chore: bump version to 0.4.0

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "aerofetch",
-  "version": "0.2.0",
+  "version": "0.4.0",
   "description": "A yt-dlp frontend for Windows",
   "main": "./out/main/index.js",
   "author": "AeroFetch",

src/main/backup.ts

@@ -2,6 +2,7 @@ import { dialog, type BrowserWindow } from 'electron'
 import { readFileSync, writeFileSync } from 'fs'
 import { getSettings, setSettings } from './settings'
 import { listTemplates, replaceTemplates } from './templates'
+import { isTemplateLike } from './validation'
 import type {
   BackupExportResult,
   BackupImportResult,
@@ -55,8 +56,12 @@ export async function importBackup(win: BrowserWindow | undefined): Promise<Back
     file.settings && typeof file.settings === 'object'
       ? (file.settings as Partial<Settings>)
       : undefined
+  // Drop non-object / id-less entries up front (audit T3) so both the consent
+  // check below and replaceTemplates see only well-shaped rows. Without this a
+  // backup with a null/garbage templates entry throws in sanitize() instead of
+  // degrading gracefully as this function promises.
   const incomingTemplates = Array.isArray(file.templates)
-    ? (file.templates as CommandTemplate[])
+    ? (file.templates as CommandTemplate[]).filter(isTemplateLike)
     : []
 
   // A custom-command template's `args` are extra yt-dlp flags that get spawned on

src/main/binaries.ts

@@ -35,3 +35,15 @@ export function getFfprobePath(): string {
 export function getAria2cPath(): string {
   return join(getBinDir(), 'aria2c.exe')
 }
+
+/**
+ * Absolute path to a Windows system executable (e.g. taskkill.exe, schtasks.exe).
+ *
+ * SECURITY (audit F3): system tools are resolved by full path under System32
+ * rather than by bare name, so a same-named binary planted in the current
+ * working directory or earlier on PATH can't be invoked in their place — a real
+ * risk for the portable build, which runs from user-writable locations.
+ */
+export function getSystem32Path(exe: string): string {
+  return join(process.env.SystemRoot || 'C:\\Windows', 'System32', exe)
+}

src/main/buildArgs.ts

@@ -14,7 +14,8 @@ import {
   type StartDownloadOptions,
   type DownloadOptions,
   type CollectionContext,
-  type CookieBrowser
+  type CookieBrowser,
+  type CommandTemplate
 } from '@shared/ipc'
 
 // --- Quality → yt-dlp selector mapping --------------------------------------
@@ -127,6 +128,39 @@ export function parseExtraArgs(raw: string): string[] {
   return args
 }
 
+/**
+ * Resolve the extra yt-dlp args for a download, enforcing the custom-command
+ * consent gate (audit F2).
+ *
+ * Extra args are powerful enough to run arbitrary code (e.g. `--exec`), so they
+ * are honoured ONLY when custom commands are explicitly enabled in settings —
+ * the same persisted flag the Settings UI and backup-import treat as consent. A
+ * per-download override wins over the persisted default template, but NEITHER is
+ * applied while the gate is off. This keeps a compromised renderer from smuggling
+ * code-exec flags through a lone `startDownload({ extraArgs })` call: it would
+ * first have to flip the visible `customCommandEnabled` setting, leaving a trace
+ * (the same defence-in-depth posture as the main-side maxConcurrent cap).
+ *
+ *  - customCommandEnabled off               → [] (always)
+ *  - perDownloadExtraArgs defined (even '')  → those args
+ *  - else a matching defaultTemplateId       → that template's args
+ *  - else                                    → []
+ */
+export function selectExtraArgs(params: {
+  customCommandEnabled: boolean
+  perDownloadExtraArgs: string | undefined
+  defaultTemplateId: string | null
+  templates: Pick<CommandTemplate, 'id' | 'args'>[]
+}): string[] {
+  if (!params.customCommandEnabled) return []
+  if (params.perDownloadExtraArgs !== undefined) return parseExtraArgs(params.perDownloadExtraArgs)
+  if (params.defaultTemplateId) {
+    const tpl = params.templates.find((t) => t.id === params.defaultTemplateId)
+    if (tpl) return parseExtraArgs(tpl.args)
+  }
+  return []
+}
+
 // Wrap a single argv token for human-readable display only (Phase C command
 // preview) — never used to build the real argv that gets spawned.
 function quoteForDisplay(arg: string): string {
@@ -163,7 +197,9 @@ export function sanitizeDirSegment(name: string): string {
   let s = Array.from(name ?? '', (ch) => (ch.charCodeAt(0) < 0x20 ? ' ' : ch)).join('')
   s = s.replace(/[<>:"/\\|?*]/g, ' ')
   s = s.replace(/\s+/g, ' ').trim().replace(/[. ]+$/, '').replace(/^[. ]+/, '')
-  if (/^(con|prn|aux|nul|com[1-9]|lpt[1-9])$/i.test(s)) s = `_${s}`
+  // Reserved device names are reserved even WITH an extension ('CON.txt' is still
+  // the CON device), so match an optional trailing '.<ext>' too (audit T3).
+  if (/^(con|prn|aux|nul|com[1-9]|lpt[1-9])(\..*)?$/i.test(s)) s = `_${s}`
   s = s.slice(0, 80).trim()
   return s || 'Untitled'
 }

src/main/cookies.ts

@@ -1,4 +1,4 @@
-import { app, session, BrowserWindow, type Cookie } from 'electron'
+import { app, session, BrowserWindow, type Cookie, type WebContents } from 'electron'
 import { existsSync, statSync, unlinkSync, writeFileSync } from 'fs'
 import { join } from 'path'
 import { assertHttpUrl } from './url'
@@ -11,6 +11,55 @@ import type { CookiesStatus, CookiesLoginResult } from '@shared/ipc'
  */
 const PARTITION = 'persist:aerofetch-login'
 
+/**
+ * The sign-in window renders untrusted remote content, so every navigation and
+ * popup is confined to web URLs — http(s), plus about:blank. This stops a
+ * logged-in (or malicious) page from steering the window to a file:// URL, to
+ * the app's own aerofetch:// protocol handler, or to any other external URI
+ * scheme used as a pivot. (audit T4)
+ */
+export function isAllowedLoginUrl(target: string): boolean {
+  try {
+    const { protocol } = new URL(target)
+    return protocol === 'http:' || protocol === 'https:' || protocol === 'about:'
+  } catch {
+    return false
+  }
+}
+
+/**
+ * Apply the web-only confinement to a sign-in webContents: block top-frame
+ * navigations and server redirects to non-web URLs, restrict popups to web URLs
+ * (reusing the same secure, partitioned webPreferences), and recurse into any
+ * popup the page opens so a nested window can't escape the policy either. The
+ * window-open handler alone only governs NEW windows, not navigations of an
+ * existing one — both vectors are covered here. (audit T4)
+ */
+function hardenLoginWebContents(wc: WebContents): void {
+  wc.setWindowOpenHandler((details) => {
+    if (!isAllowedLoginUrl(details.url)) return { action: 'deny' }
+    return {
+      action: 'allow',
+      overrideBrowserWindowOptions: {
+        autoHideMenuBar: true,
+        webPreferences: {
+          partition: PARTITION,
+          sandbox: true,
+          contextIsolation: true,
+          nodeIntegration: false
+        }
+      }
+    }
+  })
+  wc.on('will-navigate', (e, navUrl) => {
+    if (!isAllowedLoginUrl(navUrl)) e.preventDefault()
+  })
+  wc.on('will-redirect', (e, navUrl) => {
+    if (!isAllowedLoginUrl(navUrl)) e.preventDefault()
+  })
+  wc.on('did-create-window', (child) => hardenLoginWebContents(child.webContents))
+}
+
 export function getCookiesFilePath(): string {
   return join(app.getPath('userData'), 'cookies.txt')
 }
@@ -114,26 +163,12 @@ export function openCookieLoginWindow(url: string): Promise<CookiesLoginResult>
     }
     loginWindow = win
 
