+    // Same for a pre-encryption plaintext cookies.txt — encrypt it and delete the
+    // plaintext so a logged-in session no longer sits in the open (H7).
+    migrateLegacyCookies()
 
     // Sync the Windows "run at sign-in" entry with the persisted setting, so it
     // reflects the user's choice even if they changed it on another install.
@@ -416,9 +265,11 @@ if (isPrimaryInstance) {
       optimizer.watchWindowShortcuts(window)
     })
 
-    registerIpcHandlers()
+    registerIpcHandlers(() => mainWindow)
     registerSystemThemeBridge()
     registerSendToShortcut()
+    // Apply the persisted theme to the OS title bar before the window opens (W3).
+    applyNativeTheme(getSettings().theme)
     createWindow()
     createTray(() => mainWindow)
 
@@ -443,20 +294,20 @@ if (isPrimaryInstance) {
       if (mainWindow && !mainWindow.isDestroyed()) {
         mainWindow.webContents.send(IpcChannels.ytdlpAutoUpdateStatus, status)
       }
-    }).catch(() => {})
+    }).catch((e) => logger.error('yt-dlp auto-update failed', e))
-
-    app.on('activate', () => {
-      if (BrowserWindow.getAllWindows().length === 0) createWindow()
-    })
   })
 
   // Any real quit path (tray "Quit", OS shutdown, the updater's app.quit) must set
   // the quitting flag so the window's close handler exits instead of hiding to tray.
-  app.on('before-quit', () => markQuitting())
+  // Also flush any debounced JSON-store writes synchronously so a quit mid-debounce
-
+  // can't drop the last history/sources/template change (R3).
-  app.on('window-all-closed', () => {
+  app.on('before-quit', () => {
-    if (process.platform !== 'darwin') {
+    markQuitting()
-      app.quit()
+    flushAllStores()
-    }
   })
+
+  // Windows-only app: closing the last window quits (the tray/in-flight-download
+  // paths hide rather than close, so this only fires on a real exit). The former
+  // macOS 'activate' handler and darwin guard were dead branches here (L147).
+  app.on('window-all-closed', () => app.quit())
 }

src/main/indexer.ts

@@ -9,9 +9,10 @@
  * this module is the impure shell that spawns yt-dlp and writes to disk.
  */
 
-import { execFile } from 'child_process'
 import { existsSync } from 'fs'
-import { getYtdlpPath } from './binaries'
+import { getYtdlpPath, YTDLP_MISSING_MSG } from './binaries'
+import { execFileAsync } from './lib/exec'
+import { INDEX_MAX_BUFFER, INDEX_TIMEOUT_MS } from './constants'
 import { cleanError } from './log'
 import { assertHttpUrl } from './url'
 import {
@@ -45,29 +46,25 @@ interface FlatInfo {
  * flat upload list can be a few MB of JSON; the timeout is generous for the same
  * reason. `--` terminates option parsing so the URL can't be read as a flag.
  */
-function probeFlat(url: string): Promise<FlatInfo> {
+async function probeFlat(url: string): Promise<FlatInfo> {
-  return new Promise((resolve, reject) => {
+  const r = await execFileAsync(
-    execFile(
     getYtdlpPath(),
     ['-J', '--flat-playlist', '--no-warnings', '--', url],
-      { windowsHide: true, maxBuffer: 256 * 1024 * 1024, timeout: 180_000 },
+    { maxBuffer: INDEX_MAX_BUFFER, timeout: INDEX_TIMEOUT_MS }
-      (err, stdout, stderr) => {
+  )
-        if (err) {
+  if (!r.ok) {
-          const msg = (err as { killed?: boolean }).killed
+    throw new Error(
+      r.timedOut
         ? 'Timed out indexing source. Check the link or your connection.'
-            : cleanError(stderr) || err.message
+        : cleanError(r.stderr) || r.error?.message || ''
-          reject(new Error(msg))
+    )
-          return
   }
   try {
-          resolve(JSON.parse(stdout) as FlatInfo)
+    return JSON.parse(r.stdout) as FlatInfo
   } catch {
-          reject(new Error('Could not parse source info from yt-dlp.'))
+    throw new Error('Could not parse source info from yt-dlp.')
   }
 }
-    )
-  })
-}
 
 /** Probe a channel tab (e.g. /videos, /playlists); never throws — returns null. */
 function probeTab(url: string): Promise<FlatInfo | null> {
@@ -90,7 +87,7 @@ export async function indexSource(
     return { ok: false, error: (e as Error).message }
   }
   if (!existsSync(getYtdlpPath())) {
-    return { ok: false, error: 'yt-dlp.exe not found. Drop it into resources/bin/.' }
+    return { ok: false, error: YTDLP_MISSING_MSG }
   }
 
   const cls = classifySource(url)
@@ -152,7 +149,8 @@ export async function indexSource(
       if (entries.length === 0) {
         return {
           ok: false,
-          error: 'That link is a single video, not a channel or playlist. Use the download bar for one video.'
+          error:
+            'That link is a single video, not a channel or playlist. Use the download bar for one video.'
         }
       }
       title = data.title || 'Playlist'

src/main/indexerCore.ts

@@ -88,7 +88,10 @@ export function classifySource(raw: string): SourceClass | null {
   // A playlist is identified purely by its list= param (works on any youtube host).
   const list = u.searchParams.get('list')
   if (isYouTube && list) {
-    return { kind: 'playlist', base: `https://www.youtube.com/playlist?list=${encodeURIComponent(list)}` }
+    return {
+      kind: 'playlist',
+      base: `https://www.youtube.com/playlist?list=${encodeURIComponent(list)}`
+    }
   }
 
   if (!isYouTube) return null
@@ -163,7 +166,7 @@ export function parseRssVideoIds(xml: string): string[] {
   const ids: string[] = []
   const re = /<yt:videoId>\s*([\w-]+)\s*<\/yt:videoId>/g
   let m: RegExpExecArray | null
-  while ((m = re.exec(xml)) !== null) ids.push(m[1])
+  while ((m = re.exec(xml)) !== null) if (m[1]) ids.push(m[1])
   return ids
 }
 

src/main/ipc.ts

@@ -0,0 +1,291 @@
+/**
+ * IPC surface for the main process. Every `ipcMain.handle` (and the one
+ * fire-and-forget `taskbarProgress` receiver) lives here, extracted from index.ts
+ * so that module is just app lifecycle + window creation and this is the single
+ * place the renderer's IPC contract is wired (L2).
+ *
+ * The handful of handlers that must touch the window (folder picker parenting,
+ * theme-synced background, taskbar progress) get the current window through the
+ * `getMainWindow` accessor rather than a captured reference, so they always act on
+ * the live window. The small theme helpers they share are defined and exported
+ * here too, since index's system-theme bridge uses them as well.
+ */
+
+import { app, shell, BrowserWindow, ipcMain, dialog, clipboard, nativeTheme } from 'electron'
+import { existsSync } from 'fs'
+import {
+  IpcChannels,
+  type StartDownloadOptions,
+  type Settings,
+  type HistoryEntry,
+  type CommandTemplate,
+  type YtdlpUpdateChannel,
+  type SystemThemeInfo,
+  type TaskbarProgress,
+  type PersistedQueueItem
+} from '@shared/ipc'
+import { PAGE_BACKGROUND } from '@shared/theme'
+import { getYtdlpVersion, updateYtdlp } from './ytdlp'
+import { getFfmpegVersions } from './ffmpeg'
+import { checkForAppUpdate, downloadAppUpdate, runAppUpdate } from './updater'
+import { probeMedia } from './probe'
+import { startDownload, cancelDownload, pauseDownload, previewCommand } from './download'
+import { runTerminal, cancelTerminal } from './terminal'
+import { getSettings, setSettings } from './settings'
+import { listHistory, addHistory, removeHistory, removeManyHistory, clearHistory } from './history'
+import { listTemplates, saveTemplate, removeTemplate } from './templates'
+import { safeOpenPath, safeShowInFolder } from './reveal'
+import { openCookieLoginWindow, getCookiesStatus, clearCookies } from './cookies'
+import { listErrorLog, addErrorLog, clearErrorLog } from './errorlog'
+import { listQueue, saveQueue } from './queue'
+import { exportBackup, importBackup } from './backup'
+import {
+  listSources,
+  getSource,
+  removeSource,
+  listMediaItems,
+  setMediaItemDownloaded,
+  setSourceWatched
+} from './sources'
+import { indexSource } from './indexer'
+import { syncWatchedSources } from './sync'
+import { getScheduledSync, setScheduledSync } from './schedule'
+import { getActiveBadge, getErrorBadge } from './badge'
+import { openPoTokenWindow } from './poToken'
+import { logger } from './logger'
+
+// --- Theme helpers (shared with index's system-theme bridge) ----------------
+
+/** Resolve 'system' against the OS preference so callers always get a concrete color. */
+export function resolveBackgroundMode(theme: Settings['theme']): 'light' | 'dark' {
+  return theme === 'system' ? (nativeTheme.shouldUseDarkColors ? 'dark' : 'light') : theme
+}
+
+/**
+ * Keep the OS-drawn title bar consistent with the in-app theme (W3). Setting
+ * themeSource to 'light'/'dark' forces the caption/chrome to match; 'system'
+ * restores OS control. Called at startup and on every theme change.
+ */
+export function applyNativeTheme(theme: Settings['theme']): void {
+  nativeTheme.themeSource = theme
+}
+
+export function getSystemThemeInfo(): SystemThemeInfo {
+  return {
+    shouldUseDarkColors: nativeTheme.shouldUseDarkColors,
+    shouldUseHighContrastColors: nativeTheme.shouldUseHighContrastColors
+  }
+}
+
+// --- IPC registration -------------------------------------------------------
+
+export function registerIpcHandlers(getMainWindow: () => BrowserWindow | null): void {
+  // M30: a broken contextBridge causes the renderer to silently run in preview/mock
+  // mode. Catch it here and show a hard error so the failure is never invisible.
+  ipcMain.once(IpcChannels.preloadBridgeFailure, (_e, detail: unknown) => {
+    dialog.showErrorBox(
+      'AeroFetch could not start',
+      `The renderer bridge failed to initialize. Please reinstall the application.\n\n${String(detail)}`
+    )
+    app.quit()
+  })
+
+  // CC8: persist renderer-side failures (the M29 `logError` sites) to the main log
+  // file — the renderer console is unreachable in a packaged build. Fire-and-forget.
+  ipcMain.on(IpcChannels.logWrite, (_e, op: string, detail: string) =>
+    logger.error(`[renderer] ${op}`, detail)
+  )
+
+  ipcMain.handle(IpcChannels.appVersion, () => app.getVersion())
+
+  ipcMain.handle(IpcChannels.appUpdateCheck, () => checkForAppUpdate())
+  ipcMain.handle(IpcChannels.appUpdateDownload, (e, url: string) =>
+    downloadAppUpdate(url, e.sender)
+  )
+  ipcMain.handle(IpcChannels.appUpdateRun, (_e, filePath: string) => runAppUpdate(filePath))
+
+  ipcMain.handle(IpcChannels.ytdlpVersion, () => getYtdlpVersion())
+
+  ipcMain.handle(IpcChannels.ffmpegVersion, () => getFfmpegVersions())
+
+  ipcMain.handle(IpcChannels.probe, (_e, url: string) => probeMedia(url))
+
+  ipcMain.handle(IpcChannels.downloadStart, (e, opts: StartDownloadOptions) => {
+    const result = startDownload(e.sender, opts)
+    // Pre-spawn failures (missing yt-dlp.exe, bad URL, duplicate id) never reach
+    // download.ts's own close/error handlers, so log them here instead — unless the
+    // download is incognito, which is never recorded (L136).
+    if (!result.ok && !opts.incognito) {
+      addErrorLog({
+        id: opts.id,
+        url: opts.url,
+        kind: opts.kind,
+        error: result.error ?? 'Unknown error',
+        occurredAt: Date.now()
+      })
+    }
+    return result
+  })
+  ipcMain.handle(IpcChannels.downloadCancel, (_e, id: string) => cancelDownload(id))
+  ipcMain.handle(IpcChannels.downloadPause, (_e, id: string) => pauseDownload(id))
+  ipcMain.handle(IpcChannels.terminalRun, (e, id: string, args: string) =>
+    runTerminal(e.sender, id, args)
+  )
+  ipcMain.handle(IpcChannels.terminalCancel, (_e, id: string) => cancelTerminal(id))
+
+  ipcMain.handle(IpcChannels.chooseFolder, async (e, current?: string) => {
+    const win = BrowserWindow.fromWebContents(e.sender) ?? undefined
+    // Seed the picker at the currently-configured folder so it opens where the
+    // user already points, not a generic default (W5). 'createDirectory' is a
+    // macOS-only property and a no-op on Windows, so it's dropped (L58).
+    const defaultPath = current && existsSync(current) ? current : undefined
+    // Use the parented overload only when we actually have a window — passing a
+    // forced non-null window that's gone can throw (L53).
+    const res = win
+      ? await dialog.showOpenDialog(win, { properties: ['openDirectory'], defaultPath })
+      : await dialog.showOpenDialog({ properties: ['openDirectory'], defaultPath })
+    return res.canceled || !res.filePaths[0] ? null : res.filePaths[0]
+  })
+
+  ipcMain.handle(IpcChannels.openPath, (_e, p: string) => safeOpenPath(p))
+  ipcMain.handle(IpcChannels.openUrl, (_e, url: string) => {
+    try {
+      const { protocol } = new URL(url)
+      if (protocol === 'http:' || protocol === 'https:') void shell.openExternal(url)
+    } catch {
+      // Ignore malformed URLs.
+    }
+  })
+  ipcMain.handle(IpcChannels.showInFolder, (_e, p: string) => safeShowInFolder(p))
+
+  ipcMain.handle(IpcChannels.clipboardRead, () => clipboard.readText())
+
+  ipcMain.handle(IpcChannels.settingsGet, () => getSettings())
+  ipcMain.handle(IpcChannels.settingsSet, (e, partial: Partial<Settings>) => {
+    const result = setSettings(partial)
+    // Keep the window's native background and title bar in sync with the theme
+    // so a compositor repaint never flashes a mismatched color, and the OS-drawn
+    // caption always matches the in-app theme (W3). Use the validated result.
+    if (partial.theme) {
+      BrowserWindow.fromWebContents(e.sender)?.setBackgroundColor(
+        PAGE_BACKGROUND[resolveBackgroundMode(result.theme)]
+      )
+      applyNativeTheme(result.theme)
+    }
+    return result
+  })
+
+  ipcMain.handle(IpcChannels.systemThemeGet, () => getSystemThemeInfo())
+
+  ipcMain.handle(IpcChannels.openHighContrastSettings, () =>
+    shell.openExternal('ms-settings:easeofaccess-highcontrast')
+  )
+
+  ipcMain.handle(IpcChannels.historyList, () => listHistory())
+  ipcMain.handle(IpcChannels.historyAdd, (_e, entry: HistoryEntry) => addHistory(entry))
+  ipcMain.handle(IpcChannels.historyRemove, (_e, id: string) => removeHistory(id))
+  ipcMain.handle(IpcChannels.historyRemoveMany, (_e, ids: string[]) => removeManyHistory(ids))
+  ipcMain.handle(IpcChannels.historyClear, () => clearHistory())
+
+  ipcMain.handle(IpcChannels.cookiesLogin, (e, url: string) =>
+    // Parent the sign-in window to the app window (W6) so it groups under
+    // AeroFetch instead of spawning a second taskbar button.
+    openCookieLoginWindow(url, BrowserWindow.fromWebContents(e.sender) ?? undefined)
+  )
+  ipcMain.handle(IpcChannels.cookiesStatus, () => getCookiesStatus())
+  ipcMain.handle(IpcChannels.cookiesClear, () => clearCookies())
+
+  ipcMain.handle(IpcChannels.templatesList, () => listTemplates())
+  ipcMain.handle(IpcChannels.templatesSave, (_e, template: CommandTemplate) =>
+    saveTemplate(template)
+  )
+  ipcMain.handle(IpcChannels.templatesRemove, (_e, id: string) => removeTemplate(id))
+
+  ipcMain.handle(IpcChannels.commandPreview, (_e, opts: StartDownloadOptions) =>
+    previewCommand(opts)
+  )
+
+  ipcMain.handle(IpcChannels.ytdlpUpdate, (_e, channel: YtdlpUpdateChannel) => updateYtdlp(channel))
+
+  ipcMain.handle(IpcChannels.errorLogList, () => listErrorLog())
+  ipcMain.handle(IpcChannels.errorLogClear, () => clearErrorLog())
+
+  // Persisted download queue (M4): the renderer mirrors its durable items here and
+  // rehydrates them on launch, so saved/scheduled/pending downloads survive a quit.
+  ipcMain.handle(IpcChannels.queueList, () => listQueue())
+  ipcMain.handle(IpcChannels.queueSave, (_e, items: PersistedQueueItem[]) => saveQueue(items))
+
+  ipcMain.handle(IpcChannels.backupExport, (e) =>
+    exportBackup(BrowserWindow.fromWebContents(e.sender) ?? undefined)
+  )
+  ipcMain.handle(IpcChannels.backupImport, async (e) => {
+    const win = BrowserWindow.fromWebContents(e.sender) ?? undefined
+    const result = await importBackup(win)
+    // A restored backup may have changed the theme; keep the native window
+    // background and title bar in sync the same way settingsSet does (W3).
+    if (result.ok) {
+      const theme = getSettings().theme
+      win?.setBackgroundColor(PAGE_BACKGROUND[resolveBackgroundMode(theme)])
+      applyNativeTheme(theme)
+    }
+    return result
+  })
+
+  // --- Media-manager sources (Pinchflat-style index; see ROADMAP-PINCHFLAT.md) ---
+  ipcMain.handle(IpcChannels.sourcesList, () => listSources())
+  ipcMain.handle(IpcChannels.sourceItems, (_e, sourceId: string) => listMediaItems(sourceId))
+  ipcMain.handle(IpcChannels.sourceRemove, (_e, id: string) => removeSource(id))
+  ipcMain.handle(IpcChannels.sourceItemDownloaded, (_e, id: string, filePath?: string) =>
+    setMediaItemDownloaded(id, filePath)
+  )
+  // Indexing pushes live progress to the requesting renderer over `indexProgress`
+  // and resolves with the final result.
+  ipcMain.handle(IpcChannels.sourceIndex, (e, url: string) =>
+    indexSource(url, (p) => {
+      if (!e.sender.isDestroyed()) e.sender.send(IpcChannels.indexProgress, p)
+    })
+  )
+  ipcMain.handle(IpcChannels.sourceReindex, (e, id: string) => {
+    const src = getSource(id)
+    if (!src) return { ok: false, error: 'Source not found.' }
+    return indexSource(src.url, (p) => {
+      if (!e.sender.isDestroyed()) e.sender.send(IpcChannels.indexProgress, p)
+    })
+  })
+  ipcMain.handle(IpcChannels.sourceSetWatched, (_e, id: string, watched: boolean) =>
+    setSourceWatched(id, watched)
+  )
+  ipcMain.handle(IpcChannels.sourcesSync, (e) =>
+    syncWatchedSources((p) => {
+      if (!e.sender.isDestroyed()) e.sender.send(IpcChannels.indexProgress, p)
+    })
+  )
+  ipcMain.handle(IpcChannels.scheduledSyncGet, () => getScheduledSync())
+  ipcMain.handle(IpcChannels.scheduledSyncSet, (_e, enabled: boolean) => setScheduledSync(enabled))
+
+  // Reflect overall queue progress on the Windows taskbar and window title (SR8).
+  ipcMain.handle(IpcChannels.taskbarProgress, (_e, p: TaskbarProgress) => {
+    const win = getMainWindow()
+    if (!win || win.isDestroyed()) return
+    if (p.mode === 'none') {
+      win.setProgressBar(-1)
+      win.setOverlayIcon(null, '')
+      win.setTitle('AeroFetch')
+    } else {
+      win.setProgressBar(Math.max(0, Math.min(1, p.fraction)), { mode: p.mode })
+      const badge = p.mode === 'error' ? getErrorBadge() : getActiveBadge()
+      const n = p.badgeCount ?? 0
+      const label =
+        p.mode === 'error' ? 'Download error' : `${n} download${n !== 1 ? 's' : ''} active`
+      win.setOverlayIcon(badge, label)
+      win.setTitle(p.mode === 'error' ? 'AeroFetch — Error' : `AeroFetch — ${label}`)
+    }
+  })
+
+  // Open a YouTube WebView and extract a PO token for bot-check bypass (Phase P).
+  ipcMain.handle(IpcChannels.youtubePoTokenMint, async () => {
+    const token = await openPoTokenWindow()
+    if (token) await setSettings({ youtubePoToken: token })
+    return token
+  })
+}

src/main/jsonStore.ts

@@ -0,0 +1,151 @@
+import { app } from 'electron'
+import { join } from 'path'
+import { readFileSync, writeFileSync, renameSync, existsSync, copyFileSync, unlinkSync } from 'fs'
+import { logger } from './logger'
+
+/**
+ * One shared persistence layer for the hand-rolled JSON array stores (history,
+ * error log, templates, sources, media-items). Replaces the per-module
+ * read/parse/write copies (SIMP1) and fixes three data-safety blockers:
+ *
+ *  - R1 -- atomic writes: write a temp file then `rename` over the target, so a
+ *    crash / power-cut mid-write can never truncate the real file. (`electron-store`,
+ *    used for settings, is already atomic; these stores were not.)
+ *  - R2 -- corruption is no longer silent data loss: on a parse error the bad file
+ *    is copied aside (`<file>.corrupt-<ts>`) before we fall back to empty, so a
+ *    single bad byte can't wipe the user's history/sources from their perspective.
+ *  - R3 -- an in-memory cache + debounced batched writes: the previous code
+ *    re-read + re-parsed the entire (multi-MB) file and rewrote it synchronously
+ *    on *every* download completion (≈O(n²) over a large channel, blocking the
+ *    main thread). Reads now hit the cache; writes coalesce into one atomic flush.
+ */
+
+// Debounce window for batched writes. Long enough to coalesce a burst (e.g. many
+// items enqueued/marked at once), short enough that data lands on disk promptly.
+const FLUSH_DELAY_MS = 400
+
+/**
+ * Read + validate a JSON array from `path`. Invalid rows are dropped. On a parse
+ * error the file is backed up to `<path>.corrupt-<timestamp>` before returning []
+ * so corruption is recoverable rather than a silent wipe (R2). A missing file is
+ * simply [] (first run), with no backup.
+ */
+export function readJsonArraySafe<T>(path: string, isValid: (o: unknown) => o is T): T[] {
+  let raw: string
+  try {
+    if (!existsSync(path)) return []
+    raw = readFileSync(path, 'utf8')
+  } catch {
+    return []
+  }
+  try {
+    const data = JSON.parse(raw)
+    return Array.isArray(data) ? data.filter(isValid) : []
+  } catch {
+    try {
+      copyFileSync(path, `${path}.corrupt-${Date.now()}`)
+    } catch {
+      /* best-effort -- if we can't back it up, still don't crash the read */
+    }
+    return []
+  }
+}
+
+/**
+ * Atomically write `value` as JSON to `path`: serialise to `<path>.tmp`, then
+ * `rename` it over the target (an atomic operation on the same volume), so a
+ * crash mid-write leaves either the old file or the new one -- never a truncated
+ * one (R1). `pretty` indents for human-readable files; pass false for large
+ * machine-only stores to avoid inflating size/write time (R8). Returns whether the
+ * write landed: a failure (disk full, read-only data dir) is logged rather than
+ * swallowed silently, so a record that looked saved but vanished on restart is at
+ * least diagnosable (R6). The leftover temp file is removed on failure so a partial
+ * `.tmp` can't accumulate.
+ */
+export function writeJsonAtomic(path: string, value: unknown, pretty = true): boolean {
+  const tmp = `${path}.tmp`
+  try {
+    writeFileSync(tmp, pretty ? JSON.stringify(value, null, 2) : JSON.stringify(value))
+    renameSync(tmp, path)
+    return true
+  } catch (e) {
+    // R6: previously a silent catch — a failed persist (disk full, read-only
+    // profile) dropped the change with no trace. It now lands in the file-backed
+    // diagnostic log (CC8); the user-facing toast ties to the global status surface (UI25/UX9).
+    logger.error(`failed to write ${path}`, e)
+    try {
+      if (existsSync(tmp)) unlinkSync(tmp)
+    } catch {
+      /* best-effort temp cleanup */
+    }
+    return false
+  }
+}
+
+export interface JsonStore<T> {
+  /** All rows, validated; cached after the first read. */
+  read(): T[]
+  /** Replace all rows (capped), update the cache, and schedule an atomic flush. Returns the stored rows. */
+  write(items: T[]): T[]
+  /** Force any pending debounced write to disk synchronously (e.g. on quit). */
+  flush(): void
+}
+
+// Every store registers itself so app-quit can flush pending writes in one call.
+const registry: JsonStore<unknown>[] = []
+
+/**
+ * Create a cached, atomic JSON array store backed by `<userData>/<filename>`.
+ * `cap` bounds the row count (pass Infinity for none). The path is resolved
+ * lazily so importing this module never touches `app` before it's ready.
+ */
+export function createJsonStore<T>(
+  filename: string,
+  isValid: (o: unknown) => o is T,
+  cap: number,
+  // Pretty-print by default (small, hand-inspectable files); pass false for a
+  // large machine-only store to keep writes compact (R8).
+  pretty = true
+): JsonStore<T> {
+  let cache: T[] | null = null
+  let timer: ReturnType<typeof setTimeout> | null = null
+  let dirty = false
+
+  const filePath = (): string => join(app.getPath('userData'), filename)
+
+  function read(): T[] {
+    if (cache === null) cache = readJsonArraySafe(filePath(), isValid)
+    return cache
+  }
+
+  function flush(): void {
+    if (timer) {
+      clearTimeout(timer)
+      timer = null
+    }
+    if (!dirty) return
+    // Only clear the dirty flag once the write actually lands. A failed flush
+    // (disk full, transient lock) stays dirty so the next write() or the
+    // quit-time flushAllStores() retries it instead of silently dropping it (R6).
+    if (writeJsonAtomic(filePath(), cache ?? [], pretty)) dirty = false
+  }
+
+  function write(items: T[]): T[] {
+    // Avoid an extra copy in the common under-cap case so a per-completion write
+    // stays O(1) rather than re-slicing the whole list each time (R3).
+    cache = items.length > cap ? items.slice(0, cap) : items
+    dirty = true
+    if (timer) clearTimeout(timer)
+    timer = setTimeout(flush, FLUSH_DELAY_MS)
+    return cache
+  }
+
+  const store: JsonStore<T> = { read, write, flush }
+  registry.push(store as JsonStore<unknown>)
+  return store
+}
+
+/** Synchronously flush every store's pending write -- call on app quit. */
+export function flushAllStores(): void {
+  for (const s of registry) s.flush()
+}

src/main/lib/exec.ts

@@ -0,0 +1,53 @@
+import { execFile, type ExecFileOptions } from 'child_process'
+
+/**
+ * Normalized result of a one-shot child-process run. `ok` is true on a clean
+ * exit-0; `timedOut` distinguishes a kill-by-timeout (Node sets `err.killed` when
+ * it terminates the process on the `timeout` option) from an ordinary non-zero
+ * exit, so callers can show "Timed out …" versus the captured stderr.
+ */
+export interface ExecResult {
+  ok: boolean
+  stdout: string
+  stderr: string
+  timedOut: boolean
+  /** The raw error on a non-zero exit / spawn failure (undefined when ok). */
+  error?: Error
+}
+
+/**
+ * `execFile` as a promise that never rejects (audit SIMP2/CC4/CC5). Replaces the
+ * six hand-rolled `new Promise((resolve) => execFile(…, cb))` wrappers across
+ * probe / ytdlp (×2) / ffmpeg / indexer / download.probeMeta — each caller now maps
+ * this normalized result to its own shape instead of repeating the `err.killed`
+ * timeout check and the resolve/reject plumbing. (schedule.ts keeps its own wrapper:
+ * it needs the numeric exit code, which this helper deliberately doesn't surface.)
+ *
+ * `windowsHide` defaults on (every caller wants the console window suppressed);
+ * pass `timeout` / `maxBuffer` per call exactly as before.
+ */
+export function execFileAsync(
+  file: string,
+  args: readonly string[],
+  options: ExecFileOptions = {}
+): Promise<ExecResult> {
+  return new Promise((resolve) => {
+    execFile(file, [...args], { windowsHide: true, ...options }, (err, stdout, stderr) => {
+      // With the default (utf8) encoding stdout/stderr are strings, but ExecFileOptions
+      // permits a Buffer encoding, so normalize defensively.
+      const out = typeof stdout === 'string' ? stdout : stdout.toString()
+      const errOut = typeof stderr === 'string' ? stderr : stderr.toString()
+      if (err) {
+        resolve({
+          ok: false,
+          stdout: out,
+          stderr: errOut,
+          timedOut: (err as { killed?: boolean }).killed === true,
+          error: err
+        })
+      } else {
+        resolve({ ok: true, stdout: out, stderr: errOut, timedOut: false })
+      }
+    })
+  })
+}

src/main/lib/formatters.ts

@@ -0,0 +1,36 @@
+import type { DownloadProgress } from '@shared/ipc'
+import { fmtBytes } from '@shared/format'
+
+// yt-dlp progress-line parsing. Extracted from download.ts so it can be
+// unit-tested without pulling in the electron import chain (L37). Byte/speed/ETA
+// formatting lives in @shared/format — the one home for both sides of the IPC
+// boundary; consumers import it directly.
+
+function num(s?: string): number | undefined {
+  if (!s || s === 'NA') return undefined
+  const n = Number(s)
+  return Number.isFinite(n) ? n : undefined
+}
+
+export function parseProgress(rest: string): DownloadProgress | null {
+  const parts = rest.split('|')
+  if (parts.length < 6) return null
+  const [status, dl, total, totalEst, speed, eta] = parts
+  const downloaded = num(dl)
+  const totalBytes = num(total) ?? num(totalEst)
+  let progress = 0
+  if (totalBytes && downloaded != null) progress = Math.min(1, downloaded / totalBytes)
+  return {
+    status: status || 'downloading',
+    progress,
+    // Carry raw numbers across the IPC boundary; the renderer formats them for
+    // display AND aggregates them (combined speed / longest ETA) without having
+    // to re-parse a formatted string (H4).
+    speedBytesPerSec: num(speed),
+    etaSeconds: num(eta),
+    sizeLabel: totalBytes ? fmtBytes(totalBytes) : undefined,
+    // No (estimated) total → the % can never advance; flag it so the renderer
+    // shows an indeterminate bar rather than a stuck 0% (L137).
+    sizeUnknown: !totalBytes
+  }
+}

src/main/lib/lineBuffer.ts

@@ -0,0 +1,37 @@
+/**
+ * A newline line-splitter for streamed child-process output (audit CC3/CC4/SIMP5).
+ *
+ * `download.ts` and `terminal.ts` each had the same hand-rolled loop: accumulate
+ * chunk strings, emit every complete `\n`-terminated line (stripping a trailing
+ * `\r`), and keep the partial remainder for the next chunk. This is that logic in
+ * one place, and — being pure and synchronous — it's unit-tested directly.
+ *
+ * Usage: feed decoded chunks with `push()`, and call `flush()` on stream close to
+ * emit any trailing partial line that never saw a newline.
+ */
+export interface LineBuffer {
+  /** Accept a decoded chunk; invokes the sink for each newly-completed line. */
+  push: (chunk: string) => void
+  /** Emit any buffered remainder (a final line with no trailing newline). */
+  flush: () => void
+}
+
+export function createLineBuffer(onLine: (line: string) => void): LineBuffer {
+  let buf = ''
+  return {
+    push(chunk: string): void {
+      buf += chunk
+      let nl: number
+      while ((nl = buf.indexOf('\n')) >= 0) {
+        onLine(buf.slice(0, nl).replace(/\r$/, ''))
+        buf = buf.slice(nl + 1)
+      }
+    },
+    flush(): void {
+      if (buf) {
+        onLine(buf)
+        buf = ''
+      }
+    }
+  }
+}

src/main/logger.ts

@@ -0,0 +1,106 @@
+import { app } from 'electron'
+import { join } from 'path'
+import { appendFileSync, mkdirSync, renameSync, statSync } from 'fs'
+import { LOG_MAX_BYTES } from './constants'
+
+/**
+ * One small leveled, file-backed logger for the whole app (audit CC8). Before this,
+ * diagnostics were effectively invisible in a packaged build: main-process catches
+ * did a bare `console.error` (unreachable — the app menu/DevTools are suppressed in
+ * production, M31) and the renderer's `logError` (M29) wrote to a console nobody could
+ * open. Every catch now routes here and lands in `<userData>/logs/aerofetch.log`, so a
+ * field-reported failure is actually diagnosable.
+ *
+ * Scope: this is the diagnostic log. `errorlog.ts` remains separate — it's user-facing
+ * *download* failure data shown in Settings → Diagnostics, not app logging. The
+ * user-facing toast half of CC8 ties to the global status surface (UI25/UX9).
+ *
+ * All `app`/fs access is lazy and guarded so importing this module never touches
+ * `app` before it's ready — and so it's a safe no-op under unit tests, where
+ * `electron`'s `app` is undefined.
+ */
+
+export type LogLevel = 'error' | 'warn' | 'info' | 'debug'
+
+const LEVELS: Record<LogLevel, number> = { error: 0, warn: 1, info: 2, debug: 3 }
+
+// Write everything at or above this level to the file. `debug` is dev-only noise, so
+// it never hits the file (but still prints to the dev console).
+const FILE_THRESHOLD = LEVELS.info
+
+/** Format one log line: `2026-07-01T08:30:00.000Z [ERROR] message`. Pure, for tests. */
+export function formatLine(level: LogLevel, message: string, now: Date = new Date()): string {
+  return `${now.toISOString()} [${level.toUpperCase()}] ${message}`
+}
+
+/** Combine an operation label with an optional error/detail into one message. Pure. */
+export function composeMessage(label: string, detail?: unknown): string {
+  if (detail === undefined) return label
+  const text = detail instanceof Error ? detail.message : String(detail)
+  return `${label}: ${text}`
+}
+
+// `undefined` = not yet resolved, `null` = resolution failed (no app/userData, e.g.
+// under unit tests) so file logging is disabled; a string is the resolved path.
+let cachedFile: string | null | undefined
+function logFile(): string | null {
+  if (cachedFile !== undefined) return cachedFile
+  try {
+    const dir = join(app.getPath('userData'), 'logs')
+    mkdirSync(dir, { recursive: true })
+    cachedFile = join(dir, 'aerofetch.log')
+  } catch {
+    // No app / userData available (unit test, or app not ready) — disable the file sink.
+    cachedFile = null
+  }
+  return cachedFile
+}
+
+/** Dev mode, resolved lazily and guarded (app is undefined in the test env). */
+function isDev(): boolean {
+  try {
+    return !app.isPackaged
+  } catch {
+    return false
+  }
+}
+
+// Rotate to `<file>.1` (single generation) once the live file passes the cap, so the
+// log can't grow without bound. Best-effort: any fs error here is swallowed — logging
+// must never throw into a catch handler.
+function rotateIfNeeded(file: string): void {
+  try {
+    if (statSync(file).size > LOG_MAX_BYTES) renameSync(file, `${file}.1`)
+  } catch {
+    /* file missing (first write) or rename race — ignore */
+  }
+}
+
+function writeToFile(line: string): void {
+  const file = logFile()
+  if (!file) return
+  rotateIfNeeded(file)
+  try {
+    appendFileSync(file, line + '\n')
+  } catch {
+    /* disk full / read-only profile — nothing more we can safely do */
+  }
+}
+
+function emit(level: LogLevel, label: string, detail?: unknown): void {
+  const message = composeMessage(label, detail)
+  // Console in dev keeps the familiar `--inspect` workflow; the file is the sink that
+  // survives into a packaged build.
+  if (isDev()) {
+    const fn = level === 'error' ? console.error : level === 'warn' ? console.warn : console.log
+    fn(`[AeroFetch] ${message}`)
+  }
+  if (LEVELS[level] <= FILE_THRESHOLD) writeToFile(formatLine(level, message))
+}
+
+export const logger = {
+  error: (label: string, detail?: unknown): void => emit('error', label, detail),
+  warn: (label: string, detail?: unknown): void => emit('warn', label, detail),
+  info: (label: string, detail?: unknown): void => emit('info', label, detail),
+  debug: (label: string, detail?: unknown): void => emit('debug', label, detail)
+}

src/main/paths.ts

@@ -0,0 +1,40 @@
+import { app } from 'electron'
+import { join } from 'path'
+import { mkdirSync } from 'fs'
+
+/**
+ * Filesystem path helpers for the main process. Kept separate from settings.ts
+ * (the electron-store persistence layer) so path derivation and the settings
+ * store don't share a module — they have different concerns and dependencies (L69).
+ * All resolve app paths, so callers must run post-`app.ready`.
+ */
+
+/** Fixed path for the --download-archive file; not user-configurable. */
+export function getDownloadArchivePath(): string {
+  return join(app.getPath('userData'), 'download-archive.txt')
+}
+
+/**
+ * The default per-kind download destination: video → Documents\Video,
+ * audio → Documents\Audio. Used when the user hasn't set an explicit output
+ * folder (Settings → Download folder), so downloads are sorted by type.
+ */
+export function getDefaultMediaDir(kind: 'video' | 'audio'): string {
+  return join(app.getPath('documents'), kind === 'audio' ? 'Audio' : 'Video')
+}
+
+/**
+ * Create the Documents\Video and Documents\Audio folders up front (called once
+ * at startup) so they exist the moment the app opens, not just after the first
+ * download. Best-effort: yt-dlp also creates the output dir at download time, so
+ * a failure here (read-only Documents, redirected folder) is non-fatal.
+ */
+export function ensureMediaDirs(): void {
+  for (const kind of ['video', 'audio'] as const) {
+    try {
+      mkdirSync(getDefaultMediaDir(kind), { recursive: true })
+    } catch {
+      /* non-fatal — the download path will be created on demand instead */
+    }
+  }
+}

src/main/poToken.ts

@@ -0,0 +1,148 @@
+import { BrowserWindow, type WebContents } from 'electron'
+import { LOGIN_PARTITION } from './cookies'
+
+/** A public YouTube video used as the extraction target (stable, always accessible). */
+const YT_VIDEO = 'https://www.youtube.com/watch?v=jNQXAC9IVRw'
+
+/**
+ * Restrict a PO-token window to *.youtube.com and accounts.google.com (for
+ * sign-in). Mirrors hardenLoginWebContents in cookies.ts.
+ */
+function isAllowedPoTokenUrl(target: string): boolean {
+  try {
+    const { protocol, hostname } = new URL(target)
+    if (protocol !== 'http:' && protocol !== 'https:') return false
+    return (
+      hostname === 'youtube.com' ||
+      hostname.endsWith('.youtube.com') ||
+      hostname === 'accounts.google.com' ||
+      hostname.endsWith('.accounts.google.com')
+    )
+  } catch {
+    return false
+  }
+}
+
+function hardenPoTokenWebContents(wc: WebContents): void {
+  wc.setWindowOpenHandler((details) => {
+    if (!isAllowedPoTokenUrl(details.url)) return { action: 'deny' }
+    return {
+      action: 'allow',
+      overrideBrowserWindowOptions: {
+        autoHideMenuBar: true,
+        webPreferences: {
+          partition: LOGIN_PARTITION,
+          sandbox: true,
+          contextIsolation: true,
+          nodeIntegration: false
+        }
+      }
+    }
+  })
+  wc.on('will-navigate', (e, navUrl) => {
+    if (!isAllowedPoTokenUrl(navUrl)) e.preventDefault()
+  })
+  wc.on('will-redirect', (e, navUrl) => {
+    if (!isAllowedPoTokenUrl(navUrl)) e.preventDefault()
+  })
+  wc.on('did-create-window', (child) => hardenPoTokenWebContents(child.webContents))
+}
+
+/**
+ * Async IIFE injected into the YouTube page after load. Polls
+ * ytInitialPlayerResponse.serviceIntegrityDimensions.poToken (the field
+ * yt-dlp's youtube extractor reads) for up to 8 s, returning the token
+ * string or null if it never appears. The poll loop is needed because the
+ * player JS initialises asynchronously after the DOM is ready.
+ */
+const EXTRACT_SCRIPT = `
+(async function() {
+  for (let i = 0; i < 16; i++) {
+    try {
+      const pot = window.ytInitialPlayerResponse
+        && window.ytInitialPlayerResponse.serviceIntegrityDimensions
+        && window.ytInitialPlayerResponse.serviceIntegrityDimensions.poToken
+      if (typeof pot === 'string' && pot.length > 0) return pot
+    } catch (_) {}
+    await new Promise(r => setTimeout(r, 500))
+  }
+  return null
+})()
+`
+
+let mintWindow: BrowserWindow | null = null
+
+/**
+ * Open a visible BrowserWindow on a YouTube video page and extract the
+ * Proof-of-Origin token from the page runtime. The window uses the shared
+ * login session so a signed-in user's credentials are available.
+ *
+ * Resolves with the token string on success, or null if the window was closed
+ * by the user before extraction completed or if the field was not found.
+ */
+export function openPoTokenWindow(): Promise<string | null> {
+  // If a minting window is already open, bring it to the front rather than
+  // opening a second one.
+  if (mintWindow && !mintWindow.isDestroyed()) {
+    mintWindow.focus()
+    // Return a promise that resolves when the existing window closes.
+    return new Promise((resolve) => {
+      mintWindow!.once('closed', () => resolve(null))
+    })
+  }
+
+  return new Promise((resolve) => {
+    let resolved = false
+    const finish = (token: string | null): void => {
+      if (resolved) return
+      resolved = true
+      resolve(token)
+    }
+
+    let win: BrowserWindow
+    try {
+      win = new BrowserWindow({
+        width: 960,
+        height: 640,
+        title: 'AeroFetch — Fetch YouTube token',
+        autoHideMenuBar: true,
+        webPreferences: {
+          partition: LOGIN_PARTITION,
+          sandbox: true,
+          contextIsolation: true,
+          nodeIntegration: false
+        }
+      })
+    } catch {
+      finish(null)
+      return
+    }
+
+    mintWindow = win
+    hardenPoTokenWebContents(win.webContents)
+    win.webContents.session.setPermissionRequestHandler((_wc, _perm, cb) => cb(false))
+
+    win.webContents.once('did-finish-load', () => {
+      win.webContents
+        .executeJavaScript(EXTRACT_SCRIPT, true)
+        .then((result: unknown) => {
+          const token = typeof result === 'string' && result.length > 0 ? result : null
+          finish(token)
+          win.close()
+        })
+        .catch(() => {
+          finish(null)
+          win.close()
+        })
+    })
+
+    win.on('closed', () => {
+      mintWindow = null
+      finish(null)
+    })
+
+    win.loadURL(YT_VIDEO).catch(() => {
+      /* navigation errors surface as Chromium's own error page */
+    })
+  })
+}

src/main/probe.ts

@@ -1,7 +1,8 @@
-import { execFile } from 'child_process'
 import { existsSync } from 'fs'
-import { getYtdlpPath } from './binaries'
+import { getYtdlpPath, YTDLP_MISSING_MSG } from './binaries'
-import { fmtBytes } from './download'
+import { execFileAsync } from './lib/exec'
+import { PROBE_MAX_BUFFER, PROBE_TIMEOUT_MS } from './constants'
+import { fmtBytes } from '@shared/format'
 import { cleanError } from './log'
 import { assertHttpUrl } from './url'
 import { entryUrl, fmtDuration, type RawEntry } from './indexerCore'
@@ -69,7 +70,10 @@ function buildVideoFormats(raw: RawFormat[]): FormatOption[] {
   const options = [...bestByHeight.values()]
     .sort((a, b) => (b.height ?? 0) - (a.height ?? 0))
     .map(toOption)
-  options.unshift({ id: BEST_FORMAT_ID, label: 'Best available', ext: 'mp4', hasAudio: true })
+  // No `ext`: the final container for the auto-best pick depends on the user's
+  // videoContainer setting (mp4/mkv/webm), unknown here -- claiming 'mp4' would
+  // mislabel mkv/webm outputs (L62). hasAudio is always true (best merges audio).
+  options.unshift({ id: BEST_FORMAT_ID, label: 'Best available', hasAudio: true })
   return options
 }
 