-    // Some sites log in via an OAuth/SSO popup. Let those open as real windows
-    // sharing the same partition, rather than silently swallowing the click.
-    // Restrict popups to http(s) only — the same defence the main window applies
-    // (index.ts) — so a logged-in page can't open a file:// popup to exfil cookies
-    // to disk or use a custom-protocol popup as a pivot.
-    win.webContents.setWindowOpenHandler((details) => {
-      try {
-        const { protocol } = new URL(details.url)
-        if (protocol !== 'http:' && protocol !== 'https:') return { action: 'deny' }
-      } catch {
-        return { action: 'deny' } // unparseable URL — never open it
-      }
-      return {
-        action: 'allow',
-        overrideBrowserWindowOptions: {
-          autoHideMenuBar: true,
-          webPreferences: { partition: PARTITION, sandbox: true, contextIsolation: true, nodeIntegration: false }
-        }
-      }
-    })
+    // Confine every navigation/popup to web URLs (recursively, so OAuth/SSO
+    // popups sharing the cookie partition are covered too), and deny all gated
+    // web permissions — signing in needs no camera/mic/geolocation/etc., and the
+    // page is untrusted. (audit T4)
+    hardenLoginWebContents(win.webContents)
+    win.webContents.session.setPermissionRequestHandler((_wc, _permission, cb) => cb(false))
 
     win.on('closed', () => {
       loginWindow = null

src/main/deeplink.ts

@@ -1,27 +1,40 @@
 import { app, shell, type BrowserWindow } from 'electron'
-import { existsSync, readFileSync } from 'fs'
+import { existsSync, openSync, readSync, closeSync } from 'fs'
 import { join } from 'path'
+import { assertHttpUrl } from './url'
 
 /** 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. */
+ *  external-link window-open handler in index.ts applies to in-page links.
+ *  Delegates to the download path's guard so an incoming deep-link target is
+ *  validated AND parser-normalised (no embedded tabs/newlines/control chars
+ *  reach the renderer); returns null instead of throwing for the argv scan.
+ *  (audit T3 / F5) */
 function asHttpUrl(candidate: string): string | null {
   try {
-    const u = new URL(candidate)
-    return u.protocol === 'http:' || u.protocol === 'https:' ? candidate : null
+    return assertHttpUrl(candidate)
   } catch {
     return null
   }
 }
 
 /** Reads a Windows Internet Shortcut (.url) file's target — what Explorer's
- *  "Send to" menu hands us when the user sends a saved link to AeroFetch. */
+ *  "Send to" menu hands us when the user sends a saved link to AeroFetch.
+ *  Only the first 64 KB is read: a real shortcut is a few hundred bytes, so this
+ *  caps memory and limits exposure if argv points at a pathological or oversized
+ *  file that merely ends in `.url`. (audit T5) */
+const MAX_URL_FILE_BYTES = 64 * 1024
 function readUrlShortcut(path: string): string | null {
+  let fd: number | null = null
   try {
-    const text = readFileSync(path, 'utf8')
-    const match = /^URL=(.+)$/im.exec(text)
+    fd = openSync(path, 'r')
+    const buf = Buffer.alloc(MAX_URL_FILE_BYTES)
+    const bytes = readSync(fd, buf, 0, buf.length, 0)
+    const match = /^URL=(.+)$/im.exec(buf.toString('utf8', 0, bytes))
     return match ? asHttpUrl(match[1].trim()) : null
   } catch {
     return null
+  } finally {
+    if (fd !== null) closeSync(fd)
   }
 }
 
@@ -32,7 +45,7 @@ function readUrlShortcut(path: string): string | null {
  */
 export function extractIncomingUrl(argv: string[]): string | null {
   for (const arg of argv) {
-    if (arg.startsWith('aerofetch://')) {
+    if (/^aerofetch:\/\//i.test(arg)) {
       try {
         const target = new URL(arg).searchParams.get('url')
         const valid = target && asHttpUrl(target)

src/main/download.ts

@@ -1,15 +1,23 @@
 import { spawn, execFile, type ChildProcess } from 'child_process'
 import { existsSync } from 'fs'
 import { join } from 'path'
-import { app, BrowserWindow, Notification, type WebContents } from 'electron'
-import { getYtdlpPath, getBinDir, getAria2cPath, getFfmpegPath, getFfprobePath } from './binaries'
-import { getSettings, getDownloadArchivePath } from './settings'
+import { BrowserWindow, Notification, type WebContents } from 'electron'
+import {
+  getYtdlpPath,
+  getBinDir,
+  getAria2cPath,
+  getFfmpegPath,
+  getFfprobePath,
+  getSystem32Path
+} from './binaries'
+import { getSettings, getDownloadArchivePath, getDefaultMediaDir } from './settings'
 import { getCookiesFilePath } from './cookies'
 import { listTemplates } from './templates'
 import { assertHttpUrl } from './url'
+import { isSafeOutputDir } from './validation'
 import {
   buildArgs,
-  parseExtraArgs,
+  selectExtraArgs,
   formatCommandLine,
   collectionOutputTemplate
 } from './buildArgs'
@@ -151,21 +159,34 @@ function probeMeta(ytdlp: string, url: string): Promise<DownloadMeta | null> {
 
 // --- Argv construction (shared by startDownload and the command preview) ---
 
-// A per-download override (opts.extraArgs, even '') always wins; otherwise
-// fall back to the persisted default template when custom-command mode is on.
+// A per-download override (opts.extraArgs, even '') wins over the persisted
+// default template — but BOTH are gated on the customCommandEnabled consent flag
+// (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[] {
-  if (opts.extraArgs !== undefined) return parseExtraArgs(opts.extraArgs)
-  if (settings.customCommandEnabled && settings.defaultTemplateId) {
-    const tpl = listTemplates().find((t) => t.id === settings.defaultTemplateId)
-    if (tpl) return parseExtraArgs(tpl.args)
-  }
-  return []
+  return selectExtraArgs({
+    customCommandEnabled: settings.customCommandEnabled,
+    perDownloadExtraArgs: opts.extraArgs,
+    defaultTemplateId: settings.defaultTemplateId,
+    templates: listTemplates()
+  })
 }
 
 /** Resolve settings + per-download overrides into the full yt-dlp argv. */
 export function buildCommand(opts: StartDownloadOptions): string[] {
   const settings = getSettings()
-  const outDir = opts.outputDir?.trim() || settings.outputDir || app.getPath('downloads')
+  // 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
+  // blank — the per-kind default (Documents\Video for video, Documents\Audio for audio).
+  //
+  // A per-download outputDir override must clear the same safety check the persisted
+  // setting does (absolute path only); a renderer-supplied override is otherwise
+  // untrusted — it dictates where downloaded files get written. An unsafe override is
+  // ignored in favour of the per-kind folder, then the per-kind default. (audit F4)
+  const override = opts.outputDir?.trim()
+  const safeOverride = override && isSafeOutputDir(override) ? override : ''
+  const perKindDir = (opts.kind === 'audio' ? settings.audioDir : settings.videoDir)?.trim()
+  const outDir = safeOverride || perKindDir || getDefaultMediaDir(opts.kind)
   // A collection (media-manager) download is filed into <channel>/<playlist>/
   // <NNN> - <title> folders; an ordinary download uses the flat filenameTemplate.
   const filenameTemplate = settings.filenameTemplate?.trim() || '%(title)s.%(ext)s'
@@ -198,13 +219,16 @@ export function buildCommand(opts: StartDownloadOptions): string[] {
 
 /** Build the exact command line for the current form state, without running it. */
 export function previewCommand(opts: StartDownloadOptions): CommandPreviewResult {
+  let normalized: StartDownloadOptions
   try {
-    assertHttpUrl(opts.url)
+    // Use the parser-normalised URL (audit F5), so the previewed command matches
+    // exactly what startDownload would spawn.
+    normalized = { ...opts, url: assertHttpUrl(opts.url) }
   } catch (e) {
     return { ok: false, error: (e as Error).message }
   }
   try {
-    return { ok: true, command: formatCommandLine(getYtdlpPath(), buildCommand(opts)) }
+    return { ok: true, command: formatCommandLine(getYtdlpPath(), buildCommand(normalized)) }
   } catch (e) {
     return { ok: false, error: (e as Error).message }
   }
@@ -239,9 +263,13 @@ export function startDownload(
         `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.
+  // Reject anything that isn't an http(s) URL before it reaches yt-dlp's argv,
+  // and replace opts.url with the parser-normalised form so the exact string we
+  // validated is the one that gets spawned/probed — not a raw variant carrying
+  // interior tabs/newlines or leading control chars that URL parsing silently
+  // tolerates. (audit F5)
   try {
-    assertHttpUrl(opts.url)
+    opts = { ...opts, url: assertHttpUrl(opts.url) }
   } catch (e) {
     return { ok: false, error: (e as Error).message }
   }
@@ -344,8 +372,15 @@ export function cancelDownload(id: string): void {
   rec.canceled = true
   const pid = rec.child.pid
   if (pid != null) {
-    // Kill the whole tree (/T) so the spawned ffmpeg child dies too.
-    execFile('taskkill', ['/pid', String(pid), '/T', '/F'], { windowsHide: true }, () => {})
+    // Kill the whole tree (/T) so the spawned ffmpeg child dies too. Resolve
+    // taskkill from System32 by absolute path, never the bare name, so a planted
+    // taskkill.exe on PATH / in the CWD can't run in its place. (audit F3)
+    execFile(
+      getSystem32Path('taskkill.exe'),
+      ['/pid', String(pid), '/T', '/F'],
+      { windowsHide: true },
+      () => {}
+    )
   } else {
     rec.child.kill()
   }

src/main/index.ts

@@ -13,7 +13,7 @@ import {
 import { getYtdlpVersion, updateYtdlp } from './ytdlp'
 import { probeMedia } from './probe'
 import { startDownload, cancelDownload, previewCommand } from './download'
-import { getSettings, setSettings } from './settings'
+import { getSettings, setSettings, ensureMediaDirs } from './settings'
 import { listHistory, addHistory, removeHistory, removeManyHistory, clearHistory } from './history'
 import { listTemplates, saveTemplate, removeTemplate } from './templates'
 import { setupPortableData } from './portable'
@@ -90,6 +90,25 @@ function getSystemThemeInfo(): SystemThemeInfo {
   }
 }
 
+// Web permissions a download manager never needs. They're denied for the app
+// window as defence-in-depth (audit T6): even if the renderer were compromised
+// (e.g. XSS via remote video metadata) it can't open the camera/mic, read
+// location, or reach USB/HID/serial/Bluetooth devices — none of which the IPC
+// surface grants either. Clipboard (paste/copy) and everything else is left to
+// the default so the app's own features keep working.
+const DENIED_PERMISSIONS = new Set([
+  'media', // camera + microphone
+  'geolocation',
+  'midi',
+  'midiSysex',
+  'hid',
+  'serial',
+  'usb',
+  'bluetooth',
+  'speaker-selection',
+  'idle-detection'
+])
+
 function createWindow(): void {
   const win = new BrowserWindow({
     width: 920,
@@ -143,6 +162,15 @@ function createWindow(): void {
   // away from it (defence in depth; HMR uses websockets, not navigation).
   win.webContents.on('will-navigate', (e) => e.preventDefault())
 
+  // Deny the sensitive hardware/location web permissions the app never uses, so
+  // a compromised renderer can't escalate to capabilities the IPC surface
+  // doesn't grant. Both the async request and the sync check are covered. (audit T6)
+  const ses = win.webContents.session
+  ses.setPermissionRequestHandler((_wc, permission, callback) =>
+    callback(!DENIED_PERMISSIONS.has(permission))
+  )
+  ses.setPermissionCheckHandler((_wc, permission) => !DENIED_PERMISSIONS.has(permission))
+
   if (is.dev && process.env['ELECTRON_RENDERER_URL']) {
     win.loadURL(process.env['ELECTRON_RENDERER_URL'])
   } else {
@@ -151,6 +179,8 @@ function createWindow(): void {
 }
 
 function registerIpcHandlers(): void {
+  ipcMain.handle(IpcChannels.appVersion, () => app.getVersion())
+
   ipcMain.handle(IpcChannels.ytdlpVersion, () => getYtdlpVersion())
 
   ipcMain.handle(IpcChannels.probe, (_e, url: string) => probeMedia(url))
@@ -303,6 +333,10 @@ if (isPrimaryInstance) {
   app.whenReady().then(() => {
     electronApp.setAppUserModelId('com.aerofetch.app')
 
+    // Create the default Documents\Video and Documents\Audio destinations so they
+    // exist from first launch (downloads are routed into them by kind).
+    ensureMediaDirs()
+
     app.on('browser-window-created', (_, window) => {
       optimizer.watchWindowShortcuts(window)
     })

src/main/indexer.ts

@@ -83,8 +83,9 @@ export async function indexSource(
   url: string,
   onProgress: (p: IndexProgress) => void
 ): Promise<IndexSourceResult> {
+  let normalizedUrl: string
   try {
-    assertHttpUrl(url)
+    normalizedUrl = assertHttpUrl(url) // normalised form for spawning (audit F5)
   } catch (e) {
     return { ok: false, error: (e as Error).message }
   }
@@ -146,7 +147,7 @@ export async function indexSource(
       // resolve to a playlist when probed. A lone video has no entries → error.
       kind = cls?.kind ?? 'playlist'
       onProgress({ url, phase: 'uploads', message: 'Indexing playlist…' })
-      const data = await probeFlat(cls?.base ?? url)
+      const data = await probeFlat(cls?.base ?? normalizedUrl)
       const entries = data.entries ?? []
       if (entries.length === 0) {
         return {

src/main/indexerCore.ts

@@ -34,7 +34,9 @@ export interface RawEntry {
 export function entryUrl(e: RawEntry): string | null {
   const cand = e.url || e.webpage_url
   if (cand && /^https?:\/\//i.test(cand)) return cand
-  if (e.id) return `https://www.youtube.com/watch?v=${e.id}`
+  // e.id is untrusted JSON from yt-dlp, so percent-encode it rather than splicing
+  // it raw into the query string (audit T2). A normal 11-char id is unaffected.
+  if (e.id) return `https://www.youtube.com/watch?v=${encodeURIComponent(e.id)}`
   return null
 }
 
@@ -138,6 +140,24 @@ export function buildFeedUrl(kind: SourceKind, ytId: string | undefined): string
   return `https://www.youtube.com/feeds/videos.xml?${param}=${encodeURIComponent(ytId)}`
 }
 