@@ -110,52 +114,40 @@ function buildPlaylist(data: RawInfo): PlaylistInfo {
  * its format list) or, when the URL is a playlist, the flat list of its entries.
  * `--flat-playlist` is a no-op for a lone video, so one call covers both cases.
  */
-export function probeMedia(url: string): Promise<ProbeResult> {
+export async function probeMedia(url: string): Promise<ProbeResult> {
   const ytdlp = getYtdlpPath()
   if (!existsSync(ytdlp)) {
-    return Promise.resolve({
+    return { ok: false, error: YTDLP_MISSING_MSG }
-      ok: false,
-      error: `yt-dlp.exe not found at ${ytdlp}\nDrop it into resources/bin/ (see the README there).`
-    })
   }
   let target: string
   try {
     target = assertHttpUrl(url) // normalised form (audit F5)
   } catch (e) {
-    return Promise.resolve({ ok: false, error: (e as Error).message })
+    return { ok: false, error: (e as Error).message }
   }
 
-  return new Promise((resolve) => {
-    execFile(
-      ytdlp,
   // `--` terminates option parsing so the URL can never be read as a flag.
-      ['-J', '--flat-playlist', '--no-warnings', '--', target],
+  const r = await execFileAsync(ytdlp, ['-J', '--flat-playlist', '--no-warnings', '--', target], {
-      { windowsHide: true, maxBuffer: 64 * 1024 * 1024, timeout: 60_000 },
+    maxBuffer: PROBE_MAX_BUFFER,
-      (err, stdout, stderr) => {
+    timeout: PROBE_TIMEOUT_MS
-        if (err) {
+  })
-          // execFile sets `killed` when it terminated the process on timeout.
+  if (!r.ok) {
-          const msg = (err as { killed?: boolean }).killed
+    const msg = r.timedOut
       ? 'Timed out fetching video info. Check the link or your connection.'
-            : cleanError(stderr) || err.message
+      : cleanError(r.stderr) || r.error?.message || ''
-          resolve({ ok: false, error: msg })
+    return { ok: false, error: msg }
-          return
   }
   try {
-          const data = JSON.parse(stdout) as RawInfo
+    const data = JSON.parse(r.stdout) as RawInfo
     if (data._type === 'playlist' || Array.isArray(data.entries)) {
       const playlist = buildPlaylist(data)
       if (playlist.count === 0) {
-              resolve({ ok: false, error: 'This playlist has no downloadable entries.' })
+        return { ok: false, error: 'This playlist has no downloadable entries.' }
-              return
       }
-            resolve({ ok: true, kind: 'playlist', playlist })
+      return { ok: true, kind: 'playlist', playlist }
-          } else {
-            resolve({ ok: true, kind: 'video', info: buildInfo(data) })
     }
+    return { ok: true, kind: 'video', info: buildInfo(data) }
   } catch {
-          resolve({ ok: false, error: 'Could not parse video info from yt-dlp.' })
+    return { ok: false, error: 'Could not parse video info from yt-dlp.' }
   }
 }
-    )
-  })
-}

src/main/queue.ts

@@ -0,0 +1,46 @@
+import { createJsonStore } from './jsonStore'
+import { QUEUE_MAX } from './constants'
+import type { PersistedQueueItem, PersistedQueueStatus } from '@shared/ipc'
+
+/**
+ * Persistence for the download queue (M4). The queue lived only in renderer memory,
+ * so `saved` / scheduled and other pending downloads were silently lost on quit.
+ * The renderer now mirrors its durable items here (via `queueSave`) and rehydrates
+ * them on launch (via `queueList`), so a parked/scheduled download returns.
+ *
+ * Reuses the shared cached-atomic `createJsonStore` (R1/R2/R3), so writes are atomic
+ * and coalesced — the renderer can call `queueSave` freely on queue changes.
+ */
+
+const PERSISTED_STATUSES: readonly PersistedQueueStatus[] = [
+  'queued',
+  'downloading',
+  'paused',
+  'saved',
+  'error'
+]
+
+/** Defensive row validator (a hand-edited or partially-written file can't crash a read). */
+function isValidQueueItem(o: unknown): o is PersistedQueueItem {
+  if (typeof o !== 'object' || o === null) return false
+  const it = o as Record<string, unknown>
+  return (
+    typeof it.id === 'string' &&
+    typeof it.url === 'string' &&
+    typeof it.title === 'string' &&
+    (it.kind === 'video' || it.kind === 'audio') &&
+    typeof it.quality === 'string' &&
+    typeof it.status === 'string' &&
+    (PERSISTED_STATUSES as readonly string[]).includes(it.status)
+  )
+}
+
+const store = createJsonStore('queue.json', isValidQueueItem, QUEUE_MAX)
+
+export function listQueue(): PersistedQueueItem[] {
+  return store.read()
+}
+
+export function saveQueue(items: PersistedQueueItem[]): void {
+  store.write(items)
+}

src/main/reveal.ts

@@ -13,11 +13,29 @@ import { extname, isAbsolute } from 'path'
  */
 const OPENABLE_EXTENSIONS = new Set([
   // video
-  '.mp4', '.mkv', '.webm', '.mov', '.avi', '.flv', '.ts', '.m4v', '.3gp', '.ogv',
+  '.mp4',
+  '.mkv',
+  '.webm',
+  '.mov',
+  '.avi',
+  '.flv',
+  '.ts',
+  '.m4v',
+  '.3gp',
+  '.ogv',
   // audio
-  '.mp3', '.m4a', '.opus', '.ogg', '.oga', '.aac', '.flac', '.wav', '.wma',
+  '.mp3',
+  '.m4a',
+  '.opus',
+  '.ogg',
+  '.oga',
+  '.aac',
+  '.flac',
+  '.wav',
+  '.wma',
   // subtitle sidecars (plain text — safe to open)
-  '.vtt', '.srt'
+  '.vtt',
+  '.srt'
 ])
 
 /** Open a downloaded media file with its default app. Returns '' on success,
@@ -35,8 +53,11 @@ export async function safeOpenPath(p: unknown): Promise<string> {
   return shell.openPath(p)
 }
 
-/** Reveal a path in the OS file manager. No-op for missing/invalid paths. */
+/** Reveal a path in the OS file manager. Returns '' on success, or an error
-export function safeShowInFolder(p: unknown): void {
+ *  string (mirroring safeOpenPath) so the renderer can surface it (UX6). */
-  if (typeof p !== 'string' || !isAbsolute(p) || !existsSync(p)) return
+export function safeShowInFolder(p: unknown): string {
+  if (typeof p !== 'string' || !isAbsolute(p)) return 'Invalid path.'
+  if (!existsSync(p)) return 'File not found — it may have been moved or deleted.'
   shell.showItemInFolder(p)
+  return ''
 }

src/main/schedule.ts

@@ -21,10 +21,15 @@ function schtasks(args: string[]): Promise<{ code: number; stdout: string; stder
   return new Promise((resolve) => {
     // Resolve schtasks from System32 by absolute path, not the bare name, so a
     // planted schtasks.exe on PATH / in the CWD can't be invoked instead. (audit F3)
-    execFile(getSystem32Path('schtasks.exe'), args, { windowsHide: true }, (err, stdout, stderr) => {
+    execFile(
+      getSystem32Path('schtasks.exe'),
+      args,
+      { windowsHide: true },
+      (err, stdout, stderr) => {
         const code = err ? ((err as { code?: number }).code ?? 1) : 0
         resolve({ code, stdout: String(stdout), stderr: String(stderr) })
-    })
+      }
+    )
   })
 }
 

src/main/settings.ts

@@ -1,8 +1,7 @@
 import { app, safeStorage } from 'electron'
-import { join } from 'path'
-import { mkdirSync } from 'fs'
 import Store from 'electron-store'
 import { isSafeFilenameTemplate, isSafeOutputDir } from './validation'
+import { logger } from './logger'
 import {
   AUDIO_FORMATS,
   VIDEO_CONTAINERS,
@@ -10,50 +9,24 @@ import {
   SPONSORBLOCK_CATEGORIES,
   COOKIE_BROWSERS,
   ACCENT_COLORS,
+  VIDEO_QUALITY_OPTIONS,
+  AUDIO_QUALITY_OPTIONS,
   DEFAULT_DOWNLOAD_OPTIONS,
+  DEFAULT_SETTINGS,
   isYtdlpUpdateChannel,
   type Settings,
   type DownloadOptions,
-  type SponsorBlockCategory
+  type SponsorBlockCategory,
+  type AudioFormat,
+  type VideoContainer,
+  type VideoCodecPref
 } from '@shared/ipc'
 
-const DEFAULTS: Settings = {
+// The electron-store defaults are the canonical DEFAULT_SETTINGS from the shared
-  // Both blank by default → downloads land in Documents\Video / Documents\Audio
+// contract — single-sourced so the renderer FALLBACK and the preview mock can't
-  // (see getDefaultMediaDir). A non-empty value is an explicit per-kind override.
+// drift from main (C1). The rationale for individual defaults (SR1/SR2/SR3) lives
-  videoDir: '',
+// alongside DEFAULT_SETTINGS in shared/ipc.ts.
-  audioDir: '',
+const DEFAULTS: Settings = DEFAULT_SETTINGS
-  defaultKind: 'video',
-  defaultVideoQuality: 'Best available',
-  defaultAudioQuality: 'Best (MP3)',
-  maxConcurrent: 2,
-  filenameTemplate: '%(title)s.%(ext)s',
-  theme: 'light',
-  accentColor: 'teal',
-  clipboardWatch: true,
-  downloadOptions: DEFAULT_DOWNLOAD_OPTIONS,
-  proxy: '',
-  rateLimit: '',
-  useAria2c: false,
-  cookieSource: 'none',
-  cookiesBrowser: 'chrome',
-  youtubePlayerClient: '',
-  youtubePoToken: '',
-  restrictFilenames: false,
-  downloadArchive: false,
-  // yt-dlp is self-managed: a writable copy under userData, auto-updated on the
-  // nightly channel (fastest to follow YouTube changes that cause 403s).
-  autoUpdateYtdlp: true,
-  ytdlpChannel: 'nightly',
-  ytdlpLastUpdateCheck: 0,
-  customCommandEnabled: false,
-  defaultTemplateId: null,
-  notifyOnComplete: true,
-  autoDownloadNew: true,
-  hasCompletedOnboarding: false,
-  minimizeToTray: false,
-  launchAtStartup: false,
-  updateToken: ''
-}
 
 /**
  * Sync the OS "run at sign-in" entry with the launchAtStartup setting. Called at
@@ -69,56 +42,29 @@ export function applyLaunchAtStartup(enabled: boolean): void {
   }
 }
 
-/** Fixed path for the --download-archive file; not user-configurable. */
-export function getDownloadArchivePath(): string {
-  return join(app.getPath('userData'), 'download-archive.txt')
-}
-
-/**
- * The default per-kind download destination: video → Documents\Video,
- * audio → Documents\Audio. Used when the user hasn't set an explicit output
- * folder (Settings → Download folder), so downloads are sorted by type.
- */
-export function getDefaultMediaDir(kind: 'video' | 'audio'): string {
-  return join(app.getPath('documents'), kind === 'audio' ? 'Audio' : 'Video')
-}
-
-/**
- * Create the Documents\Video and Documents\Audio folders up front (called once
- * at startup) so they exist the moment the app opens, not just after the first
- * download. Best-effort: yt-dlp also creates the output dir at download time, so
- * a failure here (read-only Documents, redirected folder) is non-fatal.
- */
-export function ensureMediaDirs(): void {
-  for (const kind of ['video', 'audio'] as const) {
-    try {
-      mkdirSync(getDefaultMediaDir(kind), { recursive: true })
-    } catch {
-      /* non-fatal — the download path will be created on demand instead */
-    }
-  }
-}
-
 // Coerce an untrusted partial into a valid DownloadOptions, falling back to the
 // defaults for any missing/invalid field. Used both to migrate older settings
 // files (which predate downloadOptions) and to validate renderer writes.
 function sanitizeOptions(input: unknown): DownloadOptions {
   const o = (input && typeof input === 'object' ? input : {}) as Partial<DownloadOptions>
   const d = DEFAULT_DOWNLOAD_OPTIONS
-  const bool = (v: unknown, fallback: boolean): boolean =>
+  const bool = (v: unknown, fallback: boolean): boolean => (typeof v === 'boolean' ? v : fallback)
-    typeof v === 'boolean' ? v : fallback
   const cats = Array.isArray(o.sponsorBlockCategories)
     ? (o.sponsorBlockCategories.filter((c) =>
         (SPONSORBLOCK_CATEGORIES as readonly string[]).includes(c)
       ) as SponsorBlockCategory[])
     : d.sponsorBlockCategories
   return {
-    audioFormat: AUDIO_FORMATS.includes(o.audioFormat as never) ? o.audioFormat! : d.audioFormat,
+    audioFormat: (AUDIO_FORMATS as readonly string[]).includes(o.audioFormat as string)
-    videoContainer: VIDEO_CONTAINERS.includes(o.videoContainer as never)
+      ? (o.audioFormat as AudioFormat)
-      ? o.videoContainer!
+      : d.audioFormat,
+    videoContainer: (VIDEO_CONTAINERS as readonly string[]).includes(o.videoContainer as string)
+      ? (o.videoContainer as VideoContainer)
       : d.videoContainer,
-    preferredVideoCodec: VIDEO_CODECS.includes(o.preferredVideoCodec as never)
+    preferredVideoCodec: (VIDEO_CODECS as readonly string[]).includes(
-      ? o.preferredVideoCodec!
+      o.preferredVideoCodec as string
+    )
+      ? (o.preferredVideoCodec as VideoCodecPref)
       : d.preferredVideoCodec,
     formatSort: typeof o.formatSort === 'string' ? o.formatSort.trim() : d.formatSort,
     embedSubtitles: bool(o.embedSubtitles, d.embedSubtitles),
@@ -133,6 +79,9 @@ function sanitizeOptions(input: unknown): DownloadOptions {
     embedChapters: bool(o.embedChapters, d.embedChapters),
     splitChapters: bool(o.splitChapters, d.splitChapters),
     embedMetadata: bool(o.embedMetadata, d.embedMetadata),
+    metadataTitle: typeof o.metadataTitle === 'string' ? o.metadataTitle : undefined,
+    metadataArtist: typeof o.metadataArtist === 'string' ? o.metadataArtist : undefined,
+    metadataAlbum: typeof o.metadataAlbum === 'string' ? o.metadataAlbum : undefined,
     embedThumbnail: bool(o.embedThumbnail, d.embedThumbnail),
     cropThumbnail: bool(o.cropThumbnail, d.cropThumbnail),
     writeInfoJson: bool(o.writeInfoJson, d.writeInfoJson),
@@ -149,13 +98,19 @@ function getStore(): Store<Settings> {
   return store
 }
 
+// Decrypted-settings cache — avoids repeated DPAPI calls on hot paths such as
+// buildCommand, the maxConcurrent check, completion notify, and the system-theme
+// bridge (PERF1). Invalidated by every setSettings write and by the one-time
+// migrateSecretsAtRest so callers always see the current values.
+let cachedSettings: Settings | null = null
+
 // --- Credential encryption at rest ------------------------------------------
 // proxy / youtubePoToken / updateToken can carry secrets (a proxy password, API
 // tokens). They're stored encrypted via Electron safeStorage (DPAPI on Windows)
-// so a leaked settings.json doesn't expose them. They're still decrypted before
+// so a leaked settings.json doesn't expose them. They're decrypted before
-// reaching the renderer and exported in clear by backup — this guards the file at
+// reaching the renderer; backup export strips them entirely (see backup.ts, M22).
-// rest only.
+// Exported so backup.ts shares this one list rather than keeping a parallel copy.
-const SECRET_KEYS = ['proxy', 'youtubePoToken', 'updateToken'] as const
+export const SECRET_KEYS = ['proxy', 'youtubePoToken', 'updateToken'] as const
 
 // Marks a value produced by encryptSecret, so a read can tell ciphertext from a
 // legacy plaintext value (written before encryption existed, or while safeStorage
@@ -172,6 +127,11 @@ function encryptSecret(plain: string): string {
   } catch {
     /* fall through — store plaintext, as it was before encryption existed */
   }
+  // R7: OS encryption (DPAPI/keychain) is unavailable, so this credential is about
+  // to be written in cleartext. Warn rather than fall back silently — a leaked
+  // settings.json would then expose the proxy password / API token. (DPAPI is
+  // effectively always present on Windows, so this should never fire in practice.)
+  logger.warn('OS secret encryption unavailable — storing credential as plaintext')
   return plain
 }
 
@@ -213,9 +173,11 @@ export function migrateSecretsAtRest(): void {
     const raw = s.get(key) ?? ''
     if (raw && !raw.startsWith(ENC_PREFIX)) s.set(key, encryptSecret(raw))
   }
+  cachedSettings = null
 }
 
 export function getSettings(): Settings {
+  if (cachedSettings) return cachedSettings
   const s = getStore()
   // getSettings() is on hot paths (buildCommand, notification checks, the system-
   // theme bridge, several IPC handlers). electron-store writes to disk on every
@@ -236,9 +198,15 @@ export function getSettings(): Settings {
   if (!(ACCENT_COLORS as readonly string[]).includes(cur.accentColor)) {
     s.set('accentColor', DEFAULTS.accentColor)
   }
+  // Migrate the legacy audio-quality label 'Best (MP3)' to the format-agnostic
+  // 'Best' so the dropdown matches and the label no longer names a format (M18).
+  if (cur.defaultAudioQuality === 'Best (MP3)') {
+    s.set('defaultAudioQuality', 'Best')
+  }
   // Hand callers (and, via IPC, the renderer) plaintext credentials — they're
   // only encrypted on disk (see withDecryptedSecrets / encryptSecret).
-  return withDecryptedSecrets(s.store)
+  cachedSettings = withDecryptedSecrets(s.store)
+  return cachedSettings
 }
 
 /** Shallow structural equality for DownloadOptions (sponsorBlockCategories compared by value). */
@@ -264,6 +232,20 @@ function downloadOptionsEqual(a: DownloadOptions, b: unknown): boolean {
 // background (theme), so an out-of-range or malformed value shouldn't get stored.
 export function setSettings(partial: Partial<Settings>): Settings {
   const s = getStore()
+  try {
+    applySettings(s, partial)
+  } catch (e) {
+    // R5: a write failure (disk full, read-only profile) must not crash the IPC
+    // handler or surface as an unhandled rejection. Log it; getSettings() below
+    // returns the store's ACTUAL persisted state, so the renderer's reconciliation
+    // (M34) reflects what truly saved instead of the optimistic value.
+    logger.error('settings write failed', e)
+  }
+  cachedSettings = null
+  return getSettings()
+}
+
+function applySettings(s: Store<Settings>, partial: Partial<Settings>): void {
   for (const key of Object.keys(partial) as (keyof Settings)[]) {
     const value = partial[key]
     if (value === undefined) continue
@@ -294,6 +276,7 @@ export function setSettings(partial: Partial<Settings>): Settings {
       case 'autoDownloadNew':
       case 'hasCompletedOnboarding':
       case 'minimizeToTray':
+      case 'sidebarCollapsed':
         if (typeof value === 'boolean') s.set(key, value)
         break
       case 'launchAtStartup':
@@ -343,23 +326,42 @@ export function setSettings(partial: Partial<Settings>): Settings {
         }
         break
       case 'defaultVideoQuality':
+        if (
+          typeof value === 'string' &&
+          (VIDEO_QUALITY_OPTIONS as readonly string[]).includes(value)
+        ) {
+          s.set('defaultVideoQuality', value)
+        }
+        break
       case 'defaultAudioQuality':
+        if (
+          typeof value === 'string' &&
+          (AUDIO_QUALITY_OPTIONS as readonly string[]).includes(value)
+        ) {
+          s.set('defaultAudioQuality', value)
+        }
+        break
       case 'rateLimit':
+        // yt-dlp rate-limit format: empty (disabled) or e.g. "500K", "2.5M", "1G".
+        if (typeof value === 'string' && /^(\d+\.?\d*[KMGkmg]?B?)?$/.test(value.trim())) {
+          s.set('rateLimit', value.trim())
+        }
+        break
       case 'youtubePlayerClient':
-        if (typeof value === 'string') s.set(key, value)
+        // Power-user field; yt-dlp's client list evolves. Accept any trimmed string.
+        if (typeof value === 'string') s.set('youtubePlayerClient', value.trim())
         break
       // Credential-bearing fields — encrypted at rest (see encryptSecret). proxy
-      // may embed user:pass@host; youtubePoToken is an access token. exportBackup
+      // may embed user:pass@host; youtubePoToken is an access token. Both are
-      // still writes them in clear (via the decrypted getSettings), as documented.
+      // stripped from backup exports (see SECRET_KEYS / backup.ts).
       case 'proxy':
       case 'youtubePoToken':
         if (typeof value === 'string') s.set(key, encryptSecret(value))
         break
       case 'updateToken':
-        // A Gitea token has no spaces; trim before encrypting (like proxy creds).
+        // An access token has no spaces; trim before encrypting (like proxy creds).
         if (typeof value === 'string') s.set('updateToken', encryptSecret(value.trim()))
         break
     }
   }
-  return getSettings()
 }

src/main/sources.ts

@@ -2,58 +2,39 @@
  * Persistence for the media-manager index (Pinchflat-style; see
  * ROADMAP-PINCHFLAT.md). Two plain-JSON stores in userData, mirroring the
  * history.ts pattern (and the same deliberate choice to stay on JSON rather than
- * better-sqlite3 — revisit if a user indexes many large channels, see the
+ * better-sqlite3 -- revisit if a user indexes many large channels, see the
  * Phase H risk note in the roadmap):
  *
- *   sources.json      — one Source record per added channel/playlist
+ *   sources.json      -- one Source record per added channel/playlist
- *   media-items.json  — every MediaItem across all sources (queried by sourceId)
+ *   media-items.json  -- every MediaItem across all sources (queried by sourceId)
  *
  * Per-row validation on read (validation.ts) so a hand-edited or corrupted file
  * can't feed the UI malformed records (same approach as history/errorlog).
  */
 
-import { app } from 'electron'
-import { join } from 'path'
-import { readFileSync, writeFileSync, existsSync } from 'fs'
 import type { Source, MediaItem } from '@shared/ipc'
 import { isValidSource, isValidMediaItem } from './validation'
 import { mergeItemsPreservingState } from './indexerCore'
+import { createJsonStore } from './jsonStore'
+// A generous global cap (MEDIA_ITEMS_MAX, see constants.ts) so a runaway index
+// can't grow the file unbounded; large enough for several big channels. When
+// exceeded, the most-recently-written source's items are kept (they're placed
+// first by replaceMediaItems).
+import { MEDIA_ITEMS_MAX as MAX_ITEMS } from './constants'
 
-// A generous global cap so a runaway index can't grow the file unbounded; large
+// Two cached, atomically-written stores (R1–R3 via the shared jsonStore). The
-// enough for several big channels. When exceeded, the most-recently-written
+// media-items store is the hot path: setMediaItemDownloaded used to re-read and
-// source's items are kept (they're placed first by replaceMediaItems).
+// rewrite the whole (≤MAX_ITEMS) file on every completion; now reads hit the
-const MAX_ITEMS = 20000
+// cache and writes are batched. Sources are few, so that store is uncapped.
-
+const sourcesStore = createJsonStore('sources.json', isValidSource, Infinity)
-function sourcesFile(): string {
+// Compact (not pretty) -- this store can hold up to MAX_ITEMS rows; indentation
-  return join(app.getPath('userData'), 'sources.json')
+// would needlessly inflate its size and write time (R8).
-}
+const itemsStore = createJsonStore('media-items.json', isValidMediaItem, MAX_ITEMS, false)
-
-function itemsFile(): string {
-  return join(app.getPath('userData'), 'media-items.json')
-}
-
-function readJsonArray<T>(path: string, isValid: (o: unknown) => o is T): T[] {
-  try {
-    if (!existsSync(path)) return []
-    const data = JSON.parse(readFileSync(path, 'utf8'))
-    return Array.isArray(data) ? data.filter(isValid) : []
-  } catch {
-    return []
-  }
-}
-
-function writeJson(path: string, value: unknown): void {
-  try {
-    writeFileSync(path, JSON.stringify(value, null, 2))
-  } catch {
-    /* best-effort; a read-only data dir just means no persisted index */
-  }
-}
 
 // --- Sources ----------------------------------------------------------------
 
 export function listSources(): Source[] {
-  return readJsonArray(sourcesFile(), isValidSource)
+  return sourcesStore.read()
 }
 
 export function getSource(id: string): Source | undefined {
@@ -62,31 +43,25 @@ export function getSource(id: string): Source | undefined {
 
 /** Insert or replace a source by id (a re-index updates the existing record). */
 export function upsertSource(source: Source): Source[] {
-  const sources = [source, ...listSources().filter((s) => s.id !== source.id)]
+  return sourcesStore.write([source, ...listSources().filter((s) => s.id !== source.id)])
-  writeJson(sourcesFile(), sources)
-  return sources
 }
 
 /** Toggle whether a source is watched for new uploads (Phase J). Returns all sources. */
 export function setSourceWatched(id: string, watched: boolean): Source[] {
-  const sources = listSources().map((s) => (s.id === id ? { ...s, watched } : s))
+  return sourcesStore.write(listSources().map((s) => (s.id === id ? { ...s, watched } : s)))
-  writeJson(sourcesFile(), sources)
-  return sources
 }
 
 /** Remove a source and all of its media items. Returns the remaining sources. */
 export function removeSource(id: string): Source[] {
-  const sources = listSources().filter((s) => s.id !== id)
+  const sources = sourcesStore.write(listSources().filter((s) => s.id !== id))
-  writeJson(sourcesFile(), sources)
+  itemsStore.write(listAllItems().filter((m) => m.sourceId !== id))
-  const items = listAllItems().filter((m) => m.sourceId !== id)
-  writeJson(itemsFile(), items)
   return sources
 }
 
 // --- Media items ------------------------------------------------------------
 
 function listAllItems(): MediaItem[] {
-  return readJsonArray(itemsFile(), isValidMediaItem)
+  return itemsStore.read()
 }
 
 export function listMediaItems(sourceId: string): MediaItem[] {
@@ -95,12 +70,14 @@ export function listMediaItems(sourceId: string): MediaItem[] {
 
 /**
  * Replace all media items for one source with a fresh set (the result of a
- * (re)index). Other sources' items are preserved; the new items are placed first
+ * (re)index). Other sources' items are preserved in full; only the source being
- * so they survive the MAX_ITEMS cap.
+ * written here absorbs the MAX_ITEMS cap, so re-indexing one (large) source can
+ * never silently evict another source's items past the global limit (M23).
  */
 export function replaceMediaItems(sourceId: string, items: MediaItem[]): void {
   const others = listAllItems().filter((m) => m.sourceId !== sourceId)
-  writeJson(itemsFile(), [...items, ...others].slice(0, MAX_ITEMS))
+  const budget = Math.max(0, MAX_ITEMS - others.length)
+  itemsStore.write([...items.slice(0, budget), ...others])
 }
 
 /**
@@ -130,6 +107,6 @@ export function setMediaItemDownloaded(id: string, filePath?: string): MediaItem
   const updated = all.map((m) =>
     m.id === id ? { ...m, downloaded: true, downloadedAt: Date.now(), filePath } : m
   )
-  writeJson(itemsFile(), updated)
+  itemsStore.write(updated)
   return updated.filter((m) => m.sourceId === target.sourceId)
 }

src/main/sync.ts

@@ -8,6 +8,7 @@
 import { listSources, listMediaItems } from './sources'
 import { indexSource } from './indexer'
 import { parseRssVideoIds, isYouTubeFeedUrl } from './indexerCore'
+import { FEED_FETCH_TIMEOUT_MS } from './constants'
 import type { IndexProgress, MediaItem, SyncResult } from '@shared/ipc'
 
 /** Fetch a YouTube RSS feed and return its recent video ids. Throws on failure. */
@@ -16,7 +17,7 @@ async function fetchFeedIds(feedUrl: string): Promise<string[]> {
   // corrupted sources.json might carry (SSRF guard, audit T7). A throw here is
   // caught by the caller, which then falls back to a full yt-dlp re-index.
   if (!isYouTubeFeedUrl(feedUrl)) throw new Error('Refusing to fetch a non-YouTube feed URL.')
-  const res = await fetch(feedUrl, { signal: AbortSignal.timeout(15_000) })
+  const res = await fetch(feedUrl, { signal: AbortSignal.timeout(FEED_FETCH_TIMEOUT_MS) })
   if (!res.ok) throw new Error(`feed responded ${res.status}`)
   return parseRssVideoIds(await res.text())
 }

src/main/templates.ts

@@ -1,38 +1,20 @@
-import { app } from 'electron'
-import { join } from 'path'
-import { readFileSync, writeFileSync, existsSync } from 'fs'
 import type { CommandTemplate } from '@shared/ipc'
 import { isTemplateLike } from './validation'
+import { createJsonStore } from './jsonStore'
+import { TEMPLATES_MAX } from './constants'
 
-// Plain JSON in userData, same shape as history.ts.
+// Plain JSON in userData, same shape as history.ts. Atomic writes / corruption
-const MAX_TEMPLATES = 100
+// backup / caching come from the shared jsonStore (R1–R3).
-
-function templatesFile(): string {
-  return join(app.getPath('userData'), 'templates.json')
-}
-
 // A persisted template entry must at least be an object carrying an id (see
 // isTemplateLike in validation.ts); everything else is coerced by sanitize().
 // Drop anything that isn't, so a hand-edited templates.json can't inject
 // malformed entries. (audit S5)
-export function listTemplates(): CommandTemplate[] {
+const store = createJsonStore('templates.json', isTemplateLike, TEMPLATES_MAX)
-  try {
-    if (!existsSync(templatesFile())) return []
-    const data = JSON.parse(readFileSync(templatesFile(), 'utf8'))
-    // Validate shape, then normalise each surviving entry through sanitize() so
-    // name/args are always well-formed strings regardless of what was on disk.
-    return Array.isArray(data) ? data.filter(isTemplateLike).map(sanitize) : []
-  } catch {
-    return []
-  }
-}
 
-function save(templates: CommandTemplate[]): void {
+export function listTemplates(): CommandTemplate[] {
-  try {
+  // Normalise each surviving entry through sanitize() so name/args are always
-    writeFileSync(templatesFile(), JSON.stringify(templates.slice(0, MAX_TEMPLATES), null, 2))
+  // well-formed strings regardless of what was on disk.
-  } catch {
+  return store.read().map(sanitize)
-    /* best-effort; a read-only data dir just means no persisted templates */
-  }
 }
 
 function sanitize(t: CommandTemplate): CommandTemplate {
@@ -49,20 +31,14 @@ function sanitize(t: CommandTemplate): CommandTemplate {
 /** Add a new template, or update an existing one (matched by id). */
 export function saveTemplate(template: CommandTemplate): CommandTemplate[] {
   const clean = sanitize(template)
-  const templates = [clean, ...listTemplates().filter((t) => t.id !== clean.id)]
+  return store.write([clean, ...listTemplates().filter((t) => t.id !== clean.id)])
-  save(templates)
-  return templates
 }
 
 export function removeTemplate(id: string): CommandTemplate[] {
-  const templates = listTemplates().filter((t) => t.id !== id)
+  return store.write(listTemplates().filter((t) => t.id !== id))
-  save(templates)
-  return templates
 }
 
 /** Replace the entire template list (backup restore) rather than merge-by-id. */
 export function replaceTemplates(templates: CommandTemplate[]): CommandTemplate[] {
-  const clean = templates.map(sanitize)
+  return store.write(templates.map(sanitize))
-  save(clean)
-  return clean
 }

src/main/terminal.ts

@@ -14,6 +14,7 @@ import { getYtdlpPath, getBinDir, getSystem32Path } from './binaries'
 import { getSettings } from './settings'
 import { ensureManagedYtdlp } from './ytdlp'
 import { parseExtraArgs } from './buildArgs'
+import { createLineBuffer } from './lib/lineBuffer'
 import { IpcChannels, type TerminalEvent, type TerminalRunResult } from '@shared/ipc'
 
 const active = new Map<string, ChildProcess>()
@@ -47,18 +48,12 @@ export function runTerminal(wc: WebContents, id: string, argsRaw: string): Termi
   active.set(id, child)
 
   // Buffer each stream and emit on newline boundaries (flush the remainder on close).
-  const buffers: Record<'stdout' | 'stderr', string> = { stdout: '', stderr: '' }
+  const lineBufs = {
-  function feed(stream: 'stdout' | 'stderr', chunk: string): void {
+    stdout: createLineBuffer((line) => send(wc, { type: 'output', id, line, stream: 'stdout' })),
-    buffers[stream] += chunk
+    stderr: createLineBuffer((line) => send(wc, { type: 'output', id, line, stream: 'stderr' }))
-    let nl: number
-    while ((nl = buffers[stream].indexOf('\n')) >= 0) {
-      const line = buffers[stream].slice(0, nl).replace(/\r$/, '')
-      buffers[stream] = buffers[stream].slice(nl + 1)
-      send(wc, { type: 'output', id, line, stream })
   }
-  }
+  child.stdout?.on('data', (c: Buffer) => lineBufs.stdout.push(c.toString()))
-  child.stdout?.on('data', (c: Buffer) => feed('stdout', c.toString()))
+  child.stderr?.on('data', (c: Buffer) => lineBufs.stderr.push(c.toString()))
-  child.stderr?.on('data', (c: Buffer) => feed('stderr', c.toString()))
 
   let settled = false
   child.on('error', (err) => {
@@ -72,9 +67,8 @@ export function runTerminal(wc: WebContents, id: string, argsRaw: string): Termi
     settled = true
     active.delete(id)
     // Flush any trailing partial lines that never hit a newline.
-    for (const stream of ['stdout', 'stderr'] as const) {
+    lineBufs.stdout.flush()
-      if (buffers[stream]) send(wc, { type: 'output', id, line: buffers[stream], stream })
+    lineBufs.stderr.flush()
-    }
     send(wc, { type: 'done', id, code })
   })
 

src/main/tray.ts

@@ -44,7 +44,8 @@ export function createTray(getWindow: () => BrowserWindow | null): void {
   // Prefer the real app icon; fall back to the embedded glyph when no icon.ico
   // ships, so minimize-to-tray always has a tray to restore from.
   let icon = nativeImage.createFromPath(getAppIconPath())
-  if (icon.isEmpty()) icon = nativeImage.createFromDataURL(`data:image/png;base64,${FALLBACK_TRAY_PNG}`)
+  if (icon.isEmpty())
+    icon = nativeImage.createFromDataURL(`data:image/png;base64,${FALLBACK_TRAY_PNG}`)
   if (icon.isEmpty()) return
 
   tray = new Tray(icon)

src/main/updater.ts

@@ -68,9 +68,10 @@ function updateDir(): string {
  * an "upgrade" over the same shipped version.
  */
 function parseVersion(v: string): number[] {
-  return v
+  // split() always yields at least one element; `?? ''` only satisfies the type
-    .replace(/^v/i, '')
+  // checker (noUncheckedIndexedAccess) for the [0] access.
-    .split(/[-+]/)[0]
+  const core = v.replace(/^v/i, '').split(/[-+]/)[0] ?? ''
+  return core
     .split('.')
     .map((p) => parseInt(p, 10))
     .filter((n) => !Number.isNaN(n))
@@ -105,9 +106,28 @@ interface GiteaRelease {
  * output (`<hash>  file`), or PowerShell Get-FileHash (uppercase). Returns the
  * lowercase digest, or null if there's no standalone 64-char hex token (so a
  * longer run like a sha512 digest is ignored rather than sliced).
+ *
+ * When `fileName` is given (the installer asset's name), a multi-line / combined
+ * checksum file is matched line-by-line and the hash on the line naming THIS
+ * asset wins — so a `<asset>.sha256` that happens to list several files can't
+ * verify the installer against the wrong line's hash (B3). Falls back to the
+ * first standalone digest for bare single-hash files (no filename present).
  */
-export function extractSha256(text: string): string | null {
+export function extractSha256(text: string, fileName?: string): string | null {
-  const m = text.match(/\b[a-f0-9]{64}\b/i)
+  const hashRe = /\b[a-f0-9]{64}\b/i
+  if (fileName) {
+    const base = fileName.toLowerCase()
+    for (const line of text.split(/\r?\n/)) {
+      const m = line.match(hashRe)
+      if (!m) continue
+      // The filename is the last whitespace-delimited token on a sha256sum /
+      // Get-FileHash line (optionally with a '*' binary-mode marker). Match it
+      // exactly — a loose substring would let 'App.exe' match a 'MyApp.exe' line.
+      const last = (line.trim().split(/\s+/).pop() ?? '').replace(/^\*/, '')
+      if (last.toLowerCase() === base) return m[0].toLowerCase()
+    }
+  }
+  const m = text.match(hashRe)
   return m ? m[0].toLowerCase() : null
 }
 
@@ -200,7 +220,9 @@ function fetchTrustedText(
 ): Promise<{ ok: true; text: string } | { ok: false; status?: number; error: string }> {
   return new Promise((resolve) => {
     let settled = false
-    const done = (r: { ok: true; text: string } | { ok: false; status?: number; error: string }): void => {
+    const done = (
+      r: { ok: true; text: string } | { ok: false; status?: number; error: string }
+    ): void => {
       if (settled) return
       settled = true
       clearTimeout(timer)
@@ -261,7 +283,7 @@ export async function downloadAppUpdate(url: string, wc: WebContents): Promise<A
   const sum = await fetchTrustedText(checksumUrl)
   let expectedSha: string | null = null
   if (sum.ok) {
-    expectedSha = extractSha256(sum.text)
+    expectedSha = extractSha256(sum.text, safeName)
     if (!expectedSha) return { ok: false, error: "The update's checksum file is malformed." }
   } else if (sum.status === 404) {
     if (REQUIRE_CHECKSUM) {
@@ -391,9 +413,6 @@ export async function downloadAppUpdate(url: string, wc: WebContents): Promise<A
   })
 }
 
-/** Let the launched installer spawn before we quit to release our files (ms). */
-const INSTALLER_HANDOFF_MS = 1500
-
 /** Launch a freshly-downloaded installer, then quit so it can replace the app. */
 export async function runAppUpdate(filePath: string): Promise<{ ok: boolean; error?: string }> {
   try {
@@ -406,10 +425,15 @@ export async function runAppUpdate(filePath: string): Promise<{ ok: boolean; err
       return { ok: false, error: 'Refused to run an unexpected file.' }
     }
     await stat(target) // throws if the file is missing
-    const err = await shell.openPath(target) // hand the installer to the OS
+    // Hand the installer to the OS via ShellExecute, which (unlike a raw
+    // CreateProcess/spawn) honors the NSIS elevation manifest — needed if the
+    // build ever flips to perMachine. openPath resolves once the launch is
+    // initiated, so the installer process already exists when we quit.
+    const err = await shell.openPath(target)
     if (err) return { ok: false, error: err }
-    // Give the installer a beat to spawn, then quit so it can overwrite our files.
+    // Quit on the next tick so this IPC response reaches the renderer first; the
-    setTimeout(() => app.quit(), INSTALLER_HANDOFF_MS)
+    // launched installer is independent of our process and survives the quit.
+    setImmediate(() => app.quit())
     return { ok: true }
   } catch (e) {
     return { ok: false, error: e instanceof Error ? e.message : String(e) }

src/main/windowState.ts

@@ -0,0 +1,82 @@
+import { app, screen, type BrowserWindow, type Rectangle } from 'electron'
+import { join } from 'path'
+import { readFileSync, writeFileSync } from 'fs'
+import { logger } from './logger'
+
+/**
+ * Persist and restore the main window's size / position / maximized state across
+ * launches (W2 / UX19) — Windows apps are expected to reopen where you left them.
+ * Stored as one small JSON object in `<userData>/window-state.json`; a disconnected
+ * monitor is handled by a visibility check so the window can never restore off-screen.
+ */
+
+interface WindowState {
+  bounds: Rectangle
+  maximized: boolean
+}
+
+// Matches the createWindow() defaults; used on first run and when a saved position
+// is no longer on any connected display.
+const DEFAULT_SIZE = { width: 920, height: 700 }
+
+function stateFile(): string {
+  return join(app.getPath('userData'), 'window-state.json')
+}
+
+function readState(): WindowState | null {
+  try {
+    const s = JSON.parse(readFileSync(stateFile(), 'utf8')) as Partial<WindowState>
+    if (s?.bounds && typeof s.bounds.width === 'number' && typeof s.bounds.height === 'number') {
+      return { bounds: s.bounds as Rectangle, maximized: !!s.maximized }
+    }
+  } catch {
+    /* first run or corrupt — fall back to defaults */
+  }
+  return null
+}
+
+/** True when `b` overlaps the work area of some connected display (i.e. is reachable). */
+function isOnSomeDisplay(b: Rectangle): boolean {
+  return screen.getAllDisplays().some((d) => {
+    const wa = d.workArea
+    return (
+      b.x < wa.x + wa.width &&
+      b.x + b.width > wa.x &&
+      b.y < wa.y + wa.height &&
+      b.y + b.height > wa.y
+    )
+  })
+}
+
+/**
+ * The bounds + maximized flag to open the window with. Returns just a size (Electron
+ * then centers it) when there's no usable saved position — first run, or the saved
+ * monitor is gone.
+ */
+export function initialWindowState(): {
+  width: number
+  height: number
+  x?: number
+  y?: number
+  maximized: boolean
+} {
+  const saved = readState()
+  if (saved && isOnSomeDisplay(saved.bounds)) {
+    return { ...saved.bounds, maximized: saved.maximized }
+  }
+  return { ...DEFAULT_SIZE, maximized: saved?.maximized ?? false }
+}
+
+/**
+ * Persist the window's current *normal* bounds (un-maximized) + maximized flag.
+ * Best-effort; a write failure is logged, never thrown. Callers should debounce.
+ */
+export function saveWindowState(win: BrowserWindow): void {
+  if (win.isDestroyed() || win.isMinimized()) return
+  try {
+    const state: WindowState = { bounds: win.getNormalBounds(), maximized: win.isMaximized() }
+    writeFileSync(stateFile(), JSON.stringify(state))
+  } catch (e) {
+    logger.warn('failed to save window state', e)
+  }
+}

src/main/ytdlp.ts

@@ -1,7 +1,9 @@
-import { execFile } from 'child_process'
 import { existsSync, mkdirSync, copyFileSync } from 'fs'
 import { dirname } from 'path'
-import { getYtdlpPath, getBundledYtdlpPath } from './binaries'
+import { getYtdlpPath, getBundledYtdlpPath, YTDLP_MISSING_MSG } from './binaries'
+import { execFileAsync } from './lib/exec'
+import { cleanError } from './log'
+import { VERSION_TIMEOUT_MS, YTDLP_UPDATE_TIMEOUT_MS } from './constants'
 import { getSettings, setSettings } from './settings'
 import { shouldAutoCheckYtdlp } from './ytdlpPolicy'
 import {
@@ -32,32 +34,24 @@ export function ensureManagedYtdlp(): void {
   }
 }
 
-/**
+/** Spawn the bundled yt-dlp and read back its `--version` for the Settings panel. */
- * Step-1 spike: spawn the bundled yt-dlp and read back `--version`.
+export async function getYtdlpVersion(): Promise<YtdlpVersionResult> {
- * Proves the main-process → bundled-binary → IPC path end to end.
- */
-export function getYtdlpVersion(): Promise<YtdlpVersionResult> {
   const ytdlpPath = getYtdlpPath()
 
   if (!existsSync(ytdlpPath)) {
-    return Promise.resolve({
+    return { ok: false, error: YTDLP_MISSING_MSG }
-      ok: false,
-      error: `yt-dlp.exe not found at ${ytdlpPath}\nDownload it into resources/bin/ (see the README there).`
-    })
   }
 
-  return new Promise((resolve) => {
+  const r = await execFileAsync(ytdlpPath, ['--version'], { timeout: VERSION_TIMEOUT_MS })
-    execFile(ytdlpPath, ['--version'], { windowsHide: true, timeout: 15_000 }, (err, stdout, stderr) => {
+  if (!r.ok) {
-      if (err) {
+    // Run stderr through the shared cleaner so yt-dlp's noisy output collapses to
-        const msg = (err as { killed?: boolean }).killed
+    // its trailing error line, consistent with download/probe/indexer (CC6).
+    const msg = r.timedOut
       ? 'Timed out running yt-dlp.'
-          : (stderr || err.message).trim()
+      : cleanError(r.stderr) || r.error?.message || ''
-        resolve({ ok: false, error: msg })
+    return { ok: false, error: msg }
-        return
   }
-      resolve({ ok: true, version: stdout.trim() })
+  return { ok: true, version: r.stdout.trim() }
-    })
-  })
 }
 
 /**
@@ -66,13 +60,13 @@ export function getYtdlpVersion(): Promise<YtdlpVersionResult> {
  * yt-dlp.exe lives in, which holds for both the dev resources/bin checkout and
  * a per-user install; it would fail under a locked-down system install.
  */
-export function updateYtdlp(channel: YtdlpUpdateChannel): Promise<YtdlpUpdateResult> {
+export async function updateYtdlp(channel: YtdlpUpdateChannel): Promise<YtdlpUpdateResult> {
   // Validate against the channel allowlist BEFORE the value reaches `--update-to`.
   // That flag also accepts `OWNER/REPO@TAG`, which would download and install an
   // arbitrary binary over yt-dlp.exe — so an unrecognised value (e.g. forged by a
   // compromised renderer over IPC) must never be forwarded. (audit F1)
   if (!isYtdlpUpdateChannel(channel)) {
-    return Promise.resolve({ ok: false, error: 'Unsupported update channel.' })
+    return { ok: false, error: 'Unsupported update channel.' }
   }
 
   // Self-heal: restore the managed copy from the bundled seed before updating, so
@@ -81,29 +75,19 @@ export function updateYtdlp(channel: YtdlpUpdateChannel): Promise<YtdlpUpdateRes
   const ytdlpPath = getYtdlpPath()
 
   if (!existsSync(ytdlpPath)) {
-    return Promise.resolve({
+    return { ok: false, error: YTDLP_MISSING_MSG }
-      ok: false,
-      error: `yt-dlp.exe not found at ${ytdlpPath}\nDownload it into resources/bin/ (see the README there).`
-    })
   }
 
-  return new Promise((resolve) => {
+  const r = await execFileAsync(ytdlpPath, ['--update-to', channel], {
-    execFile(
+    timeout: YTDLP_UPDATE_TIMEOUT_MS
-      ytdlpPath,
-      ['--update-to', channel],
-      { windowsHide: true, timeout: 60_000 },
-      (err, stdout, stderr) => {
-        if (err) {
-          const msg = (err as { killed?: boolean }).killed
-            ? 'Timed out updating yt-dlp.'
-            : (stderr || err.message).trim()
-          resolve({ ok: false, error: msg })
-          return
-        }
-        resolve({ ok: true, output: stdout.trim() })
-      }
-    )
   })
+  if (!r.ok) {
+    const msg = r.timedOut
+      ? 'Timed out updating yt-dlp.'
+      : cleanError(r.stderr) || r.error?.message || ''
+    return { ok: false, error: msg }
+  }
+  return { ok: true, output: r.stdout.trim() }
 }
 
 /**

src/main/ytdlpPolicy.ts

@@ -21,5 +21,10 @@ export function shouldAutoCheckYtdlp(
 ): boolean {
   if (!enabled) return false
   if (!lastCheck) return true
+  // A backward system-clock correction can leave `lastCheck` in the "future"
+  // relative to `now`, making `now - lastCheck` negative so the daily check would
+  // never come due again. Treat a future timestamp as skewed/bogus and run the
+  // check rather than waiting out a negative interval (R9).
+  if (lastCheck > now) return true
   return now - lastCheck >= intervalMs
 }

src/preload/index.ts

@@ -31,7 +31,8 @@ import {
   type ScheduledSyncStatus,
   type TerminalEvent,
   type TerminalRunResult,
-  type TaskbarProgress
+  type TaskbarProgress,
+  type PersistedQueueItem
 } from '@shared/ipc'
 
 // The surface exposed to the renderer. Keep this thin: it only forwards to IPC.
@@ -57,8 +58,7 @@ const api = {
     return () => ipcRenderer.removeListener(IpcChannels.appUpdateProgress, listener)
   },
 
-  getYtdlpVersion: (): Promise<YtdlpVersionResult> =>
+  getYtdlpVersion: (): Promise<YtdlpVersionResult> => ipcRenderer.invoke(IpcChannels.ytdlpVersion),
-    ipcRenderer.invoke(IpcChannels.ytdlpVersion),
 
   /** Versions of the bundled ffmpeg + ffprobe (display-only; not auto-updated). */
   getFfmpegVersions: (): Promise<FfmpegVersionResult> =>
@@ -69,23 +69,26 @@ const api = {
   startDownload: (opts: StartDownloadOptions): Promise<StartDownloadResult> =>
     ipcRenderer.invoke(IpcChannels.downloadStart, opts),
 
-  cancelDownload: (id: string): Promise<void> =>
+  cancelDownload: (id: string): Promise<void> => ipcRenderer.invoke(IpcChannels.downloadCancel, id),
-    ipcRenderer.invoke(IpcChannels.downloadCancel, id),
 
-  pauseDownload: (id: string): Promise<void> =>
+  pauseDownload: (id: string): Promise<void> => ipcRenderer.invoke(IpcChannels.downloadPause, id),
-    ipcRenderer.invoke(IpcChannels.downloadPause, id),
 
-  getDefaultFolder: (): Promise<string> => ipcRenderer.invoke(IpcChannels.defaultFolder),
+  chooseFolder: (current?: string): Promise<string | null> =>
-
+    ipcRenderer.invoke(IpcChannels.chooseFolder, current),
-  chooseFolder: (): Promise<string | null> => ipcRenderer.invoke(IpcChannels.chooseFolder),
 
   openPath: (path: string): Promise<string> => ipcRenderer.invoke(IpcChannels.openPath, path),
 
-  showInFolder: (path: string): Promise<void> =>
+  openUrl: (url: string): Promise<void> => ipcRenderer.invoke(IpcChannels.openUrl, url),
+
+  showInFolder: (path: string): Promise<string> =>
     ipcRenderer.invoke(IpcChannels.showInFolder, path),
 
   readClipboard: (): Promise<string> => ipcRenderer.invoke(IpcChannels.clipboardRead),
 
+  /** Forward a renderer-side failure to the main diagnostic log (CC8). Fire-and-forget. */
+  logError: (op: string, detail: string): void =>
+    ipcRenderer.send(IpcChannels.logWrite, op, detail),
+
   getSettings: (): Promise<Settings> => ipcRenderer.invoke(IpcChannels.settingsGet),
 
   setSettings: (partial: Partial<Settings>): Promise<Settings> =>
@@ -138,6 +141,13 @@ const api = {
 
   clearErrorLog: (): Promise<ErrorLogEntry[]> => ipcRenderer.invoke(IpcChannels.errorLogClear),
 
+  /** Load the persisted download queue on launch (M4). */
+  listQueue: (): Promise<PersistedQueueItem[]> => ipcRenderer.invoke(IpcChannels.queueList),
+
+  /** Mirror the renderer's durable queue items to disk so they survive a quit (M4). */
+  saveQueue: (items: PersistedQueueItem[]): Promise<void> =>
+    ipcRenderer.invoke(IpcChannels.queueSave, items),
+
   /** Opens a save dialog and writes settings + templates to the chosen JSON file. */
   exportBackup: (): Promise<BackupExportResult> => ipcRenderer.invoke(IpcChannels.backupExport),
 
@@ -184,22 +194,23 @@ const api = {
   reindexSource: (id: string): Promise<IndexSourceResult> =>
     ipcRenderer.invoke(IpcChannels.sourceReindex, id),
 
-  removeSource: (id: string): Promise<Source[]> =>
+  removeSource: (id: string): Promise<Source[]> => ipcRenderer.invoke(IpcChannels.sourceRemove, id),
-    ipcRenderer.invoke(IpcChannels.sourceRemove, id),
 
   listSourceItems: (sourceId: string): Promise<MediaItem[]> =>
     ipcRenderer.invoke(IpcChannels.sourceItems, sourceId),
 
-  /** Persist that a media item has finished downloading (drives incremental sync). */
+  /** Persist that a media item has finished downloading (drives incremental sync).
-  markSourceItemDownloaded: (id: string, filePath?: string): Promise<MediaItem[]> =>
+   *  Named to match the main handler `setMediaItemDownloaded` (L92). */
+  setMediaItemDownloaded: (id: string, filePath?: string): Promise<MediaItem[]> =>
     ipcRenderer.invoke(IpcChannels.sourceItemDownloaded, id, filePath),
 
   /** Toggle whether a source is watched for new uploads. */
   setSourceWatched: (id: string, watched: boolean): Promise<Source[]> =>
     ipcRenderer.invoke(IpcChannels.sourceSetWatched, id, watched),
 
-  /** Re-index all watched sources; resolves with the videos found new. */
+  /** Re-index all watched sources; resolves with the videos found new. Named to
-  syncSources: (): Promise<SyncResult> => ipcRenderer.invoke(IpcChannels.sourcesSync),
+   *  match the main function `syncWatchedSources` (L92). */
+  syncWatchedSources: (): Promise<SyncResult> => ipcRenderer.invoke(IpcChannels.sourcesSync),
 
   /** Read / write the Windows daily-sync scheduled task. */
   getScheduledSync: (): Promise<ScheduledSyncStatus> =>
@@ -220,8 +231,7 @@ const api = {
   runTerminal: (id: string, args: string): Promise<TerminalRunResult> =>
     ipcRenderer.invoke(IpcChannels.terminalRun, id, args),
 
-  cancelTerminal: (id: string): Promise<void> =>
+  cancelTerminal: (id: string): Promise<void> => ipcRenderer.invoke(IpcChannels.terminalCancel, id),
-    ipcRenderer.invoke(IpcChannels.terminalCancel, id),
 
   /** Subscribe to live terminal output. Returns an unsubscribe function. */
   onTerminalOutput: (cb: (ev: TerminalEvent) => void): (() => void) => {
@@ -230,9 +240,13 @@ const api = {
     return () => ipcRenderer.removeListener(IpcChannels.terminalOutput, listener)
   },
 
-  /** Reflect overall queue progress on the Windows taskbar (fire-and-forget). */
+  /** Reflect overall queue progress on the Windows taskbar. */
-  setTaskbarProgress: (p: TaskbarProgress): void =>
+  setTaskbarProgress: (p: TaskbarProgress): Promise<void> =>
-    ipcRenderer.send(IpcChannels.taskbarProgress, p)
+    ipcRenderer.invoke(IpcChannels.taskbarProgress, p),
+
+  /** Open a YouTube WebView to automatically extract a PO token (Phase P). */
+  mintPoToken: (): Promise<string | null> =>
+    ipcRenderer.invoke(IpcChannels.youtubePoTokenMint) as Promise<string | null>
 }
 
 export type Api = typeof api
@@ -248,11 +262,19 @@ if (process.contextIsolated) {
     contextBridge.exposeInMainWorld('electron', electron)
     contextBridge.exposeInMainWorld('api', api)
   } catch (error) {
-    console.error(error)
+    // M30: a broken bridge causes the renderer to silently run in preview/mock mode.
+    // Notify the main process so it can show a hard error dialog — without this the
+    // failure is completely invisible to the user.
+    console.error('[AeroFetch preload] contextBridge failed:', error)
+    try {
+      ipcRenderer.send(IpcChannels.preloadBridgeFailure, String(error))
+    } catch {
+      /* if IPC itself is broken there is nothing more we can do */
+    }
   }
 } else {
-  // @ts-ignore (defined in index.d.ts)
+  // @ts-ignore window.electron is declared in index.d.ts
   window.electron = electron
-  // @ts-ignore (defined in index.d.ts)
+  // @ts-ignore window.api is declared in index.d.ts
   window.api = api
 }

src/renderer/src/App.tsx

@@ -1,18 +1,47 @@
-import { useState, useEffect } from 'react'
+import { useState, useEffect, useMemo, useRef, lazy, Suspense } from 'react'
 import { FluentProvider, makeStyles, tokens } from '@fluentui/react-components'
-import { Sidebar, type TabValue } from './components/Sidebar'
+import { Sidebar } from './components/Sidebar'
 import { DownloadsView } from './components/DownloadsView'
-import { LibraryView } from './components/LibraryView'
-import { HistoryView } from './components/HistoryView'
-import { TerminalView } from './components/TerminalView'
-import { SettingsView } from './components/SettingsView'
 import { Onboarding } from './components/Onboarding'
 import { CommandPalette, type PaletteAction } from './components/CommandPalette'
+import { LiveRegion } from './components/LiveRegion'
+import { Toaster } from './components/ui/Toaster'
 import { getTheme, pageBackground } from './theme'
+import { SPACE } from './components/ui/tokens'
 import { useSettings } from './store/settings'
+import { useNav } from './store/nav'
 import { useDownloads } from './store/downloads'
-import { summarizeQueue } from './store/queueStats'
+// Eagerly load the sources store for its startup side-effects (load persisted
+// sources + the watched-source / scheduled `--sync` kickoff) and its cross-store
+// subscription (coordinator's downloadCompleted → markDownloaded). Before C2 this
+// was guaranteed by downloads.ts importing it; now that the cycle is broken, App
+// owns the eager load so it survives the views becoming lazy-loaded (PERF8).
+import './store/sources'
+import { queueSummaryOf } from './store/queueStats'
 import { useResolvedDark } from './store/systemTheme'
+import { logError } from './reportError'
+
+// Code-split the non-default tabs (PERF8): Downloads is the launch tab and stays
+// eager, but Library/History/Terminal/Settings load their chunks on first visit so
+// they (and their slice of Fluent) aren't in the initial bundle. The stores these
+// views use are imported eagerly above (`useDownloads` + `./store/sources`, and
+// downloads → history), so lazy-loading the *view* never delays store startup.
+const LibraryView = lazy(() =>
+  import('./components/LibraryView').then((m) => ({ default: m.LibraryView }))
+)
+const HistoryView = lazy(() =>
+  import('./components/HistoryView').then((m) => ({ default: m.HistoryView }))
+)
+const TerminalView = lazy(() =>
+  import('./components/TerminalView').then((m) => ({ default: m.TerminalView }))
+)
+const SettingsView = lazy(() =>
+  import('./components/SettingsView').then((m) => ({ default: m.SettingsView }))
+)
+
+// How often to check whether a scheduled ('saved' + due) download should promote
+// to the queue. 15s is plenty for the minute-granularity times the picker offers.
+const SCHEDULE_TICK_MS = 15_000
 
 const useStyles = makeStyles({
   provider: {
@@ -27,7 +56,8 @@ const useStyles = makeStyles({
     flexGrow: 1,
     minWidth: 0,
     overflowY: 'auto',
-    padding: '24px 28px'
+    // Symmetric page padding (UI4): the old 28px horizontal appeared nowhere else.
+    padding: SPACE.page
   }
 })
 
@@ -36,16 +66,30 @@ function App(): React.JSX.Element {
   const theme = useSettings((s) => s.theme)
   const accentColor = useSettings((s) => s.accentColor)
   const updateSettings = useSettings((s) => s.update)
+  const showTerminal = useSettings((s) => s.customCommandEnabled)
   const isDark = useResolvedDark()
-  const [tab, setTab] = useState<TabValue>('downloads')
+  const tab = useNav((s) => s.tab)
+  const setTab = useNav((s) => s.setTab)
+  // Active-download count for the sidebar Downloads badge (UX9/UI25), so a run in
+  // progress is visible from any tab. A number selector only re-renders when the
+  // count actually changes -- not on every progress tick.
+  const activeCount = useDownloads(
+    (s) => s.items.filter((i) => i.status === 'downloading' || i.status === 'queued').length
+  )
   const [paletteOpen, setPaletteOpen] = useState(false)
+  // Track the element that was focused before the palette opened so we can restore it on close.
+  const prePaletteRef = useRef<Element | null>(null)
 
-  // Ctrl/Cmd+K toggles the command palette.
+  // Ctrl+K: command palette. Ctrl+,: Settings. (W8/W9)
   useEffect(() => {
     function onKey(e: KeyboardEvent): void {
       if ((e.ctrlKey || e.metaKey) && (e.key === 'k' || e.key === 'K')) {
         e.preventDefault()
+        prePaletteRef.current = document.activeElement
         setPaletteOpen((o) => !o)
+      } else if (e.ctrlKey && e.key === ',') {
+        e.preventDefault()
+        setTab('settings')
       }
     }
     window.addEventListener('keydown', onKey)
@@ -54,30 +98,101 @@ function App(): React.JSX.Element {
 
   // Mirror overall queue progress onto the Windows taskbar. Subscribe to the store
   // directly (not via a selector) so taskbar updates don't re-render the app.
+  // Compare against the last IPC call and skip when nothing changed -- the store
+  // fires on every progress tick and this avoids one IPC roundtrip per tick (L25).
   useEffect(() => {
+    let lastFraction = -1
+    let lastMode = ''
+    let lastBadge = -1
     function push(items: ReturnType<typeof useDownloads.getState>['items']): void {
-      const s = summarizeQueue(items)
+      const s = queueSummaryOf(items)
       const mode = s.active ? (s.failed > 0 ? 'error' : 'normal') : 'none'
-      window.api?.setTaskbarProgress?.({ fraction: s.progress, mode })
+      if (s.progress === lastFraction && mode === lastMode && s.downloading === lastBadge) return
+      lastFraction = s.progress
+      lastMode = mode
+      lastBadge = s.downloading
+      void window.api?.setTaskbarProgress?.({
+        fraction: s.progress,
+        mode,
+        badgeCount: s.downloading
+      })
     }
     push(useDownloads.getState().items)
     return useDownloads.subscribe((st) => push(st.items))
   }, [])
 
-  const paletteActions: PaletteAction[] = [
+  // Rehydrate the persisted download queue on launch (M4) so saved/scheduled and
-    { id: 'go-downloads', label: 'Go to Downloads', hint: 'Navigate', run: () => setTab('downloads') },
+  // other pending items return from the previous session.
+  useEffect(() => {
+    useDownloads.getState().hydrate()
+  }, [])
+
+  // UX16: focus the URL field on launch so the user can paste + type immediately
+  // (Downloads is the default tab). Double-rAF waits for paint + the DownloadBar to
+  // register its focuser (L118), matching the command palette's "New download" focus.
+  useEffect(() => {
+    if (useNav.getState().tab !== 'downloads') return
+    requestAnimationFrame(() => requestAnimationFrame(() => useNav.getState().focusUrlField()))
+  }, [])
+
+  // Promote scheduled ('saved' + a due scheduledFor) items when their time arrives.
+  // The queue is persisted (M4), so a scheduled item survives a quit and fires on the
+  // next launch once its time has passed. A 15s tick is plenty for minute-granularity
+  // times. Lives here (not at the downloads store's module load) so importing the store
+  // in tests/preview doesn't start a stray timer, and the interval is cleared cleanly
+  // on unmount (L1).
+  useEffect(() => {
+    const tick = setInterval(() => {
+      const st = useDownloads.getState()
+      const now = Date.now()
+      if (
+        st.items.some(
+          (i) => i.status === 'saved' && i.scheduledFor != null && i.scheduledFor <= now
+        )
+      ) {
+        st.promoteDueScheduled()
+      }
+    }, SCHEDULE_TICK_MS)
+    return () => clearInterval(tick)
+  }, [])
+
+  // Memoized so CommandPalette sees a stable array reference between renders --
+  // only rebuilds when the theme label needs to change (L32).
+  const paletteActions = useMemo<PaletteAction[]>(
+    () => [
+      {
+        id: 'go-downloads',
+        label: 'Go to Downloads',
+        hint: 'Navigate',
+        run: () => setTab('downloads')
+      },
       { id: 'go-library', label: 'Go to Library', hint: 'Navigate', run: () => setTab('library') },
       { id: 'go-history', label: 'Go to History', hint: 'Navigate', run: () => setTab('history') },
-    { id: 'go-terminal', label: 'Go to Terminal', hint: 'Navigate', run: () => setTab('terminal') },
+      {
-    { id: 'go-settings', label: 'Go to Settings', hint: 'Navigate', run: () => setTab('settings') },
+        id: 'go-terminal',
+        label: 'Go to Terminal',
+        hint: 'Navigate',
+        run: () => setTab('terminal')
+      },
+      {
+        id: 'go-settings',
+        label: 'Go to Settings',
+        // Surface the real shortcut here so the palette doubles as shortcut
+        // discovery (UX21).
+        hint: 'Ctrl ,',
+        run: () => setTab('settings')
+      },
       {
         id: 'new-download',
         label: 'New download',
         hint: 'Focus URL',
         run: () => {
           setTab('downloads')
-        // Wait for the download bar to mount after the tab switch, then focus.
+          // Double-rAF waits for React's re-render + paint (so the DownloadBar has
-        setTimeout(() => document.getElementById('aerofetch-url')?.focus(), 60)
+          // mounted and registered its focuser) before requesting focus (L118).
+          requestAnimationFrame(() =>
+            requestAnimationFrame(() => useNav.getState().focusUrlField())
+          )
         }
       },
       {
@@ -86,24 +201,19 @@ function App(): React.JSX.Element {
         hint: 'Appearance',
         run: () => updateSettings({ theme: isDark ? 'light' : 'dark' })
       }
-  ]
+    ],
+    [isDark, setTab, updateSettings]
+  )
 
   // AeroFetch's own version, shown in the sidebar. Loaded once over IPC.
   const [version, setVersion] = useState('')
   useEffect(() => {
-    window.api?.getAppVersion?.().then(setVersion).catch(() => {})
+    window.api?.getAppVersion?.().then(setVersion).catch(logError('getAppVersion'))
   }, [])
 
-  // Sidebar collapse, persisted across launches in localStorage.
+  const collapsed = useSettings((s) => s.sidebarCollapsed)
-  const [collapsed, setCollapsed] = useState(
-    () => localStorage.getItem('aerofetch.sidebarCollapsed') === '1'
-  )
   function toggleCollapsed(): void {
-    setCollapsed((c) => {
+    updateSettings({ sidebarCollapsed: !collapsed })
-      const next = !c
-      localStorage.setItem('aerofetch.sidebarCollapsed', next ? '1' : '0')
-      return next
-    })
   }
   // Gate on `loaded` so a returning user's real settings never get clobbered
   // by a one-frame flash of the (default-false) onboarding state.
@@ -136,21 +246,34 @@ function App(): React.JSX.Element {
               version={version}
               collapsed={collapsed}
               onToggleCollapsed={toggleCollapsed}
+              showTerminal={showTerminal}
+              downloadCount={activeCount}
             />
 
             <main className={styles.content}>
               {tab === 'downloads' && <DownloadsView />}
+              <Suspense fallback={null}>
                 {tab === 'library' && <LibraryView />}
                 {tab === 'history' && <HistoryView />}
                 {tab === 'terminal' && <TerminalView />}
                 {tab === 'settings' && <SettingsView />}
+              </Suspense>
             </main>
 
             {paletteOpen && (
-              <CommandPalette actions={paletteActions} onClose={() => setPaletteOpen(false)} />
+              <CommandPalette
+                actions={paletteActions}
+                onClose={() => {
+                  setPaletteOpen(false)
+                  const el = prePaletteRef.current
+                  if (el instanceof HTMLElement) requestAnimationFrame(() => el.focus())
+                }}
+              />
             )}
           </>
         )}
+        <LiveRegion />
+        <Toaster />
       </div>
     </FluentProvider>
   )

src/renderer/src/assets/base.css

@@ -1,11 +1,57 @@
+*,
+*::before,
+*::after {
+  box-sizing: border-box;
+}
+
+:focus-visible {
+  outline: 2px solid var(--colorBrandStroke1, #0078d4);
+  outline-offset: 2px;
+}
+
+/*
+ * Zero the UA heading margin (UI33). Titles are rendered as real headings
+ * (h1/h2) for Narrator heading-navigation, but they carry Fluent's typography
+ * classes for their visual ramp (font size/weight/line-height); those classes
+ * out-specify this element selector, so only the browser's default heading
+ * margin needs removing to keep the layout identical to the former span titles.
+ */
+h1,
+h2,
+h3,
+h4,
+h5,
+h6 {
+  margin: 0;
+}
+
 html,
 body {
   margin: 0;
   padding: 0;
   height: 100%;
   overflow: hidden;
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
 }
 
 #root {
   height: 100vh;
 }
+
+/*
+ * One motion policy (UI26): honor the OS "reduce motion" preference everywhere.
+ * The app's transitions are subtle (see MOTION in components/ui/tokens.ts), but a
+ * user who asks for less motion gets none — this near-instant override covers any
+ * current or future transition/animation without each component opting in.
+ */
+@media (prefers-reduced-motion: reduce) {
+  *,
+  *::before,
+  *::after {
+    transition-duration: 0.01ms !important;
+    animation-duration: 0.01ms !important;
+    animation-iteration-count: 1 !important;
+    scroll-behavior: auto !important;
+  }
+}

src/renderer/src/components/CommandPalette.tsx

@@ -1,5 +1,7 @@
 import { useEffect, useRef, useState } from 'react'
 import { makeStyles, mergeClasses, tokens, shorthands } from '@fluentui/react-components'
+import { useFocusStyles } from './ui/focusRing'
+import { Z, SCRIM, ELEVATION, RADIUS } from './ui/tokens'
 
 export interface PaletteAction {
   id: string
@@ -10,32 +12,31 @@ export interface PaletteAction {
 }
 
 const useStyles = makeStyles({
-  // A plain fixed overlay — NOT a Fluent Dialog, since this app avoids Fluent's
+  // A plain fixed overlay -- NOT a Fluent Dialog, since this app avoids Fluent's
   // portal-based overlays (GPU/driver blank-overlay issue, see Select.tsx).
   backdrop: {
     position: 'fixed',
     inset: 0,
-    zIndex: 1000,
+    zIndex: Z.overlay,
     display: 'flex',
     justifyContent: 'center',
     alignItems: 'flex-start',
     paddingTop: '14vh',
-    backgroundColor: 'rgba(0,0,0,0.32)'
+    backgroundColor: SCRIM
   },
   panel: {
     width: 'min(560px, 92vw)',
     display: 'flex',
     flexDirection: 'column',
     backgroundColor: tokens.colorNeutralBackground1,
-    ...shorthands.borderRadius(tokens.borderRadiusXLarge),
+    ...shorthands.borderRadius(RADIUS.card),
     border: `1px solid ${tokens.colorNeutralStroke2}`,
-    boxShadow: tokens.shadow28,
+    boxShadow: ELEVATION.overlay,
     overflow: 'hidden'
   },
   input: {
     appearance: 'none',
     border: 'none',
-    outline: 'none',
     padding: '14px 16px',
     fontSize: tokens.fontSizeBase400,
     fontFamily: tokens.fontFamilyBase,
@@ -91,11 +92,16 @@ export function CommandPalette({
   onClose: () => void
 }): React.JSX.Element {
   const styles = useStyles()
+  const focus = useFocusStyles()
   const [q, setQ] = useState('')
   const [sel, setSel] = useState(0)
   const inputRef = useRef<HTMLInputElement>(null)
+  const listRef = useRef<HTMLDivElement>(null)
 
   const filtered = actions.filter((a) => a.label.toLowerCase().includes(q.trim().toLowerCase()))
+  const listId = 'cmdpalette-list'
+  const optionId = (id: string): string => `cmdpalette-option-${id}`
+  const activeId = filtered[sel] ? optionId(filtered[sel].id) : undefined
 
   useEffect(() => {
     inputRef.current?.focus()
@@ -103,6 +109,10 @@ export function CommandPalette({
   useEffect(() => {
     setSel(0)
   }, [q])
+  useEffect(() => {
+    const row = listRef.current?.querySelector<HTMLElement>(`[data-sel="true"]`)
+    row?.scrollIntoView({ block: 'nearest' })
+  }, [sel])
 
   function onKeyDown(e: React.KeyboardEvent): void {
     if (e.key === 'Escape') {
@@ -133,21 +143,33 @@ export function CommandPalette({
       >
         <input
           ref={inputRef}
-          className={styles.input}
+          className={mergeClasses(styles.input, focus.focusRing)}
           value={q}
           onChange={(e) => setQ(e.target.value)}
           onKeyDown={onKeyDown}
           placeholder="Type a command…"
+          role="combobox"
+          aria-expanded={filtered.length > 0}
+          aria-controls={listId}
+          aria-activedescendant={activeId}
+          aria-autocomplete="list"
           aria-label="Command palette search"
         />
-        <div className={styles.list}>
+        <div className={styles.list} ref={listRef} id={listId} role="listbox" aria-label="Commands">
           {filtered.length === 0 ? (
             <div className={styles.empty}>No matching commands</div>
           ) : (
             filtered.map((a, i) => (
-              <button
+              // A non-focusable option: focus stays on the combobox input and the
+              // active row is announced via aria-activedescendant (UI27), the
+              // standard combobox+listbox pattern. onMouseEnter keeps the pointer
+              // and keyboard highlight unified on one `sel` state.
+              <div
                 key={a.id}
-                type="button"
+                id={optionId(a.id)}
+                role="option"
+                aria-selected={i === sel}
+                data-sel={i === sel ? 'true' : undefined}
                 className={mergeClasses(styles.item, i === sel && styles.itemActive)}
                 onClick={() => {
                   a.run()
@@ -157,7 +179,7 @@ export function CommandPalette({
               >
                 <span>{a.label}</span>
                 {a.hint && <span className={styles.itemHint}>{a.hint}</span>}
-              </button>
+              </div>
             ))
           )}
         </div>

src/renderer/src/components/DownloadOptionsForm.tsx

@@ -1,4 +1,4 @@
-import {
+import {
   Field,
   Input,
   Switch,
@@ -83,6 +83,8 @@ const useStyles = makeStyles({
 interface Props {
   value: DownloadOptions
   onChange: (next: DownloadOptions) => void
+  /** When provided, hides controls that don't apply to this media kind. */
+  kind?: 'video' | 'audio'
 }
 
 /**
@@ -90,7 +92,7 @@ interface Props {
  * Used both for the persisted defaults (Settings) and for a per-download
  * override (the download bar), so the two never drift apart.
  */
-export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Element {
+export function DownloadOptionsForm({ value, onChange, kind }: Props): React.JSX.Element {
   const styles = useStyles()
 
   function setOpt<K extends keyof DownloadOptions>(key: K, v: DownloadOptions[K]): void {
@@ -107,35 +109,47 @@ export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Eleme
   return (
     <div className={styles.root}>
       <div className={styles.grid}>
+        {kind !== 'video' && (
           <Field label="Audio format" hint="For audio-only downloads.">
             <Select
-            aria-label="Audio format"
               value={value.audioFormat}
               options={AUDIO_FORMATS.map((f) => ({ value: f, label: AUDIO_FORMAT_LABELS[f] }))}
               onChange={(v) => setOpt('audioFormat', v as AudioFormat)}
             />
           </Field>
-        <Field label="Video container" hint="Container for merged video.">
+        )}
+        {kind !== 'audio' && (
+          <Field
+            label="Video container"
+            hint="The file format used when video and audio are combined into one file."
+          >
             <Select
-            aria-label="Video container"
               value={value.videoContainer}
-            options={VIDEO_CONTAINERS.map((c) => ({ value: c, label: VIDEO_CONTAINER_LABELS[c] }))}
+              options={VIDEO_CONTAINERS.map((c) => ({
+                value: c,
+                label: VIDEO_CONTAINER_LABELS[c]
+              }))}
               onChange={(v) => setOpt('videoContainer', v as VideoContainer)}
             />
           </Field>
-        <Field label="Preferred codec" hint="Tiebreaker, not a hard filter.">
+        )}
+        {kind !== 'audio' && (
+          <Field
+            label="Preferred codec"
+            hint="A preference when several formats match -- not a strict filter."
+          >
             <Select
-            aria-label="Preferred video codec"
               value={value.preferredVideoCodec}
               options={VIDEO_CODECS.map((c) => ({ value: c, label: VIDEO_CODEC_LABELS[c] }))}
               onChange={(v) => setOpt('preferredVideoCodec', v as VideoCodecPref)}
             />
           </Field>
+        )}
       </div>
 
       <Field
         label="Format sorting (advanced)"
-        hint="Raw yt-dlp -S string to rank formats by priority, e.g. res:1080,vcodec:av01,size. Overrides the preferred-codec tiebreaker. Leave empty unless you know yt-dlp's -S syntax."
+        hint="Custom expression to rank available formats, e.g. res:1080,vcodec:av01,size. Leave blank to use the Preferred codec setting above. See yt-dlp docs for the full syntax."
       >
         <Input
           value={value.formatSort}
@@ -144,11 +158,10 @@ export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Eleme
         />
       </Field>
 
-      <Field label="Embed subtitles" hint="Download subtitles and mux them into the video.">
+      <Field label="Embed subtitles" hint="Download subtitles and embed them in the video file.">
         <Switch
           checked={value.embedSubtitles}
           onChange={(_, d) => setOpt('embedSubtitles', d.checked)}
-          label={value.embedSubtitles ? 'On' : 'Off'}
         />
       </Field>
       {value.embedSubtitles && (
@@ -177,14 +190,12 @@ export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Eleme
         <Switch
           checked={value.sponsorBlock}
           onChange={(_, d) => setOpt('sponsorBlock', d.checked)}
-          label={value.sponsorBlock ? 'On' : 'Off'}
         />
       </Field>
       {value.sponsorBlock && (
         <div className={styles.subGroup}>
           <Field label="Action">
             <Select
-              aria-label="SponsorBlock action"
               value={value.sponsorBlockMode}
               options={[
                 { value: 'remove', label: 'Remove segments (cut from file)' },
@@ -193,7 +204,15 @@ export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Eleme
               onChange={(v) => setOpt('sponsorBlockMode', v as SponsorBlockMode)}
             />
           </Field>
-          <Field label="Categories">
+          <Field
+            label="Categories"
+            validationState={value.sponsorBlockCategories.length === 0 ? 'warning' : 'none'}
+            validationMessage={
+              value.sponsorBlockCategories.length === 0
+                ? 'No categories selected -- no segments will be skipped.'
+                : undefined
+            }
+          >
             <div className={styles.categoryGrid}>
               {SPONSORBLOCK_CATEGORIES.map((cat) => (
                 <Checkbox
@@ -208,11 +227,13 @@ export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Eleme
         </div>
       )}
 
-      <Field label="Embed chapters">
+      <Field
+        label="Embed chapters"
+        hint="Write chapter markers into the file. Only useful if the video has chapters."
+      >
         <Switch
           checked={value.embedChapters}
           onChange={(_, d) => setOpt('embedChapters', d.checked)}
-          label={value.embedChapters ? 'On' : 'Off'}
         />
       </Field>
       <Field
@@ -222,21 +243,40 @@ export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Eleme
         <Switch
           checked={value.splitChapters}
           onChange={(_, d) => setOpt('splitChapters', d.checked)}
-          label={value.splitChapters ? 'On' : 'Off'}
         />
       </Field>
       <Field label="Embed metadata" hint="Title, artist, date and similar tags.">
         <Switch
           checked={value.embedMetadata}
           onChange={(_, d) => setOpt('embedMetadata', d.checked)}
-          label={value.embedMetadata ? 'On' : 'Off'}
         />
       </Field>
+      <Field
+        label="Metadata overrides"
+        hint="Override specific tags before embedding. Leave blank to keep the extracted value. Automatically enables embed metadata."
+      >
+        <div className={styles.subGroup}>
+          <Input
+            placeholder="Title"
+            value={value.metadataTitle ?? ''}
+            onChange={(_, d) => setOpt('metadataTitle', d.value)}
+          />
+          <Input
+            placeholder="Artist"
+            value={value.metadataArtist ?? ''}
+            onChange={(_, d) => setOpt('metadataArtist', d.value)}
+          />
+          <Input
+            placeholder="Album"
+            value={value.metadataAlbum ?? ''}
+            onChange={(_, d) => setOpt('metadataAlbum', d.value)}
+          />
+        </div>
+      </Field>
       <Field label="Embed thumbnail" hint="Cover art for audio; poster frame for MP4/MKV.">
         <Switch
           checked={value.embedThumbnail}
           onChange={(_, d) => setOpt('embedThumbnail', d.checked)}
-          label={value.embedThumbnail ? 'On' : 'Off'}
         />
       </Field>
       {value.embedThumbnail && (
@@ -254,7 +294,7 @@ export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Eleme
 
       <Field
         label="Sidecar files"
-        hint="Write separate metadata/poster/description files next to each download — handy for Jellyfin, Plex or Kodi libraries."
+        hint="Write separate metadata/poster/description files next to each download -- handy for Jellyfin, Plex or Kodi libraries."
       >
         <div className={styles.subGroup}>
           <Checkbox

src/renderer/src/components/DownloadsView.tsx

@@ -1,19 +1,28 @@
-import {
+import {
   Subtitle2,
-  Body1,
   Caption1,
   Button,
   ProgressBar,
   makeStyles,
+  mergeClasses,
   tokens,
   shorthands
 } from '@fluentui/react-components'
-import { ArrowDownloadRegular, ArrowClockwiseRegular } from '@fluentui/react-icons'
+import { ArrowDownloadRegular, ArrowClockwiseRegular, DismissRegular } from '@fluentui/react-icons'
-import { useDownloads } from '../store/downloads'
+import { useDownloads, type DownloadItem } from '../store/downloads'
-import { summarizeQueue } from '../store/queueStats'
+import { queueSummaryOf } from '../store/queueStats'
 import { DownloadBar } from './DownloadBar'
 import { QueueItem } from './QueueItem'
 import { VirtualList } from './VirtualList'
+import { ScreenHeader, useScreenStyles } from './ui/Screen'
+import { EmptyState } from './ui/EmptyState'
+import { SPACE, ICON, META_SEP } from './ui/tokens'
+
+// Hoisted so the virtualizer gets stable function identities and doesn't churn its
+// measurement/key cache on every render (PERF5).
+const estimateRowSize = (): number => 100
+const getItemKey = (item: DownloadItem): string => item.id
+const renderQueueRow = (item: DownloadItem): React.JSX.Element => <QueueItem item={item} />
 
 const useStyles = makeStyles({
   root: {
@@ -22,7 +31,8 @@ const useStyles = makeStyles({
     // growing to thousands of rows.
     display: 'flex',
     flexDirection: 'column',
-    gap: '20px',
+    // One section gap on every screen (UI2).
+    gap: SPACE.section,
     height: '100%'
   },
   queueHeader: {
@@ -56,47 +66,59 @@ const useStyles = makeStyles({
     // min-height:0 lets this flex child shrink below its content height so it,
     // not the page, owns the scrolling.
     minHeight: 0
-  },
-  empty: {
-    display: 'flex',
-    flexDirection: 'column',
-    alignItems: 'center',
-    gap: '8px',
-    padding: '56px 16px',
-    color: tokens.colorNeutralForeground3,
-    textAlign: 'center'
   }
 })
 
 export function DownloadsView(): React.JSX.Element {
   const styles = useStyles()
+  const screen = useScreenStyles()
   const items = useDownloads((s) => s.items)
   const clearFinished = useDownloads((s) => s.clearFinished)
   const retryAll = useDownloads((s) => s.retryAll)
+  const cancelAll = useDownloads((s) => s.cancelAll)
 