+/**
+ * Guard for the watched-source RSS pre-check (audit T7). The only feed AeroFetch
+ * ever builds is a YouTube videos.xml feed (see buildFeedUrl), so the sync refuses
+ * to fetch anything else — this keeps a hand-edited / corrupted sources.json from
+ * pointing fetch() at an internal service, a cloud-metadata endpoint, or any other
+ * arbitrary host (SSRF). Requires https, the youtube.com host (www optional), and
+ * the exact feed path; the channel_id/playlist_id query is free.
+ */
+export function isYouTubeFeedUrl(url: string): boolean {
+  try {
+    const u = new URL(url)
+    const host = u.hostname.replace(/^www\./i, '').toLowerCase()
+    return u.protocol === 'https:' && host === 'youtube.com' && u.pathname === '/feeds/videos.xml'
+  } catch {
+    return false
+  }
+}
+
 /** Extract the video ids from a YouTube RSS/Atom feed body (the <yt:videoId> tags). */
 export function parseRssVideoIds(xml: string): string[] {
   const ids: string[] = []

src/main/probe.ts

@@ -118,8 +118,9 @@ export function probeMedia(url: string): Promise<ProbeResult> {
       error: `yt-dlp.exe not found at ${ytdlp}\nDrop it into resources/bin/ (see the README there).`
     })
   }
+  let target: string
   try {
-    assertHttpUrl(url)
+    target = assertHttpUrl(url) // normalised form (audit F5)
   } catch (e) {
     return Promise.resolve({ ok: false, error: (e as Error).message })
   }
@@ -128,7 +129,7 @@ export function probeMedia(url: string): Promise<ProbeResult> {
     execFile(
       ytdlp,
       // `--` terminates option parsing so the URL can never be read as a flag.
-      ['-J', '--flat-playlist', '--no-warnings', '--', url],
+      ['-J', '--flat-playlist', '--no-warnings', '--', target],
       { windowsHide: true, maxBuffer: 64 * 1024 * 1024, timeout: 60_000 },
       (err, stdout, stderr) => {
         if (err) {

src/main/schedule.ts

@@ -10,6 +10,7 @@
  */
 
 import { execFile } from 'child_process'
+import { getSystem32Path } from './binaries'
 import type { ScheduledSyncStatus } from '@shared/ipc'
 
 const TASK_NAME = 'AeroFetchDailySync'
@@ -18,7 +19,9 @@ export const SYNC_FLAG = '--sync'
 
 function schtasks(args: string[]): Promise<{ code: number; stdout: string; stderr: string }> {
   return new Promise((resolve) => {
-    execFile('schtasks', args, { windowsHide: true }, (err, stdout, stderr) => {
+    // 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) => {
       const code = err ? ((err as { code?: number }).code ?? 1) : 0
       resolve({ code, stdout: String(stdout), stderr: String(stderr) })
     })

src/main/settings.ts

@@ -1,5 +1,6 @@
 import { app } from 'electron'
 import { join } from 'path'
+import { mkdirSync } from 'fs'
 import Store from 'electron-store'
 import { isSafeFilenameTemplate, isSafeOutputDir } from './validation'
 import {
@@ -16,7 +17,10 @@ import {
 } from '@shared/ipc'
 
 const DEFAULTS: Settings = {
-  outputDir: '', // resolved to the OS Downloads folder on first read
+  // Both blank by default → downloads land in Documents\Video / Documents\Audio
+  // (see getDefaultMediaDir). A non-empty value is an explicit per-kind override.
+  videoDir: '',
+  audioDir: '',
   defaultKind: 'video',
   defaultVideoQuality: 'Best available',
   defaultAudioQuality: 'Best (MP3)',
@@ -45,6 +49,31 @@ 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.
@@ -100,10 +129,9 @@ export function getSettings(): Settings {
   // `set`, so only write when something actually changed — otherwise this churns
   // the settings file on every read. (audit P1)
   const cur = s.store
-  if (!cur.outputDir) {
-    // Fill in the real Downloads path the first time, and persist it once.
-    s.set('outputDir', app.getPath('downloads'))
-  }
+  // videoDir/audioDir are intentionally left blank by default — an empty value
+  // routes that kind into Documents\Video / Documents\Audio (see buildCommand).
+  // Only an explicit user choice (Settings → folders) overrides that.
   // Migrate settings files that predate downloadOptions (or hold a partial one),
   // but only persist when sanitizing actually altered the stored value.
   const sanitized = sanitizeOptions(cur.downloadOptions)
@@ -187,8 +215,13 @@ export function setSettings(partial: Partial<Settings>): Settings {
         // group (it merges field changes locally before calling setSettings).
         s.set('downloadOptions', sanitizeOptions(value))
         break
-      case 'outputDir':
-        if (typeof value === 'string' && isSafeOutputDir(value.trim())) s.set('outputDir', value.trim())
+      case 'videoDir':
+      case 'audioDir':
+        // An empty string is allowed — it clears the override and restores the
+        // Documents\Video / Documents\Audio default for that kind.
+        if (typeof value === 'string' && (value.trim() === '' || isSafeOutputDir(value.trim()))) {
+          s.set(key, value.trim())
+        }
         break
       case 'filenameTemplate':
         if (typeof value === 'string' && isSafeFilenameTemplate(value.trim())) {

src/main/sync.ts

@@ -7,11 +7,15 @@
 
 import { listSources, listMediaItems } from './sources'
 import { indexSource } from './indexer'
-import { parseRssVideoIds } from './indexerCore'
+import { parseRssVideoIds, isYouTubeFeedUrl } from './indexerCore'
 import type { IndexProgress, MediaItem, SyncResult } from '@shared/ipc'
 
 /** Fetch a YouTube RSS feed and return its recent video ids. Throws on failure. */
 async function fetchFeedIds(feedUrl: string): Promise<string[]> {
+  // Only ever fetch a genuine YouTube feed — refuse an arbitrary host that a
+  // 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) })
   if (!res.ok) throw new Error(`feed responded ${res.status}`)
   return parseRssVideoIds(await res.text())

src/main/url.ts

@@ -10,17 +10,23 @@
  * (Call sites also pass `--` before the positional URL as defence in depth.)
  *
  * Throws a user-friendly Error on anything that isn't an http(s) URL.
+ *
+ * Returns the parser-NORMALISED URL (`u.href`), not the raw input (audit F5).
+ * The WHATWG URL parser silently tolerates interior tab/newline characters and
+ * leading C0 control bytes (which `String.trim()` does not strip), so returning
+ * the raw string could hand a downstream consumer — argv, or the sign-in
+ * window's loadURL — a value subtly different from the one actually validated.
+ * Emitting `u.href` guarantees callers use exactly the URL that passed the check.
  */
 export function assertHttpUrl(raw: string): string {
-  const trimmed = (raw ?? '').trim()
   let u: URL
   try {
-    u = new URL(trimmed)
+    u = new URL((raw ?? '').trim())
   } catch {
     throw new Error('That doesn’t look like a valid URL.')
   }
   if (u.protocol !== 'http:' && u.protocol !== 'https:') {
     throw new Error('Only http and https links are supported.')
   }
-  return trimmed
+  return u.href
 }

src/main/validation.ts

@@ -13,15 +13,21 @@ import type { HistoryEntry, ErrorLogEntry, CommandTemplate, Source, MediaItem }
 
 /**
  * A filenameTemplate is joined onto the output directory and handed to yt-dlp's
- * `-o`. Reject anything that could write outside that directory — an absolute
- * path, or any `..` path segment — so a malicious backup/settings write can't
- * traverse out of the chosen folder (e.g. '%(title)s\..\..\win32.exe'). The
- * template still legitimately contains yt-dlp `%(field)s` tokens and `/` or `\`
- * for sub-folders, which are fine.
+ * `-o`. Reject anything that could write outside that directory so a malicious
+ * backup/settings write can't traverse out of the chosen folder (e.g.
+ * '%(title)s\..\..\win32.exe'). Legitimate templates still contain yt-dlp
+ * `%(field)s` tokens and `/` or `\` for sub-folders, which are fine.
+ *
+ * Two Windows-specific bypasses are guarded beyond the obvious cases (audit T1):
+ *  - drive-relative prefixes like 'C:foo' — `path.isAbsolute` returns FALSE for
+ *    these, yet they escape the output dir, so a leading drive letter is rejected.
+ *  - a '..' segment dressed up with trailing dots/spaces ('.. ', '.. .') —
+ *    Windows silently trims those, so an exact `=== '..'` check would miss them.
  */
+const TRAVERSAL_SEGMENT = /^[. ]*\.\.[. ]*$/
 export function isSafeFilenameTemplate(template: string): boolean {
-  if (isAbsolute(template)) return false
-  return !template.split(/[\\/]/).some((segment) => segment === '..')
+  if (isAbsolute(template) || /^[a-zA-Z]:/.test(template)) return false
+  return !template.split(/[\\/]/).some((segment) => TRAVERSAL_SEGMENT.test(segment))
 }
 