-  const summary = summarizeQueue(items)
+  const summary = queueSummaryOf(items)
   const hasFinished = items.some(
     (i) => i.status === 'completed' || i.status === 'error' || i.status === 'canceled'
   )
+  // The header count is the live queue (work not yet finished), not the whole
+  // list -- completed/canceled/error rows linger until "Clear finished" (L11).
+  const queueCount = items.filter(
+    (i) =>
+      i.status === 'downloading' ||
+      i.status === 'queued' ||
+      i.status === 'paused' ||
+      i.status === 'saved'
+  ).length
+  // Cancelable = the items with a live/pending run (downloading + queued); this is
+  // exactly what "Cancel all" acts on (UX15).
+  const cancelable = items.filter((i) => i.status === 'downloading' || i.status === 'queued').length
 
   return (
-    <div className={styles.root}>
+    <div className={mergeClasses(styles.root, screen.width)}>
+      <ScreenHeader title="Downloads" description="Fetch a video, playlist, or channel by URL." />
+
       <DownloadBar />
 
       {summary.active && (
         <div className={styles.summary}>
-          <ProgressBar className={styles.summaryBar} value={summary.progress} thickness="large" />
+          <ProgressBar
+            className={styles.summaryBar}
+            value={summary.progress}
+            thickness="large"
+            aria-label="Overall download progress"
+          />
           <Caption1 className={styles.summaryText}>
             {summary.downloading} downloading
             {summary.queued ? `, ${summary.queued} queued` : ''}
-            {summary.speedLabel ? `  •  ${summary.speedLabel}` : ''}
+            {summary.speedLabel ? `${META_SEP}${summary.speedLabel}` : ''}
-            {summary.etaLabel ? `  •  ~${summary.etaLabel} left` : ''}
+            {summary.etaLabel ? `${META_SEP}~${summary.etaLabel} left` : ''}
           </Caption1>
         </div>
       )}
 
       <div className={styles.queueHeader}>
-        <Subtitle2>Queue ({items.length})</Subtitle2>
+        <Subtitle2 as="h2">Queue ({queueCount})</Subtitle2>
         <div className={styles.headerActions}>
           {summary.failed > 0 && (
             <Button
@@ -108,6 +130,11 @@ export function DownloadsView(): React.JSX.Element {
               Retry all failed ({summary.failed})
             </Button>
           )}
+          {cancelable > 0 && (
+            <Button size="small" appearance="subtle" icon={<DismissRegular />} onClick={cancelAll}>
+              Cancel all ({cancelable})
+            </Button>
+          )}
           {hasFinished && (
             <Button size="small" appearance="subtle" onClick={clearFinished}>
               Clear finished
@@ -117,19 +144,19 @@ export function DownloadsView(): React.JSX.Element {
       </div>
 
       {items.length === 0 ? (
-        <div className={styles.empty}>
+        <EmptyState
-          <ArrowDownloadRegular fontSize={40} />
+          icon={<ArrowDownloadRegular fontSize={ICON.hero} />}
-          <Body1>Nothing queued yet. Paste a URL above to get started.</Body1>
+          message="Nothing queued yet. Paste a URL above, then click Download."
-        </div>
+        />
       ) : (
         <VirtualList
           items={items}
           className={styles.listScroll}
           gap={10}
           overscan={6}
-          estimateSize={() => 100}
+          estimateSize={estimateRowSize}
-          getKey={(item) => item.id}
+          getKey={getItemKey}
-          renderItem={(item) => <QueueItem item={item} />}
+          renderItem={renderQueueRow}
         />
       )}
     </div>

src/renderer/src/components/ErrorBoundary.tsx

@@ -0,0 +1,100 @@
+import React from 'react'
+
+interface Props {
+  children: React.ReactNode
+}
+interface State {
+  error: Error | null
+}
+
+/**
+ * Top-level renderer error boundary (M16). Before this, an exception thrown in
+ * render by any view unmounted the whole shell to a blank white window with no
+ * way out. This catches it, logs it (so it reaches the dev console / future log
+ * sink), and shows a recover affordance.
+ *
+ * The fallback is intentionally dependency-free — no Fluent components, no theme
+ * provider — because the error may have come from inside that very tree. It paints
+ * its own full-window dark surface (matching the app's dark charcoal + toffee
+ * accent) rather than reading theme tokens, so it renders identically regardless
+ * of the active theme and uses only inline CSS that can't itself throw.
+ */
+export class ErrorBoundary extends React.Component<Props, State> {
+  state: State = { error: null }
+
+  static getDerivedStateFromError(error: Error): State {
+    return { error }
+  }
+
+  componentDidCatch(error: Error, info: React.ErrorInfo): void {
+    console.error('[AeroFetch] renderer crashed:', error, info.componentStack)
+  }
+
+  private handleReload = (): void => {
+    // A full reload re-runs the renderer from a clean state; persisted data
+    // (settings/history/sources) lives in main, so nothing is lost.
+    window.location.reload()
+  }
+
+  render(): React.ReactNode {
+    const { error } = this.state
+    if (!error) return this.props.children
+
+    return (
+      <div
+        role="alert"
+        style={{
+          display: 'flex',
+          flexDirection: 'column',
+          alignItems: 'center',
+          justifyContent: 'center',
+          gap: 16,
+          minHeight: '100vh',
+          padding: 32,
+          textAlign: 'center',
+          fontFamily: 'Segoe UI, system-ui, sans-serif',
+          color: '#c8c6c4',
+          background: '#201f1e'
+        }}
+      >
+        <div style={{ fontSize: 18, fontWeight: 600, color: '#f3f2f1' }}>Something went wrong</div>
+        <div style={{ maxWidth: 440, fontSize: 13, lineHeight: 1.5 }}>
+          AeroFetch hit an unexpected error and couldn’t continue. Your downloads and settings are
+          saved — reloading the window should bring you back.
+        </div>
+        <pre
+          style={{
+            maxWidth: 480,
+            maxHeight: 120,
+            overflow: 'auto',
+            margin: 0,
+            padding: '8px 12px',
+            fontSize: 11,
+            textAlign: 'left',
+            color: '#d29ca0',
+            background: '#2b2a29',
+            borderRadius: 6
+          }}
+        >
+          {error.message || String(error)}
+        </pre>
+        <button
+          type="button"
+          onClick={this.handleReload}
+          style={{
+            padding: '8px 20px',
+            fontSize: 14,
+            fontWeight: 600,
+            color: '#1c1611',
+            background: '#b5917d',
+            border: 'none',
+            borderRadius: 8,
+            cursor: 'pointer'
+          }}
+        >
+          Reload AeroFetch
+        </button>
+      </div>
+    )
+  }
+}

src/renderer/src/components/Hint.tsx

@@ -1,4 +1,5 @@
 import { makeStyles, mergeClasses, tokens, shorthands } from '@fluentui/react-components'
+import { Z } from './ui/tokens'
 
 // An instant, theme-styled tooltip implemented entirely in CSS — shown via a
 // `:hover` / `:focus-within` visibility toggle on an absolutely-positioned child
@@ -17,7 +18,7 @@ const useStyles = makeStyles({
   },
   bubble: {
     position: 'absolute',
-    zIndex: 1000,
+    zIndex: Z.tooltip,
     visibility: 'hidden',
     pointerEvents: 'none',
     whiteSpace: 'nowrap',
@@ -36,12 +37,17 @@ const useStyles = makeStyles({
   alignEnd: { right: 0 }
 })
 
-interface HintProps {
+// `align` only shifts a top/bottom bubble left/right; it does nothing for a
+// left/right placement. The union makes that explicit — passing `align` with
+// `placement="left"|"right"` is a type error now, instead of being silently
+// ignored (L129).
+type HintProps = {
   label: string
-  placement?: 'top' | 'bottom' | 'left' | 'right'
-  align?: 'start' | 'end'
   children: React.ReactNode
-}
+} & (
+  | { placement?: 'top' | 'bottom'; align?: 'start' | 'end' }
+  | { placement: 'left' | 'right'; align?: never }
+)
 
 export function Hint({
   label,

src/renderer/src/components/HistoryView.tsx

@@ -1,12 +1,12 @@
-import { useMemo, useState } from 'react'
+import { useEffect, useMemo, useState } from 'react'
 import {
   Text,
   Caption1,
   Button,
   Checkbox,
   Input,
-  Body1,
   makeStyles,
+  mergeClasses,
   tokens,
   shorthands
 } from '@fluentui/react-components'
@@ -22,6 +22,7 @@ import {
 } from '@fluentui/react-icons'
 import type { HistoryEntry, MediaKind } from '@shared/ipc'
 import { useHistory } from '../store/history'
+import { formatWhen } from '../datetime'
 import { useResolvedDark } from '../store/systemTheme'
 import { useDownloads } from '../store/downloads'
 import { thumbColors } from '../theme'
@@ -29,12 +30,18 @@ import { thumbUrl } from '../thumb'
 import { MediaThumb } from './MediaThumb'
 import { Hint } from './Hint'
 import { Select } from './Select'
+import { ScreenHeader, useScreenStyles } from './ui/Screen'
+import { EmptyState } from './ui/EmptyState'
+import { useFocusStyles } from './ui/focusRing'
+import { useTextStyles } from './ui/text'
+import { SPACE, ICON, META_SEP } from './ui/tokens'
+import { THUMB_SM } from '../thumbSizes'
 
 const useStyles = makeStyles({
   root: {
     display: 'flex',
     flexDirection: 'column',
-    gap: '12px'
+    gap: SPACE.section
   },
   header: {
     display: 'flex',
@@ -74,8 +81,8 @@ const useStyles = makeStyles({
   },
   thumb: {
     flexShrink: 0,
-    width: '72px',
+    width: `${THUMB_SM.w}px`,
-    height: '44px',
+    height: `${THUMB_SM.h}px`,
     display: 'flex',
     alignItems: 'center',
     justifyContent: 'center',
@@ -87,27 +94,15 @@ const useStyles = makeStyles({
     display: 'flex',
     flexDirection: 'column'
   },
-  title: {
-    fontWeight: tokens.fontWeightSemibold,
-    overflow: 'hidden',
-    textOverflow: 'ellipsis',
-    whiteSpace: 'nowrap'
-  },
-  meta: {
-    color: tokens.colorNeutralForeground3
-  },
   actions: {
     display: 'flex',
     gap: '4px',
-    flexShrink: 0
+    flexShrink: 0,
-  },
+    // >=40px hit target for the icon-only row actions (W16).
-  empty: {
+    '& button': {
-    display: 'flex',
+      minWidth: '40px',
-    flexDirection: 'column',
+      minHeight: '40px'
-    alignItems: 'center',
+    }
-    gap: '10px',
-    padding: '56px 16px',
-    textAlign: 'center'
   },
   emptyBadge: {
     width: '56px',
@@ -115,11 +110,9 @@ const useStyles = makeStyles({
     display: 'flex',
     alignItems: 'center',
     justifyContent: 'center',
-    borderRadius: '50%',
+    borderRadius: tokens.borderRadiusCircular,
-    fontSize: '26px'
+    // Empty-state badge glyph, snapped to the nearest ICON tier (UI11).
-  },
+    fontSize: `${ICON.section}px`
-  emptyHint: {
-    color: tokens.colorNeutralForeground3
   },
   noMatches: {
     padding: '32px 16px',
@@ -134,19 +127,11 @@ const KIND_FILTER_OPTIONS = [
   { value: 'audio', label: 'Audio' }
 ]
 
-function formatWhen(ts: number): string {
-  const d = new Date(ts)
-  const time = d.toLocaleTimeString(undefined, { hour: '2-digit', minute: '2-digit' })
-  const now = new Date()
-  const startOfToday = new Date(now.getFullYear(), now.getMonth(), now.getDate()).getTime()
-  const dayMs = 1000 * 60 * 60 * 24
-  if (ts >= startOfToday) return `Today, ${time}`
-  if (ts >= startOfToday - dayMs) return `Yesterday, ${time}`
-  return d.toLocaleDateString(undefined, { month: 'short', day: 'numeric', year: 'numeric' })
-}
-
 export function HistoryView(): React.JSX.Element {
   const styles = useStyles()
+  const screen = useScreenStyles()
+  const focus = useFocusStyles()
+  const text = useTextStyles()
   const isDark = useResolvedDark()
   const tc = thumbColors[isDark ? 'dark' : 'light']
   const entries = useHistory((s) => s.entries)
@@ -161,6 +146,8 @@ export function HistoryView(): React.JSX.Element {
   const [kindFilter, setKindFilter] = useState<'all' | MediaKind>('all')
   const [selectMode, setSelectMode] = useState(false)
   const [selected, setSelected] = useState<Set<string>>(new Set())
+  const [confirmClear, setConfirmClear] = useState(false)
+  const [confirmDelete, setConfirmDelete] = useState(false)
 
   const filtered = useMemo(() => {
     const q = query.trim().toLowerCase()
@@ -175,8 +162,31 @@ export function HistoryView(): React.JSX.Element {
     })
   }, [entries, query, kindFilter])
 
+  // Clear selections that are no longer visible after a filter change (L86).
+  useEffect(() => {
+    if (selected.size === 0) return
+    const visible = new Set(filtered.map((h) => h.id))
+    setSelected((prev) => {
+      const next = new Set([...prev].filter((id) => visible.has(id)))
+      return next.size === prev.size ? prev : next
+    })
+  }, [filtered])
+
   function redownload(h: HistoryEntry): void {
-    addFromUrl(h.url, h.kind, h.quality, { title: h.title, channel: h.channel })
+    // Strip compound format labels ("720p · mp4 · 184 MB" → "720p") when there is
+    // no stored formatId, so videoFormat() can still match the preset (H5).
+    const quality = (h.quality.split(' · ')[0] ?? h.quality).trim()
+    addFromUrl(h.url, h.kind, quality, {
+      title: h.title,
+      channel: h.channel,
+      thumbnail: h.thumbnail,
+      // Replay the original post-processing options (L87); undefined falls back to
+      // the global defaults for entries recorded before this was carried.
+      options: h.options,
+      format: h.formatId
+        ? { id: h.formatId, hasAudio: h.formatHasAudio ?? false, label: h.quality }
+        : undefined
+    })
   }
 
   function toggleSelected(id: string, on: boolean): void {
@@ -196,6 +206,7 @@ export function HistoryView(): React.JSX.Element {
   function exitSelectMode(): void {
     setSelectMode(false)
     setSelected(new Set())
+    setConfirmDelete(false)
   }
 
   function deleteSelected(): void {
@@ -205,21 +216,27 @@ export function HistoryView(): React.JSX.Element {
 
   if (entries.length === 0) {
     return (
-      <div className={styles.empty}>
+      <div className={mergeClasses(styles.root, screen.width)}>
+        <ScreenHeader title="History" description="Files you've finished downloading." />
+        <EmptyState
+          icon={
             <div
               className={styles.emptyBadge}
               style={{ backgroundColor: tc.video.bg, color: tc.video.fg }}
             >
               <HistoryRegular />
             </div>
-        <Body1>No downloads yet.</Body1>
+          }
-        <Caption1 className={styles.emptyHint}>Finished downloads will show up here.</Caption1>
+          message="No downloads yet."
+          hint="Finished downloads will show up here."
+        />
       </div>
     )
   }
 
   return (
-    <div className={styles.root}>
+    <div className={mergeClasses(styles.root, screen.width)}>
+      <ScreenHeader title="History" description="Files you've finished downloading." />
       <div className={styles.header}>
         {selectMode ? (
           <>
@@ -228,19 +245,45 @@ export function HistoryView(): React.JSX.Element {
               {allFilteredSelected ? 'Select none' : 'Select all'}
             </Button>
             <div className={styles.spacer} />
+            {confirmDelete ? (
+              <>
+                <Caption1 className={styles.count}>
+                  Delete {selected.size} {selected.size === 1 ? 'entry' : 'entries'}?
+                </Caption1>
                 <Button
                   size="small"
                   appearance="primary"
                   icon={<DeleteRegular />}
                   onClick={deleteSelected}
+                >
+                  Delete
+                </Button>
+                <Button size="small" appearance="subtle" onClick={() => setConfirmDelete(false)}>
+                  Cancel
+                </Button>
+              </>
+            ) : (
+              <>
+                <Button
+                  size="small"
+                  appearance="primary"
+                  icon={<DeleteRegular />}
+                  onClick={() => setConfirmDelete(true)}
                   disabled={selected.size === 0}
                 >
                   Delete selected
                 </Button>
-            <Button size="small" appearance="subtle" icon={<DismissRegular />} onClick={exitSelectMode}>
+                <Button
+                  size="small"
+                  appearance="subtle"
+                  icon={<DismissRegular />}
+                  onClick={exitSelectMode}
+                >
                   Cancel
                 </Button>
               </>
+            )}
+          </>
         ) : (
           <>
             <Caption1 className={styles.count}>
@@ -248,6 +291,7 @@ export function HistoryView(): React.JSX.Element {
             </Caption1>
             <Input
               className={styles.search}
+              input={{ 'aria-label': 'Search history' }}
               size="small"
               value={query}
               onChange={(_, d) => setQuery(d.value)}
@@ -270,9 +314,36 @@ export function HistoryView(): React.JSX.Element {
             >
               Select
             </Button>
-            <Button size="small" appearance="subtle" icon={<DeleteRegular />} onClick={clear}>
+            {confirmClear ? (
+              <>
+                <Caption1 className={styles.count}>
+                  Clear all {entries.length} {entries.length === 1 ? 'entry' : 'entries'}?
+                </Caption1>
+                <Button
+                  size="small"
+                  appearance="primary"
+                  icon={<DeleteRegular />}
+                  onClick={() => {
+                    clear()
+                    setConfirmClear(false)
+                  }}
+                >
+                  Clear all
+                </Button>
+                <Button size="small" appearance="subtle" onClick={() => setConfirmClear(false)}>
+                  Cancel
+                </Button>
+              </>
+            ) : (
+              <Button
+                size="small"
+                appearance="subtle"
+                icon={<DeleteRegular />}
+                onClick={() => setConfirmClear(true)}
+              >
                 Clear history
               </Button>
+            )}
           </>
         )}
       </div>
@@ -280,10 +351,33 @@ export function HistoryView(): React.JSX.Element {
       {filtered.length === 0 ? (
         <Caption1 className={styles.noMatches}>No downloads match your search.</Caption1>
       ) : (
-        <div className={styles.list}>
+        <div
+          className={styles.list}
+          onKeyDown={(e) => {
+            // W7: Ctrl/Cmd+A within the list selects every visible row (entering
+            // select mode if needed). Scoped to the list, so it never hijacks
+            // Ctrl+A in the search field, which lives in the header above.
+            if ((e.ctrlKey || e.metaKey) && (e.key === 'a' || e.key === 'A')) {
+              e.preventDefault()
+              setSelectMode(true)
+              setSelected(new Set(filtered.map((x) => x.id)))
+            }
+          }}
+        >
           {filtered.map((h: HistoryEntry) => {
             return (
-              <div key={h.id} className={styles.row}>
+              <div
+                key={h.id}
+                className={mergeClasses(styles.row, focus.focusRing)}
+                tabIndex={0}
+                onKeyDown={(e) => {
+                  // Delete removes the focused row (not when a child button is focused).
+                  if (e.key === 'Delete' && e.target === e.currentTarget) {
+                    e.preventDefault()
+                    remove(h.id)
+                  }
+                }}
+              >
                 {selectMode && (
                   <Checkbox
                     checked={selected.has(h.id)}
@@ -298,11 +392,11 @@ export function HistoryView(): React.JSX.Element {
                   iconSize={22}
                 />
                 <div className={styles.body}>
-                  <Text className={styles.title}>{h.title}</Text>
+                  <Text className={text.title}>{h.title}</Text>
-                  <Caption1 className={styles.meta}>
+                  <Caption1 className={text.muted}>
                     {[h.quality, h.sizeLabel, formatWhen(h.completedAt)]
                       .filter(Boolean)
-                      .join('  •  ')}
+                      .join(META_SEP)}
                   </Caption1>
                 </div>
                 <div className={styles.actions}>

src/renderer/src/components/LibraryView.tsx

@@ -1,7 +1,5 @@
-import { useEffect, useMemo, useState } from 'react'
+import { useEffect, useMemo, useState } from 'react'
 import {
-  Subtitle2,
-  Body1,
   Caption1,
   Text,
   Input,
@@ -15,9 +13,8 @@ import {
   shorthands
 } from '@fluentui/react-components'
 import {
-  SearchRegular,
+  AddRegular,
   ArrowSyncRegular,
-  ArrowClockwiseRegular,
   DeleteRegular,
   ArrowDownloadRegular,
   ChevronDownRegular,
@@ -25,21 +22,30 @@ import {
   AppsListRegular,
   VideoClipMultipleRegular,
   AlertRegular,
-  LibraryRegular,
+  LibraryRegular
-  LinkRegular,
-  DismissRegular
 } from '@fluentui/react-icons'
-import type { MediaItem, Source } from '@shared/ipc'
+import type { MediaItem, Source, MediaKind } from '@shared/ipc'
+import { isPreview as PREVIEW } from '../isPreview'
 import { useSources } from '../store/sources'
 import { useSettings } from '../store/settings'
+import { useNav } from '../store/nav'
 import { useClipboardLink, looksLikeSingleVideo } from '../useClipboardLink'
+import { logError } from '../reportError'
 import { useDownloads, type DownloadStatus } from '../store/downloads'
 import { thumbUrl } from '../thumb'
+import { relTime } from '../datetime'
 import { MediaThumb } from './MediaThumb'
 import { VirtualList } from './VirtualList'
-
+import { Hint } from './Hint'
-// True in the standalone browser preview (no Electron preload).
+import { ScreenHeader, useScreenStyles } from './ui/Screen'
-const PREVIEW = typeof window === 'undefined' || !window.electron
+import { StatusChip } from './ui/StatusChip'
+import { SegmentedControl } from './ui/SegmentedControl'
+import { EmptyState } from './ui/EmptyState'
+import { LinkSuggestion } from './ui/LinkSuggestion'
+import { useFocusStyles } from './ui/focusRing'
+import { useTextStyles } from './ui/text'
+import { SPACE, RADIUS, ICON, META_SEP } from './ui/tokens'
+import { THUMB_XS } from '../thumbSizes'
 
 /** Per-item status shown in the library: a live queue status, or pending/downloaded. */
 type ItemStatus = DownloadStatus | 'pending'
@@ -50,45 +56,28 @@ type ItemStatus = DownloadStatus | 'pending'
  * window cleanly (one virtualizer over a flat array, headers included).
  */
 type LibRow =
-  | { kind: 'header'; title: string; items: MediaItem[] }
+  { kind: 'header'; title: string; items: MediaItem[] } | { kind: 'item'; item: MediaItem }
-  | { kind: 'item'; item: MediaItem }
 
 /** Above this many flattened rows, the item list switches to a virtualized panel. */
 const VIRTUALIZE_AT = 100
 
-const STATUS_LABEL: Record<ItemStatus, string> = {
+// When a URL appears more than once in the queue ("Download anyway" duplicates),
-  pending: 'Pending',
+// the library row should reflect the most meaningful state: a finished copy wins,
-  queued: 'Queued',
+// then anything in flight, then terminal failures (M17).
-  downloading: 'Downloading',
+const STATUS_PRIORITY: Record<DownloadStatus, number> = {
-  paused: 'Paused',
+  completed: 6,
-  saved: 'Saved',
+  downloading: 5,
-  completed: 'Downloaded',
+  queued: 4,
-  error: 'Failed',
+  saved: 3,
-  canceled: 'Canceled'
+  paused: 2,
+  error: 1,
+  canceled: 0
 }
 
 const useStyles = makeStyles({
-  root: { display: 'flex', flexDirection: 'column', gap: '18px' },
+  root: { display: 'flex', flexDirection: 'column', gap: SPACE.section },
-  header: { display: 'flex', flexDirection: 'column', gap: '2px' },
-  sub: { color: tokens.colorNeutralForeground3 },
   addRow: { display: 'flex', gap: '8px' },
   addInput: { flexGrow: 1 },
-  suggestion: {
-    display: 'flex',
-    alignItems: 'center',
-    gap: '8px',
-    padding: '8px 8px 8px 12px',
-    backgroundColor: tokens.colorBrandBackground2,
-    color: tokens.colorBrandForeground2,
-    ...shorthands.borderRadius(tokens.borderRadiusLarge)
-  },
-  suggestionText: {
-    flexGrow: 1,
-    minWidth: 0,
-    overflow: 'hidden',
-    textOverflow: 'ellipsis',
-    whiteSpace: 'nowrap'
-  },
   toolbar: {
     display: 'flex',
     alignItems: 'center',
@@ -111,15 +100,6 @@ const useStyles = makeStyles({
     fontSize: tokens.fontSizeBase200
   },
   error: { color: tokens.colorPaletteRedForeground1 },
-  empty: {
-    display: 'flex',
-    flexDirection: 'column',
-    alignItems: 'center',
-    gap: '8px',
-    padding: '56px 16px',
-    color: tokens.colorNeutralForeground3,
-    textAlign: 'center'
-  },
   list: { display: 'flex', flexDirection: 'column', gap: '10px' },
   card: {
     border: `1px solid ${tokens.colorNeutralStroke2}`,
@@ -132,6 +112,14 @@ const useStyles = makeStyles({
     alignItems: 'center',
     gap: '12px',
     padding: '12px 14px',
+    width: '100%',
+    border: 'none',
+    backgroundColor: 'transparent',
+    // A native <button> doesn't inherit color; set it so the chevron (currentColor)
+    // matches the page foreground in dark mode instead of UA ButtonText.
+    color: tokens.colorNeutralForeground1,
+    fontFamily: tokens.fontFamilyBase,
+    textAlign: 'left',
     cursor: 'pointer',
     ':hover': { backgroundColor: tokens.colorNeutralBackground1Hover }
   },
@@ -145,7 +133,8 @@ const useStyles = makeStyles({
     display: 'flex',
     alignItems: 'center',
     justifyContent: 'center',
-    fontSize: '18px'
+    // Source tile glyph, snapped to the nearest ICON tier (UI11 — no literal px).
+    fontSize: `${ICON.control}px`
   },
   srcMeta: { display: 'flex', flexDirection: 'column', minWidth: 0, flexGrow: 1 },
   srcTitleRow: { display: 'flex', alignItems: 'center', gap: '8px', minWidth: 0 },
@@ -158,7 +147,6 @@ const useStyles = makeStyles({
     backgroundColor: tokens.colorBrandBackground2,
     color: tokens.colorBrandForeground2
   },
-  srcSub: { color: tokens.colorNeutralForeground3 },
   detail: {
     borderTop: `1px solid ${tokens.colorNeutralStroke2}`,
     padding: '12px 14px',
@@ -172,9 +160,22 @@ const useStyles = makeStyles({
     display: 'flex',
     alignItems: 'center',
     gap: '8px',
-    padding: '6px 4px',
+    padding: '2px 4px'
+  },
+  groupToggle: {
+    display: 'flex',
+    alignItems: 'center',
+    gap: '8px',
+    flexGrow: 1,
+    minWidth: 0,
+    padding: '4px 4px',
+    border: 'none',
+    backgroundColor: 'transparent',
     color: tokens.colorNeutralForeground2,
     cursor: 'pointer',
+    fontFamily: tokens.fontFamilyBase,
+    fontSize: tokens.fontSizeBase300,
+    textAlign: 'left',
     ...shorthands.borderRadius(tokens.borderRadiusMedium),
     ':hover': { backgroundColor: tokens.colorNeutralBackground1Hover }
   },
@@ -187,38 +188,12 @@ const useStyles = makeStyles({
   },
   plainList: { display: 'flex', flexDirection: 'column' },
   rowThumb: {
-    width: '60px',
+    width: `${THUMB_XS.w}px`,
-    height: '34px',
+    height: `${THUMB_XS.h}px`,
-    ...shorthands.borderRadius(tokens.borderRadiusSmall)
+    // One thumbnail radius app-wide (UI6): control tier / Medium.
+    ...shorthands.borderRadius(RADIUS.control)
   },
-  rowMain: { display: 'flex', flexDirection: 'column', minWidth: 0, flexGrow: 1 },
+  rowMain: { display: 'flex', flexDirection: 'column', minWidth: 0, flexGrow: 1 }
-  rowTitle: {
-    whiteSpace: 'nowrap',
-    overflow: 'hidden',
-    textOverflow: 'ellipsis',
-    color: tokens.colorNeutralForeground1
-  },
-  rowMeta: { color: tokens.colorNeutralForeground3 },
-  pill: {
-    flexShrink: 0,
-    fontSize: tokens.fontSizeBase200,
-    padding: '1px 8px',
-    ...shorthands.borderRadius(tokens.borderRadiusCircular),
-    backgroundColor: tokens.colorNeutralBackground3,
-    color: tokens.colorNeutralForeground3
-  },
-  pillDownloading: {
-    backgroundColor: tokens.colorBrandBackground2,
-    color: tokens.colorBrandForeground2
-  },
-  pillCompleted: {
-    backgroundColor: tokens.colorPaletteGreenBackground2,
-    color: tokens.colorPaletteGreenForeground2
-  },
-  pillError: {
-    backgroundColor: tokens.colorPaletteRedBackground2,
-    color: tokens.colorPaletteRedForeground2
-  }
 })
 
 /** Group items by playlist, sorted by index within a group; 'Uploads' sinks last. */
@@ -241,18 +216,11 @@ function groupByPlaylist(items: MediaItem[]): { title: string; items: MediaItem[
   return groups
 }
 
-function relTime(ms?: number): string {
-  if (!ms) return 'never'
-  const mins = Math.round((Date.now() - ms) / 60000)
-  if (mins < 1) return 'just now'
-  if (mins < 60) return `${mins} min ago`
-  const hrs = Math.round(mins / 60)
-  if (hrs < 24) return `${hrs} h ago`
-  return `${Math.round(hrs / 24)} d ago`
-}
-
 export function LibraryView(): React.JSX.Element {
   const styles = useStyles()
+  const screen = useScreenStyles()
+  const focus = useFocusStyles()
+  const text = useTextStyles()
   const sources = useSources((s) => s.sources)
   const itemsBySource = useSources((s) => s.itemsBySource)
   const selectedSourceId = useSources((s) => s.selectedSourceId)
@@ -271,10 +239,32 @@ export function LibraryView(): React.JSX.Element {
 
   const [url, setUrl] = useState('')
   const [error, setError] = useState<string | null>(null)
+  const [confirmRemoveId, setConfirmRemoveId] = useState<string | null>(null)
+
+  // A channel/playlist URL handed over from the Downloads bar (UX3): pre-fill the
+  // add field with it once, so the user lands here ready to add it.
+  const pendingLibraryUrl = useNav((s) => s.pendingLibraryUrl)
+  const consumeLibraryUrl = useNav((s) => s.consumeLibraryUrl)
+  useEffect(() => {
+    if (pendingLibraryUrl === null) return
+    const handed = consumeLibraryUrl()
+    if (handed) setUrl(handed)
+  }, [pendingLibraryUrl, consumeLibraryUrl])
+
+  // Reset any pending Remove confirmation when the expanded source changes so a
+  // stale confirm can't reappear after navigating between sources.
+  useEffect(() => {
+    setConfirmRemoveId(null)
+  }, [selectedSourceId])
   // Offer a freshly-copied link the way the Downloads tab does, but skip single
-  // videos — a library source is a channel/playlist to sync, not a one-off.
+  // videos -- a library source is a channel/playlist to sync, not a one-off.
   const clip = useClipboardLink(url, (u) => !looksLikeSingleVideo(u))
   const [selected, setSelected] = useState<Set<string>>(new Set())
+  // Per-batch video/audio choice for queueing items, seeded from the global
+  // default so behavior is unchanged until the user flips it (M27).
+  const [enqueueKind, setEnqueueKind] = useState<MediaKind>(
+    () => useSettings.getState().defaultKind
+  )
   const [batchNote, setBatchNote] = useState<string | null>(null)
   const [syncNote, setSyncNote] = useState<string | null>(null)
   // Which playlist groups are expanded. Empty = all collapsed (the default), so
@@ -287,7 +277,10 @@ export function LibraryView(): React.JSX.Element {
   // Load the current scheduled-sync (Task Scheduler) state once.
   useEffect(() => {
     if (PREVIEW) return
-    window.api.getScheduledSync().then((s) => setScheduled(s.enabled)).catch(() => {})
+    window.api
+      .getScheduledSync()
+      .then((s) => setScheduled(s.enabled))
+      .catch(logError('getScheduledSync'))
   }, [])
 
   async function onCheckNew(): Promise<void> {
@@ -314,7 +307,13 @@ export function LibraryView(): React.JSX.Element {
   // Live per-URL queue status so a video row reflects its real download state.
   const statusByUrl = useMemo(() => {
     const m = new Map<string, DownloadStatus>()
-    for (const d of downloadItems) m.set(d.url, d.status)
+    for (const d of downloadItems) {
+      const prev = m.get(d.url)
+      // Keep the highest-priority status when a URL has duplicate queue entries.
+      if (prev === undefined || STATUS_PRIORITY[d.status] > STATUS_PRIORITY[prev]) {
+        m.set(d.url, d.status)
+      }
+    }
     return m
   }, [downloadItems])
 
@@ -322,8 +321,7 @@ export function LibraryView(): React.JSX.Element {
   const groups = useMemo(() => groupByPlaylist(items), [items])
   // A group is shown when toggled open, or auto-expanded when it's the only group
   // (a single "Uploads" channel shouldn't need a second click to reach its videos).
-  const isGroupOpen = (title: string): boolean =>
+  const isGroupOpen = (title: string): boolean => groups.length === 1 || expandedGroups.has(title)
-    groups.length === 1 || expandedGroups.has(title)
   // Flatten groups → [header, ...its items, header, ...] for the virtualized list.
   const flatRows = useMemo<LibRow[]>(() => {
     const rows: LibRow[] = []
@@ -360,7 +358,7 @@ export function LibraryView(): React.JSX.Element {
     if (!u || indexing.active) return
     const res = await indexSource(u)
     if (res.ok) setUrl('')
-    else setError(res.error ?? 'Could not index that link.')
+    else setError(res.error ?? 'Could not add that link.')
   }
 
   function toggle(id: string, on: boolean): void {
@@ -385,6 +383,9 @@ export function LibraryView(): React.JSX.Element {
     setSelected((prev) => {
       const next = new Set(prev)
       for (const it of groupItems) {
+        // Only actionable rows are selectable, so the selection count can never
+        // exceed what "Download N selected" will actually queue (M36).
+        if (!actionable(it)) continue
         if (on) next.add(it.id)
         else next.delete(it.id)
       }
@@ -397,18 +398,18 @@ export function LibraryView(): React.JSX.Element {
     setSelected(on ? new Set(actionableItems.map((it) => it.id)) : new Set())
   }
 
-  // One click queues every chosen item — maxConcurrent gates how many actually
+  // One click queues every chosen item -- maxConcurrent gates how many actually
   // run, the rest wait in the queue. Selection clears since nothing is held back.
   function downloadSelected(): void {
     if (!selectedSourceId || selectedActionable.length === 0) return
-    const n = enqueueItems(selectedSourceId, selectedActionable)
+    const n = enqueueItems(selectedSourceId, selectedActionable, enqueueKind)
     setSelected(new Set())
     setBatchNote(`Queued ${n} download${n === 1 ? '' : 's'}.`)
   }
 
   function downloadPending(): void {
     if (!selectedSourceId || pendingItems.length === 0) return
-    const n = enqueueItems(selectedSourceId, pendingItems)
+    const n = enqueueItems(selectedSourceId, pendingItems, enqueueKind)
     setBatchNote(`Queued ${n} download${n === 1 ? '' : 's'}.`)
   }
 
@@ -418,18 +419,11 @@ export function LibraryView(): React.JSX.Element {
     if (!selectedSourceId) return
     const toQueue = groupItems.filter(actionable)
     if (toQueue.length === 0) return
-    const n = enqueueItems(selectedSourceId, toQueue)
+    const n = enqueueItems(selectedSourceId, toQueue, enqueueKind)
     setBatchNote(`Queued ${n} download${n === 1 ? '' : 's'}.`)
   }
 
-  function pillClass(status: ItemStatus): string {
+  // One row of the item list -- a playlist header or a video -- shared by the
-    if (status === 'downloading' || status === 'queued') return mergeClasses(styles.pill, styles.pillDownloading)
-    if (status === 'completed') return mergeClasses(styles.pill, styles.pillCompleted)
-    if (status === 'error') return mergeClasses(styles.pill, styles.pillError)
-    return styles.pill
-  }
-
-  // One row of the item list — a playlist header or a video — shared by the
   // inline (small source) and virtualized (large source) render paths.
   function rowKey(row: LibRow): string {
     return row.kind === 'header' ? `h:${row.title}` : row.item.id
@@ -437,32 +431,27 @@ export function LibraryView(): React.JSX.Element {
 
   function renderRow(row: LibRow): React.JSX.Element {
     if (row.kind === 'header') {
-      const allOn = row.items.every((it) => selected.has(it.id))
       const open = isGroupOpen(row.title)
-      const groupActionable = row.items.filter(actionable).length
+      // "All on" is judged over the ACTIONABLE rows only -- downloaded rows aren't
+      // selectable, so they must not keep the group from reading as fully selected (M36).
+      const groupActionableItems = row.items.filter(actionable)
+      const groupActionable = groupActionableItems.length
+      const allOn = groupActionable > 0 && groupActionableItems.every((it) => selected.has(it.id))
       return (
-        <div
+        <div className={styles.groupHead}>
-          className={styles.groupHead}
+          <button
+            type="button"
+            className={mergeClasses(styles.groupToggle, focus.focusRing)}
             onClick={() => toggleGroupExpand(row.title)}
-          role="button"
-          tabIndex={0}
-          onKeyDown={(e) =>
-            (e.key === 'Enter' || e.key === ' ') && toggleGroupExpand(row.title)
-          }
             aria-expanded={open}
+            aria-label={`${row.title}, ${row.items.length} items`}
           >
             {open ? <ChevronDownRegular /> : <ChevronRightRegular />}
             <AppsListRegular />
-          <span className={styles.groupTitle}>{row.title}</span>
+            <Text className={styles.groupTitle}>{row.title}</Text>
-          <Caption1 className={styles.srcSub}>{row.items.length}</Caption1>
+            <Caption1 className={text.muted}>{row.items.length}</Caption1>
-          <Button
+          </button>
-            size="small"
+          <Button size="small" appearance="subtle" onClick={() => toggleGroup(row.items, !allOn)}>
-            appearance="subtle"
-            onClick={(e) => {
-              e.stopPropagation()
-              toggleGroup(row.items, !allOn)
-            }}
-          >
             {allOn ? 'None' : 'All'}
           </Button>
           <Button
@@ -470,10 +459,7 @@ export function LibraryView(): React.JSX.Element {
             appearance="subtle"
             icon={<ArrowDownloadRegular />}
             disabled={groupActionable === 0}
-            onClick={(e) => {
+            onClick={() => downloadGroup(row.items)}
-              e.stopPropagation()
-              downloadGroup(row.items)
-            }}
           >
             Download{groupActionable > 0 ? ` ${groupActionable}` : ''}
           </Button>
@@ -486,6 +472,7 @@ export function LibraryView(): React.JSX.Element {
       <div className={styles.row}>
         <Checkbox
           checked={selected.has(it.id)}
+          disabled={!actionable(it)}
           onChange={(_, d) => toggle(it.id, !!d.checked)}
           aria-label={`Select ${it.title}`}
         />
@@ -496,32 +483,31 @@ export function LibraryView(): React.JSX.Element {
           iconSize={16}
         />
         <div className={styles.rowMain}>
-          <span className={styles.rowTitle}>
+          <Text className={text.truncate}>
             {it.playlistIndex}. {it.title}
-          </span>
+          </Text>
-          {it.durationLabel && <Caption1 className={styles.rowMeta}>{it.durationLabel}</Caption1>}
+          {it.durationLabel && <Caption1 className={text.muted}>{it.durationLabel}</Caption1>}
         </div>
-        <span className={pillClass(status)}>{STATUS_LABEL[status]}</span>
+        <StatusChip status={status} />
       </div>
     )
   }
 
   return (
-    <div className={styles.root}>
+    <div className={mergeClasses(styles.root, screen.width)}>
-      <div className={styles.header}>
+      <ScreenHeader
-        <Subtitle2>Library</Subtitle2>
+        title="Library"
-        <Caption1 className={styles.sub}>
+        description="Add a channel or playlist once, then download its videos into organized folders."
-          Index a channel or playlist once, then download it into organized folders.
+      />
-        </Caption1>
-      </div>
 
       <div className={styles.addRow}>
         <Input
           className={styles.addInput}
+          input={{ 'aria-label': 'Channel or playlist URL' }}
           value={url}
           onChange={(_, d) => setUrl(d.value)}
           onKeyDown={(e) => e.key === 'Enter' && onIndex()}
-          placeholder="Paste a channel or playlist URL…"
+          placeholder="Paste a channel or playlist URL to add it…"
           size="large"
           contentBefore={<LibraryRegular />}
           disabled={indexing.active}
@@ -529,49 +515,51 @@ export function LibraryView(): React.JSX.Element {
         <Button
           size="large"
           appearance="primary"
-          icon={indexing.active ? <Spinner size="tiny" /> : <SearchRegular />}
+          icon={indexing.active ? <Spinner size="tiny" /> : <AddRegular />}
           onClick={onIndex}
           disabled={!url.trim() || indexing.active}
         >
-          Index
+          Add
         </Button>
       </div>
 
       {clip.suggestion && (
-        <div className={styles.suggestion}>
+        <LinkSuggestion
-          <LinkRegular />
+          prefix="Use copied link? "
-          <Caption1 className={styles.suggestionText}>Use copied link? {clip.suggestion}</Caption1>
+          link={clip.suggestion}
-          <Button
+          onAccept={() => {
-            size="small"
-            appearance="primary"
-            onClick={() => {
             const link = clip.accept()
             if (link) setUrl(link)
           }}
-          >
+          onDismiss={clip.dismiss}
-            Use
+          dismissLabel="Dismiss suggested link"
-          </Button>
-          <Button
-            size="small"
-            appearance="subtle"
-            icon={<DismissRegular />}
-            onClick={clip.dismiss}
-            aria-label="Dismiss"
         />
-        </div>
       )}
 
       <div className={styles.toolbar}>
+        <Hint
+          label={
+            watchedCount === 0
+              ? 'Turn on "Watch" for a channel or playlist below first, then this checks them for new uploads.'
+              : 'Check your watched sources for new uploads'
+          }
+          placement="top"
+          align="start"
+        >
           <Button
             size="small"
-          appearance="secondary"
+            appearance="subtle"
-          icon={syncing ? <Spinner size="tiny" /> : <ArrowClockwiseRegular />}
+            icon={syncing ? <Spinner size="tiny" /> : <ArrowSyncRegular />}
             onClick={onCheckNew}
-          disabled={syncing || watchedCount === 0}
+            // disabledFocusable (not disabled) when nothing is watched, so the
+            // button still shows its explanatory tooltip on hover/focus (UX24).
+            disabled={syncing}
+            disabledFocusable={watchedCount === 0}
           >
             Check {watchedCount > 0 ? `${watchedCount} watched` : 'watched'} for new
           </Button>
-        {syncNote && <Caption1 className={styles.sub}>{syncNote}</Caption1>}
+        </Hint>
+        {syncNote && <Caption1 className={text.muted}>{syncNote}</Caption1>}
         <div className={styles.toolbarSpacer} />
         <span className={styles.switchRow}>
           <Caption1>Auto-download new</Caption1>
@@ -595,7 +583,7 @@ export function LibraryView(): React.JSX.Element {
         <div className={styles.progress}>
           <Spinner size="tiny" />
           <Text>
-            {indexing.message ?? 'Indexing…'}
+            {indexing.message ?? 'Adding…'}
             {indexing.current && indexing.total ? `  (${indexing.current}/${indexing.total})` : ''}
           </Text>
         </div>
@@ -603,10 +591,10 @@ export function LibraryView(): React.JSX.Element {
       {error && <Caption1 className={styles.error}>{error}</Caption1>}
 
       {sources.length === 0 && !indexing.active ? (
-        <div className={styles.empty}>
+        <EmptyState
-          <LibraryRegular fontSize={40} />
+          icon={<LibraryRegular fontSize={ICON.hero} />}
-          <Body1>No channels or playlists yet. Paste one above to index it.</Body1>
+          message="No channels or playlists yet. Paste one above to add it."
-        </div>
+        />
       ) : (
         <div className={styles.list}>
           {sources.map((src) => (
@@ -615,9 +603,7 @@ export function LibraryView(): React.JSX.Element {
               styles={styles}
               source={src}
               expanded={selectedSourceId === src.id}
-              onToggleExpand={() =>
+              onToggleExpand={() => selectSource(selectedSourceId === src.id ? null : src.id)}
-                selectSource(selectedSourceId === src.id ? null : src.id)
-              }
             >
               <div className={styles.detail}>
                 <div className={styles.actionRow}>
@@ -627,14 +613,27 @@ export function LibraryView(): React.JSX.Element {
                     label="Select all"
                     disabled={actionableItems.length === 0}
                   />
-                  <Caption1 className={styles.srcSub}>
+                  <Caption1 className={text.muted}>
-                    {items.length} videos · {pendingItems.length} pending · indexed{' '}
+                    {items.length} videos{META_SEP}
-                    {relTime(src.lastIndexedAt)}
+                    {pendingItems.length} pending{META_SEP}indexed {relTime(src.lastIndexedAt)}
                   </Caption1>
                   <div className={styles.actionSpacer} />
+                  <SegmentedControl<MediaKind>
+                    value={enqueueKind}
+                    options={[
+                      { value: 'video', label: 'Video' },
+                      { value: 'audio', label: 'Audio' }
+                    ]}
+                    onChange={setEnqueueKind}
+                    ariaLabel="Download as video or audio"
+                  />
                   {selected.size > 0 ? (
                     <>
-                      <Button size="small" appearance="subtle" onClick={() => setSelected(new Set())}>
+                      <Button
+                        size="small"
+                        appearance="subtle"
+                        onClick={() => setSelected(new Set())}
+                      >
                         Clear
                       </Button>
                       <Button
@@ -673,19 +672,43 @@ export function LibraryView(): React.JSX.Element {
                     onClick={() => reindexSource(src.id)}
                     disabled={indexing.active}
                   >
-                    Re-index
+                    Refresh
+                  </Button>
+                  {confirmRemoveId === src.id ? (
+                    <>
+                      <Caption1 className={text.muted}>Remove {src.title}?</Caption1>
+                      <Button
+                        size="small"
+                        appearance="primary"
+                        icon={<DeleteRegular />}
+                        onClick={() => {
+                          removeSource(src.id)
+                          setConfirmRemoveId(null)
+                        }}
+                      >
+                        Remove
                       </Button>
+                      <Button
+                        size="small"
+                        appearance="subtle"
+                        onClick={() => setConfirmRemoveId(null)}
+                      >
+                        Cancel
+                      </Button>
+                    </>
+                  ) : (
                     <Button
                       size="small"
                       appearance="subtle"
                       icon={<DeleteRegular />}
-                    onClick={() => removeSource(src.id)}
+                      onClick={() => setConfirmRemoveId(src.id)}
                     >
                       Remove
                     </Button>
+                  )}
                 </div>
 
-                {batchNote && <Caption1 className={styles.srcSub}>{batchNote}</Caption1>}
+                {batchNote && <Caption1 className={text.muted}>{batchNote}</Caption1>}
 
                 {flatRows.length > VIRTUALIZE_AT ? (
                   // Big source: a fixed-height, internally-scrolling virtualized
@@ -695,7 +718,7 @@ export function LibraryView(): React.JSX.Element {
                     items={flatRows}
                     style={{ height: '58vh' }}
                     overscan={10}
-                    estimateSize={(i) => (flatRows[i].kind === 'header' ? 40 : 46)}
+                    estimateSize={(i) => (flatRows[i]?.kind === 'header' ? 40 : 46)}
                     getKey={(row) => rowKey(row)}
                     renderItem={(row) => renderRow(row)}
                   />
@@ -730,15 +753,16 @@ function SourceCard({
   onToggleExpand: () => void
   children: React.ReactNode
 }): React.JSX.Element {
+  const focus = useFocusStyles()
+  const text = useTextStyles()
   return (
     <div className={styles.card}>
-      <div
+      <button
-        className={styles.cardHead}
+        type="button"
+        className={mergeClasses(styles.cardHead, focus.focusRing)}
         onClick={onToggleExpand}
-        role="button"
-        tabIndex={0}
-        onKeyDown={(e) => (e.key === 'Enter' || e.key === ' ') && onToggleExpand()}
         aria-expanded={expanded}
+        aria-label={source.title}
       >
         {expanded ? <ChevronDownRegular /> : <ChevronRightRegular />}
         <div className={styles.srcIcon}>
@@ -746,19 +770,23 @@ function SourceCard({
         </div>
         <div className={styles.srcMeta}>
           <span className={styles.srcTitleRow}>
-            <span className={styles.srcTitle}>{source.title}</span>
+            <Text className={styles.srcTitle}>{source.title}</Text>
             {source.watched && (
               <span className={styles.watchBadge}>
                 <AlertRegular fontSize={11} /> Watching
               </span>
             )}
           </span>
-          <Caption1 className={styles.srcSub}>
+          <Caption1 className={text.muted}>
-            {source.kind === 'channel' ? 'Channel' : 'Playlist'} · {source.itemCount} videos
+            {source.kind === 'channel' ? 'Channel' : 'Playlist'}
-            {source.channel && source.channel !== source.title ? ` · ${source.channel}` : ''}
+            {META_SEP}
+            {source.itemCount} videos
+            {source.channel && source.channel !== source.title
+              ? `${META_SEP}${source.channel}`
+              : ''}
           </Caption1>
         </div>
-      </div>
+      </button>
       {expanded && children}
     </div>
   )

src/renderer/src/components/LiveRegion.tsx

@@ -0,0 +1,52 @@
+import { useEffect, useRef, useState } from 'react'
+import { makeStyles } from '@fluentui/react-components'
+import { useDownloads, type DownloadStatus } from '../store/downloads'
+
+const useStyles = makeStyles({
+  // Visually hidden, but present for screen readers (the standard sr-only recipe).
+  srOnly: {
+    position: 'absolute',
+    width: '1px',
+    height: '1px',
+    padding: 0,
+    margin: '-1px',
+    overflow: 'hidden',
+    clip: 'rect(0, 0, 0, 0)',
+    whiteSpace: 'nowrap'
+  }
+})
+
+/**
+ * A polite ARIA live region (W17) so Narrator announces download completions and
+ * failures even when the user isn't on the Downloads tab. Subscribes to the store
+ * directly and announces only terminal transitions (→ completed / error), so it
+ * never chatters on progress ticks. Mounted once, near the app root.
+ */
+export function LiveRegion(): React.JSX.Element {
+  const styles = useStyles()
+  const [message, setMessage] = useState('')
+  const prev = useRef<Map<string, DownloadStatus>>(new Map())
+
+  useEffect(() => {
+    function check(items: ReturnType<typeof useDownloads.getState>['items']): void {
+      const announcements: string[] = []
+      for (const it of items) {
+        if (prev.current.get(it.id) !== it.status) {
+          if (it.status === 'completed') announcements.push(`Finished downloading ${it.title}`)
+          else if (it.status === 'error') announcements.push(`Download failed: ${it.title}`)
+        }
+      }
+      prev.current = new Map(items.map((i) => [i.id, i.status]))
+      if (announcements.length > 0) setMessage(announcements.join('. '))
+    }
+    // Seed the baseline without announcing the items already present on mount.
+    prev.current = new Map(useDownloads.getState().items.map((i) => [i.id, i.status]))
+    return useDownloads.subscribe((st) => check(st.items))
+  }, [])
+
+  return (
+    <div className={styles.srOnly} role="status" aria-live="polite" aria-atomic="true">
+      {message}
+    </div>
+  )
+}

src/renderer/src/components/MediaThumb.tsx

@@ -41,7 +41,7 @@ export function MediaThumb({
 }): React.JSX.Element {
   const styles = useStyles()
   const isDark = useResolvedDark()
-  const colors = thumbColors[isDark ? 'dark' : 'light'][kind === 'audio' ? 'audio' : 'video']
+  const colors = thumbColors[isDark ? 'dark' : 'light'][kind]
   const [failedSrc, setFailedSrc] = useState<string | null>(null)
   const showImg = !!src && failedSrc !== src
 
@@ -53,13 +53,7 @@ export function MediaThumb({
       style={{ backgroundColor: colors.bg, color: colors.fg }}
     >
       {showImg ? (
-        <img
+        <img className={styles.img} src={src} alt="" onError={() => setFailedSrc(src ?? null)} />
-          className={styles.img}
-          src={src}
-          alt=""
-          loading="lazy"
-          onError={() => setFailedSrc(src ?? null)}
-        />
       ) : kind === 'audio' ? (
         <MusicNote2Regular fontSize={iconSize} />
       ) : (

src/renderer/src/components/Onboarding.tsx

@@ -6,6 +6,7 @@ import {
   Field,
   Button,
   makeStyles,
+  mergeClasses,
   tokens,
   shorthands
 } from '@fluentui/react-components'
@@ -14,9 +15,14 @@ import {
   ClipboardPasteRegular,
   HistoryRegular,
   OptionsRegular,
-  RocketRegular
+  RocketRegular,
+  FolderRegular,
+  MusicNote2Regular,
+  VideoClipRegular,
+  KeyboardRegular
 } from '@fluentui/react-icons'
 import { useSettings } from '../store/settings'
+import { SPACE, ICON } from './ui/tokens'
 
 const useStyles = makeStyles({
   root: {
@@ -26,13 +32,14 @@ const useStyles = makeStyles({
     alignItems: 'center',
     justifyContent: 'center',
     overflowY: 'auto',
-    padding: '24px'
+    padding: SPACE.page
   },
   card: {
     display: 'flex',
     flexDirection: 'column',
-    gap: '20px',
+    gap: SPACE.roomy,
-    padding: '32px',
+    // The welcome hero card (UI3 hero tier).
+    padding: SPACE.hero,
     maxWidth: '460px',
     width: '100%',
     ...shorthands.borderRadius(tokens.borderRadiusXLarge)
@@ -52,10 +59,45 @@ const useStyles = makeStyles({
     display: 'flex',
     alignItems: 'center',
     justifyContent: 'center',
-    fontSize: '26px'
+    // Brand tile glyph, snapped to the nearest ICON tier (UI11 — no literal px).
+    fontSize: `${ICON.section}px`
   },
   folderNote: {
-    color: tokens.colorNeutralForeground3
+    color: tokens.colorNeutralForeground3,
+    marginBottom: SPACE.tight
+  },
+  folderRow: {
+    display: 'flex',
+    alignItems: 'center',
+    gap: '10px',
+    padding: '8px 10px',
+    backgroundColor: tokens.colorNeutralBackground2,
+    ...shorthands.borderRadius(tokens.borderRadiusMedium),
+    border: `1px solid ${tokens.colorNeutralStroke2}`
+  },
+  folderRowGap: {
+    marginTop: SPACE.tight
+  },
+  folderIcon: {
+    fontSize: `${ICON.control}px`,
+    flexShrink: 0,
+    color: tokens.colorCompoundBrandForeground1
+  },
+  folderCol: {
+    display: 'flex',
+    flexDirection: 'column',
+    minWidth: 0,
+    flexGrow: 1
+  },
+  folderLabel: {
+    fontWeight: tokens.fontWeightSemibold,
+    color: tokens.colorNeutralForeground1
+  },
+  folderPath: {
+    color: tokens.colorNeutralForeground3,
+    overflow: 'hidden',
+    textOverflow: 'ellipsis',
+    whiteSpace: 'nowrap'
   },
   tips: {
     display: 'flex',
@@ -68,9 +110,9 @@ const useStyles = makeStyles({
     gap: '10px'
   },
   tipIcon: {
-    fontSize: '18px',
+    fontSize: `${ICON.control}px`,
     flexShrink: 0,
-    marginTop: '2px',
+    marginTop: SPACE.hairline,
     color: tokens.colorCompoundBrandForeground1
   }
 })
@@ -78,7 +120,7 @@ const useStyles = makeStyles({
 const TIPS: { icon: React.JSX.Element; text: string }[] = [
   {
     icon: <ClipboardPasteRegular />,
-    text: 'Copy a video link and AeroFetch offers to fetch it as soon as you switch back.'
+    text: 'Turn on clipboard detection in Settings and AeroFetch will offer to fetch links you copy.'
   },
   {
     icon: <HistoryRegular />,
@@ -87,12 +129,19 @@ const TIPS: { icon: React.JSX.Element; text: string }[] = [
   {
     icon: <OptionsRegular />,
     text: 'Subtitles, SponsorBlock, custom yt-dlp commands, and more live in Settings.'
+  },
+  {
+    icon: <KeyboardRegular />,
+    text: 'Press Ctrl+K anytime to jump to any screen or start a new download.'
   }
 ]
 
 export function Onboarding(): React.JSX.Element {
   const styles = useStyles()
   const update = useSettings((s) => s.update)
+  const videoDir = useSettings((s) => s.videoDir)
+  const audioDir = useSettings((s) => s.audioDir)
+  const chooseDir = useSettings((s) => s.chooseDir)
 
   return (
     <div className={styles.root}>
@@ -101,7 +150,7 @@ export function Onboarding(): React.JSX.Element {
           <div className={styles.mark}>
             <ArrowDownloadFilled />
           </div>
-          <Title2>Welcome to AeroFetch</Title2>
+          <Title2 as="h1">Welcome to AeroFetch</Title2>
         </div>
 
         <Body1>
@@ -111,10 +160,33 @@ export function Onboarding(): React.JSX.Element {
 
         <Field label="Where downloads go">
           <Caption1 className={styles.folderNote}>
-            Videos save to your <strong>Documents\Video</strong> folder and audio to{' '}
+            Videos and audio save to your Documents folders by default. Pick a different folder now,
-            <strong>Documents\Audio</strong>. You can point each to a different folder any time
+            or change it any time in Settings.
-            in Settings.
           </Caption1>
+          <div className={styles.folderRow}>
+            <VideoClipRegular className={styles.folderIcon} />
+            <div className={styles.folderCol}>
+              <Caption1 className={styles.folderLabel}>Video</Caption1>
+              <Caption1 className={styles.folderPath} title={videoDir || 'Documents\\Video'}>
+                {videoDir || 'Documents\\Video'}
+              </Caption1>
+            </div>
+            <Button size="small" icon={<FolderRegular />} onClick={() => chooseDir('videoDir')}>
+              Choose…
+            </Button>
+          </div>
+          <div className={mergeClasses(styles.folderRow, styles.folderRowGap)}>
+            <MusicNote2Regular className={styles.folderIcon} />
+            <div className={styles.folderCol}>
+              <Caption1 className={styles.folderLabel}>Audio</Caption1>
+              <Caption1 className={styles.folderPath} title={audioDir || 'Documents\\Audio'}>
+                {audioDir || 'Documents\\Audio'}
+              </Caption1>
+            </div>
+            <Button size="small" icon={<FolderRegular />} onClick={() => chooseDir('audioDir')}>
+              Choose…
+            </Button>
+          </div>
         </Field>
 
         <div className={styles.tips}>

src/renderer/src/components/QueueItem.tsx

@@ -1,12 +1,12 @@
-import { memo } from 'react'
+import { memo } from 'react'
 import {
   Text,
   Caption1,
   Button,
   ProgressBar,
-  Badge,
   Spinner,
   makeStyles,
+  mergeClasses,
   tokens,
   shorthands
 } from '@fluentui/react-components'
@@ -25,28 +25,38 @@ import {
   ErrorCircleFilled,
   EyeOffRegular
 } from '@fluentui/react-icons'
-import { useDownloads, type DownloadItem, type DownloadStatus } from '../store/downloads'
+import { useShallow } from 'zustand/react/shallow'
+import { useDownloads, type DownloadItem } from '../store/downloads'
 import { thumbUrl } from '../thumb'
+import { fmtSchedule } from '../datetime'
+import { fmtSpeed, fmtEta } from '@shared/format'
 import { MediaThumb } from './MediaThumb'
 import { Hint } from './Hint'
+import { StatusChip } from './ui/StatusChip'
+import { useFocusStyles } from './ui/focusRing'
+import { useTextStyles } from './ui/text'
+import { SPACE, RADIUS, ICON, META_SEP } from './ui/tokens'
+import { THUMB_MD } from '../thumbSizes'
 
 const useStyles = makeStyles({
   root: {
     display: 'flex',
     gap: '14px',
-    padding: '14px',
+    // List-item card: card padding + list-item radius (UI3/UI7).
+    padding: SPACE.section,
     backgroundColor: tokens.colorNeutralBackground1,
-    ...shorthands.borderRadius(tokens.borderRadiusLarge),
+    ...shorthands.borderRadius(RADIUS.surface),
     border: `1px solid ${tokens.colorNeutralStroke2}`
   },
   thumb: {
     flexShrink: 0,
-    width: '108px',
+    width: `${THUMB_MD.w}px`,
-    height: '64px',
+    height: `${THUMB_MD.h}px`,
     display: 'flex',
     alignItems: 'center',
     justifyContent: 'center',
-    ...shorthands.borderRadius(tokens.borderRadiusLarge)
+    // One thumbnail radius app-wide (UI6): control tier / Medium.
+    ...shorthands.borderRadius(RADIUS.control)
   },
   body: {
     flexGrow: 1,
@@ -60,20 +70,11 @@ const useStyles = makeStyles({
     alignItems: 'center',
     gap: '8px'
   },
-  title: {
-    fontWeight: tokens.fontWeightSemibold,
-    overflow: 'hidden',
-    textOverflow: 'ellipsis',
-    whiteSpace: 'nowrap'
-  },
-  meta: {
-    color: tokens.colorNeutralForeground3
-  },
   progressRow: {
     display: 'flex',
     alignItems: 'center',
     gap: '10px',
-    marginTop: '4px'
+    marginTop: SPACE.xtight
   },
   progressBar: {
     flexGrow: 1
@@ -88,63 +89,88 @@ const useStyles = makeStyles({
   actions: {
     display: 'flex',
     alignItems: 'center',
-    gap: '4px',
+    gap: SPACE.xtight,
-    flexShrink: 0
+    flexShrink: 0,
+    // Icon-only row actions get a >=40px hit target for touch/pen (W16); the
+    // glyph stays its normal size, the subtle button just carries more padding.
+    '& button': {
+      minWidth: '40px',
+      minHeight: '40px'
+    }
   }
 })
 
-const STATUS_BADGE: Record<DownloadStatus, { label: string; color: 'brand' | 'success' | 'danger' | 'warning' | 'subtle' }> = {
-  queued: { label: 'Queued', color: 'subtle' },
-  downloading: { label: 'Downloading', color: 'brand' },
-  paused: { label: 'Paused', color: 'warning' },
-  saved: { label: 'Saved', color: 'subtle' },
-  completed: { label: 'Completed', color: 'success' },
-  error: { label: 'Failed', color: 'danger' },
-  canceled: { label: 'Canceled', color: 'warning' }
-}
-
 function pct(progress: number): string {
   return `${Math.round(progress * 100)}%`
 }
 
-function fmtSchedule(ms: number): string {
-  try {
-    return new Date(ms).toLocaleString([], { dateStyle: 'medium', timeStyle: 'short' })
-  } catch {
-    return ''
-  }
-}
-
 export const QueueItem = memo(function QueueItem({
   item
 }: {
   item: DownloadItem
 }): React.JSX.Element {
   const styles = useStyles()
-  const cancel = useDownloads((s) => s.cancel)
+  const focus = useFocusStyles()
-  const pause = useDownloads((s) => s.pause)
+  const text = useTextStyles()
-  const resume = useDownloads((s) => s.resume)
+  // One shallow-compared selection instead of 10 separate subscriptions per row
-  const prioritize = useDownloads((s) => s.prioritize)
+  // (L163). The actions are stable, so this never re-renders from the store.
-  const saveForLater = useDownloads((s) => s.saveForLater)
+  const {
-  const queueNow = useDownloads((s) => s.queueNow)
+    cancel,
-  const remove = useDownloads((s) => s.remove)
+    pause,
-  const retry = useDownloads((s) => s.retry)
+    resume,
-  const openFile = useDownloads((s) => s.openFile)
+    prioritize,
-  const showInFolder = useDownloads((s) => s.showInFolder)
+    saveForLater,
+    queueNow,
+    remove,
+    retry,
+    openFile,
+    showInFolder
+  } = useDownloads(
+    useShallow((s) => ({
+      cancel: s.cancel,
+      pause: s.pause,
+      resume: s.resume,
+      prioritize: s.prioritize,
+      saveForLater: s.saveForLater,
+      queueNow: s.queueNow,
+      remove: s.remove,
+      retry: s.retry,
+      openFile: s.openFile,
+      showInFolder: s.showInFolder
+    }))
+  )
 
-  const badge = STATUS_BADGE[item.status]
   const active = item.status === 'downloading' || item.status === 'queued'
 
+  // W7: Delete on a focused row removes it -- cancelling first if it's still running,
+  // since an in-flight download can't just be dropped from the list. Only when the
+  // row itself holds focus, so Delete on one of its action buttons is unaffected.
+  function onKeyDown(e: React.KeyboardEvent): void {
+    if (e.key === 'Delete' && e.target === e.currentTarget) {
+      e.preventDefault()
+      if (active) cancel(item.id)
+      else remove(item.id)
+    }
+  }
+
+  // Format the raw progress numbers for display (H4: main sends bytes/sec + secs,
+  // the renderer owns formatting via the one shared formatter).
+  const speedLabel = fmtSpeed(item.speedBytesPerSec)
+  const etaLabel = fmtEta(item.etaSeconds)
+
+  // L55: a probed-format quality label already carries the size ("720p · mp4 ·
+  // 184 MB"); skip sizeLabel when it's already embedded to avoid showing it twice.
+  const sizeAlreadyInQuality = item.sizeLabel && item.quality.includes(item.sizeLabel)
   const metaParts = [
     item.channel,
     item.durationLabel,
     item.quality,
     item.kind === 'audio' ? 'Audio' : 'Video',
-    item.sizeLabel
+    !sizeAlreadyInQuality ? item.sizeLabel : undefined
   ].filter(Boolean)
 
   return (
-    <div className={styles.root}>
+    <div className={mergeClasses(styles.root, focus.focusRing)} tabIndex={0} onKeyDown={onKeyDown}>
       <MediaThumb
         className={styles.thumb}
         src={thumbUrl({ thumbnail: item.thumbnail, url: item.url })}
@@ -156,57 +182,82 @@ export const QueueItem = memo(function QueueItem({
         <div className={styles.titleRow}>
           {item.status === 'completed' && (
             <CheckmarkCircleFilled
-              fontSize={16}
+              fontSize={ICON.inline}
               style={{ color: tokens.colorPaletteGreenForeground1, flexShrink: 0 }}
             />
           )}
           {item.status === 'error' && (
             <ErrorCircleFilled
-              fontSize={16}
+              fontSize={ICON.inline}
               style={{ color: tokens.colorPaletteRedForeground1, flexShrink: 0 }}
             />
           )}
-          <Text className={styles.title}>{item.title}</Text>
+          <Text className={text.title}>{item.title}</Text>
-          <Badge appearance="tint" color={badge.color}>
+          <StatusChip status={item.status} />
-            {badge.label}
-          </Badge>
           {item.incognito && (
-            <Hint label="Private — not saved to history" placement="top" align="start">
+            <Hint label="Private -- not saved to history" placement="top" align="start">
-              <EyeOffRegular fontSize={14} style={{ color: tokens.colorNeutralForeground3 }} />
+              <EyeOffRegular
+                fontSize={ICON.inline}
+                style={{ color: tokens.colorNeutralForeground3 }}
+              />
             </Hint>
           )}
         </div>
 
-        <Caption1 className={styles.meta}>{metaParts.join('  •  ')}</Caption1>
+        <Caption1 className={text.muted}>{metaParts.join(META_SEP)}</Caption1>
 
         {item.status === 'downloading' && (
           <div className={styles.progressRow}>
-            <ProgressBar className={styles.progressBar} value={item.progress} thickness="large" />
+            {/* Indeterminate when finishing (the second stream / merge reads as
+                "working" rather than a 0→100% restart, SR7) or when yt-dlp can't
+                report a total size, so the bar never sits frozen at 0% (L137). */}
+            <ProgressBar
+              className={styles.progressBar}
+              value={item.finishing || item.sizeUnknown ? undefined : item.progress}
+              thickness="large"
+              aria-label={`Download progress for ${item.title ?? item.url}`}
+            />
             <Caption1 className={styles.stats}>
-              {pct(item.progress)}
+              {item.finishing ? (
-              {item.speed ? `  •  ${item.speed}` : ''}
+                'Finishing…'
-              {item.eta ? `  •  ${item.eta} left` : ''}
+              ) : (
+                <>
+                  {item.sizeUnknown ? 'Downloading…' : pct(item.progress)}
+                  {speedLabel ? `${META_SEP}${speedLabel}` : ''}
+                  {etaLabel ? `${META_SEP}${etaLabel} left` : ''}
+                </>
+              )}
             </Caption1>
           </div>
         )}
 
         {item.status === 'queued' && (
           <div className={styles.progressRow}>
-            <Spinner size="extra-tiny" />
+            <Spinner size="tiny" />
             <Caption1 className={styles.stats}>Waiting to start…</Caption1>
           </div>
         )}
 
         {item.status === 'paused' && (
           <div className={styles.progressRow}>
-            <ProgressBar className={styles.progressBar} value={item.progress} thickness="large" />
+            <ProgressBar
-            <Caption1 className={styles.stats}>Paused • {pct(item.progress)}</Caption1>
+              className={styles.progressBar}
+              value={item.progress}
+              thickness="large"
+              aria-label={`Download progress for ${item.title ?? item.url}`}
+            />
+            <Caption1 className={styles.stats}>
+              Paused{META_SEP}
+              {pct(item.progress)}
+            </Caption1>
           </div>
         )}
 
         {item.status === 'saved' && (
           <Caption1 className={styles.stats}>
-            {item.scheduledFor ? `Scheduled for ${fmtSchedule(item.scheduledFor)}` : 'Saved for later'}
+            {item.scheduledFor
+              ? `Scheduled for ${fmtSchedule(item.scheduledFor)}`
+              : 'Saved for later'}
           </Caption1>
         )}
 

src/renderer/src/components/Select.tsx

@@ -1,9 +1,15 @@
-import { makeStyles, mergeClasses, tokens, shorthands } from '@fluentui/react-components'
+import {
+  makeStyles,
+  mergeClasses,
+  tokens,
+  shorthands,
+  useFieldControlProps_unstable
+} from '@fluentui/react-components'
 
 // A native <select> styled to match Fluent inputs. We use this instead of
 // Fluent's <Dropdown> because Fluent's portal/popover menu is a composited
 // overlay in the WebContents, and on this dev machine's GPU/driver that overlay
-// paint blanks the whole window (same family as the documented flicker —
+// paint blanks the whole window (same family as the documented flicker --
 // hardware acceleration is already disabled; see memory "aerofetch-gpu-flicker").
 // The native <select> popup is drawn by the OS, so it can't trigger the blank.
 // The popup's light/dark styling follows the `color-scheme` set on the app root
@@ -27,6 +33,20 @@ const useStyles = makeStyles({
       outline: 'none',
       ...shorthands.borderColor(tokens.colorCompoundBrandStroke)
     }
+  },
+  large: {
+    height: '40px',
+    padding: '0 12px',
+    fontSize: tokens.fontSizeBase400
+  },
+  disabled: {
+    cursor: 'not-allowed',
+    color: tokens.colorNeutralForegroundDisabled,
+    backgroundColor: tokens.colorNeutralBackgroundDisabled,
+    ...shorthands.borderColor(tokens.colorNeutralStrokeDisabled),
+    ':hover': {
+      ...shorthands.borderColor(tokens.colorNeutralStrokeDisabled)
+    }
   }
 })
 
@@ -41,6 +61,8 @@ interface SelectProps {
   onChange: (value: string) => void
   className?: string
   'aria-label'?: string
+  size?: 'medium' | 'large'
+  disabled?: boolean
 }
 
 export function Select({
@@ -48,15 +70,30 @@ export function Select({
   options,
   onChange,
   className,
-  'aria-label': ariaLabel
+  'aria-label': ariaLabel,
+  size,
+  disabled
 }: SelectProps): React.JSX.Element {
   const styles = useStyles()
+  // Integrate with a wrapping Fluent <Field> (L133): pick up the id + label/hint
+  // association so the Field's visible label names the select natively (via
+  // `htmlFor`), instead of every call site repeating the name in an `aria-label`.
+  // Outside a Field this returns the props unchanged, so standalone selects keep
+  // their own `aria-label`. `supportsLabelFor` = native <label for>, not aria-labelledby.
+  const fieldProps = useFieldControlProps_unstable({}, { supportsLabelFor: true })
   return (
     <select
-      className={mergeClasses(styles.select, className)}
+      {...fieldProps}
+      aria-label={ariaLabel}
+      className={mergeClasses(
+        styles.select,
+        size === 'large' && styles.large,
+        disabled && styles.disabled,
+        className
+      )}
       value={value}
       onChange={(e) => onChange(e.target.value)}
-      aria-label={ariaLabel}
+      disabled={disabled}
     >
       {options.map((o) => (
         <option key={o.value} value={o.value}>

src/renderer/src/components/Sidebar.tsx

@@ -1,4 +1,11 @@
-import { Caption1, makeStyles, mergeClasses, tokens, shorthands } from '@fluentui/react-components'
+import {
+  Caption1,
+  CounterBadge,
+  makeStyles,
+  mergeClasses,
+  tokens,
+  shorthands
+} from '@fluentui/react-components'
 import {
   ArrowDownloadFilled,
   ArrowDownloadRegular,
@@ -14,6 +21,11 @@ import {
 } from '@fluentui/react-icons'
 import type { ThemeMode } from '@shared/ipc'
 import { Hint } from './Hint'
+import { SegmentedControl } from './ui/SegmentedControl'
+import { IconButton } from './ui/IconButton'
+import { useFocusStyles } from './ui/focusRing'
+import { useTextStyles } from './ui/text'
+import { MOTION, ICON } from './ui/tokens'
 
 export type TabValue = 'downloads' | 'library' | 'history' | 'terminal' | 'settings'
 
@@ -27,7 +39,8 @@ const useStyles = makeStyles({
     padding: '16px 12px',
     backgroundColor: tokens.colorNeutralBackground1,
     borderRight: `1px solid ${tokens.colorNeutralStroke2}`,
-    transition: 'width 0.15s ease'
+    // The app's one motion timing, gated globally on prefers-reduced-motion (UI26).
+    transition: `width ${MOTION.duration} ${MOTION.curve}`
   },
   rootCollapsed: {
     width: '60px',
@@ -41,24 +54,6 @@ const useStyles = makeStyles({
   topBarCollapsed: {
     justifyContent: 'center'
   },
-  iconBtn: {
-    appearance: 'none',
-    border: 'none',
-    backgroundColor: 'transparent',
-    color: tokens.colorNeutralForeground3,
-    display: 'flex',
-    alignItems: 'center',
-    justifyContent: 'center',
-    width: '32px',
-    height: '32px',
-    fontSize: '18px',
-    cursor: 'pointer',
-    ...shorthands.borderRadius(tokens.borderRadiusMedium),
-    ':hover': {
-      backgroundColor: tokens.colorNeutralBackground1Hover,
-      color: tokens.colorNeutralForeground2
-    }
-  },
   brand: {
     display: 'flex',
     alignItems: 'center',
@@ -79,7 +74,8 @@ const useStyles = makeStyles({
     display: 'flex',
     alignItems: 'center',
     justifyContent: 'center',
-    fontSize: '20px'
+    // Brand tile glyph, snapped to the nearest ICON tier (UI11 — no literal px).
+    fontSize: `${ICON.control}px`
   },
   brandText: {
     display: 'flex',
@@ -92,9 +88,6 @@ const useStyles = makeStyles({
     lineHeight: tokens.lineHeightBase400,
     color: tokens.colorNeutralForeground1
   },
-  caption: {
-    color: tokens.colorNeutralForeground3
-  },
   nav: {
     display: 'flex',
     flexDirection: 'column',
@@ -102,6 +95,8 @@ const useStyles = makeStyles({
     alignSelf: 'stretch'
   },
   navItem: {
+    // relative so the collapsed count badge can pin to the icon's corner.
+    position: 'relative',
     display: 'flex',
     alignItems: 'center',
     gap: '11px',
@@ -119,6 +114,16 @@ const useStyles = makeStyles({
       backgroundColor: tokens.colorNeutralBackground1Hover
     }
   },
+  // Expanded: the active-download count sits at the far right of the nav row.
+  navBadge: {
+    marginLeft: 'auto'
+  },
+  // Collapsed: pin the count to the top-right corner of the centered icon.
+  navBadgeCollapsed: {
+    position: 'absolute',
+    top: '4px',
+    right: '8px'
+  },
   navItemCollapsed: {
     justifyContent: 'center',
     padding: '9px 0'
@@ -132,47 +137,12 @@ const useStyles = makeStyles({
     }
   },
   navIcon: {
-    fontSize: '18px',
+    fontSize: `${ICON.control}px`,
     flexShrink: 0,
     display: 'flex'
   },
   spacer: {
     flexGrow: 1
-  },
-  // --- theme control (expanded): a 3-way Light / Dark / Auto segmented switch ---
-  themeGroup: {
-    alignSelf: 'stretch',
-    display: 'flex',
-    width: '100%',
-    border: `1px solid ${tokens.colorNeutralStroke1}`,
-    ...shorthands.borderRadius(tokens.borderRadiusMedium),
-    overflow: 'hidden'
-  },
-  themeSeg: {
-    flex: 1,
-    appearance: 'none',
-    border: 'none',
-    backgroundColor: 'transparent',
-    color: tokens.colorNeutralForeground2,
-    display: 'flex',
-    alignItems: 'center',
-    justifyContent: 'center',
-    gap: '5px',
-    padding: '7px 4px',
-    fontSize: tokens.fontSizeBase200,
-    fontFamily: tokens.fontFamilyBase,
-    cursor: 'pointer',
-    ':hover': {
-      backgroundColor: tokens.colorNeutralBackground1Hover
-    }
-  },
-  themeSegActive: {
-    backgroundColor: tokens.colorBrandBackground,
-    color: tokens.colorNeutralForegroundOnBrand,
-    fontWeight: tokens.fontWeightSemibold,
-    ':hover': {
-      backgroundColor: tokens.colorBrandBackgroundHover
-    }
   }
 })
 
@@ -202,6 +172,10 @@ interface SidebarProps {
   version: string
   collapsed: boolean
   onToggleCollapsed: () => void
+  /** Show the Terminal nav item (only when custom commands are enabled) */
+  showTerminal: boolean
+  /** Active (downloading + queued) count, badged on the Downloads nav item (UX9). */
+  downloadCount: number
 }
 
 export function Sidebar({
@@ -212,22 +186,27 @@ export function Sidebar({
   onSetTheme,
   version,
   collapsed,
-  onToggleCollapsed
+  onToggleCollapsed,
+  showTerminal,
+  downloadCount
 }: SidebarProps): React.JSX.Element {
   const styles = useStyles()
+  const focus = useFocusStyles()
+  const text = useTextStyles()
 
   // Collapsed view shows one button that cycles Light → Dark → Auto.
   const order: ThemeMode[] = ['light', 'dark', 'system']
   function cycleTheme(): void {
-    onSetTheme(order[(order.indexOf(theme) + 1) % order.length])
+    const next = order[(order.indexOf(theme) + 1) % order.length]
+    if (next) onSetTheme(next)
   }
   const themeIcon =
     theme === 'system' ? (
-      <DesktopRegular fontSize={18} />
+      <DesktopRegular fontSize={ICON.control} />
     ) : isDark ? (
-      <WeatherMoonRegular fontSize={18} />
+      <WeatherMoonRegular fontSize={ICON.control} />
     ) : (
-      <WeatherSunnyRegular fontSize={18} />
+      <WeatherSunnyRegular fontSize={ICON.control} />
     )
   const themeLabel = theme === 'system' ? 'Auto (system)' : isDark ? 'Dark' : 'Light'
 
@@ -235,15 +214,12 @@ export function Sidebar({
     <nav className={mergeClasses(styles.root, collapsed && styles.rootCollapsed)}>
       <div className={mergeClasses(styles.topBar, collapsed && styles.topBarCollapsed)}>
         <Hint label={collapsed ? 'Expand sidebar' : 'Collapse sidebar'} placement="right">
-          <button
+          <IconButton
-            type="button"
+            icon={collapsed ? <PanelLeftExpandRegular /> : <PanelLeftContractRegular />}
-            className={styles.iconBtn}
             onClick={onToggleCollapsed}
             aria-label={collapsed ? 'Expand sidebar' : 'Collapse sidebar'}
             aria-pressed={collapsed}
-          >
+          />
-            {collapsed ? <PanelLeftExpandRegular /> : <PanelLeftContractRegular />}
-          </button>
         </Hint>
       </div>
 
@@ -254,13 +230,18 @@ export function Sidebar({
         {!collapsed && (
           <div className={styles.brandText}>
             <span className={styles.brandName}>AeroFetch</span>
-            <Caption1 className={styles.caption}>{version ? `v${version}` : 'yt-dlp frontend'}</Caption1>
+            {/* Stable tagline so the caption never flips from text to a version
+                string once it loads (L66); the version shows on hover and in
+                Settings → About. */}
+            <Caption1 className={text.muted} title={version ? `Version ${version}` : undefined}>
+              Video downloader
+            </Caption1>
           </div>
         )}
       </div>
 
       <div className={styles.nav}>
-        {NAV.map((n) => {
+        {NAV.filter((n) => n.value !== 'terminal' || showTerminal).map((n) => {
           const active = tab === n.value
           const btn = (
             <button
@@ -269,7 +250,8 @@ export function Sidebar({
               className={mergeClasses(
                 styles.navItem,
                 collapsed && styles.navItemCollapsed,
-                active && styles.navItemActive
+                active && styles.navItemActive,
+                focus.focusRing
               )}
               style={
                 active && !collapsed
@@ -278,10 +260,23 @@ export function Sidebar({
               }
               onClick={() => onTabChange(n.value)}
               aria-current={active ? 'page' : undefined}
-              aria-label={n.label}
+              aria-label={
+                n.value === 'downloads' && downloadCount > 0
+                  ? `${n.label}, ${downloadCount} active`
+                  : n.label
+              }
             >
               <span className={styles.navIcon}>{n.icon}</span>
               {!collapsed && n.label}
+              {n.value === 'downloads' && downloadCount > 0 && (
+                <CounterBadge
+                  className={collapsed ? styles.navBadgeCollapsed : styles.navBadge}
+                  count={downloadCount}
+                  size="small"
+                  color="brand"
+                  aria-hidden
+                />
+              )}
             </button>
           )
           return collapsed ? (
@@ -298,34 +293,20 @@ export function Sidebar({
 
       {collapsed ? (
         <Hint label={`Theme: ${themeLabel}`} placement="right">
-          <button
+          <IconButton
-            type="button"
+            icon={themeIcon}
-            className={styles.iconBtn}
             onClick={cycleTheme}
-            aria-label={`Theme: ${themeLabel}. Click to change.`}
+            aria-label={`Change theme (currently ${themeLabel})`}
-          >
+          />
-            {themeIcon}
-          </button>
         </Hint>
       ) : (
-        <div className={styles.themeGroup} role="radiogroup" aria-label="Theme">
+        <SegmentedControl<ThemeMode>
-          {THEMES.map((t) => {
+          fitted
-            const on = theme === t.value
+          value={theme}
-            return (
+          options={THEMES}
-              <button
+          onChange={onSetTheme}
-                key={t.value}
+          ariaLabel="Theme"
-                type="button"
+        />
-                role="radio"
-                aria-checked={on}
-                className={mergeClasses(styles.themeSeg, on && styles.themeSegActive)}
-                onClick={() => onSetTheme(t.value)}
-              >
-                <span className={styles.navIcon}>{t.icon}</span>
-                {t.label}
-              </button>
-            )
-          })}
-        </div>
       )}
     </nav>
   )

src/renderer/src/components/TemplateManager.tsx

@@ -1,6 +1,7 @@
 import { useState } from 'react'
 import {
   Button,
+  Field,
   Input,
   Textarea,
   Caption1,
@@ -9,10 +10,18 @@ import {
   tokens,
   shorthands
 } from '@fluentui/react-components'
-import { AddRegular, EditRegular, DeleteRegular, SaveRegular, DismissRegular } from '@fluentui/react-icons'
+import {
+  AddRegular,
+  EditRegular,
+  DeleteRegular,
+  SaveRegular,
+  DismissRegular
+} from '@fluentui/react-icons'
 import type { CommandTemplate } from '@shared/ipc'
 import { useTemplates } from '../store/templates'
+import { newId } from '../id'
 import { Hint } from './Hint'
+import { EmptyState } from './ui/EmptyState'
 
 const useStyles = makeStyles({
   root: {
@@ -63,9 +72,6 @@ const useStyles = makeStyles({
     display: 'flex',
     gap: '8px',
     justifyContent: 'flex-end'
-  },
-  empty: {
-    color: tokens.colorNeutralForeground3
   }
 })
 