 /** An output directory must be an absolute path ('' resolves to OS Downloads). */
@@ -88,6 +94,10 @@ export function isValidSource(o: unknown): o is Source {
     typeof s.addedAt === 'number' &&
     typeof s.itemCount === 'number' &&
     isOptionalString(s.channel) &&
+    // feedUrl drives a network fetch in the sync, so validate its shape here too
+    // (audit T7); the host is additionally restricted at the fetch boundary.
+    isOptionalString(s.feedUrl) &&
+    (s.watched === undefined || typeof s.watched === 'boolean') &&
     (s.lastIndexedAt === undefined || typeof s.lastIndexedAt === 'number')
   )
 }

src/main/ytdlp.ts

@@ -1,7 +1,12 @@
 import { execFile } from 'child_process'
 import { existsSync } from 'fs'
 import { getYtdlpPath } from './binaries'
-import type { YtdlpVersionResult, YtdlpUpdateChannel, YtdlpUpdateResult } from '@shared/ipc'
+import {
+  isYtdlpUpdateChannel,
+  type YtdlpVersionResult,
+  type YtdlpUpdateChannel,
+  type YtdlpUpdateResult
+} from '@shared/ipc'
 
 /**
  * Step-1 spike: spawn the bundled yt-dlp and read back `--version`.
@@ -38,6 +43,14 @@ export function getYtdlpVersion(): Promise<YtdlpVersionResult> {
  * a per-user install; it would fail under a locked-down system install.
  */
 export 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.' })
+  }
+
   const ytdlpPath = getYtdlpPath()
 
   if (!existsSync(ytdlpPath)) {

src/preload/index.ts

@@ -28,6 +28,9 @@ import {
 
 // The surface exposed to the renderer. Keep this thin: it only forwards to IPC.
 const api = {
+  /** AeroFetch's own version string (e.g. '0.3.1'). */
+  getAppVersion: (): Promise<string> => ipcRenderer.invoke(IpcChannels.appVersion),
+
   getYtdlpVersion: (): Promise<YtdlpVersionResult> =>
     ipcRenderer.invoke(IpcChannels.ytdlpVersion),
 

src/renderer/src/App.tsx

@@ -1,4 +1,4 @@
-import { useState } from 'react'
+import { useState, useEffect } from 'react'
 import { FluentProvider, makeStyles, tokens } from '@fluentui/react-components'
 import { Sidebar, type TabValue } from './components/Sidebar'
 import { DownloadsView } from './components/DownloadsView'
@@ -8,7 +8,7 @@ import { SettingsView } from './components/SettingsView'
 import { Onboarding } from './components/Onboarding'
 import { getTheme, pageBackground } from './theme'
 import { useSettings } from './store/settings'
-import { useSystemTheme } from './store/systemTheme'
+import { useResolvedDark } from './store/systemTheme'
 
 const useStyles = makeStyles({
   provider: {
@@ -32,9 +32,26 @@ function App(): React.JSX.Element {
   const theme = useSettings((s) => s.theme)
   const accentColor = useSettings((s) => s.accentColor)
   const updateSettings = useSettings((s) => s.update)
-  const systemPrefersDark = useSystemTheme((s) => s.shouldUseDarkColors)
-  const isDark = theme === 'system' ? systemPrefersDark : theme === 'dark'
+  const isDark = useResolvedDark()
   const [tab, setTab] = useState<TabValue>('downloads')
+
+  // AeroFetch's own version, shown in the sidebar. Loaded once over IPC.
+  const [version, setVersion] = useState('')
+  useEffect(() => {
+    window.api?.getAppVersion?.().then(setVersion).catch(() => {})
+  }, [])
+
+  // Sidebar collapse, persisted across launches in localStorage.
+  const [collapsed, setCollapsed] = useState(
+    () => localStorage.getItem('aerofetch.sidebarCollapsed') === '1'
+  )
+  function toggleCollapsed(): void {
+    setCollapsed((c) => {
+      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.
   const loaded = useSettings((s) => s.loaded)
@@ -60,9 +77,12 @@ function App(): React.JSX.Element {
             <Sidebar
               tab={tab}
               onTabChange={setTab}
+              theme={theme}
               isDark={isDark}
-              followingSystem={theme === 'system'}
-              onToggleTheme={() => updateSettings({ theme: isDark ? 'light' : 'dark' })}
+              onSetTheme={(mode) => updateSettings({ theme: mode })}
+              version={version}
+              collapsed={collapsed}
+              onToggleCollapsed={toggleCollapsed}
             />
 
             <main className={styles.content}>

src/renderer/src/components/DownloadBar.tsx

@@ -3,8 +3,6 @@ import {
   Input,
   Button,
   Checkbox,
-  Switch,
-  Field,
   Spinner,
   Text,
   Caption1,
@@ -16,36 +14,19 @@ import {
 import {
   ArrowDownloadRegular,
   ClipboardPasteRegular,
-  FolderRegular,
   SearchRegular,
   VideoClipRegular,
   MusicNote2Regular,
   ErrorCircleRegular,
   LinkRegular,
   DismissRegular,
-  OptionsRegular,
-  ChevronDownRegular,
-  ChevronUpRegular,
-  AppsListRegular,
-  CodeRegular,
-  EyeRegular,
-  EyeOffRegular,
-  CopyRegular
+  AppsListRegular
 } from '@fluentui/react-icons'
-import type {
-  MediaInfo,
-  FormatOption,
-  PlaylistInfo,
-  DownloadOptions,
-  CommandPreviewResult,
-  StartDownloadOptions
-} from '@shared/ipc'
+import type { MediaInfo, FormatOption, PlaylistInfo } from '@shared/ipc'
 import { useDownloads, QUALITY_OPTIONS, type MediaKind } from '../store/downloads'
 import { useSettings } from '../store/settings'
-import { useTemplates } from '../store/templates'
 import { Select } from './Select'
 import { Hint } from './Hint'
-import { DownloadOptionsForm } from './DownloadOptionsForm'
 
 /** A quick heuristic for "this clipboard text is a link worth offering". */
 function looksLikeUrl(text: string): boolean {
@@ -184,33 +165,6 @@ const useStyles = makeStyles({
   spacer: {
     flexGrow: 1
   },
-  // --- per-download options panel ---
-  optionsBar: {
-    display: 'flex',
-    alignItems: 'center',
-    gap: '8px'
-  },
-  optionsPanel: {
-    padding: '14px',
-    backgroundColor: tokens.colorNeutralBackground2,
-    ...shorthands.borderRadius(tokens.borderRadiusLarge),
-    border: `1px solid ${tokens.colorNeutralStroke2}`
-  },
-  // --- command preview ---
-  previewPanel: {
-    display: 'flex',
-    flexDirection: 'column',
-    gap: '8px',
-    padding: '14px',
-    backgroundColor: tokens.colorNeutralBackground2,
-    ...shorthands.borderRadius(tokens.borderRadiusLarge),
-    border: `1px solid ${tokens.colorNeutralStroke2}`
-  },
-  previewCommandText: {
-    fontFamily: tokens.fontFamilyMonospace,
-    whiteSpace: 'pre-wrap',
-    wordBreak: 'break-all'
-  },
   // --- playlist selection ---
   plPanel: {
     display: 'flex',
@@ -258,63 +212,21 @@ const useStyles = makeStyles({
   },
   plItemMeta: {
     color: tokens.colorNeutralForeground3
-  },
-  folder: {
-    display: 'flex',
-    alignItems: 'center',
-    gap: '6px',
-    color: tokens.colorNeutralForeground3,
-    maxWidth: '360px'
-  },
-  folderPath: {
-    overflow: 'hidden',
-    textOverflow: 'ellipsis',
-    whiteSpace: 'nowrap'
   }
 })
 
 export function DownloadBar(): React.JSX.Element {
   const styles = useStyles()
   const addFromUrl = useDownloads((s) => s.addFromUrl)
-  const outputDir = useSettings((s) => s.outputDir)
-  const chooseOutputDir = useSettings((s) => s.chooseOutputDir)
   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 downloadOptions = useSettings((s) => s.downloadOptions)
 
   const [url, setUrl] = useState('')
   const [kind, setKind] = useState<MediaKind>('video')
   const [quality, setQuality] = useState(QUALITY_OPTIONS.video[0])
 
-  // Per-download options override (null = use the persisted defaults).
-  const [override, setOverride] = useState<DownloadOptions | null>(null)
-  const [showOptions, setShowOptions] = useState(false)
-  const effectiveOptions = override ?? downloadOptions
-
-  // Private mode — sticky like an incognito tab; the download still runs and
-  // appears in the queue, but its completion is never recorded to history.
-  const [incognito, setIncognito] = useState(false)
-
-  // Per-download custom-command override: undefined = defer to the settings
-  // default (customCommandEnabled + defaultTemplateId); null = explicit
-  // "None" for just this download; a string = a chosen template id override.
-  const [templateOverride, setTemplateOverride] = useState<string | null | undefined>(undefined)
-  const [showCustomCommand, setShowCustomCommand] = useState(false)
-  const customCommandEnabled = useSettings((s) => s.customCommandEnabled)
-  const settingsDefaultTemplateId = useSettings((s) => s.defaultTemplateId)
-  const templates = useTemplates((s) => s.templates)
-  const effectiveTemplateId =
-    templateOverride !== undefined
-      ? templateOverride
-      : customCommandEnabled
-        ? settingsDefaultTemplateId
-        : null
-
-  const [previewResult, setPreviewResult] = useState<CommandPreviewResult | null>(null)
-  const [previewing, setPreviewing] = useState(false)
-
   // Apply the saved default format once, when persisted settings first arrive.
   const appliedDefaults = useRef(false)
   useEffect(() => {
@@ -393,7 +305,6 @@ export function DownloadBar(): React.JSX.Element {
     setSuggestion(null)
   }
 
-  const folder = outputDir || 'your Downloads folder'
   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]
@@ -468,61 +379,6 @@ export function DownloadBar(): React.JSX.Element {
     setSelected(allSelected ? new Set() : new Set(playlist.entries.map((e) => e.index)))
   }
 
-  // Resolves the per-download custom-command override to the raw extra-args
-  // string sent to main; undefined defers to the settings default there.
-  function resolveExtraArgs(): string | undefined {
-    if (templateOverride === undefined) return undefined
-    if (templateOverride === null) return ''
-    return templates.find((t) => t.id === templateOverride)?.args ?? ''
-  }
-
-  // The StartDownloadOptions the current form state would produce — shared by
-  // the real download() call and the command-preview button so they can never
-  // drift apart.
-  function currentStartOptions(): StartDownloadOptions {
-    const base: StartDownloadOptions = {
-      id: 'preview',
-      url: url.trim(),
-      kind,
-      quality,
-      outputDir: outputDir || undefined,
-      options: override ?? undefined,
-      extraArgs: resolveExtraArgs()
-    }
-    if (usingFormats && selectedFormat) {
-      return {
-        ...base,
-        kind: 'video',
-        quality: selectedFormat.label,
-        formatId: selectedFormat.id,
-        formatHasAudio: selectedFormat.hasAudio
-      }
-    }
-    return base
-  }
-
-  async function previewCommand(): Promise<void> {
-    if (!url.trim() || previewing) return
-    setPreviewing(true)
-    setPreviewResult(null)
-    try {
-      setPreviewResult(await window.api.previewCommand(currentStartOptions()))
-    } catch (e) {
-      setPreviewResult({ ok: false, error: e instanceof Error ? e.message : String(e) })
-    } finally {
-      setPreviewing(false)
-    }
-  }
-
-  async function copyPreview(): Promise<void> {
-    if (!previewResult?.command) return
-    try {
-      await navigator.clipboard.writeText(previewResult.command)
-    } catch {
-      /* clipboard blocked — ignore in preview */
-    }
-  }
-
   function download(): void {
     const trimmed = url.trim()
     if (!trimmed) return
@@ -543,18 +399,10 @@ export function DownloadBar(): React.JSX.Element {
           id: selectedFormat.id,
           hasAudio: selectedFormat.hasAudio,
           label: selectedFormat.label
-        },
-        options: override ?? undefined,
-        extraArgs: resolveExtraArgs(),
-        incognito
+        }
       })
     } else {
-      addFromUrl(trimmed, kind, quality, {
-        ...meta,
-        options: override ?? undefined,
-        extraArgs: resolveExtraArgs(),
-        incognito
-      })
+      addFromUrl(trimmed, kind, quality, meta)
     }
 