@@ -79,10 +85,6 @@ interface Draft {
 }
 const BLANK_DRAFT: Draft = { id: null, name: '', args: '', urlPattern: '' }
 
-function newId(): string {
-  return typeof crypto !== 'undefined' && crypto.randomUUID ? crypto.randomUUID() : `tpl-${Date.now()}`
-}
-
 /**
  * Inline (no-modal — see the Hint/Select comments re: composited overlays
  * flickering on this dev machine's GPU) CRUD list + add/edit form for
@@ -100,13 +102,24 @@ export function TemplateManager(): React.JSX.Element {
     setDraft({ id: t.id, name: t.name, args: t.args, urlPattern: t.urlPattern ?? '' })
   }
 
+  function patternError(): string | undefined {
+    const p = draft?.urlPattern.trim()
+    if (!p) return undefined
+    try {
+      new RegExp(p)
+      return undefined
+    } catch {
+      return 'Invalid regex — this pattern will never match.'
+    }
+  }
+
   function commit(): void {
     if (!draft) return
     const name = draft.name.trim()
-    if (!name) return
+    if (!name || patternError()) return
     const urlPattern = draft.urlPattern.trim()
     save({
-      id: draft.id ?? newId(),
+      id: draft.id ?? newId('tpl'),
       name,
       args: draft.args.trim(),
       ...(urlPattern ? { urlPattern } : {})
@@ -117,7 +130,7 @@ export function TemplateManager(): React.JSX.Element {
   return (
     <div className={styles.root}>
       {templates.length === 0 && !draft && (
-        <Caption1 className={styles.empty}>No custom command templates yet.</Caption1>
+        <EmptyState compact message="No custom command templates yet." />
       )}
 
       {templates.map((t) => (
@@ -162,11 +175,16 @@ export function TemplateManager(): React.JSX.Element {
             resize="vertical"
             onChange={(_, d) => setDraft({ ...draft, args: d.value })}
           />
+          <Field
+            validationState={patternError() ? 'error' : 'none'}
+            validationMessage={patternError()}
+          >
             <Input
               value={draft.urlPattern}
               placeholder="Auto-apply to URLs matching (regex, optional) — e.g. soundcloud\.com"
               onChange={(_, d) => setDraft({ ...draft, urlPattern: d.value })}
             />
+          </Field>
           <div className={styles.formActions}>
             <Button appearance="subtle" icon={<DismissRegular />} onClick={() => setDraft(null)}>
               Cancel
@@ -182,7 +200,11 @@ export function TemplateManager(): React.JSX.Element {
           </div>
         </div>
       ) : (
-        <Button appearance="subtle" icon={<AddRegular />} onClick={() => setDraft({ ...BLANK_DRAFT })}>
+        <Button
+          appearance="subtle"
+          icon={<AddRegular />}
+          onClick={() => setDraft({ ...BLANK_DRAFT })}
+        >
           Add template
         </Button>
       )}

src/renderer/src/components/TerminalView.tsx

@@ -1,28 +1,42 @@
-import { useEffect, useRef, useState } from 'react'
+import { useEffect, useRef, useState } from 'react'
 import {
   Button,
   Textarea,
-  Subtitle2,
   Body1,
   Caption1,
   makeStyles,
+  mergeClasses,
   tokens,
   shorthands
 } from '@fluentui/react-components'
 import { PlayRegular, DismissRegular, DeleteRegular } from '@fluentui/react-icons'
 import { useSettings } from '../store/settings'
+import { newId } from '../id'
+import { ScreenHeader, useScreenStyles } from './ui/Screen'
+import { EmptyState } from './ui/EmptyState'
+import { SPACE } from './ui/tokens'
 
 type LineKind = 'stdout' | 'stderr' | 'cmd' | 'sys'
 interface Line {
+  id: number
   text: string
   kind: LineKind
 }
+let lineSeq = 0
+const mkLine = (text: string, kind: LineKind): Line => ({ id: ++lineSeq, text, kind })
+
+// Verbose yt-dlp runs (--verbose, -F on a large channel) can emit thousands of
+// lines in seconds. Cap the visible log to prevent unbounded React state growth
+// and keep the <pre> scrollable (H6); older lines are dropped from the front.
+const MAX_LOG_LINES = 2000
 
 const useStyles = makeStyles({
-  root: { display: 'flex', flexDirection: 'column', gap: '16px', height: '100%' },
+  root: { display: 'flex', flexDirection: 'column', gap: SPACE.section, height: '100%' },
-  header: { display: 'flex', flexDirection: 'column', gap: '2px' },
-  sub: { color: tokens.colorNeutralForeground3 },
   gate: {
+    display: 'flex',
+    flexDirection: 'column',
+    alignItems: 'flex-start',
+    gap: '8px',
     padding: '12px 14px',
     backgroundColor: tokens.colorStatusWarningBackground1,
     color: tokens.colorStatusWarningForeground1,
@@ -48,24 +62,24 @@ const useStyles = makeStyles({
     whiteSpace: 'pre-wrap',
     wordBreak: 'break-word'
   },
+  // Center the "no output yet" placeholder in the log box, so it reads as an
+  // empty state rather than a stray line of text at the top (L117).
+  logEmpty: { display: 'flex', alignItems: 'center', justifyContent: 'center' },
   cmd: { color: tokens.colorBrandForeground1, fontWeight: tokens.fontWeightSemibold },
   stderr: { color: tokens.colorPaletteRedForeground1 },
-  sys: { color: tokens.colorNeutralForeground3 },
+  sys: { color: tokens.colorNeutralForeground3 }
-  empty: { color: tokens.colorNeutralForeground3 }
 })
 
-function newId(): string {
-  return typeof crypto !== 'undefined' && crypto.randomUUID ? crypto.randomUUID() : `t-${Date.now()}`
-}
-
 /**
  * Built-in yt-dlp terminal (Phase N): type raw yt-dlp args, run the bundled
  * binary, and watch its output stream. Gated on the customCommandEnabled consent
- * flag (enforced again in main — see src/main/terminal.ts).
+ * flag (enforced again in main -- see src/main/terminal.ts).
  */
 export function TerminalView(): React.JSX.Element {
   const styles = useStyles()
+  const screen = useScreenStyles()
   const customCommandEnabled = useSettings((s) => s.customCommandEnabled)
+  const updateSettings = useSettings((s) => s.update)
 
   const [args, setArgs] = useState('')
   const [lines, setLines] = useState<Line[]>([])
@@ -79,13 +93,15 @@ export function TerminalView(): React.JSX.Element {
       window.api.onTerminalOutput((ev) => {
         if (ev.id !== runId.current) return
         if (ev.type === 'output') {
-          setLines((ls) => [...ls, { text: ev.line, kind: ev.stream }])
+          setLines((ls) => [...ls, mkLine(ev.line, ev.stream)].slice(-MAX_LOG_LINES))
         } else if (ev.type === 'error') {
-          setLines((ls) => [...ls, { text: ev.error, kind: 'stderr' }])
+          setLines((ls) => [...ls, mkLine(ev.error, 'stderr')].slice(-MAX_LOG_LINES))
           setRunning(false)
           runId.current = null
         } else {
-          setLines((ls) => [...ls, { text: `— exited (code ${ev.code ?? '?'})`, kind: 'sys' }])
+          setLines((ls) =>
+            [...ls, mkLine(`-- exited (code ${ev.code ?? '?'})`, 'sys')].slice(-MAX_LOG_LINES)
+          )
           setRunning(false)
           runId.current = null
         }
@@ -101,21 +117,21 @@ export function TerminalView(): React.JSX.Element {
   function run(): void {
     const a = args.trim()
     if (!a || running) return
-    const id = newId()
+    const id = newId('t')
     runId.current = id
-    setLines((ls) => [...ls, { text: `> yt-dlp ${a}`, kind: 'cmd' }])
+    setLines((ls) => [...ls, mkLine(`> yt-dlp ${a}`, 'cmd')])
     setRunning(true)
     window.api
       .runTerminal(id, a)
       .then((res) => {
         if (!res.ok) {
-          setLines((ls) => [...ls, { text: res.error ?? 'Failed to start.', kind: 'stderr' }])
+          setLines((ls) => [...ls, mkLine(res.error ?? 'Failed to start.', 'stderr')])
           setRunning(false)
           runId.current = null
         }
       })
       .catch((e: unknown) => {
-        setLines((ls) => [...ls, { text: String(e), kind: 'stderr' }])
+        setLines((ls) => [...ls, mkLine(String(e), 'stderr')])
         setRunning(false)
         runId.current = null
       })
@@ -126,29 +142,47 @@ export function TerminalView(): React.JSX.Element {
   }
 
   const lineClass = (kind: LineKind): string | undefined =>
-    kind === 'cmd' ? styles.cmd : kind === 'stderr' ? styles.stderr : kind === 'sys' ? styles.sys : undefined
+    kind === 'cmd'
+      ? styles.cmd
+      : kind === 'stderr'
+        ? styles.stderr
+        : kind === 'sys'
+          ? styles.sys
+          : undefined
 
   return (
-    <div className={styles.root}>
+    <div className={mergeClasses(styles.root, screen.width)}>
-      <div className={styles.header}>
+      <ScreenHeader
-        <Subtitle2>Terminal</Subtitle2>
+        title="Terminal"
-        <Caption1 className={styles.sub}>
+        description={
+          <>
             Run the bundled yt-dlp with your own arguments. The URL goes in the args too, e.g.{' '}
             <code>-F https://youtu.be/…</code>. ffmpeg is wired up automatically.
-        </Caption1>
+          </>
-      </div>
+        }
+      />
 
       {!customCommandEnabled && (
-        <Body1 className={styles.gate}>
+        <div className={styles.gate}>
-          The terminal is part of custom commands. Turn on “Run custom commands” in Settings →
+          <Body1>
-          Custom commands to use it.
+            The terminal runs the bundled yt-dlp with your own arguments — part of custom commands,
+            which can pass arbitrary yt-dlp flags. Turn it on to use the terminal.
           </Body1>
+          <Button
+            appearance="primary"
+            size="small"
+            onClick={() => updateSettings({ customCommandEnabled: true })}
+          >
+            Enable custom commands
+          </Button>
+        </div>
       )}
 
       <div className={styles.inputRow}>
         <div className={styles.inputCol}>
           <Caption1 className={styles.prefix}>yt-dlp</Caption1>
           <Textarea
+            textarea={{ 'aria-label': 'yt-dlp arguments' }}
             value={args}
             onChange={(_, d) => setArgs(d.value)}
             onKeyDown={(e) => {
@@ -164,7 +198,7 @@ export function TerminalView(): React.JSX.Element {
         </div>
         <div className={styles.buttons}>
           {running ? (
-            <Button appearance="secondary" icon={<DismissRegular />} onClick={stop}>
+            <Button appearance="subtle" icon={<DismissRegular />} onClick={stop}>
               Stop
             </Button>
           ) : (
@@ -187,12 +221,12 @@ export function TerminalView(): React.JSX.Element {
         </div>
       </div>
 
-      <pre className={styles.log} ref={logRef}>
+      <pre className={mergeClasses(styles.log, lines.length === 0 && styles.logEmpty)} ref={logRef}>
         {lines.length === 0 ? (
-          <span className={styles.empty}>Output will appear here.</span>
+          <EmptyState compact message="No output yet." hint="Run yt-dlp above to see its output." />
         ) : (
-          lines.map((l, i) => (
+          lines.map((l) => (
-            <div key={i} className={lineClass(l.kind)}>
+            <div key={l.id} className={lineClass(l.kind)}>
               {l.text}
             </div>
           ))

src/renderer/src/components/VirtualList.tsx

@@ -42,13 +42,19 @@ export function VirtualList<T>({
     estimateSize,
     overscan,
     gap,
-    getItemKey: (index) => getKey(items[index], index)
+    getItemKey: (index) => {
+      const it = items[index]
+      return it !== undefined ? getKey(it, index) : index
+    }
   })
 
   return (
     <div ref={scrollRef} className={className} style={{ overflowY: 'auto', ...style }}>
       <div style={{ height: virtualizer.getTotalSize(), position: 'relative', width: '100%' }}>
-        {virtualizer.getVirtualItems().map((vrow) => (
+        {virtualizer.getVirtualItems().map((vrow) => {
+          const item = items[vrow.index]
+          if (item === undefined) return null
+          return (
             <div
               key={vrow.key}
               data-index={vrow.index}
@@ -61,9 +67,10 @@ export function VirtualList<T>({
                 transform: `translateY(${vrow.start}px)`
               }}
             >
-            {renderItem(items[vrow.index], vrow.index)}
+              {renderItem(item, vrow.index)}
             </div>
-        ))}
+          )
+        })}
       </div>
     </div>
   )

src/renderer/src/components/downloadBar/PlaylistPanel.tsx

@@ -0,0 +1,97 @@
+import { Button, Checkbox, Caption1, mergeClasses } from '@fluentui/react-components'
+import { AppsListRegular, VideoClipRegular, MusicNote2Regular } from '@fluentui/react-icons'
+import { type PlaylistInfo } from '@shared/ipc'
+import { type MediaKind } from '../../store/downloads'
+import { Hint } from '../Hint'
+import { IconButton } from '../ui/IconButton'
+import { useTextStyles } from '../ui/text'
+import { META_SEP } from '../ui/tokens'
+import { useDownloadBarStyles } from './styles'
+
+interface PlaylistPanelProps {
+  playlist: PlaylistInfo
+  selected: Set<number>
+  allSelected: boolean
+  onToggleAll: () => void
+  onSetAllKinds: (k: MediaKind) => void
+  onToggleEntry: (index: number, on: boolean) => void
+  effKind: (index: number) => MediaKind
+  onToggleItemKind: (index: number) => void
+}
+
+export function PlaylistPanel({
+  playlist,
+  selected,
+  allSelected,
+  onToggleAll,
+  onSetAllKinds,
+  onToggleEntry,
+  effKind,
+  onToggleItemKind
+}: PlaylistPanelProps): React.JSX.Element {
+  const styles = useDownloadBarStyles()
+  const text = useTextStyles()
+  return (
+    <div className={styles.plPanel}>
+      <div className={styles.plHeader}>
+        <AppsListRegular />
+        <Caption1 className={mergeClasses(styles.plHeaderGrow, text.title)}>
+          {playlist.title}
+          {playlist.uploader ? `${META_SEP}${playlist.uploader}` : ''}
+        </Caption1>
+        <Caption1 className={text.muted}>
+          {selected.size} of {playlist.count} selected
+        </Caption1>
+        <Button size="small" appearance="subtle" onClick={onToggleAll}>
+          {allSelected ? 'Select none' : 'Select all'}
+        </Button>
+        <Button size="small" appearance="subtle" onClick={() => onSetAllKinds('video')}>
+          All video
+        </Button>
+        <Button size="small" appearance="subtle" onClick={() => onSetAllKinds('audio')}>
+          All audio
+        </Button>
+      </div>
+      <div className={styles.plList}>
+        {playlist.entries.map((e) => (
+          <div key={e.index} className={styles.plItemRow}>
+            <Checkbox
+              className={styles.plItem}
+              checked={selected.has(e.index)}
+              onChange={(_, d) => onToggleEntry(e.index, !!d.checked)}
+              label={
+                <span className={styles.plItemLabel}>
+                  <span className={text.truncate}>
+                    {e.index}. {e.title}
+                  </span>
+                  {(e.durationLabel || e.uploader) && (
+                    <Caption1 className={text.muted}>
+                      {[e.durationLabel, e.uploader].filter(Boolean).join(META_SEP)}
+                    </Caption1>
+                  )}
+                </span>
+              }
+            />
+            <Hint
+              label={
+                effKind(e.index) === 'audio'
+                  ? 'Audio -- click for video'
+                  : 'Video -- click for audio'
+              }
+              placement="top"
+              align="end"
+            >
+              <IconButton
+                size="sm"
+                style={{ flexShrink: 0 }}
+                icon={effKind(e.index) === 'audio' ? <MusicNote2Regular /> : <VideoClipRegular />}
+                onClick={() => onToggleItemKind(e.index)}
+                aria-label={`Download type for ${e.title}: ${effKind(e.index)}`}
+              />
+            </Hint>
+          </div>
+        ))}
+      </div>
+    </div>
+  )
+}

src/renderer/src/components/downloadBar/styles.ts

@@ -0,0 +1,191 @@
+import { makeStyles, tokens, shorthands } from '@fluentui/react-components'
+import { THUMB_LG } from '../../thumbSizes'
+import { SPACE, RADIUS, ELEVATION } from '../ui/tokens'
+
+export const useDownloadBarStyles = makeStyles({
+  root: {
+    display: 'flex',
+    flexDirection: 'column',
+    gap: SPACE.cozy,
+    // Page-level card: card padding + card radius, and the app's one "raised"
+    // elevation — the download bar floats above the queue (UI3/UI7/L100).
+    padding: SPACE.section,
+    backgroundColor: tokens.colorNeutralBackground1,
+    ...shorthands.borderRadius(RADIUS.card),
+    boxShadow: ELEVATION.raised
+  },
+  // Highlight while a link / .url file is dragged over the card.
+  rootDragging: {
+    outline: `2px dashed ${tokens.colorBrandStroke1}`,
+    outlineOffset: '-2px'
+  },
+  urlRow: {
+    display: 'flex',
+    gap: '8px'
+  },
+  url: {
+    flexGrow: 1
+  },
+  // --- metadata preview card ---
+  preview: {
+    display: 'flex',
+    gap: '12px',
+    padding: '10px',
+    backgroundColor: tokens.colorNeutralBackground2,
+    ...shorthands.borderRadius(tokens.borderRadiusLarge),
+    border: `1px solid ${tokens.colorNeutralStroke2}`
+  },
+  previewThumb: {
+    flexShrink: 0,
+    width: `${THUMB_LG.w}px`,
+    height: `${THUMB_LG.h}px`,
+    objectFit: 'cover',
+    display: 'flex',
+    alignItems: 'center',
+    justifyContent: 'center',
+    backgroundColor: tokens.colorBrandBackground2,
+    color: tokens.colorBrandForeground1,
+    // One thumbnail radius app-wide (UI6): control tier / Medium.
+    ...shorthands.borderRadius(RADIUS.control)
+  },
+  previewBody: {
+    flexGrow: 1,
+    minWidth: 0,
+    display: 'flex',
+    flexDirection: 'column',
+    justifyContent: 'center',
+    gap: '2px'
+  },
+  statusRow: {
+    display: 'flex',
+    alignItems: 'center',
+    gap: '8px',
+    color: tokens.colorNeutralForeground3
+  },
+  errorRow: {
+    color: tokens.colorPaletteRedForeground1
+  },
+  controls: {
+    display: 'flex',
+    alignItems: 'flex-end',
+    gap: '16px',
+    flexWrap: 'wrap'
+  },
+  control: {
+    display: 'flex',
+    flexDirection: 'column',
+    gap: '4px'
+  },
+  quality: {
+    minWidth: '220px'
+  },
+  spacer: {
+    flexGrow: 1
+  },
+  // --- playlist selection ---
+  plPanel: {
+    display: 'flex',
+    flexDirection: 'column',
+    gap: '8px',
+    padding: '12px',
+    backgroundColor: tokens.colorNeutralBackground2,
+    ...shorthands.borderRadius(tokens.borderRadiusLarge),
+    border: `1px solid ${tokens.colorNeutralStroke2}`
+  },
+  plHeader: {
+    display: 'flex',
+    alignItems: 'center',
+    gap: '8px'
+  },
+  // Just the layout role; the truncation + weight come from the shared text.title
+  // (L114/L126), merged on at the call site.
+  plHeaderGrow: {
+    flexGrow: 1
+  },
+  plList: {
+    display: 'flex',
+    flexDirection: 'column',
+    maxHeight: '260px',
+    overflowY: 'auto',
+    paddingRight: '4px'
+  },
+  plItemRow: {
+    display: 'flex',
+    alignItems: 'center',
+    gap: '8px'
+  },
+  plItem: {
+    display: 'flex',
+    alignItems: 'flex-start',
+    padding: '2px 0',
+    flexGrow: 1,
+    minWidth: 0
+  },
+  plItemLabel: {
+    display: 'flex',
+    flexDirection: 'column',
+    minWidth: 0
+  },
+  // --- trim / schedule panels ---
+  trimBlock: {
+    display: 'flex',
+    flexDirection: 'column',
+    gap: '8px',
+    alignItems: 'flex-start'
+  },
+  optButtons: {
+    display: 'flex',
+    gap: '8px'
+  },
+  trimPanel: {
+    alignSelf: 'stretch',
+    padding: '12px',
+    backgroundColor: tokens.colorNeutralBackground2,
+    ...shorthands.borderRadius(tokens.borderRadiusLarge),
+    border: `1px solid ${tokens.colorNeutralStroke2}`
+  },
+  // Native datetime-local input, themed to sit beside the Fluent controls.
+  // No explicit `colorScheme` here (UI32): it inherits the resolved in-app scheme
+  // set on the app root in App.tsx, so the native calendar popup follows the app's
+  // Light/Dark theme — consistent with the native <Select> — rather than the OS
+  // preference (which the former `'light dark'` value tied it to).
+  dtInput: {
+    fontFamily: tokens.fontFamilyBase,
+    fontSize: tokens.fontSizeBase300,
+    padding: '6px 10px',
+    ...shorthands.borderRadius(tokens.borderRadiusMedium),
+    border: `1px solid ${tokens.colorNeutralStroke1}`,
+    backgroundColor: tokens.colorNeutralBackground1,
+    color: tokens.colorNeutralForeground1
+  },
+  // --- command preview & options panels ---
+  commandBlock: {
+    display: 'flex',
+    flexDirection: 'column',
+    gap: '8px'
+  },
+  commandPreviewPanel: {
+    padding: '12px',
+    backgroundColor: tokens.colorNeutralBackground2,
+    ...shorthands.borderRadius(tokens.borderRadiusLarge),
+    border: `1px solid ${tokens.colorNeutralStroke2}`,
+    fontFamily: tokens.fontFamilyMonospace,
+    fontSize: tokens.fontSizeBase200,
+    overflowX: 'auto',
+    whiteSpace: 'pre-wrap',
+    wordBreak: 'break-all',
+    color: tokens.colorNeutralForeground1
+  },
+  commandError: {
+    color: tokens.colorStatusDangerForeground1
+  },
+  optionsPanel: {
+    display: 'flex',
+    flexDirection: 'column',
+    gap: '12px',
+    padding: '12px',
+    backgroundColor: tokens.colorNeutralBackground2,
+    ...shorthands.borderRadius(tokens.borderRadiusLarge),
+    border: `1px solid ${tokens.colorNeutralStroke2}`
+  }
+})

src/renderer/src/components/downloadBar/useDownloadBar.ts

@@ -0,0 +1,606 @@
+import { useState, useEffect, useRef, type Dispatch, type SetStateAction } from 'react'
+import {
+  parseUrlShortcutContent,
+  type MediaInfo,
+  type FormatOption,
+  type PlaylistInfo,
+  type DownloadOptions,
+  DEFAULT_DOWNLOAD_OPTIONS,
+  type CommandPreviewResult
+} from '@shared/ipc'
+import { useDownloads, type MediaKind } from '../../store/downloads'
+import { useHistory } from '../../store/history'
+import { QUALITY_OPTIONS } from '../../qualityOptions'
+import { sameVideo } from '../../store/queueStats'
+import { useSettings } from '../../store/settings'
+import { useNav } from '../../store/nav'
+import {
+  useClipboardLink,
+  looksLikeUrl,
+  looksLikeChannelOrPlaylist,
+  firstUrlInText,
+  type SuggestionSource
+} from '../../useClipboardLink'
+import { logError } from '../../reportError'
+
+/** Pull the URL= target out of a dropped Windows .url Internet Shortcut file. */
+function parseUrlFile(content: string): string | null {
+  const url = parseUrlShortcutContent(content)
+  return url && looksLikeUrl(url) ? url : null
+}
+
+// Format a Date as the `YYYY-MM-DDTHH:mm` value a datetime-local input expects,
+// in LOCAL time -- used as the picker's `min` so a past time can't be chosen and
+// then silently download immediately (L156/L57).
+export function toLocalDatetimeValue(d: Date): string {
+  const pad = (n: number): string => String(n).padStart(2, '0')
+  return `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}T${pad(d.getHours())}:${pad(d.getMinutes())}`
+}
+
+/** Everything the DownloadBar render needs — the hook's public surface. */
+export interface DownloadBarController {
+  // form state
+  url: string
+  kind: MediaKind
+  quality: string
+  // trim / schedule
+  showTrim: boolean
+  setShowTrim: Dispatch<SetStateAction<boolean>>
+  trim: string
+  showSchedule: boolean
+  setShowSchedule: Dispatch<SetStateAction<boolean>>
+  scheduleAt: string
+  setScheduleAt: Dispatch<SetStateAction<string>>
+  // drag / dup
+  dragActive: boolean
+  setDragActive: Dispatch<SetStateAction<boolean>>
+  dup: string | null
+  setDup: Dispatch<SetStateAction<string | null>>
+  /** true when the duplicate was found in history (already downloaded) vs the live queue (L144). */
+  dupInHistory: boolean
+  // advanced / preview
+  showAdvanced: boolean
+  setShowAdvanced: Dispatch<SetStateAction<boolean>>
+  downloadOptions: DownloadOptions
+  incognito: boolean
+  setIncognito: Dispatch<SetStateAction<boolean>>
+  commandPreview: CommandPreviewResult | null
+  previewLoading: boolean
+  // probe (single video)
+  info: MediaInfo | null
+  thumbFailed: string | null
+  setThumbFailed: Dispatch<SetStateAction<string | null>>
+  probing: boolean
+  probeError: string | null
+  usingFormats: boolean
+  selectedFormat: FormatOption | undefined
+  // playlist
+  playlist: PlaylistInfo | null
+  selected: Set<number>
+  allSelected: boolean
+  // suggestion banner
+  suggestion: string | null
+  suggestionSource: SuggestionSource
+  dismissSuggestion: () => void
+  // channel/playlist nudge → Library (UX3)
+  channelHint: boolean
+  openInLibrary: () => void
+  dismissChannelHint: () => void
+  // handlers
+  onDragEnter: (e: React.DragEvent) => void
+  onDragOver: (e: React.DragEvent) => void
+  onDragLeave: () => void
+  onDrop: (e: React.DragEvent) => void
+  onUrlChange: (next: string) => void
+  onKindChange: (next: MediaKind) => void
+  onQualityChange: (v: string) => void
+  onFormatIdChange: (v: string) => void
+  onTrimChange: (v: string) => void
+  onDownloadOptionsChange: (next: DownloadOptions) => void
+  toggleCommandPreview: () => Promise<void>
+  fetchFormats: () => Promise<void>
+  paste: () => Promise<void>
+  acceptSuggestion: () => void
+  download: () => void
+  downloadAnyway: () => void
+  addPlaylist: () => void
+  toggleEntry: (index: number, on: boolean) => void
+  toggleAll: () => void
+  effKind: (index: number) => MediaKind
+  toggleItemKind: (index: number) => void
+  setAllKinds: (k: MediaKind) => void
+}
+
+/**
+ * All state and behaviour for the DownloadBar. Extracted from the component so
+ * the ~17 interdependent state hooks and their handlers live in one place and
+ * the component is render-only.
+ */
+export function useDownloadBar(): DownloadBarController {
+  const addFromUrl = useDownloads((s) => s.addFromUrl)
+  const addMany = useDownloads((s) => s.addMany)
+  const openLibraryWith = useNav((s) => s.openLibraryWith)
+  const settingsLoaded = useSettings((s) => s.loaded)
+  const defaultKind = useSettings((s) => s.defaultKind)
+  const defaultVideoQuality = useSettings((s) => s.defaultVideoQuality)
+  const defaultAudioQuality = useSettings((s) => s.defaultAudioQuality)
+
+  const [url, setUrl] = useState('')
+  const [kind, setKind] = useState<MediaKind>('video')
+  const [quality, setQuality] = useState<string>(QUALITY_OPTIONS.video[0])
+
+  // Optional trim: keep only certain time ranges. Raw text, normalised in main.
+  const [showTrim, setShowTrim] = useState(false)
+  const [trim, setTrim] = useState('')
+
+  // Optional schedule: a datetime-local value; a future time parks the download.
+  const [showSchedule, setShowSchedule] = useState(false)
+  const [scheduleAt, setScheduleAt] = useState('')
+
+  // Drag-and-drop: highlight while a link / .url file hovers the card.
+  const [dragActive, setDragActive] = useState(false)
+
+  // Channel/playlist nudge: a whole channel/playlist belongs in the Library, not
+  // the one-off queue. Once dismissed for the current URL, stay quiet (UX3).
+  const [channelHintDismissed, setChannelHintDismissed] = useState(false)
+
+  // Duplicate guard: warn before enqueuing a URL already in the active queue.
+  const [dup, setDup] = useState<string | null>(null)
+  // Whether the duplicate matched a history entry (already downloaded) rather than
+  // a live queue item (L144) — the banner wording differs.
+  const [dupInHistory, setDupInHistory] = useState(false)
+  const confirmDup = useRef(false)
+
+  // Per-download options (M5/M6/UX1): advanced features.
+  const [showAdvanced, setShowAdvanced] = useState(false)
+  const [downloadOptions, setDownloadOptions] = useState<DownloadOptions>(DEFAULT_DOWNLOAD_OPTIONS)
+  const [incognito, setIncognito] = useState(false)
+  const [commandPreview, setCommandPreview] = useState<CommandPreviewResult | null>(null)
+  const [previewLoading, setPreviewLoading] = useState(false)
+
+  // Probe state for the single-video format picker.
+  const [info, setInfo] = useState<MediaInfo | null>(null)
+  const [thumbFailed, setThumbFailed] = useState<string | null>(null)
+  const [probing, setProbing] = useState(false)
+  const [probeError, setProbeError] = useState<string | null>(null)
+  const [formatId, setFormatId] = useState<string>('')
+
+  // Probe state for a playlist URL.
+  const [playlist, setPlaylist] = useState<PlaylistInfo | null>(null)
+  const [selected, setSelected] = useState<Set<number>>(new Set())
+  // Per-entry kind override (entry.index → 'video' | 'audio'); absent = use the
+  // bar's global kind. Lets a playlist mix video and audio downloads.
+  const [itemKinds, setItemKinds] = useState<Record<number, MediaKind>>({})
+
+  // Drag highlight is gated on a depth counter, not raw enter/leave (L158): a
+  // dragleave fires every time the cursor crosses onto a child element, so toggling
+  // on leave made the dashed outline blink. Count enters vs leaves and only clear
+  // the highlight when the drag has actually left the whole card (depth back to 0).
+  const dragDepth = useRef(0)
+  function onDragEnter(e: React.DragEvent): void {
+    e.preventDefault()
+    dragDepth.current += 1
+    if (!dragActive) setDragActive(true)
+  }
+  function onDragOver(e: React.DragEvent): void {
+    // Required so the element is a valid drop target; the highlight is owned by
+    // onDragEnter/onDragLeave.
+    e.preventDefault()
+  }
+  function onDragLeave(): void {
+    dragDepth.current = Math.max(0, dragDepth.current - 1)
+    if (dragDepth.current === 0) setDragActive(false)
+  }
+  function onDrop(e: React.DragEvent): void {
+    e.preventDefault()
+    dragDepth.current = 0
+    setDragActive(false)
+    const dt = e.dataTransfer
+    const fromText = firstUrlInText(dt.getData('text/uri-list') || dt.getData('text/plain') || '')
+    if (fromText) {
+      onUrlChange(fromText)
+      return
+    }
+    // A dropped Windows .url Internet Shortcut -- read its URL= line.
+    const file = Array.from(dt.files).find((f) => f.name.toLowerCase().endsWith('.url'))
+    if (file) {
+      file
+        .text()
+        .then((content) => {
+          const u = parseUrlFile(content)
+          if (u) onUrlChange(u)
+        })
+        .catch(logError('dropped .url file read'))
+    }
+  }
+
+  // When settings load or change, update kind/quality -- but only while the bar
+  // is idle (URL empty) so an in-progress setup isn't unexpectedly reset.
+  useEffect(() => {
+    if (!settingsLoaded || url.trim()) return
+    setKind(defaultKind)
+    setQuality(defaultKind === 'audio' ? defaultAudioQuality : defaultVideoQuality)
+  }, [settingsLoaded, defaultKind, defaultVideoQuality, defaultAudioQuality, url])
+
+  // Clipboard auto-detect and links handed to AeroFetch from outside (the
+  // aerofetch:// protocol or a "Send to" .url file) share one suggestion banner,
+  // driven by the same hook the library's add-source field uses. An external link
+  // always takes priority over a clipboard guess -- it's a direct request.
+  const {
+    suggestion,
+    source: suggestionSource,
+    accept: acceptLink,
+    dismiss: dismissSuggestion,
+    offer: offerLink
+  } = useClipboardLink(url)
+  useEffect(
+    () => window.api.onExternalUrl((incoming) => offerLink(incoming, 'external')),
+    [offerLink]
+  )
+
+  function acceptSuggestion(): void {
+    const link = acceptLink()
+    if (link) onUrlChange(link)
+  }
+
+  const usingFormats = kind === 'video' && info !== null && info.formats.length > 0
+  const selectedFormat: FormatOption | undefined = usingFormats
+    ? (info.formats.find((f) => f.id === formatId) ?? info.formats[0])
+    : undefined
+
+  // Show the "add this in the Library" nudge for a clear channel/playlist URL,
+  // but only while the bar is still idle for it (nothing probed/resolved yet) and
+  // the user hasn't waved it away (UX3).
+  const channelHint =
+    looksLikeChannelOrPlaylist(url) &&
+    !channelHintDismissed &&
+    info === null &&
+    playlist === null &&
+    probeError === null
+
+  function clearProbe(): void {
+    setInfo(null)
+    setProbeError(null)
+    setFormatId('')
+    setPlaylist(null)
+    setSelected(new Set())
+    setItemKinds({})
+  }
+
+  // Reset the whole bar after a download / playlist is enqueued: clear the URL +
+  // probe and drop the one-shot overrides (trim / schedule / advanced / incognito /
+  // per-download options) so the next download starts from the global defaults.
+  // Shared by download() and addPlaylist() so a playlist add resets the same state
+  // a single download does (L132 — addPlaylist previously left trim/schedule open).
+  function resetForm(): void {
+    setUrl('')
+    setTrim('')
+    setShowTrim(false)
+    setScheduleAt('')
+    setShowSchedule(false)
+    setShowAdvanced(false)
+    setCommandPreview(null)
+    setIncognito(false)
+    setDownloadOptions(DEFAULT_DOWNLOAD_OPTIONS)
+    clearProbe()
+  }
+
+  // Fetch (or toggle off) the exact yt-dlp command line for the current form
+  // state. The options mirror what download() sends so the preview matches the
+  // command that will actually run -- including a probe-selected format and any
+  // trim spec (M5).
+  async function toggleCommandPreview(): Promise<void> {
+    if (commandPreview) {
+      setCommandPreview(null)
+      return
+    }
+    const trimmed = url.trim()
+    if (!trimmed) return
+    setPreviewLoading(true)
+    try {
+      const result = await window.api.previewCommand({
+        id: 'preview',
+        url: trimmed,
+        kind: usingFormats ? 'video' : kind,
+        quality: usingFormats && selectedFormat ? selectedFormat.label : quality,
+        formatId: usingFormats ? selectedFormat?.id : undefined,
+        formatHasAudio: usingFormats ? selectedFormat?.hasAudio : undefined,
+        options: downloadOptions,
+        trim: trim.trim() || undefined
+      })
+      setCommandPreview(result)
+    } catch (e) {
+      setCommandPreview({ ok: false, error: (e as Error).message })
+    } finally {
+      setPreviewLoading(false)
+    }
+  }
+
+  function onUrlChange(next: string): void {
+    setUrl(next)
+    // Any probed info -- or a duplicate warning -- is stale once the URL changes.
+    if (info || probeError || playlist) clearProbe()
+    if (dup) setDup(null)
+    setCommandPreview(null)
+    confirmDup.current = false
+    // A new URL gets a fresh chance to nudge toward the Library.
+    setChannelHintDismissed(false)
+  }
+
+  function onKindChange(next: MediaKind): void {
+    setKind(next)
+    setQuality(QUALITY_OPTIONS[next][0])
+    // The command changes with kind/quality, so any shown preview is now stale.
+    setCommandPreview(null)
+  }
+
+  // Any change to quality / format / trim / options invalidates a shown preview.
+  function onQualityChange(v: string): void {
+    setQuality(v)
+    setCommandPreview(null)
+  }
+  function onFormatIdChange(v: string): void {
+    setFormatId(v)
+    setCommandPreview(null)
+  }
+  function onTrimChange(v: string): void {
+    setTrim(v)
+    setCommandPreview(null)
+  }
+  function onDownloadOptionsChange(next: DownloadOptions): void {
+    setDownloadOptions(next)
+    setCommandPreview(null)
+  }
+
+  async function fetchFormats(): Promise<void> {
+    const trimmed = url.trim()
+    if (!trimmed || probing) return
+    setProbing(true)
+    setProbeError(null)
+    setInfo(null)
+    setPlaylist(null)
+    // Probing may switch the URL to the format-picker path, changing the command.
+    setCommandPreview(null)
+    try {
+      const res = await window.api.probe(trimmed)
+      if (res.ok && res.kind === 'playlist' && res.playlist) {
+        setPlaylist(res.playlist)
+        // Pre-select every entry; the user can trim the list.
+        setSelected(new Set(res.playlist.entries.map((e) => e.index)))
+      } else if (res.ok && res.info) {
+        setInfo(res.info)
+        setFormatId(res.info.formats[0]?.id ?? '')
+      } else {
+        setProbeError(res.error ?? 'Could not fetch video info.')
+      }
+    } catch (e) {
+      setProbeError(String(e))
+    } finally {
+      setProbing(false)
+    }
+  }
+
+  async function paste(): Promise<void> {
+    try {
+      const text = (await window.api?.readClipboard?.()) ?? ''
+      if (text) onUrlChange(text.trim())
+    } catch {
+      /* ignore in preview */
+    }
+  }
+
+  // Hand the current channel/playlist URL to the Library tab, which pre-fills its
+  // add field with it, and clear the bar (the URL now lives over there) (UX3).
+  function openInLibrary(): void {
+    const trimmed = url.trim()
+    if (!trimmed) return
+    openLibraryWith(trimmed)
+    setUrl('')
+    // Clear the URL-specific command preview too, so no stale command lingers over
+    // the now-empty bar (the same invariant onUrlChange keeps).
+    setCommandPreview(null)
+    clearProbe()
+  }
+  function dismissChannelHint(): void {
+    setChannelHintDismissed(true)
+  }
+
+  // Selection helpers for the playlist panel.
+  const allSelected = playlist !== null && selected.size === playlist.entries.length
+  function toggleEntry(index: number, on: boolean): void {
+    setSelected((prev) => {
+      const next = new Set(prev)
+      if (on) next.add(index)
+      else next.delete(index)
+      return next
+    })
+  }
+  function toggleAll(): void {
+    if (!playlist) return
+    setSelected(allSelected ? new Set() : new Set(playlist.entries.map((e) => e.index)))
+  }
+
+  // Per-entry kind: the override if set, else the bar's global kind.
+  function effKind(index: number): MediaKind {
+    return itemKinds[index] ?? kind
+  }
+  function toggleItemKind(index: number): void {
+    setItemKinds((m) => ({ ...m, [index]: effKind(index) === 'audio' ? 'video' : 'audio' }))
+  }
+  function setAllKinds(k: MediaKind): void {
+    if (!playlist) return
+    const all: Record<number, MediaKind> = {}
+    for (const e of playlist.entries) all[e.index] = k
+    setItemKinds(all)
+  }
+
+  function download(): void {
+    const trimmed = url.trim()
+    if (!trimmed) return
+
+    // Duplicate guard: if this URL is already in the queue (and the user hasn't
+    // confirmed via "Download anyway"), warn instead of silently enqueuing a copy.
+    // Canceled/failed items don't count -- re-adding those is a legitimate retry.
+    if (!confirmDup.current) {
+      const existing = useDownloads
+        .getState()
+        .items.find(
+          (i) => i.status !== 'canceled' && i.status !== 'error' && sameVideo(i.url, trimmed)
+        )
+      if (existing) {
+        // Use the URL as fallback if the title is still the placeholder generated
+        // by titleFromUrl() before metadata loads (L76).
+        const isPlaceholder =
+          /video \(\w+\)$/.test(existing.title) ||
+          existing.title.endsWith(' download') ||
+          existing.title === 'New download'
+        setDup(isPlaceholder ? existing.url : existing.title)
+        setDupInHistory(false)
+        return
+      }
+      // Not in the queue, but maybe already downloaded earlier (L144): warn so a
+      // re-download is a deliberate choice, not an accidental duplicate.
+      const downloaded = useHistory.getState().entries.find((h) => sameVideo(h.url, trimmed))
+      if (downloaded) {
+        setDup(downloaded.title || downloaded.url)
+        setDupInHistory(true)
+        return
+      }
+    }
+    confirmDup.current = false
+    setDup(null)
+
+    const meta = info
+      ? {
+          title: info.title,
+          channel: info.channel,
+          durationLabel: info.durationLabel,
+          thumbnail: info.thumbnail
+        }
+      : {}
+
+    const trimSpec = trim.trim() || undefined
+    const scheduledFor = scheduleAt ? new Date(scheduleAt).getTime() : undefined
+
+    if (usingFormats && selectedFormat) {
+      addFromUrl(trimmed, 'video', selectedFormat.label, {
+        ...meta,
+        trim: trimSpec,
+        scheduledFor,
+        options: downloadOptions,
+        incognito,
+        format: {
+          id: selectedFormat.id,
+          hasAudio: selectedFormat.hasAudio,
+          label: selectedFormat.label
+        }
+      })
+    } else {
+      addFromUrl(trimmed, kind, quality, {
+        ...meta,
+        trim: trimSpec,
+        scheduledFor,
+        options: downloadOptions,
+        incognito
+      })
+    }
+
+    resetForm()
+  }
+
+  function downloadAnyway(): void {
+    confirmDup.current = true
+    download()
+  }
+
+  function addPlaylist(): void {
+    if (!playlist) return
+    const chosen = playlist.entries.filter((e) => selected.has(e.index))
+    // Each entry uses its own kind override; quality falls back to that kind's
+    // default unless the entry matches the bar's current kind/quality.
+    addMany(
+      chosen.map((e) => {
+        const k = effKind(e.index)
+        return {
+          url: e.url,
+          kind: k,
+          quality: k === kind ? quality : QUALITY_OPTIONS[k][0],
+          opts: { title: e.title, channel: e.uploader, durationLabel: e.durationLabel }
+        }
+      })
+    )
+    resetForm()
+  }
+
+  return {
+    // form state
+    url,
+    kind,
+    quality,
+    // trim / schedule
+    showTrim,
+    setShowTrim,
+    trim,
+    showSchedule,
+    setShowSchedule,
+    scheduleAt,
+    setScheduleAt,
+    // drag / dup
+    dupInHistory,
+    dragActive,
+    setDragActive,
+    dup,
+    setDup,
+    // advanced / preview
+    showAdvanced,
+    setShowAdvanced,
+    downloadOptions,
+    incognito,
+    setIncognito,
+    commandPreview,
+    previewLoading,
+    // probe (single video)
+    info,
+    thumbFailed,
+    setThumbFailed,
+    probing,
+    probeError,
+    usingFormats,
+    selectedFormat,
+    // playlist
+    playlist,
+    selected,
+    allSelected,
+    // suggestion banner
+    suggestion,
+    suggestionSource,
+    dismissSuggestion,
+    // channel/playlist nudge → Library (UX3)
+    channelHint,
+    openInLibrary,
+    dismissChannelHint,
+    // handlers
+    onDragEnter,
+    onDragOver,
+    onDragLeave,
+    onDrop,
+    onUrlChange,
+    onKindChange,
+    onQualityChange,
+    onFormatIdChange,
+    onTrimChange,
+    onDownloadOptionsChange,
+    toggleCommandPreview,
+    fetchFormats,
+    paste,
+    acceptSuggestion,
+    download,
+    downloadAnyway,
+    addPlaylist,
+    toggleEntry,
+    toggleAll,
+    effKind,
+    toggleItemKind,
+    setAllKinds
+  }
+}