     setUrl('')
@@ -568,10 +416,7 @@ export function DownloadBar(): React.JSX.Element {
       addFromUrl(e.url, kind, quality, {
         title: e.title,
         channel: e.uploader,
-        durationLabel: e.durationLabel,
-        options: override ?? undefined,
-        extraArgs: resolveExtraArgs(),
-        incognito
+        durationLabel: e.durationLabel
       })
     }
     setUrl('')
@@ -769,136 +614,6 @@ export function DownloadBar(): React.JSX.Element {
           </Button>
         )}
       </div>
-
-      <div className={styles.optionsBar}>
-        {incognito ? <EyeOffRegular /> : <EyeRegular />}
-        <Switch
-          checked={incognito}
-          onChange={(_, d) => setIncognito(d.checked)}
-          label={incognito ? 'Private — won’t be saved to history' : 'Private mode'}
-        />
-      </div>
-
-      <div className={styles.optionsBar}>
-        <Button
-          appearance="subtle"
-          size="small"
-          icon={<OptionsRegular />}
-          iconPosition="before"
-          onClick={() => setShowOptions((v) => !v)}
-        >
-          Options {showOptions ? <ChevronUpRegular /> : <ChevronDownRegular />}
-        </Button>
-        {override && (
-          <>
-            <Caption1 className={styles.previewMeta}>Customised for this download</Caption1>
-            <Button appearance="subtle" size="small" onClick={() => setOverride(null)}>
-              Reset to defaults
-            </Button>
-          </>
-        )}
-      </div>
-
-      {showOptions && (
-        <div className={styles.optionsPanel}>
-          <DownloadOptionsForm value={effectiveOptions} onChange={(o) => setOverride(o)} />
-        </div>
-      )}
-
-      <div className={styles.optionsBar}>
-        <Button
-          appearance="subtle"
-          size="small"
-          icon={<CodeRegular />}
-          iconPosition="before"
-          onClick={() => setShowCustomCommand((v) => !v)}
-        >
-          Custom command {showCustomCommand ? <ChevronUpRegular /> : <ChevronDownRegular />}
-        </Button>
-        {templateOverride !== undefined && (
-          <>
-            <Caption1 className={styles.previewMeta}>Customised for this download</Caption1>
-            <Button appearance="subtle" size="small" onClick={() => setTemplateOverride(undefined)}>
-              Reset to default
-            </Button>
-          </>
-        )}
-        <div className={styles.spacer} />
-        <Hint label="Build and show the exact yt-dlp command line" placement="top" align="end">
-          <Button
-            appearance="subtle"
-            size="small"
-            icon={previewing ? <Spinner size="tiny" /> : <EyeRegular />}
-            iconPosition="before"
-            onClick={previewCommand}
-            disabled={!url.trim() || previewing}
-          >
-            Preview command
-          </Button>
-        </Hint>
-      </div>
-
-      {showCustomCommand && (
-        <div className={styles.optionsPanel}>
-          <Field label="Template" hint="Extra yt-dlp flags layered onto this download, after every other option.">
-            <Select
-              aria-label="Custom command template"
-              value={effectiveTemplateId ?? 'none'}
-              options={[
-                { value: 'none', label: 'None' },
-                ...templates.map((t) => ({ value: t.id, label: t.name }))
-              ]}
-              onChange={(v) => setTemplateOverride(v === 'none' ? null : v)}
-            />
-          </Field>
-          {templates.length === 0 && (
-            <Caption1 className={styles.previewMeta}>
-              No templates yet — add one in Settings → Custom commands.
-            </Caption1>
-          )}
-        </div>
-      )}
-
-      {previewResult && (
-        <div className={styles.previewPanel}>
-          <div className={styles.plHeader}>
-            <Caption1 className={styles.plHeaderText}>
-              {previewResult.ok ? 'Command preview' : 'Could not build the command'}
-            </Caption1>
-            {previewResult.ok && (
-              <Button size="small" icon={<CopyRegular />} onClick={copyPreview}>
-                Copy
-              </Button>
-            )}
-            <Button
-              size="small"
-              appearance="subtle"
-              icon={<DismissRegular />}
-              onClick={() => setPreviewResult(null)}
-              aria-label="Dismiss preview"
-            />
-          </div>
-          {previewResult.ok ? (
-            <Text className={styles.previewCommandText}>{previewResult.command}</Text>
-          ) : (
-            <Caption1 className={mergeClasses(styles.previewMeta, styles.errorRow)}>
-              {previewResult.error}
-            </Caption1>
-          )}
-        </div>
-      )}
-
-      <div className={styles.folder}>
-        <FolderRegular />
-        <Caption1 className={styles.folderPath} title={folder}>
-          Saving to {folder}
-        </Caption1>
-        <Hint label="Change download folder" placement="top" align="start">
-          <Button size="small" appearance="transparent" onClick={chooseOutputDir}>
-            Change
-          </Button>
-        </Hint>
-      </div>
     </div>
   )
 }

src/renderer/src/components/Hint.tsx

@@ -30,13 +30,15 @@ const useStyles = makeStyles({
   },
   top: { bottom: 'calc(100% + 6px)' },
   bottom: { top: 'calc(100% + 6px)' },
+  right: { left: 'calc(100% + 6px)', top: '50%', transform: 'translateY(-50%)' },
+  left: { right: 'calc(100% + 6px)', top: '50%', transform: 'translateY(-50%)' },
   alignStart: { left: 0 },
   alignEnd: { right: 0 }
 })
 
 interface HintProps {
   label: string
-  placement?: 'top' | 'bottom'
+  placement?: 'top' | 'bottom' | 'left' | 'right'
   align?: 'start' | 'end'
   children: React.ReactNode
 }
@@ -56,8 +58,16 @@ export function Hint({
         aria-hidden
         className={mergeClasses(
           styles.bubble,
-          placement === 'bottom' ? styles.bottom : styles.top,
-          align === 'end' ? styles.alignEnd : styles.alignStart
+          placement === 'bottom'
+            ? styles.bottom
+            : placement === 'right'
+              ? styles.right
+              : placement === 'left'
+                ? styles.left
+                : styles.top,
+          // start/end alignment only applies to vertical (top/bottom) placements
+          (placement === 'top' || placement === 'bottom') &&
+            (align === 'end' ? styles.alignEnd : styles.alignStart)
         )}
       >
         {label}

src/renderer/src/components/HistoryView.tsx

@@ -14,8 +14,6 @@ import {
   OpenRegular,
   FolderRegular,
   DeleteRegular,
-  VideoClipRegular,
-  MusicNote2Regular,
   HistoryRegular,
   SearchRegular,
   ArrowClockwiseRegular,
@@ -24,9 +22,11 @@ import {
 } from '@fluentui/react-icons'
 import type { HistoryEntry, MediaKind } from '@shared/ipc'
 import { useHistory } from '../store/history'
-import { useSettings } from '../store/settings'
+import { useResolvedDark } from '../store/systemTheme'
 import { useDownloads } from '../store/downloads'
 import { thumbColors } from '../theme'
+import { thumbUrl } from '../thumb'
+import { MediaThumb } from './MediaThumb'
 import { Hint } from './Hint'
 import { Select } from './Select'
 
@@ -147,7 +147,7 @@ function formatWhen(ts: number): string {
 
 export function HistoryView(): React.JSX.Element {
   const styles = useStyles()
-  const isDark = useSettings((s) => s.theme === 'dark')
+  const isDark = useResolvedDark()
   const tc = thumbColors[isDark ? 'dark' : 'light']
   const entries = useHistory((s) => s.entries)
   const openFile = useHistory((s) => s.openFile)
@@ -282,7 +282,6 @@ export function HistoryView(): React.JSX.Element {
       ) : (
         <div className={styles.list}>
           {filtered.map((h: HistoryEntry) => {
-            const t = h.kind === 'audio' ? tc.audio : tc.video
             return (
               <div key={h.id} className={styles.row}>
                 {selectMode && (
@@ -292,13 +291,12 @@ export function HistoryView(): React.JSX.Element {
                     aria-label={`Select ${h.title}`}
                   />
                 )}
-                <div className={styles.thumb} style={{ backgroundColor: t.bg, color: t.fg }}>
-                  {h.kind === 'audio' ? (
-                    <MusicNote2Regular fontSize={22} />
-                  ) : (
-                    <VideoClipRegular fontSize={22} />
-                  )}
-                </div>
+                <MediaThumb
+                  className={styles.thumb}
+                  src={thumbUrl({ thumbnail: h.thumbnail, url: h.url })}
+                  kind={h.kind}
+                  iconSize={22}
+                />
                 <div className={styles.body}>
                   <Text className={styles.title}>{h.title}</Text>
                   <Caption1 className={styles.meta}>

src/renderer/src/components/LibraryView.tsx

@@ -31,6 +31,8 @@ import type { MediaItem, Source } from '@shared/ipc'
 import { useSources, MAX_ENQUEUE_BATCH } from '../store/sources'
 import { useSettings } from '../store/settings'
 import { useDownloads, type DownloadStatus } from '../store/downloads'
+import { thumbUrl } from '../thumb'
+import { MediaThumb } from './MediaThumb'
 