src/renderer/src/components/settings/AboutCard.tsx

@@ -0,0 +1,181 @@
+import { useEffect, useState } from 'react'
+import {
+  Field,
+  Switch,
+  Button,
+  Card,
+  Subtitle2,
+  Caption1,
+  Text,
+  Spinner
+} from '@fluentui/react-components'
+import { InfoRegular, ArrowSyncRegular } from '@fluentui/react-icons'
+import {
+  type YtdlpVersionResult,
+  type YtdlpUpdateChannel,
+  type YtdlpUpdateResult,
+  type FfmpegVersionResult
+} from '@shared/ipc'
+import { useSettings } from '../../store/settings'
+import { Select } from '../Select'
+import { useErrorTextStyles } from '../ui/errorText'
+import { logError } from '../../reportError'
+import { useSettingsStyles } from './settingsStyles'
+
+const UPDATE_CHANNEL_OPTIONS = [
+  { value: 'stable', label: 'Stable' },
+  { value: 'nightly', label: 'Nightly' }
+]
+
+export function AboutCard(): React.JSX.Element {
+  const styles = useSettingsStyles()
+  const errText = useErrorTextStyles()
+  const autoUpdateYtdlp = useSettings((s) => s.autoUpdateYtdlp)
+  const ytdlpChannel = useSettings((s) => s.ytdlpChannel)
+  const ytdlpLastUpdateCheck = useSettings((s) => s.ytdlpLastUpdateCheck)
+  const update = useSettings((s) => s.update)
+
+  const [checking, setChecking] = useState(false)
+  const [version, setVersion] = useState<YtdlpVersionResult | null>(null)
+  const [ffmpeg, setFfmpeg] = useState<FfmpegVersionResult | null>(null)
+  const [updating, setUpdating] = useState(false)
+  const [updateResult, setUpdateResult] = useState<YtdlpUpdateResult | null>(null)
+
+  useEffect(() => {
+    // Show the current yt-dlp version without a manual click, and reflect a
+    // background auto-update (which may run on launch) live in this panel.
+    window.api.getYtdlpVersion().then(setVersion).catch(logError('getYtdlpVersion'))
+    // ffmpeg/ffprobe are display-only (bundled, not auto-updated); load them once.
+    window.api.getFfmpegVersions().then(setFfmpeg).catch(logError('getFfmpegVersions'))
+    return window.api.onYtdlpAutoUpdateStatus((s) => {
+      if (s.phase === 'checking') {
+        setChecking(true)
+        return
+      }
+      setChecking(false)
+      if (s.version) setVersion({ ok: true, version: s.version })
+      if (s.checkedAt) useSettings.setState({ ytdlpLastUpdateCheck: s.checkedAt })
+      if (s.phase === 'updated') {
+        setUpdateResult({ ok: true, output: `Updated to yt-dlp ${s.version ?? ''}`.trim() })
+      } else if (s.phase === 'error' && s.error) {
+        setUpdateResult({ ok: false, error: s.error })
+      }
+    })
+  }, [])
+
+  async function checkVersion(): Promise<void> {
+    setChecking(true)
+    setVersion(null)
+    try {
+      setVersion(await window.api.getYtdlpVersion())
+    } catch (e) {
+      setVersion({ ok: false, error: e instanceof Error ? e.message : String(e) })
+    } finally {
+      setChecking(false)
+    }
+  }
+
+  async function runUpdate(): Promise<void> {
+    setUpdating(true)
+    setUpdateResult(null)
+    try {
+      const result = await window.api.updateYtdlp(ytdlpChannel)
+      setUpdateResult(result)
+      if (result.ok) setVersion(null) // stale -- prompt a re-check rather than show a wrong version
+    } catch (e) {
+      setUpdateResult({ ok: false, error: e instanceof Error ? e.message : String(e) })
+    } finally {
+      setUpdating(false)
+    }
+  }
+
+  return (
+    <Card className={styles.card}>
+      <div className={styles.sectionHeader}>
+        <InfoRegular className={styles.sectionIcon} />
+        <Subtitle2 as="h2">About</Subtitle2>
+      </div>
+      <Caption1 className={styles.hint}>
+        AeroFetch is a generic frontend for yt-dlp. It bundles ffmpeg and manages its own copy of
+        yt-dlp, keeping it up to date automatically.
+      </Caption1>
+      <div className={styles.folderRow}>
+        {/* Re-show the first-run welcome/tips screen on demand (UX22). */}
+        <Button size="small" onClick={() => update({ hasCompletedOnboarding: false })}>
+          Show welcome tips again
+        </Button>
+      </div>
+
+      <Field
+        label="Keep yt-dlp updated automatically"
+        hint="Checks once a day on launch and updates the downloader in the background, so site changes don't start breaking your downloads."
+      >
+        <Switch
+          checked={autoUpdateYtdlp}
+          onChange={(_, d) => update({ autoUpdateYtdlp: d.checked })}
+        />
+      </Field>
+
+      {version?.ok && <Text className={styles.mono}>yt-dlp {version.version}</Text>}
+      {version && !version.ok && <Caption1 className={errText.errorPre}>{version.error}</Caption1>}
+      {ffmpeg && (
+        <div className={styles.folderRow}>
+          <div>
+            <Text className={styles.monoBlock}>ffmpeg {ffmpeg.ffmpeg ?? 'not found'}</Text>
+            <Text className={styles.monoBlock}>ffprobe {ffmpeg.ffprobe ?? 'not found'}</Text>
+          </div>
+          <Button
+            appearance="subtle"
+            icon={<ArrowSyncRegular />}
+            onClick={() =>
+              window.api.getFfmpegVersions().then(setFfmpeg).catch(logError('getFfmpegVersions'))
+            }
+            aria-label="Re-check ffmpeg versions"
+          />
+        </div>
+      )}
+      {ytdlpLastUpdateCheck > 0 && (
+        <Caption1 className={styles.hint}>
+          Last checked for updates {new Date(ytdlpLastUpdateCheck).toLocaleString()}.
+        </Caption1>
+      )}
+      <div className={styles.folderRow}>
+        <Button
+          icon={checking ? <Spinner size="tiny" /> : <ArrowSyncRegular />}
+          onClick={checkVersion}
+          disabled={checking}
+        >
+          Check yt-dlp version
+        </Button>
+      </div>
+
+      <Field
+        label="Update channel"
+        hint="Nightly tracks yt-dlp's daily build; stable is the tagged release. Nightly follows YouTube changes fastest."
+      >
+        <Select
+          value={ytdlpChannel}
+          options={UPDATE_CHANNEL_OPTIONS}
+          onChange={(v) => update({ ytdlpChannel: v as YtdlpUpdateChannel })}
+        />
+      </Field>
+      <div className={styles.folderRow}>
+        <Button
+          icon={updating ? <Spinner size="tiny" /> : <ArrowSyncRegular />}
+          onClick={runUpdate}
+          disabled={updating}
+        >
+          {updating ? 'Updating…' : 'Update yt-dlp'}
+        </Button>
+      </div>
+      {updateResult?.ok && (
+        <Text className={styles.monoPre}>
+          {updateResult.output || 'yt-dlp is already up to date.'}
+        </Text>
+      )}
+      {updateResult && !updateResult.ok && (
+        <Caption1 className={errText.errorPre}>{updateResult.error}</Caption1>
+      )}
+    </Card>
+  )
+}

src/renderer/src/components/settings/AppearanceCard.tsx

@@ -0,0 +1,110 @@
+import { useRef } from 'react'
+import { Field, Button, Card, Subtitle2, Caption1, mergeClasses } from '@fluentui/react-components'
+import { PaintBucketRegular, AccessibilityRegular } from '@fluentui/react-icons'
+import { type ThemeMode, type AccentColor } from '@shared/ipc'
+import { useSettings } from '../../store/settings'
+import { useSystemTheme } from '../../store/systemTheme'
+import { Select } from '../Select'
+import { ACCENT_OPTIONS } from '../../theme'
+import { useFocusStyles } from '../ui/focusRing'
+import { useSettingsStyles } from './settingsStyles'
+
+const THEME_MODE_OPTIONS = [
+  { value: 'light', label: 'Light' },
+  { value: 'dark', label: 'Dark' },
+  { value: 'system', label: 'Follow system' }
+]
+
+export function AppearanceCard(): React.JSX.Element {
+  const styles = useSettingsStyles()
+  const focus = useFocusStyles()
+  const theme = useSettings((s) => s.theme)
+  const accentColor = useSettings((s) => s.accentColor)
+  const highContrast = useSystemTheme((s) => s.shouldUseHighContrastColors)
+  const update = useSettings((s) => s.update)
+
+  // Roving-tabindex arrow-key navigation for the accent radiogroup (L155), so the
+  // single-select swatches behave like the Theme radio pattern rather than a row
+  // of plain buttons.
+  const swatchRefs = useRef<(HTMLButtonElement | null)[]>([])
+  function onSwatchKey(e: React.KeyboardEvent, index: number): void {
+    const n = ACCENT_OPTIONS.length
+    let next = -1
+    if (e.key === 'ArrowRight' || e.key === 'ArrowDown') next = (index + 1) % n
+    else if (e.key === 'ArrowLeft' || e.key === 'ArrowUp') next = (index - 1 + n) % n
+    else if (e.key === 'Home') next = 0
+    else if (e.key === 'End') next = n - 1
+    else return
+    const opt = ACCENT_OPTIONS[next]
+    if (!opt) return
+    e.preventDefault()
+    update({ accentColor: opt.value as AccentColor })
+    swatchRefs.current[next]?.focus()
+  }
+
+  return (
+    <Card className={styles.card}>
+      <div className={styles.sectionHeader}>
+        <PaintBucketRegular className={styles.sectionIcon} />
+        <Subtitle2 as="h2">Appearance</Subtitle2>
+      </div>
+
+      <Field label="Theme">
+        <Select
+          value={theme}
+          options={THEME_MODE_OPTIONS}
+          onChange={(v) => update({ theme: v as ThemeMode })}
+        />
+      </Field>
+
+      <Field label="Accent color">
+        <div className={styles.swatchRow} role="radiogroup" aria-label="Accent color">
+          {ACCENT_OPTIONS.map((opt, i) => {
+            const selected = accentColor === opt.value
+            return (
+              <button
+                key={opt.value}
+                ref={(el) => {
+                  swatchRefs.current[i] = el
+                }}
+                type="button"
+                role="radio"
+                aria-checked={selected}
+                // Roving tabindex: only the selected swatch is a tab stop; arrows
+                // move within the group (L155).
+                tabIndex={selected ? 0 : -1}
+                className={mergeClasses(
+                  styles.swatch,
+                  selected && styles.swatchActive,
+                  focus.focusRing
+                )}
+                style={{ backgroundColor: opt.swatch }}
+                onClick={() => update({ accentColor: opt.value as AccentColor })}
+                onKeyDown={(e) => onSwatchKey(e, i)}
+                aria-label={opt.label}
+                title={opt.label}
+              />
+            )
+          })}
+        </div>
+      </Field>
+
+      <Caption1 className={styles.hint}>
+        {highContrast
+          ? 'A Windows high-contrast theme is active -- AeroFetch follows your system colors.'
+          : 'AeroFetch automatically follows a Windows high-contrast theme if you turn one on.'}
+      </Caption1>
+      {highContrast && (
+        <div className={styles.folderRow}>
+          <Button
+            size="small"
+            icon={<AccessibilityRegular />}
+            onClick={() => window.api.openHighContrastSettings()}
+          >
+            Open accessibility settings
+          </Button>
+        </div>
+      )}
+    </Card>
+  )
+}

src/renderer/src/components/settings/BackupCard.tsx

@@ -0,0 +1,84 @@
+import { useState } from 'react'
+import { Button, Card, Subtitle2, Caption1 } from '@fluentui/react-components'
+import { DocumentArrowDownRegular, DocumentArrowUpRegular } from '@fluentui/react-icons'
+import { type BackupExportResult, type BackupImportResult } from '@shared/ipc'
+import { useSettings } from '../../store/settings'
+import { useTemplates } from '../../store/templates'
+import { useErrorTextStyles } from '../ui/errorText'
+import { useSettingsStyles } from './settingsStyles'
+
+export function BackupCard(): React.JSX.Element {
+  const styles = useSettingsStyles()
+  const errText = useErrorTextStyles()
+
+  const [exporting, setExporting] = useState(false)
+  const [exportResult, setExportResult] = useState<BackupExportResult | null>(null)
+  const [importing, setImporting] = useState(false)
+  const [importResult, setImportResult] = useState<BackupImportResult | null>(null)
+
+  async function exportBackup(): Promise<void> {
+    setExporting(true)
+    setExportResult(null)
+    try {
+      setExportResult(await window.api.exportBackup())
+    } catch (e) {
+      setExportResult({ ok: false, error: e instanceof Error ? e.message : String(e) })
+    } finally {
+      setExporting(false)
+    }
+  }
+
+  async function importBackup(): Promise<void> {
+    setImporting(true)
+    setImportResult(null)
+    try {
+      const result = await window.api.importBackup()
+      setImportResult(result)
+      if (result.ok) {
+        // Settings + templates changed underneath the stores -- reload both.
+        const [s, t] = await Promise.all([window.api.getSettings(), window.api.listTemplates()])
+        useSettings.setState({ ...s, loaded: true })
+        useTemplates.setState({ templates: t })
+      }
+    } catch (e) {
+      setImportResult({ ok: false, error: e instanceof Error ? e.message : String(e) })
+    } finally {
+      setImporting(false)
+    }
+  }
+
+  return (
+    <Card className={styles.card}>
+      <div className={styles.sectionHeader}>
+        <DocumentArrowDownRegular className={styles.sectionIcon} />
+        <Subtitle2 as="h2">Backup &amp; restore</Subtitle2>
+      </div>
+      <Caption1 className={styles.hint}>
+        Save your settings and custom-command templates to a JSON file, or restore them on another
+        machine. Does not include download history or credentials (proxy, API tokens -- re-enter
+        those after import).
+      </Caption1>
+
+      <div className={styles.folderRow}>
+        <Button icon={<DocumentArrowDownRegular />} onClick={exportBackup} disabled={exporting}>
+          {exporting ? 'Exporting…' : 'Export backup…'}
+        </Button>
+        <Button icon={<DocumentArrowUpRegular />} onClick={importBackup} disabled={importing}>
+          {importing ? 'Importing…' : 'Import backup…'}
+        </Button>
+      </div>
+      {exportResult?.ok && exportResult.path && (
+        <Caption1 className={styles.hint}>Saved to {exportResult.path}</Caption1>
+      )}
+      {exportResult && !exportResult.ok && exportResult.error && (
+        <Caption1 className={errText.error}>{exportResult.error}</Caption1>
+      )}
+      {importResult?.ok && (
+        <Caption1 className={styles.hint}>Settings and templates restored.</Caption1>
+      )}
+      {importResult && !importResult.ok && importResult.error && (
+        <Caption1 className={errText.error}>{importResult.error}</Caption1>
+      )}
+    </Card>
+  )
+}

src/renderer/src/components/settings/CookiesCard.tsx

@@ -0,0 +1,136 @@
+import { useEffect, useState } from 'react'
+import { Field, Input, Button, Card, Subtitle2, Caption1 } from '@fluentui/react-components'
+import { CookiesRegular } from '@fluentui/react-icons'
+import {
+  COOKIE_BROWSERS,
+  type CookieSource,
+  type CookieBrowser,
+  type CookiesStatus
+} from '@shared/ipc'
+import { useSettings } from '../../store/settings'
+import { Select } from '../Select'
+import { useErrorTextStyles } from '../ui/errorText'
+import { useSettingsStyles } from './settingsStyles'
+
+const COOKIE_SOURCE_OPTIONS = [
+  { value: 'none', label: 'None' },
+  { value: 'browser', label: "From a browser's cookie store" },
+  { value: 'login', label: 'Sign-in window (built into AeroFetch)' }
+]
+
+const COOKIE_BROWSER_OPTIONS = COOKIE_BROWSERS.map((b) => ({
+  value: b,
+  label: b.charAt(0).toUpperCase() + b.slice(1)
+}))
+
+export function CookiesCard(): React.JSX.Element {
+  const styles = useSettingsStyles()
+  const errText = useErrorTextStyles()
+  const cookieSource = useSettings((s) => s.cookieSource)
+  const cookiesBrowser = useSettings((s) => s.cookiesBrowser)
+  const update = useSettings((s) => s.update)
+
+  const [cookiesStatus, setCookiesStatus] = useState<CookiesStatus | null>(null)
+  const [loginUrl, setLoginUrl] = useState('https://www.youtube.com')
+  const [signingIn, setSigningIn] = useState(false)
+  const [loginError, setLoginError] = useState<string | null>(null)
+
+  useEffect(() => {
+    window.api.cookiesStatus().then(setCookiesStatus)
+  }, [])
+
+  async function signIn(): Promise<void> {
+    setSigningIn(true)
+    setLoginError(null)
+    try {
+      const result = await window.api.cookiesLogin(loginUrl)
+      if (result.ok && result.cookieCount === 0) {
+        // Window closed without capturing anything -- don't imply success (L50).
+        setLoginError('No cookies were captured -- did you sign in before closing the window?')
+      } else if (result.ok) {
+        setCookiesStatus(await window.api.cookiesStatus())
+      } else {
+        setLoginError(result.error ?? 'Sign-in failed.')
+      }
+    } catch (e) {
+      setLoginError(e instanceof Error ? e.message : String(e))
+    } finally {
+      setSigningIn(false)
+    }
+  }
+
+  async function clearSavedCookies(): Promise<void> {
+    await window.api.cookiesClear()
+    setCookiesStatus({ exists: false })
+  }
+
+  return (
+    <Card className={styles.card}>
+      <div className={styles.sectionHeader}>
+        <CookiesRegular className={styles.sectionIcon} />
+        <Subtitle2 as="h2">Cookies</Subtitle2>
+      </div>
+      <Caption1 className={styles.hint}>
+        Some sites only serve full quality, age-restricted, or members-only video to a logged-in
+        session. Supply cookies so yt-dlp can act like one.
+      </Caption1>
+
+      <Field label="Cookie source">
+        <Select
+          value={cookieSource}
+          options={COOKIE_SOURCE_OPTIONS}
+          onChange={(v) => update({ cookieSource: v as CookieSource })}
+        />
+      </Field>
+
+      {cookieSource === 'browser' && (
+        <Field
+          label="Browser"
+          hint="Reads that browser's saved cookies directly. Close the browser first if it won't let AeroFetch read them."
+        >
+          <Select
+            value={cookiesBrowser}
+            options={COOKIE_BROWSER_OPTIONS}
+            onChange={(v) => update({ cookiesBrowser: v as CookieBrowser })}
+          />
+        </Field>
+      )}
+
+      {cookieSource === 'login' && (
+        <>
+          <Field
+            label="Site to sign in to"
+            hint="Opens a sign-in window. Log in, then close the window -- your cookies are saved automatically."
+          >
+            <div className={styles.folderRow}>
+              <Input
+                className={styles.folderInput}
+                value={loginUrl}
+                placeholder="https://www.youtube.com"
+                onChange={(_, d) => setLoginUrl(d.value)}
+              />
+              <Button appearance="primary" onClick={signIn} disabled={signingIn}>
+                {signingIn ? 'Signing in…' : 'Sign in…'}
+              </Button>
+            </div>
+          </Field>
+
+          <div className={styles.folderRow}>
+            <Caption1 className={styles.hint}>
+              {cookiesStatus?.exists
+                ? `Cookies saved ${new Date(cookiesStatus.savedAt!).toLocaleString()}.`
+                : 'Not signed in yet.'}
+            </Caption1>
+            {cookiesStatus?.exists && (
+              <Button size="small" onClick={clearSavedCookies}>
+                Clear saved cookies
+              </Button>
+            )}
+          </div>
+
+          {loginError && <Caption1 className={errText.error}>{loginError}</Caption1>}
+        </>
+      )}
+    </Card>
+  )
+}

src/renderer/src/components/settings/CustomCommandsCard.tsx

@@ -0,0 +1,54 @@
+import { Field, Switch, Card, Subtitle2, Caption1 } from '@fluentui/react-components'
+import { CodeRegular } from '@fluentui/react-icons'
+import { useSettings } from '../../store/settings'
+import { useTemplates } from '../../store/templates'
+import { Select } from '../Select'
+import { TemplateManager } from '../TemplateManager'
+import { useSettingsStyles } from './settingsStyles'
+
+export function CustomCommandsCard(): React.JSX.Element {
+  const styles = useSettingsStyles()
+  const customCommandEnabled = useSettings((s) => s.customCommandEnabled)
+  const defaultTemplateId = useSettings((s) => s.defaultTemplateId)
+  const update = useSettings((s) => s.update)
+  const templates = useTemplates((s) => s.templates)
+
+  return (
+    <Card className={styles.card}>
+      <div className={styles.sectionHeader}>
+        <CodeRegular className={styles.sectionIcon} />
+        <Subtitle2 as="h2">Custom commands</Subtitle2>
+      </div>
+      <Caption1 className={styles.hint}>
+        Named templates of extra yt-dlp flags -- your own power-user recipes (e.g.
+        --write-thumbnail, --no-mtime, anything yt-dlp supports). Appended after every other option,
+        so a template flag can override a setting above it.
+      </Caption1>
+
+      <Field
+        label="Run custom command"
+        hint="Applies the default template below to every new download (still overridable per download)."
+      >
+        <Switch
+          checked={customCommandEnabled}
+          onChange={(_, d) => update({ customCommandEnabled: d.checked })}
+        />
+      </Field>
+
+      {customCommandEnabled && (
+        <Field label="Default template">
+          <Select
+            value={defaultTemplateId ?? 'none'}
+            options={[
+              { value: 'none', label: 'None' },
+              ...templates.map((t) => ({ value: t.id, label: t.name }))
+            ]}
+            onChange={(v) => update({ defaultTemplateId: v === 'none' ? null : v })}
+          />
+        </Field>
+      )}
+
+      <TemplateManager />
+    </Card>
+  )
+}

src/renderer/src/components/settings/DiagnosticsCard.tsx

@@ -0,0 +1,99 @@
+import { useState } from 'react'
+import { Button, Card, Subtitle2, Caption1, Text } from '@fluentui/react-components'
+import { BugRegular, CopyRegular, DeleteRegular } from '@fluentui/react-icons'
+import { useErrorLog } from '../../store/errorlog'
+import { useErrorTextStyles } from '../ui/errorText'
+import { EmptyState } from '../ui/EmptyState'
+import { useSettingsStyles } from './settingsStyles'
+
+export function DiagnosticsCard(): React.JSX.Element {
+  const styles = useSettingsStyles()
+  const errText = useErrorTextStyles()
+  const errorEntries = useErrorLog((s) => s.entries)
+  const clearErrorLog = useErrorLog((s) => s.clear)
+
+  const [confirmClearLog, setConfirmClearLog] = useState(false)
+
+  function copyErrorReport(): void {
+    // The button is disabled when there are no entries, so `report` is always
+    // non-empty here -- no need for an unreachable empty-report fallback (L159).
+    const report = errorEntries
+      .map((e) =>
+        [new Date(e.occurredAt).toLocaleString(), e.title ?? e.url, e.url, e.error].join('\n')
+      )
+      .join('\n\n---\n\n')
+    navigator.clipboard.writeText(report).catch(() => {})
+  }
+
+  return (
+    <Card className={styles.card}>
+      <div className={styles.sectionHeader}>
+        <BugRegular className={styles.sectionIcon} />
+        <Subtitle2 as="h2">Diagnostics</Subtitle2>
+      </div>
+      <Caption1 className={styles.hint}>
+        Failed downloads are logged here even after you clear the queue, so you can copy the details
+        into a bug report.
+      </Caption1>
+
+      <div className={styles.folderRow}>
+        <Button
+          icon={<CopyRegular />}
+          onClick={copyErrorReport}
+          disabled={errorEntries.length === 0}
+        >
+          Copy full report
+        </Button>
+        {confirmClearLog ? (
+          <>
+            <Caption1>
+              Clear all {errorEntries.length} {errorEntries.length === 1 ? 'error' : 'errors'}?
+            </Caption1>
+            <Button
+              icon={<DeleteRegular />}
+              appearance="primary"
+              onClick={() => {
+                clearErrorLog()
+                setConfirmClearLog(false)
+              }}
+            >
+              Clear log
+            </Button>
+            <Button appearance="subtle" onClick={() => setConfirmClearLog(false)}>
+              Cancel
+            </Button>
+          </>
+        ) : (
+          <Button
+            icon={<DeleteRegular />}
+            onClick={() => setConfirmClearLog(true)}
+            disabled={errorEntries.length === 0}
+          >
+            Clear log
+          </Button>
+        )}
+      </div>
+
+      {errorEntries.length === 0 ? (
+        <EmptyState compact message="No errors yet." />
+      ) : (
+        <div className={styles.errorList}>
+          {errorEntries.slice(0, 20).map((e) => (
+            <div key={e.id} className={styles.errorRow}>
+              <div className={styles.errorRowHeader}>
+                <Text className={styles.errorRowTitle}>{e.title ?? e.url}</Text>
+                <Caption1 className={styles.hint}>
+                  {new Date(e.occurredAt).toLocaleString()}
+                </Caption1>
+              </div>
+              <Caption1 className={errText.errorPre}>{e.error}</Caption1>
+            </div>
+          ))}
+          {errorEntries.length > 20 && (
+            <Caption1 className={styles.hint}>Showing 20 of {errorEntries.length} errors.</Caption1>
+          )}
+        </div>
+      )}
+    </Card>
+  )
+}

src/renderer/src/components/settings/DownloadsCard.tsx

@@ -0,0 +1,180 @@
+import {
+  Field,
+  Input,
+  SpinButton,
+  Switch,
+  Button,
+  Card,
+  Subtitle2
+} from '@fluentui/react-components'
+import { FolderRegular, ArrowDownloadRegular } from '@fluentui/react-icons'
+import { type MediaKind } from '@shared/ipc'
+import { useSettings } from '../../store/settings'
+import { useDownloads } from '../../store/downloads'
+import { QUALITY_OPTIONS } from '../../qualityOptions'
+import { Select } from '../Select'
+import { SegmentedControl } from '../ui/SegmentedControl'
+import { useSettingsStyles } from './settingsStyles'
+
+export function DownloadsCard(): React.JSX.Element {
+  const styles = useSettingsStyles()
+  const videoDir = useSettings((s) => s.videoDir)
+  const audioDir = useSettings((s) => s.audioDir)
+  const chooseDir = useSettings((s) => s.chooseDir)
+  const clearDir = useSettings((s) => s.clearDir)
+  const defaultKind = useSettings((s) => s.defaultKind)
+  const defaultVideoQuality = useSettings((s) => s.defaultVideoQuality)
+  const defaultAudioQuality = useSettings((s) => s.defaultAudioQuality)
+  const maxConcurrent = useSettings((s) => s.maxConcurrent)
+  const clipboardWatch = useSettings((s) => s.clipboardWatch)
+  const notifyOnComplete = useSettings((s) => s.notifyOnComplete)
+  const minimizeToTray = useSettings((s) => s.minimizeToTray)
+  const launchAtStartup = useSettings((s) => s.launchAtStartup)
+  const update = useSettings((s) => s.update)
+
+  const formatQuality = defaultKind === 'audio' ? defaultAudioQuality : defaultVideoQuality
+
+  function onKindSelect(kind: MediaKind): void {
+    update({ defaultKind: kind })
+  }
+
+  function onQualitySelect(quality: string): void {
+    update(
+      defaultKind === 'audio' ? { defaultAudioQuality: quality } : { defaultVideoQuality: quality }
+    )
+  }
+
+  return (
+    <Card className={styles.card}>
+      <div className={styles.sectionHeader}>
+        <ArrowDownloadRegular className={styles.sectionIcon} />
+        <Subtitle2 as="h2">Downloads</Subtitle2>
+      </div>
+
+      <Field
+        label="Video folder"
+        hint="Where video downloads are saved. Leave blank to use Documents\Video."
+      >
+        <div className={styles.folderRow}>
+          <Input
+            className={styles.folderInput}
+            value={videoDir}
+            placeholder="Documents\Video (default)"
+            contentBefore={<FolderRegular />}
+            onChange={(_, d) => update({ videoDir: d.value })}
+          />
+          <Button icon={<FolderRegular />} onClick={() => chooseDir('videoDir')}>
+            Browse…
+          </Button>
+          {videoDir && (
+            <Button appearance="subtle" onClick={() => clearDir('videoDir')}>
+              Reset
+            </Button>
+          )}
+        </div>
+      </Field>
+
+      <Field
+        label="Audio folder"
+        hint="Where audio downloads are saved. Leave blank to use Documents\Audio."
+      >
+        <div className={styles.folderRow}>
+          <Input
+            className={styles.folderInput}
+            value={audioDir}
+            placeholder="Documents\Audio (default)"
+            contentBefore={<FolderRegular />}
+            onChange={(_, d) => update({ audioDir: d.value })}
+          />
+          <Button icon={<FolderRegular />} onClick={() => chooseDir('audioDir')}>
+            Browse…
+          </Button>
+          {audioDir && (
+            <Button appearance="subtle" onClick={() => clearDir('audioDir')}>
+              Reset
+            </Button>
+          )}
+        </div>
+      </Field>
+
+      <Field label="Default format">
+        <div className={styles.formatRow}>
+          <SegmentedControl<MediaKind>
+            value={defaultKind}
+            options={[
+              { value: 'video', label: 'Video' },
+              { value: 'audio', label: 'Audio' }
+            ]}
+            onChange={onKindSelect}
+            ariaLabel="Default download type"
+          />
+          <Select
+            className={styles.formatQuality}
+            value={formatQuality}
+            options={QUALITY_OPTIONS[defaultKind].map((q) => ({ value: q, label: q }))}
+            onChange={onQualitySelect}
+          />
+        </div>
+      </Field>
+
+      <Field
+        label="Maximum simultaneous downloads"
+        hint="How many downloads run at once. 2-3 is a good balance."
+      >
+        <SpinButton
+          value={maxConcurrent}
+          min={1}
+          max={5}
+          onChange={(_, d) => {
+            const v = d.value ?? Number(d.displayValue)
+            if (typeof v === 'number' && Number.isFinite(v)) {
+              update({ maxConcurrent: Math.min(5, Math.max(1, Math.round(v))) })
+              // Raising the cap should start queued items right away.
+              useDownloads.getState().pump()
+            }
+          }}
+        />
+      </Field>
+
+      <Field
+        label="Detect links from clipboard"
+        hint="When AeroFetch gains focus, offer a video link you've just copied."
+      >
+        <Switch
+          checked={clipboardWatch}
+          onChange={(_, d) => update({ clipboardWatch: d.checked })}
+        />
+      </Field>
+
+      <Field
+        label="Notify when downloads finish"
+        hint="Shows a native Windows notification when a download completes or fails."
+      >
+        <Switch
+          checked={notifyOnComplete}
+          onChange={(_, d) => update({ notifyOnComplete: d.checked })}
+        />
+      </Field>
+
+      <Field
+        label="Keep running in the tray"
+        hint="Closing the window minimizes to the system tray instead of quitting, so downloads and watched-channel syncing keep running."
+      >
+        <Switch
+          checked={minimizeToTray}
+          onChange={(_, d) => update({ minimizeToTray: d.checked })}
+        />
+      </Field>
+
+      <Field
+        label="Start with Windows"
+        hint="Launch AeroFetch automatically when you sign in -- useful with auto-download so watched channels stay current in the background."
+      >
+        <Switch
+          checked={launchAtStartup}
+          onChange={(_, d) => update({ launchAtStartup: d.checked })}
+        />
+      </Field>
+    </Card>
+  )
+}

src/renderer/src/components/settings/FilenamesCard.tsx

@@ -0,0 +1,53 @@
+import { Field, Input, Switch, Card, Subtitle2, Caption1 } from '@fluentui/react-components'
+import { DocumentRegular } from '@fluentui/react-icons'
+import { useSettings } from '../../store/settings'
+import { useSettingsStyles } from './settingsStyles'
+
+export function FilenamesCard(): React.JSX.Element {
+  const styles = useSettingsStyles()
+  const filenameTemplate = useSettings((s) => s.filenameTemplate)
+  const restrictFilenames = useSettings((s) => s.restrictFilenames)
+  const downloadArchive = useSettings((s) => s.downloadArchive)
+  const update = useSettings((s) => s.update)
+
+  return (
+    <Card className={styles.card}>
+      <div className={styles.sectionHeader}>
+        <DocumentRegular className={styles.sectionIcon} />
+        <Subtitle2 as="h2">Filenames</Subtitle2>
+      </div>
+      <Field
+        label="Filename template"
+        hint="Controls how saved files are named. Use %(title)s for the video title, %(ext)s for the extension, and similar tokens."
+      >
+        <Input
+          value={filenameTemplate}
+          onChange={(_, d) => update({ filenameTemplate: d.value })}
+        />
+      </Field>
+      <Caption1 className={styles.hint}>
+        Example: {filenameTemplate.replace('%(title)s', 'My Video').replace('%(ext)s', 'mp4')}
+      </Caption1>
+
+      <Field
+        label="Restrict filenames"
+        hint="Sanitize titles to plain ASCII letters/digits, no spaces -- safer for old filesystems and shells."
+      >
+        <Switch
+          checked={restrictFilenames}
+          onChange={(_, d) => update({ restrictFilenames: d.checked })}
+        />
+      </Field>
+
+      <Field
+        label="Skip already-downloaded videos"
+        hint="Keeps a record of completed downloads (--download-archive) and skips them on repeat playlist/channel runs."
+      >
+        <Switch
+          checked={downloadArchive}
+          onChange={(_, d) => update({ downloadArchive: d.checked })}
+        />
+      </Field>
+    </Card>
+  )
+}

src/renderer/src/components/settings/NetworkCard.tsx

@@ -0,0 +1,118 @@
+import { useState } from 'react'
+import { Field, Input, Switch, Button, Card, Subtitle2, Spinner } from '@fluentui/react-components'
+import { GlobeRegular } from '@fluentui/react-icons'
+import { useSettings } from '../../store/settings'
+import { useSettingsStyles } from './settingsStyles'
+
+export function NetworkCard(): React.JSX.Element {
+  const styles = useSettingsStyles()
+  const proxy = useSettings((s) => s.proxy)
+  const rateLimit = useSettings((s) => s.rateLimit)
+  const useAria2c = useSettings((s) => s.useAria2c)
+  const youtubePlayerClient = useSettings((s) => s.youtubePlayerClient)
+  const youtubePoToken = useSettings((s) => s.youtubePoToken)
+  const update = useSettings((s) => s.update)
+
+  const [mintingPot, setMintingPot] = useState(false)
+  const [potHint, setPotHint] = useState<string | null>(null)
+
+  return (
+    <Card className={styles.card}>
+      <div className={styles.sectionHeader}>
+        <GlobeRegular className={styles.sectionIcon} />
+        <Subtitle2 as="h2">Network</Subtitle2>
+      </div>
+
+      <Field
+        label="Proxy"
+        hint="HTTP/HTTPS/SOCKS proxy URL, e.g. socks5://127.0.0.1:1080. Leave blank to use the system default."
+      >
+        <Input
+          type="password"
+          value={proxy}
+          placeholder="socks5://127.0.0.1:1080"
+          onChange={(_, d) => update({ proxy: d.value })}
+        />
+      </Field>
+
+      <Field
+        label="Rate limit"
+        hint="Caps download speed (e.g. 500K or 2M). Leave blank for unlimited."
+      >
+        <Input
+          value={rateLimit}
+          placeholder="2M"
+          onChange={(_, d) => update({ rateLimit: d.value })}
+        />
+      </Field>
+
+      <Field
+        label="Use aria2c downloader"
+        hint="Multi-connection downloads for faster speeds on supported sites. Falls back to the standard downloader if the accelerator isn't available."
+      >
+        <Switch checked={useAria2c} onChange={(_, d) => update({ useAria2c: d.checked })} />
+      </Field>
+
+      <Field
+        label="YouTube client (advanced)"
+        hint="Override how AeroFetch identifies itself to YouTube when downloads start failing. Try web_safari, tv, or mweb. Leave blank for the automatic default."
+      >
+        <datalist id="yt-client-list">
+          {['web', 'web_safari', 'web_embedded', 'mweb', 'tv', 'ios', 'android'].map((c) => (
+            <option key={c} value={c} />
+          ))}
+        </datalist>
+        <Input
+          value={youtubePlayerClient}
+          placeholder="web_safari"
+          list="yt-client-list"
+          onChange={(_, d) => update({ youtubePlayerClient: d.value })}
+        />
+      </Field>
+
+      <Field
+        label="YouTube PO Token (advanced)"
+        hint={
+          potHint ??
+          'A token that helps get past YouTube\'s bot check. Click "Fetch" to grab one automatically, or paste it manually. Signing in with cookies (above) is usually the easier fix.'
+        }
+      >
+        <div className={styles.folderRow}>
+          <Input
+            type="password"
+            style={{ flexGrow: 1 }}
+            value={youtubePoToken}
+            placeholder="Optional -- paste a token"
+            onChange={(_, d) => {
+              update({ youtubePoToken: d.value })
+              setPotHint(null)
+            }}
+          />
+          <Button
+            size="small"
+            disabled={mintingPot}
+            icon={mintingPot ? <Spinner size="tiny" /> : undefined}
+            onClick={async () => {
+              setMintingPot(true)
+              setPotHint(null)
+              try {
+                const token = await window.api.mintPoToken()
+                if (token) {
+                  setPotHint('Token saved.')
+                } else {
+                  setPotHint('Token not found -- try signing into YouTube first via Cookies above.')
+                }
+              } catch {
+                setPotHint('Failed to open YouTube window.')
+              } finally {
+                setMintingPot(false)
+              }
+            }}
+          >
+            {mintingPot ? 'Fetching…' : 'Fetch'}
+          </Button>
+        </div>
+      </Field>
+    </Card>
+  )
+}

src/renderer/src/components/settings/PostProcessingCard.tsx

@@ -0,0 +1,30 @@
+import { Card, Subtitle2, Caption1 } from '@fluentui/react-components'
+import { OptionsRegular } from '@fluentui/react-icons'
+import { useSettings } from '../../store/settings'
+import { DownloadOptionsForm } from '../DownloadOptionsForm'
+import { useSettingsStyles } from './settingsStyles'
+
+export function PostProcessingCard(): React.JSX.Element {
+  const styles = useSettingsStyles()
+  const defaultKind = useSettings((s) => s.defaultKind)
+  const downloadOptions = useSettings((s) => s.downloadOptions)
+  const update = useSettings((s) => s.update)
+
+  return (
+    <Card className={styles.card}>
+      <div className={styles.sectionHeader}>
+        <OptionsRegular className={styles.sectionIcon} />
+        <Subtitle2 as="h2">Format &amp; post-processing</Subtitle2>
+      </div>
+      <Caption1 className={styles.hint}>
+        Defaults applied to every new download (yt-dlp and ffmpeg do the work).
+      </Caption1>
+
+      <DownloadOptionsForm
+        value={downloadOptions}
+        kind={defaultKind}
+        onChange={(o) => update({ downloadOptions: o })}
+      />
+    </Card>
+  )
+}

src/renderer/src/components/settings/SoftwareUpdateCard.tsx

@@ -0,0 +1,156 @@
+import { useEffect, useState } from 'react'
+import {
+  Field,
+  Input,
+  Button,
+  Card,
+  Subtitle2,
+  Caption1,
+  Text,
+  Spinner,
+  ProgressBar,
+  tokens
+} from '@fluentui/react-components'
+import { ArrowSyncRegular, ArrowDownloadRegular, OpenRegular } from '@fluentui/react-icons'
+import { type AppUpdateInfo } from '@shared/ipc'
+import { useSettings } from '../../store/settings'
+import { useErrorTextStyles } from '../ui/errorText'
+import { logError } from '../../reportError'
+import { useSettingsStyles } from './settingsStyles'
+
+export function SoftwareUpdateCard(): React.JSX.Element {
+  const styles = useSettingsStyles()
+  const errText = useErrorTextStyles()
+  const updateToken = useSettings((s) => s.updateToken)
+  const update = useSettings((s) => s.update)
+
+  const [appVersion, setAppVersion] = useState('')
+  const [appUpd, setAppUpd] = useState<AppUpdateInfo | null>(null)
+  const [appChecking, setAppChecking] = useState(false)
+  const [appDownloading, setAppDownloading] = useState(false)
+  const [appFraction, setAppFraction] = useState<number | undefined>(undefined)
+  const [appUpdError, setAppUpdError] = useState<string | null>(null)
+
+  useEffect(() => {
+    window.api.getAppVersion().then(setAppVersion).catch(logError('getAppVersion'))
+    return window.api.onAppUpdateProgress((p) => setAppFraction(p.fraction))
+  }, [])
+
+  async function checkAppUpdate(): Promise<void> {
+    setAppChecking(true)
+    setAppUpd(null)
+    setAppUpdError(null)
+    try {
+      const info = await window.api.checkForAppUpdate()
+      // Funnel a failed check into the single error slot rather than storing a
+      // second not-ok AppUpdateInfo, so only one error message can ever render.
+      if (info.ok) setAppUpd(info)
+      else setAppUpdError(info.error ?? 'Update check failed.')
+    } catch (e) {
+      setAppUpdError(e instanceof Error ? e.message : String(e))
+    } finally {
+      setAppChecking(false)
+    }
+  }
+
+  async function installAppUpdate(): Promise<void> {
+    if (!appUpd?.downloadUrl) return
+    setAppDownloading(true)
+    setAppFraction(undefined)
+    setAppUpdError(null)
+    try {
+      const dl = await window.api.downloadAppUpdate(appUpd.downloadUrl)
+      if (!dl.ok || !dl.filePath) {
+        setAppUpdError(dl.error ?? 'Download failed.')
+        return
+      }
+      const run = await window.api.runAppUpdate(dl.filePath)
+      // On success the app quits as the installer launches; only errors return here.
+      if (!run.ok) setAppUpdError(run.error ?? 'Could not start the installer.')
+    } catch (e) {
+      setAppUpdError(e instanceof Error ? e.message : String(e))
+    } finally {
+      setAppDownloading(false)
+    }
+  }
+
+  return (
+    <Card className={styles.card}>
+      <div className={styles.sectionHeader}>
+        <ArrowSyncRegular className={styles.sectionIcon} />
+        <Subtitle2 as="h2">Software update</Subtitle2>
+      </div>
+      <Caption1 className={styles.hint}>
+        {appVersion
+          ? `You're running AeroFetch v${appVersion}. Updates are fetched from the AeroFetch release repo.`
+          : 'Checking your AeroFetch version…'}
+      </Caption1>
+
+      <div className={styles.folderRow}>
+        <Button
+          icon={appChecking ? <Spinner size="tiny" /> : <ArrowSyncRegular />}
+          onClick={checkAppUpdate}
+          disabled={appChecking || appDownloading}
+        >
+          {appChecking ? 'Checking…' : 'Check for updates'}
+        </Button>
+      </div>
+
+      {(updateToken.trim() !== '' || !!appUpdError) && (
+        <Field
+          label="Update access token"
+          hint="Only needed if the update server requires sign-in. Paste a read-only access token to enable update checks and downloads. Stored encrypted on this device; leave blank for anonymous access."
+        >
+          <Input
+            type="password"
+            value={updateToken}
+            placeholder="Optional -- access token"
+            onChange={(_, d) => update({ updateToken: d.value })}
+            contentBefore={<ArrowSyncRegular />}
+          />
+        </Field>
+      )}
+
+      {appUpd?.ok && appUpd.available && (
+        <>
+          <Text style={{ fontWeight: tokens.fontWeightSemibold }}>
+            Version {appUpd.latestVersion} is available -- here&apos;s what changed:
+          </Text>
+          {appUpd.notes && <div className={styles.notesBox}>{appUpd.notes}</div>}
+          <div className={styles.folderRow}>
+            <Button
+              appearance="primary"
+              icon={<ArrowDownloadRegular />}
+              onClick={installAppUpdate}
+              disabled={appDownloading || !appUpd.downloadUrl}
+            >
+              {appDownloading ? 'Downloading…' : 'Update now'}
+            </Button>
+            {appUpd.htmlUrl && (
+              <Button
+                icon={<OpenRegular />}
+                onClick={() => void window.api?.openUrl?.(appUpd.htmlUrl ?? '')}
+              >
+                View release
+              </Button>
+            )}
+          </div>
+          {!appUpd.downloadUrl && (
+            <Caption1 className={styles.hint}>
+              This release has no installer attached -- use "View release" to download it manually.
+            </Caption1>
+          )}
+          {appDownloading && (
+            <ProgressBar value={appFraction} aria-label="App update download progress" />
+          )}
+        </>
+      )}
+
+      {appUpd?.ok && !appUpd.available && (
+        <Text>You&apos;re up to date -- v{appUpd.currentVersion} is the latest.</Text>
+      )}
+
+      {appUpdError && <Caption1 className={errText.errorPre}>{appUpdError}</Caption1>}
+    </Card>
+  )
+}

src/renderer/src/components/settings/settingsStyles.ts

@@ -0,0 +1,117 @@
+import { makeStyles, tokens, shorthands } from '@fluentui/react-components'
+import { SPACE, RADIUS, ICON } from '../ui/tokens'
+
+// Shared styles for the Settings cards. Each card renders a single <Card> so it
+// stays one direct child of SettingsView's root -- the search filter toggles
+// `display` per child, so the one-DOM-node-per-card shape must be preserved.
+export const useSettingsStyles = makeStyles({
+  card: {
+    display: 'flex',
+    flexDirection: 'column',
+    // Page-level card: card padding + card radius (UI3/UI7).
+    gap: SPACE.section,
+    padding: SPACE.section,
+    ...shorthands.borderRadius(RADIUS.card)
+  },
+  notesBox: {
+    maxHeight: '180px',
+    overflowY: 'auto',
+    padding: '10px 12px',
+    backgroundColor: tokens.colorNeutralBackground2,
+    ...shorthands.borderRadius(tokens.borderRadiusMedium),
+    border: `1px solid ${tokens.colorNeutralStroke2}`,
+    whiteSpace: 'pre-wrap',
+    fontSize: tokens.fontSizeBase200,
+    lineHeight: tokens.lineHeightBase300
+  },
+  sectionHeader: {
+    display: 'flex',
+    alignItems: 'center',
+    gap: '10px'
+  },
+  sectionIcon: {
+    // Section-header glyph, next to each card's <Subtitle2> title (UI12 section tier).
+    fontSize: `${ICON.section}px`,
+    color: tokens.colorCompoundBrandForeground1
+  },
+  folderRow: {
+    display: 'flex',
+    gap: '8px',
+    alignItems: 'flex-end'
+  },
+  folderInput: {
+    flexGrow: 1
+  },
+  // The "Default format" control: a Video/Audio segmented toggle beside a quality
+  // dropdown, mirroring the DownloadBar so both read as one mental model (L102).
+  formatRow: {
+    display: 'flex',
+    gap: '8px',
+    alignItems: 'center',
+    flexWrap: 'wrap'
+  },
+  formatQuality: {
+    minWidth: '200px'
+  },
+  hint: {
+    color: tokens.colorNeutralForeground3
+  },
+  // Monospace version/output text (About card). Replaces the repeated inline
+  // `style={{ fontFamily: fontFamilyMonospace }}` (L5).
+  mono: {
+    fontFamily: tokens.fontFamilyMonospace
+  },
+  monoBlock: {
+    fontFamily: tokens.fontFamilyMonospace,
+    display: 'block'
+  },
+  monoPre: {
+    fontFamily: tokens.fontFamilyMonospace,
+    whiteSpace: 'pre-wrap'
+  },
+  swatchRow: {
+    display: 'flex',
+    gap: '10px'
+  },
+  swatch: {
+    boxSizing: 'border-box',
+    width: '28px',
+    height: '28px',
+    flexShrink: 0,
+    ...shorthands.borderRadius(tokens.borderRadiusCircular),
+    ...shorthands.border('2px', 'solid', 'transparent'),
+    padding: 0,
+    cursor: 'pointer',
+    // The swatch *is* a color preview, so keep the accent color under Windows
+    // High Contrast / forced-colors (W18); otherwise every swatch flattens to one
+    // system color and the accents become indistinguishable.
+    forcedColorAdjust: 'none'
+  },
+  swatchActive: {
+    ...shorthands.borderColor(tokens.colorNeutralForeground1)
+  },
+  errorList: {
+    display: 'flex',
+    flexDirection: 'column',
+    gap: '8px'
+  },
+  errorRow: {
+    padding: '10px 12px',
+    backgroundColor: tokens.colorNeutralBackground2,
+    ...shorthands.borderRadius(tokens.borderRadiusLarge),
+    border: `1px solid ${tokens.colorNeutralStroke2}`
+  },
+  errorRowHeader: {
+    display: 'flex',
+    alignItems: 'center',
+    gap: '8px'
+  },
+  errorRowTitle: {
+    flexGrow: 1,
+    minWidth: 0,
+    fontWeight: tokens.fontWeightSemibold,
+    overflow: 'hidden',
+    textOverflow: 'ellipsis',
+    whiteSpace: 'nowrap'
+  }
+})

src/renderer/src/components/ui/Banner.tsx

@@ -0,0 +1,63 @@
+import { makeStyles, mergeClasses, tokens, shorthands } from '@fluentui/react-components'
+import { RADIUS } from './tokens'
+import { useTextStyles } from './text'
+
+/**
+ * One inline notification bar (UI19). The DownloadBar's copied-link suggestion,
+ * its channel/playlist nudge, its duplicate warning, and the Library's copied-link
+ * suggestion had each hand-rolled the same tinted row (leading icon + flex-grow
+ * text + trailing actions). This is that row, once: a leading `icon`, `children`
+ * content that truncates by default (`wrap` to let it flow onto multiple lines),
+ * and a trailing `actions` slot.
+ *
+ * `tone` picks the semantic tint — `brand` for suggestions/nudges, `warning` for
+ * the duplicate caution — matching the former per-component colors exactly.
+ */
+export type BannerTone = 'brand' | 'warning'
+
+const useStyles = makeStyles({
+  root: {
+    display: 'flex',
+    alignItems: 'center',
+    gap: '8px',
+    padding: '8px 8px 8px 12px',
+    ...shorthands.borderRadius(RADIUS.surface)
+  },
+  brand: {
+    backgroundColor: tokens.colorBrandBackground2,
+    color: tokens.colorBrandForeground2
+  },
+  warning: {
+    backgroundColor: tokens.colorStatusWarningBackground1,
+    color: tokens.colorStatusWarningForeground1
+  },
+  content: {
+    flexGrow: 1,
+    minWidth: 0
+  }
+})
+
+export function Banner({
+  icon,
+  tone = 'brand',
+  wrap = false,
+  children,
+  actions
+}: {
+  icon?: React.ReactNode
+  tone?: BannerTone
+  /** Let the content wrap onto multiple lines instead of truncating (the channel nudge). */
+  wrap?: boolean
+  children: React.ReactNode
+  actions?: React.ReactNode
+}): React.JSX.Element {
+  const styles = useStyles()
+  const text = useTextStyles()
+  return (
+    <div className={mergeClasses(styles.root, styles[tone])}>
+      {icon}
+      <div className={mergeClasses(styles.content, !wrap && text.truncate)}>{children}</div>
+      {actions}
+    </div>
+  )
+}

src/renderer/src/components/ui/EmptyState.tsx

@@ -0,0 +1,57 @@
+import { Body1, Caption1, makeStyles, mergeClasses, tokens } from '@fluentui/react-components'
+import { SPACE } from './tokens'
+
+/**
+ * One shared empty-state block (L116/L117). The screens had drifted into three
+ * shapes — Downloads (icon + line), History (colored badge + line + sub-hint),
+ * Library (icon + line, no sub-hint) — and the Terminal / Diagnostics "empty"
+ * text wasn't a centered block at all (inline text). This centers them all on one
+ * structure: an optional focal `icon` (a hero glyph or a colored badge), a `Body1`
+ * message at normal foreground, and an optional muted `hint` line.
+ *
+ * `compact` swaps the tall screen-level padding (56px) for a smaller inset (32px),
+ * for placeholders that sit inside an already-populated screen (the Terminal log,
+ * the Diagnostics list) rather than filling an empty one.
+ */
+const useStyles = makeStyles({
+  root: {
+    display: 'flex',
+    flexDirection: 'column',
+    alignItems: 'center',
+    gap: SPACE.tight,
+    padding: '56px 16px',
+    // The container is muted, so a hero glyph and the hint line read as secondary;
+    // the message overrides back to the normal foreground so it stays legible.
+    color: tokens.colorNeutralForeground3,
+    textAlign: 'center'
+  },
+  compact: {
+    padding: '32px 16px'
+  },
+  message: {
+    color: tokens.colorNeutralForeground1
+  }
+})
+
+export function EmptyState({
+  icon,
+  message,
+  hint,
+  compact = false,
+  className
+}: {
+  icon?: React.ReactNode
+  message: React.ReactNode
+  hint?: React.ReactNode
+  compact?: boolean
+  className?: string
+}): React.JSX.Element {
+  const styles = useStyles()
+  return (
+    <div className={mergeClasses(styles.root, compact && styles.compact, className)}>
+      {icon}
+      <Body1 className={styles.message}>{message}</Body1>
+      {hint && <Caption1>{hint}</Caption1>}
+    </div>
+  )
+}

src/renderer/src/components/ui/IconButton.tsx

@@ -0,0 +1,59 @@
+import { forwardRef } from 'react'
+import { makeStyles, mergeClasses, tokens } from '@fluentui/react-components'
+import { useFocusStyles } from './focusRing'
+import { ICON } from './tokens'
+
+const useStyles = makeStyles({
+  btn: {
+    appearance: 'none',
+    border: 'none',
+    backgroundColor: 'transparent',
+    color: tokens.colorNeutralForeground3,
+    display: 'flex',
+    alignItems: 'center',
+    justifyContent: 'center',
+    cursor: 'pointer',
+    borderRadius: tokens.borderRadiusMedium,
+    ':hover': {
+      backgroundColor: tokens.colorNeutralBackground1Hover,
+      color: tokens.colorNeutralForeground2
+    },
+    ':disabled': {
+      cursor: 'not-allowed',
+      color: tokens.colorNeutralForegroundDisabled,
+      backgroundColor: 'transparent'
+    }
+  },
+  md: { width: '32px', height: '32px', fontSize: `${ICON.control}px` },
+  sm: { width: '28px', height: '28px', fontSize: `${ICON.inline}px` }
+})
+
+type IconButtonProps = {
+  icon: React.JSX.Element
+  size?: 'sm' | 'md'
+} & React.ButtonHTMLAttributes<HTMLButtonElement>
+
+/**
+ * The recurring icon-only ghost button (UI15) — one implementation for the
+ * sidebar's collapse/theme toggles and the playlist row's video/audio switch,
+ * which were separate hand-rolled buttons with the same look. Carries the shared
+ * focus ring (UI29). Extra props (onClick, aria-label, aria-pressed, disabled, …)
+ * pass straight through to the underlying `<button>`.
+ */
+export const IconButton = forwardRef<HTMLButtonElement, IconButtonProps>(function IconButton(
+  { icon, size = 'md', className, type = 'button', ...rest },
+  ref
+) {
+  const styles = useStyles()
+  const focus = useFocusStyles()
+  return (
+    <button
+      ref={ref}
+      type={type}
+      className={mergeClasses(styles.btn, styles[size], focus.focusRing, className)}
+      {...rest}
+    >
+      {icon}
+    </button>
+  )
+})

src/renderer/src/components/ui/LinkSuggestion.tsx

@@ -0,0 +1,50 @@
+import { Button, Caption1 } from '@fluentui/react-components'
+import { LinkRegular, DismissRegular } from '@fluentui/react-icons'
+import { Banner } from './Banner'
+
+/**
+ * The "use this copied/received link?" banner (UI19), shared by the DownloadBar
+ * and the Library add-source field, which had identical markup + CSS. Renders the
+ * link (with an optional lead-in like "Link received: ") and Use / Dismiss actions
+ * on the shared {@link Banner}.
+ */
+export function LinkSuggestion({
+  prefix,
+  link,
+  onAccept,
+  onDismiss,
+  dismissLabel
+}: {
+  /** Short lead-in before the link, e.g. "Use copied link? " or "Link received: ". */
+  prefix: string
+  link: string
+  onAccept: () => void
+  onDismiss: () => void
+  /** Accessible name for the dismiss button — say what's being dismissed (L153). */
+  dismissLabel: string
+}): React.JSX.Element {
+  return (
+    <Banner
+      icon={<LinkRegular />}
+      actions={
+        <>
+          <Button size="small" appearance="primary" onClick={onAccept}>
+            Use
+          </Button>
+          <Button
+            size="small"
+            appearance="subtle"
+            icon={<DismissRegular />}
+            onClick={onDismiss}
+            aria-label={dismissLabel}
+          />
+        </>
+      }
+    >
+      <Caption1>
+        {prefix}
+        {link}
+      </Caption1>
+    </Banner>
+  )
+}

src/renderer/src/components/ui/Screen.tsx

@@ -0,0 +1,74 @@
+import { Subtitle2, Caption1, makeStyles, tokens } from '@fluentui/react-components'
+
+/**
+ * One shared content max-width for every screen (UI1).
+ *
+ * Settings used to be a 640px column while the list screens (Downloads, Library,
+ * History, Terminal) were full-width, so on a wide window Settings read as an odd
+ * narrow strip beside edge-to-edge siblings. This caps them all at the same
+ * reading width and centers, so they line up. On typical window sizes the content
+ * is already under the cap, so the list screens are visually unchanged — only the
+ * wide-window upper bound is now shared.
+ *
+ * Merge `screen.width` onto each screen's existing root with `mergeClasses`.
+ */
+export const useScreenStyles = makeStyles({
+  width: {
+    width: '100%',
+    maxWidth: '1200px',
+    marginLeft: 'auto',
+    marginRight: 'auto'
+  }
+})
+
+const useStyles = makeStyles({
+  header: {
+    display: 'flex',
+    alignItems: 'flex-start',
+    gap: '12px',
+    flexWrap: 'wrap'
+  },
+  titleBlock: {
+    display: 'flex',
+    flexDirection: 'column',
+    gap: '2px',
+    minWidth: 0,
+    flexGrow: 1
+  },
+  description: {
+    color: tokens.colorNeutralForeground3
+  },
+  actions: {
+    display: 'flex',
+    alignItems: 'center',
+    gap: '8px',
+    flexShrink: 0
+  }
+})
+
+/**
+ * The consistent screen header block (UI9/UI10): one page-title style on every
+ * screen, with an optional one-line description and an optional right-aligned
+ * action slot. Previously each screen rolled its own (Subtitle2 / Title2 / none),
+ * and only Library had a description.
+ */
+export function ScreenHeader({
+  title,
+  description,
+  actions
+}: {
+  title: string
+  description?: React.ReactNode
+  actions?: React.ReactNode
+}): React.JSX.Element {
+  const styles = useStyles()
+  return (
+    <div className={styles.header}>
+      <div className={styles.titleBlock}>
+        <Subtitle2 as="h1">{title}</Subtitle2>
+        {description && <Caption1 className={styles.description}>{description}</Caption1>}
+      </div>
+      {actions && <div className={styles.actions}>{actions}</div>}
+    </div>
+  )
+}

src/renderer/src/components/ui/SegmentedControl.tsx

@@ -0,0 +1,153 @@
+import { useRef } from 'react'
+import { makeStyles, mergeClasses, tokens } from '@fluentui/react-components'
+import { useFocusStyles } from './focusRing'
+import { ICON } from './tokens'
+
+export interface SegmentOption<T extends string> {
+  value: T
+  label: string
+  /** optional leading icon (used by the sidebar theme switch) */
+  icon?: React.JSX.Element
+}
+
+const useStyles = makeStyles({
+  group: {
+    display: 'inline-flex',
+    width: 'fit-content',
+    border: `1px solid ${tokens.colorNeutralStroke1}`,
+    borderRadius: tokens.borderRadiusMedium,
+    overflow: 'hidden'
+  },
+  // Full-width variant: segments split the available width (the sidebar style).
+  fitted: {
+    display: 'flex',
+    width: '100%'
+  },
+  segment: {
+    appearance: 'none',
+    border: 'none',
+    backgroundColor: 'transparent',
+    color: tokens.colorNeutralForeground2,
+    display: 'flex',
+    alignItems: 'center',
+    justifyContent: 'center',
+    gap: '5px',
+    padding: '7px 16px',
+    fontSize: tokens.fontSizeBase300,
+    fontFamily: tokens.fontFamilyBase,
+    cursor: 'pointer',
+    ':hover': {
+      backgroundColor: tokens.colorNeutralBackground1Hover
+    }
+  },
+  segmentFitted: {
+    flexGrow: 1,
+    flexBasis: 0,
+    padding: '7px 4px',
+    fontSize: tokens.fontSizeBase200
+  },
+  segmentActive: {
+    backgroundColor: tokens.colorBrandBackground,
+    color: tokens.colorNeutralForegroundOnBrand,
+    fontWeight: tokens.fontWeightSemibold,
+    ':hover': {
+      backgroundColor: tokens.colorBrandBackgroundHover
+    },
+    // Under Windows High Contrast the brand background is flattened to the system
+    // canvas, so the checked segment would be indistinguishable from the others
+    // (W18). Paint it with the system Highlight pair so the selection stays visible.
+    '@media (forced-colors: active)': {
+      backgroundColor: 'Highlight',
+      color: 'HighlightText',
+      forcedColorAdjust: 'none'
+    }
+  },
+  icon: {
+    display: 'flex',
+    fontSize: `${ICON.inline}px`,
+    flexShrink: 0
+  }
+})
+
+/**
+ * One shared segmented control (UI14) replacing the two hand-rolled versions —
+ * the DownloadBar's Video/Audio kind toggle and the Sidebar's Light/Dark/Auto
+ * theme switch. Renders an ARIA radiogroup with roving-tabindex arrow-key
+ * navigation (UI30) and the shared focus ring (UI29). `fitted` makes the segments
+ * split the full width (sidebar); the default is fit-content (download bar).
+ *
+ * Active treatment is solid brand — the app's one rule for *toggles* (a compact
+ * set where the chosen option should read as pressed). This is deliberately
+ * distinct from the brand-*tint* used for *selection within a list* (the Sidebar
+ * nav item, the CommandPalette active option): one active treatment per control
+ * class (UI20).
+ */
+export function SegmentedControl<T extends string>({
+  value,
+  options,
+  onChange,
+  ariaLabel,
+  fitted = false
+}: {
+  value: T
+  options: SegmentOption<T>[]
+  onChange: (value: T) => void
+  ariaLabel: string
+  fitted?: boolean
+}): React.JSX.Element {
+  const styles = useStyles()
+  const focus = useFocusStyles()
+  const refs = useRef<(HTMLButtonElement | null)[]>([])
+
+  function onKeyDown(e: React.KeyboardEvent, index: number): void {
+    let next = -1
+    if (e.key === 'ArrowRight' || e.key === 'ArrowDown') next = (index + 1) % options.length
+    else if (e.key === 'ArrowLeft' || e.key === 'ArrowUp')
+      next = (index - 1 + options.length) % options.length
+    else if (e.key === 'Home') next = 0
+    else if (e.key === 'End') next = options.length - 1
+    else return
+    const opt = options[next]
+    if (!opt) return
+    e.preventDefault()
+    onChange(opt.value)
+    refs.current[next]?.focus()
+  }
+
+  return (
+    <div
+      className={mergeClasses(styles.group, fitted && styles.fitted)}
+      role="radiogroup"
+      aria-label={ariaLabel}
+    >
+      {options.map((opt, i) => {
+        const on = opt.value === value
+        return (
+          <button
+            key={opt.value}
+            ref={(el) => {
+              refs.current[i] = el
+            }}
+            type="button"
+            role="radio"
+            aria-checked={on}
+            // Roving tabindex: only the selected segment is a tab stop; arrow keys
+            // move within the group, as a radiogroup is expected to behave.
+            tabIndex={on ? 0 : -1}
+            className={mergeClasses(
+              styles.segment,
+              fitted && styles.segmentFitted,
+              on && styles.segmentActive,
+              focus.focusRing
+            )}
+            onClick={() => onChange(opt.value)}
+            onKeyDown={(e) => onKeyDown(e, i)}
+          >
+            {opt.icon && <span className={styles.icon}>{opt.icon}</span>}
+            {opt.label}
+          </button>
+        )
+      })}
+    </div>
+  )
+}

src/renderer/src/components/ui/StatusChip.tsx

@@ -0,0 +1,35 @@
+import { Badge } from '@fluentui/react-components'
+import type { DownloadStatus } from '../../store/downloads'
+
+/** The item-download status shown as a chip — the queue's live status plus the
+ *  library's 'pending' (catalogued but not yet downloaded). */
+export type ChipStatus = DownloadStatus | 'pending'
+
+type ChipColor = 'brand' | 'success' | 'danger' | 'warning' | 'subtle'
+
+/**
+ * One label + color per status (UI18 / M8) — the single source of truth that
+ * replaces QueueItem's Fluent `Badge` map and LibraryView's custom color `pill`
+ * spans, so the same status concept looks and reads identically on both screens
+ * (e.g. Library no longer says "Downloaded" where the queue says "Completed").
+ */
+const STATUS_CHIP: Record<ChipStatus, { label: string; color: ChipColor }> = {
+  pending: { label: 'Pending', color: 'subtle' },
+  queued: { label: 'Queued', color: 'subtle' },
+  downloading: { label: 'Downloading', color: 'brand' },
+  paused: { label: 'Paused', color: 'warning' },
+  saved: { label: 'Saved', color: 'subtle' },
+  completed: { label: 'Completed', color: 'success' },
+  error: { label: 'Failed', color: 'danger' },
+  canceled: { label: 'Canceled', color: 'subtle' }
+}
+
+/** Shared status chip used by the download queue and the library item list. */
+export function StatusChip({ status }: { status: ChipStatus }): React.JSX.Element {
+  const { label, color } = STATUS_CHIP[status]
+  return (
+    <Badge appearance="tint" color={color}>
+      {label}
+    </Badge>
+  )
+}

src/renderer/src/components/ui/Toaster.tsx

@@ -0,0 +1,99 @@
+import {
+  Caption1,
+  Button,
+  makeStyles,
+  mergeClasses,
+  tokens,
+  shorthands
+} from '@fluentui/react-components'
+import {
+  DismissRegular,
+  ErrorCircleFilled,
+  CheckmarkCircleFilled,
+  InfoFilled
+} from '@fluentui/react-icons'
+import { useToasts, type ToastTone } from '../../store/toasts'
+import { Z, ELEVATION, RADIUS, ICON } from './tokens'
+
+/**
+ * Renders the transient-toast stack (UX6/UX9) bottom-center. Deliberately NOT a
+ * Fluent Toaster/portal — this app avoids portal-based overlays (they blank/flicker
+ * on the dev GPU; see Select.tsx / CommandPalette.tsx) — so it's a plain fixed
+ * stack. No enter/exit animation, matching the app's conservative motion policy on
+ * this machine.
+ */
+const useStyles = makeStyles({
+  stack: {
+    position: 'fixed',
+    left: '50%',
+    bottom: '24px',
+    transform: 'translateX(-50%)',
+    zIndex: Z.tooltip,
+    display: 'flex',
+    flexDirection: 'column',
+    alignItems: 'center',
+    gap: '8px',
+    // Let clicks fall through the gaps between toasts to the app underneath.
+    pointerEvents: 'none'
+  },
+  toast: {
+    pointerEvents: 'auto',
+    display: 'flex',
+    alignItems: 'center',
+    gap: '10px',
+    maxWidth: 'min(520px, 90vw)',
+    padding: '10px 8px 10px 12px',
+    backgroundColor: tokens.colorNeutralBackground1,
+    border: `1px solid ${tokens.colorNeutralStroke2}`,
+    ...shorthands.borderRadius(RADIUS.surface),
+    boxShadow: ELEVATION.overlay
+  },
+  icon: {
+    flexShrink: 0,
+    fontSize: `${ICON.control}px`,
+    display: 'flex'
+  },
+  info: { color: tokens.colorNeutralForeground3 },
+  error: { color: tokens.colorStatusDangerForeground1 },
+  success: { color: tokens.colorStatusSuccessForeground1 },
+  message: {
+    flexGrow: 1,
+    minWidth: 0
+  }
+})
+
+const ICONS: Record<ToastTone, React.JSX.Element> = {
+  info: <InfoFilled />,
+  error: <ErrorCircleFilled />,
+  success: <CheckmarkCircleFilled />
+}
+
+export function Toaster(): React.JSX.Element | null {
+  const styles = useStyles()
+  const toasts = useToasts((s) => s.toasts)
+  const dismiss = useToasts((s) => s.dismiss)
+  const toneClass: Record<ToastTone, string> = {
+    info: styles.info,
+    error: styles.error,
+    success: styles.success
+  }
+
+  if (toasts.length === 0) return null
+  return (
+    <div className={styles.stack} role="status" aria-live="polite">
+      {toasts.map((t) => (
+        <div key={t.id} className={styles.toast}>
+          <span className={mergeClasses(styles.icon, toneClass[t.tone])}>{ICONS[t.tone]}</span>
+          <Caption1 className={styles.message}>{t.message}</Caption1>
+          <Button
+            size="small"
+            appearance="subtle"
+            icon={<DismissRegular />}
+            onClick={() => dismiss(t.id)}
+            aria-label="Dismiss notification"
+          />
+        </div>
+      ))}
+    </div>
+  )
+}

src/renderer/src/components/ui/errorText.ts

@@ -0,0 +1,21 @@
+import { makeStyles, tokens } from '@fluentui/react-components'
+
+/**
+ * Shared error-text styling (M12). The red `colorPaletteRedForeground1` was being
+ * applied via inline `style={{ color: … }}` across the app; this hook is the one
+ * place that owns it.
+ *
+ * - `error` — a single line of error copy (e.g. an inline validation/result message).
+ * - `errorPre` — the same colour but preserving newlines/long tokens, for multi-line
+ *   yt-dlp/updater error output that would otherwise overflow.
+ */
+export const useErrorTextStyles = makeStyles({
+  error: {
+    color: tokens.colorPaletteRedForeground1
+  },
+  errorPre: {
+    color: tokens.colorPaletteRedForeground1,
+    whiteSpace: 'pre-wrap',
+    wordBreak: 'break-word'
+  }
+})

src/renderer/src/components/ui/focusRing.ts

@@ -0,0 +1,26 @@
+import { makeStyles, tokens } from '@fluentui/react-components'
+
+/**
+ * One focus-visible ring for every hand-rolled interactive element (UI29).
+ *
+ * Fluent's own controls draw their own focus indicator; the app's bespoke
+ * buttons, segmented controls, command-palette rows, and `role="button"` headers
+ * previously fell back to the UA default (often invisible) or removed it
+ * entirely. This gives them all the same visible, theme-aware keyboard focus.
+ *
+ * Apply with `mergeClasses(focus.focusRing, …)`. The ring is inset (negative
+ * offset) so it never clips inside `overflow: hidden` containers and follows each
+ * element's own border-radius; it shows only for `:focus-visible`, so pointer
+ * clicks stay quiet.
+ */
+export const useFocusStyles = makeStyles({
+  focusRing: {
+    outlineStyle: 'none',
+    ':focus-visible': {
+      outlineWidth: '2px',
+      outlineStyle: 'solid',
+      outlineColor: tokens.colorStrokeFocus2,
+      outlineOffset: '-2px'
+    }
+  }
+})

src/renderer/src/components/ui/text.ts

@@ -0,0 +1,52 @@
+import { makeStyles, tokens } from '@fluentui/react-components'
+
+/**
+ * Shared text-role styles + the app's type-role convention (Batch 7).
+ *
+ * The renderer had drifted on typography: the one muted color was re-declared under
+ * eight class names (L110), row titles were rendered as three different components
+ * (L114), and `Caption1`/`Body1`/`Text` were applied by feel (L123/L124). The
+ * convention below makes the roles explicit; this module supplies the two styles
+ * that back it.
+ *
+ * Type roles — reach for the Fluent type component, add `muted` for secondary color:
+ * - `<Subtitle2>` — screen titles and settings-section headers (via `ScreenHeader`
+ *   and each settings card's header).
+ * - `<Text>` — the one row/item title component (add `title` for the semibold,
+ *   single-line-with-ellipsis treatment). Previously split across `<Text>`, a bare
+ *   `<span>`, and `<Caption1>` (L114).
+ * - `<Body1>` — body copy: empty-state messages, onboarding prose, gated notices.
+ *   Not for titles or metadata (L124).
+ * - `<Caption1>` — small secondary text: metadata, hints, counts, timestamps. One
+ *   role doing several closely-related jobs, all "small secondary text" (L123).
+ */
+export const useTextStyles = makeStyles({
+  /**
+   * The single muted / secondary-text color (L110) — was re-declared as
+   * hint/sub/meta/srcSub/stats/count/emptyHint/previewMeta. Merge onto a `<Caption1>`
+   * or `<Text>`, or use alone where the element sets no other style.
+   */
+  muted: {
+    color: tokens.colorNeutralForeground3
+  },
+  /** The shared row/item title treatment (L114): semibold, single line, ellipsis. */
+  title: {
+    fontWeight: tokens.fontWeightSemibold,
+    minWidth: 0,
+    overflow: 'hidden',
+    textOverflow: 'ellipsis',
+    whiteSpace: 'nowrap'
+  },
+  /**
+   * The single-line truncation utility (L126): clip overflowing text to one line
+   * with an ellipsis. This is `title` without the semibold weight — for metadata
+   * and non-title text that should truncate rather than wrap. Needs `minWidth: 0`
+   * so it can shrink inside a flex row.
+   */
+  truncate: {
+    minWidth: 0,
+    overflow: 'hidden',
+    textOverflow: 'ellipsis',
+    whiteSpace: 'nowrap'
+  }
+})

src/renderer/src/components/ui/tokens.ts

@@ -0,0 +1,139 @@
+import { tokens } from '@fluentui/react-components'
+
+/**
+ * AeroFetch design tokens — the app's own semantic scales, layered on Fluent's.
+ *
+ * Batch 6 of the audit (UI2–UI7, UI12, UI26, L100, L101, L121, L125, L160, L164)
+ * found the same visual decisions expressed as ad-hoc literals scattered across
+ * components: four section gaps, seven card paddings, two floating shadows, two
+ * hardcoded `zIndex: 1000`s, a raw `rgba()` scrim, nine inline icon sizes, and
+ * three metadata separators. This module is the single home for those values so
+ * every screen reads as one product and a change happens in one place.
+ *
+ * Where Fluent already defines a scale (spacing, radius, shadow, motion, the
+ * overlay scrim) these alias Fluent's tokens, so the app stays pixel-aligned with
+ * Fluent's own controls. Where Fluent has no token (z-index, icon px, the
+ * metadata separator) the value lives here.
+ *
+ * Griffel evaluates `makeStyles` at runtime in this project (no build plugin — see
+ * `thumbSizes` already imported into `downloadBar/styles.ts`), so these imported
+ * constants work directly inside `makeStyles` blocks and in inline `style={{}}`.
+ */
+
+/**
+ * Spacing ramp (px). Gaps, padding, and margins all draw from this one scale; the
+ * comments record the role each step plays so call sites stay self-documenting.
+ * Values match Fluent's spacing ramp (XXS 2 · XS 4 · S 8 · MNudge 10 · M 12 · L 16
+ * · XL 20 · XXL 24 · XXXL 32).
+ */
+export const SPACE = {
+  /** 2px — optical hairline nudge (e.g. aligning an icon to a text baseline) (L160). */
+  hairline: '2px',
+  /** 4px — icon-button clusters (UI5); tight margins between stacked lines (L160). */
+  xtight: '4px',
+  /** 8px — labelled-control rows (UI5); the default inline gap. */
+  tight: '8px',
+  /** 10px — control inner padding; small tiles. */
+  snug: '10px',
+  /** 12px — list-row padding; the gap between rows inside a card. */
+  cozy: '12px',
+  /** 16px — the one gap between screen sections (UI2) and the card padding tier (UI3). */
+  section: '16px',
+  /** 20px — a larger block gap. */
+  roomy: '20px',
+  /** 24px — page content padding (UI4); the hero padding tier's floor. */
+  page: '24px',
+  /** 32px — the onboarding / welcome hero card padding (UI3 hero tier). */
+  hero: '32px'
+} as const
+
+/**
+ * Corner-radius tiers by surface (UI6/UI7). Aliases Fluent's radius tokens, which
+ * `friendlyRadii` (theme.ts) tunes to Medium 10 · Large 12 · XLarge 16.
+ *
+ * - `control` (10) — inputs, thumbnails, small tiles, popover rows.
+ * - `surface` (12) — list-item cards and inline panels.
+ * - `card` (16) — page-level cards (the download bar, settings cards, onboarding).
+ */
+export const RADIUS = {
+  control: tokens.borderRadiusMedium,
+  surface: tokens.borderRadiusLarge,
+  card: tokens.borderRadiusXLarge
+} as const
+
+/**
+ * Elevation scale (L100). Cards are flat by default (border only — the app's
+ * resting surface); only genuinely floating surfaces cast a shadow.
+ *
+ * - `flat` — the default card: no shadow, a 1px neutral-stroke border.
+ * - `raised` (shadow4) — the download bar, which floats above the queue.
+ * - `overlay` (shadow28) — the command palette and any future popover.
+ */
+export const ELEVATION = {
+  flat: 'none',
+  raised: tokens.shadow4,
+  overlay: tokens.shadow28
+} as const
+
+/**
+ * Z-index scale (L101). Replaces the two hardcoded `zIndex: 1000`s so stacking is
+ * ordered on purpose: tooltips sit above full-screen overlays.
+ */
+export const Z = {
+  /** full-screen scrims and the command palette. */
+  overlay: 1000,
+  /** hint bubbles — above overlays so a tooltip is never clipped by one. */
+  tooltip: 1100
+} as const
+
+/**
+ * Theme-aware scrim for full-screen overlays (L121). Fluent's overlay token
+ * replaces the renderer's one raw `rgba(0,0,0,0.32)` — it's the semantic dialog
+ * scrim and darkens a touch more, so the palette separates cleanly from a dark UI.
+ */
+export const SCRIM = tokens.colorBackgroundOverlay
+
+/**
+ * Icon-size scale in px (UI12/L125): one small set instead of the nine scattered
+ * `fontSize` literals. Applied as a numeric `fontSize={ICON.x}` on standalone
+ * glyphs, or `` `${ICON.x}px` `` on the rare makeStyles container.
+ *
+ * - `inline` (16) — glyphs sitting inline with text (row actions, small badges).
+ * - `control` (20) — glyphs inside buttons, nav items, toggles, and small leading
+ *   accent icons (e.g. the onboarding folder/tip rows).
+ * - `section` (24) — section/card-header glyphs (e.g. each settings card's title).
+ * - `hero` (40) — the focal icon in an empty state.
+ *
+ * Snapped to the nearest tier rather than a literal px even when centered in a
+ * fixed tile (UI11 — no literal px font sizes): the brand/source tiles
+ * (Sidebar/Onboarding `mark`, Library `srcIcon`, History `emptyBadge`) take
+ * `control` or `section`. Genuinely off this scale: the tiny `watchBadge` glyph
+ * (matched to its badge-caption text size) and the thumbnail placeholder icons
+ * (which track `thumbSizes`).
+ */
+export const ICON = {
+  inline: 16,
+  control: 20,
+  section: 24,
+  hero: 40
+} as const
+
+/**
+ * One motion policy (UI26). The app keeps a single, subtle transition timing
+ * (matching the sidebar's former `0.15s ease`) and gates *all* transitions and
+ * animations behind `prefers-reduced-motion` globally in base.css — so motion is
+ * consistent where it exists and fully off for users who ask for less.
+ */
+export const MOTION = {
+  duration: tokens.durationFast,
+  curve: tokens.curveEasyEase
+} as const
+
+/**
+ * The single metadata separator (L164). Joins independent fields on a meta line
+ * (e.g. `Channel • 12:04`, `1.2 GB/s • 3s left`). Previously three styles were in
+ * use (`'  •  '`, `' · '`, `' • '`). Note this is distinct from the *intra-value*
+ * separator inside a compound quality label ("720p · mp4 · 184 MB"), which is a
+ * data format parsed elsewhere and intentionally left alone.
+ */
+export const META_SEP = ' • '

src/renderer/src/datetime.ts

@@ -0,0 +1,48 @@
+// One home for the renderer's date/time formatters (M9). These were previously
+// three private functions — `relTime` (LibraryView), `formatWhen` (HistoryView)
+// and `fmtSchedule` (QueueItem) — each reimplementing date math inline.
+
+/** Relative "time since" label: "just now" / "5 min ago" / "3 h ago" /
+ *  "2 d ago" / "3 w ago" / "2 mo ago". Returns "never" for a missing
+ *  timestamp. (Library last-indexed.) */
+export function relTime(ms?: number): string {
+  if (!ms) return 'never'
+  const mins = Math.round((Date.now() - ms) / 60000)
+  if (mins < 1) return 'just now'
+  if (mins < 60) return `${mins} min ago`
+  const hrs = Math.round(mins / 60)
+  if (hrs < 24) return `${hrs} h ago`
+  const days = Math.round(hrs / 24)
+  if (days < 7) return `${days} d ago`
+  const weeks = Math.round(days / 7)
+  if (weeks < 5) return `${weeks} w ago`
+  return `${Math.round(days / 30)} mo ago`
+}
+
+/** Absolute "when" label: "Today, 3:04 PM" / "Yesterday, 3:04 PM" /
+ *  "Jun 5" (current year) / "Jun 5, 2024" (past year). (History rows.) */
+export function formatWhen(ts: number): string {
+  const d = new Date(ts)
+  const time = d.toLocaleTimeString(undefined, { hour: '2-digit', minute: '2-digit' })
+  const now = new Date()
+  const startOfToday = new Date(now.getFullYear(), now.getMonth(), now.getDate()).getTime()
+  const dayMs = 1000 * 60 * 60 * 24
+  if (ts >= startOfToday) return `Today, ${time}`
+  if (ts >= startOfToday - dayMs) return `Yesterday, ${time}`
+  const sameYear = d.getFullYear() === now.getFullYear()
+  return d.toLocaleDateString(undefined, {
+    month: 'short',
+    day: 'numeric',
+    ...(sameYear ? {} : { year: 'numeric' })
+  })
+}
+
+/** Full date + time for a scheduled download, e.g. "Jun 5, 2025, 3:04 PM".
+ *  Returns '' if the timestamp can't be formatted. (Queue scheduled badge.) */
+export function fmtSchedule(ms: number): string {
+  try {
+    return new Date(ms).toLocaleString([], { dateStyle: 'medium', timeStyle: 'short' })
+  } catch {
+    return ''
+  }
+}