 // True in the standalone browser preview (no Electron preload).
 const PREVIEW = typeof window === 'undefined' || !window.electron
@@ -148,6 +150,11 @@ const useStyles = makeStyles({
     gap: '10px',
     padding: '5px 4px 5px 18px'
   },
+  rowThumb: {
+    width: '60px',
+    height: '34px',
+    ...shorthands.borderRadius(tokens.borderRadiusSmall)
+  },
   rowMain: { display: 'flex', flexDirection: 'column', minWidth: 0, flexGrow: 1 },
   rowTitle: {
     whiteSpace: 'nowrap',
@@ -494,6 +501,12 @@ export function LibraryView(): React.JSX.Element {
                                 onChange={(_, d) => toggle(it.id, !!d.checked)}
                                 aria-label={`Select ${it.title}`}
                               />
+                              <MediaThumb
+                                className={styles.rowThumb}
+                                src={thumbUrl({ url: it.url, videoId: it.videoId })}
+                                kind="video"
+                                iconSize={16}
+                              />
                               <div className={styles.rowMain}>
                                 <span className={styles.rowTitle}>
                                   {it.playlistIndex}. {it.title}

src/renderer/src/components/MediaThumb.tsx

@@ -0,0 +1,70 @@
+import { useState } from 'react'
+import { makeStyles, mergeClasses } from '@fluentui/react-components'
+import { VideoClipRegular, MusicNote2Regular } from '@fluentui/react-icons'
+import type { MediaKind } from '@shared/ipc'
+import { useResolvedDark } from '../store/systemTheme'
+import { thumbColors } from '../theme'
+
+const useStyles = makeStyles({
+  box: {
+    flexShrink: 0,
+    display: 'flex',
+    alignItems: 'center',
+    justifyContent: 'center',
+    overflow: 'hidden'
+  },
+  img: {
+    width: '100%',
+    height: '100%',
+    objectFit: 'cover',
+    display: 'block'
+  }
+})
+
+/**
+ * A media preview thumbnail: shows the image at `src` when one is available and
+ * loads, otherwise a kind icon on a quiet neutral tint (the same palette the
+ * placeholders used before). The load failure is tracked per-src, so a thumbnail
+ * that arrives later (e.g. resolved after a probe) is retried rather than left on
+ * the fallback. The caller sizes the box via `className` (width/height/radius).
+ */
+export function MediaThumb({
+  src,
+  kind,
+  iconSize = 24,
+  className
+}: {
+  src?: string
+  kind: MediaKind
+  iconSize?: number
+  className?: string
+}): React.JSX.Element {
+  const styles = useStyles()
+  const isDark = useResolvedDark()
+  const colors = thumbColors[isDark ? 'dark' : 'light'][kind === 'audio' ? 'audio' : 'video']
+  const [failedSrc, setFailedSrc] = useState<string | null>(null)
+  const showImg = !!src && failedSrc !== src
+
+  // The neutral tint always backs the box, so there's a placeholder behind the
+  // image while it loads (and the kind icon stays legible when there's no image).
+  return (
+    <div
+      className={mergeClasses(styles.box, className)}
+      style={{ backgroundColor: colors.bg, color: colors.fg }}
+    >
+      {showImg ? (
+        <img
+          className={styles.img}
+          src={src}
+          alt=""
+          loading="lazy"
+          onError={() => setFailedSrc(src ?? null)}
+        />
+      ) : kind === 'audio' ? (
+        <MusicNote2Regular fontSize={iconSize} />
+      ) : (
+        <VideoClipRegular fontSize={iconSize} />
+      )}
+    </div>
+  )
+}

src/renderer/src/components/Onboarding.tsx

@@ -4,7 +4,6 @@ import {
   Body1,
   Caption1,
   Field,
-  Input,
   Button,
   makeStyles,
   tokens,
@@ -12,7 +11,6 @@ import {
 } from '@fluentui/react-components'
 import {
   ArrowDownloadFilled,
-  FolderRegular,
   ClipboardPasteRegular,
   HistoryRegular,
   OptionsRegular,
@@ -56,13 +54,8 @@ const useStyles = makeStyles({
     justifyContent: 'center',
     fontSize: '26px'
   },
-  folderRow: {
-    display: 'flex',
-    gap: '8px',
-    alignItems: 'flex-end'
-  },
-  folderInput: {
-    flexGrow: 1
+  folderNote: {
+    color: tokens.colorNeutralForeground3
   },
   tips: {
     display: 'flex',
@@ -99,8 +92,6 @@ const TIPS: { icon: React.JSX.Element; text: string }[] = [
 
 export function Onboarding(): React.JSX.Element {
   const styles = useStyles()
-  const outputDir = useSettings((s) => s.outputDir)
-  const chooseOutputDir = useSettings((s) => s.chooseOutputDir)
   const update = useSettings((s) => s.update)
 
   return (
@@ -118,18 +109,12 @@ export function Onboarding(): React.JSX.Element {
           audio. yt-dlp and ffmpeg are bundled, so there's nothing else to install.
         </Body1>
 
-        <Field label="Download folder">
-          <div className={styles.folderRow}>
-            <Input
-              readOnly
-              className={styles.folderInput}
-              value={outputDir}
-              contentBefore={<FolderRegular />}
-            />
-            <Button icon={<FolderRegular />} onClick={chooseOutputDir}>
-              Browse
-            </Button>
-          </div>
+        <Field label="Where downloads go">
+          <Caption1 className={styles.folderNote}>
+            Videos save to your <strong>Documents\Video</strong> folder and audio to{' '}
+            <strong>Documents\Audio</strong>. You can point each to a different folder any time
+            in Settings.
+          </Caption1>
         </Field>
 
         <div className={styles.tips}>

src/renderer/src/components/QueueItem.tsx

@@ -15,15 +15,13 @@ import {
   OpenRegular,
   FolderRegular,
   ArrowClockwiseRegular,
-  VideoClipRegular,
-  MusicNote2Regular,
   CheckmarkCircleFilled,
   ErrorCircleFilled,
   EyeOffRegular
 } from '@fluentui/react-icons'
 import { useDownloads, type DownloadItem, type DownloadStatus } from '../store/downloads'
-import { useSettings } from '../store/settings'
-import { thumbColors } from '../theme'
+import { thumbUrl } from '../thumb'
+import { MediaThumb } from './MediaThumb'
 import { Hint } from './Hint'
 
 const useStyles = makeStyles({
@@ -103,8 +101,6 @@ function pct(progress: number): string {
 
 export function QueueItem({ item }: { item: DownloadItem }): React.JSX.Element {
   const styles = useStyles()
-  const isDark = useSettings((s) => s.theme === 'dark')
-  const thumb = thumbColors[isDark ? 'dark' : 'light'][item.kind === 'audio' ? 'audio' : 'video']
   const cancel = useDownloads((s) => s.cancel)
   const remove = useDownloads((s) => s.remove)
   const retry = useDownloads((s) => s.retry)
@@ -124,13 +120,12 @@ export function QueueItem({ item }: { item: DownloadItem }): React.JSX.Element {
 
   return (
     <div className={styles.root}>
-      <div className={styles.thumb} style={{ backgroundColor: thumb.bg, color: thumb.fg }}>
-        {item.kind === 'audio' ? (
-          <MusicNote2Regular fontSize={28} />
-        ) : (
-          <VideoClipRegular fontSize={28} />
-        )}
-      </div>
+      <MediaThumb
+        className={styles.thumb}
+        src={thumbUrl({ thumbnail: item.thumbnail, url: item.url })}
+        kind={item.kind}
+        iconSize={28}
+      />
 
       <div className={styles.body}>
         <div className={styles.titleRow}>

src/renderer/src/components/SettingsView.tsx

@@ -170,8 +170,10 @@ const UPDATE_CHANNEL_OPTIONS = [
 export function SettingsView(): React.JSX.Element {
   const styles = useStyles()
 
-  const outputDir = useSettings((s) => s.outputDir)
-  const chooseOutputDir = useSettings((s) => s.chooseOutputDir)
+  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)
@@ -328,17 +330,49 @@ export function SettingsView(): React.JSX.Element {
           <Subtitle2>Downloads</Subtitle2>
         </div>
 
-        <Field label="Download folder">
+        <Field
+          label="Video folder"
+          hint="Where video downloads are saved. Leave blank to use Documents\Video."
+        >
           <div className={styles.folderRow}>
             <Input
               readOnly
               className={styles.folderInput}
-              value={outputDir}
+              value={videoDir}
+              placeholder="Documents\Video (default)"
               contentBefore={<FolderRegular />}
             />
-            <Button icon={<FolderRegular />} onClick={chooseOutputDir}>
+            <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
+              readOnly
+              className={styles.folderInput}
+              value={audioDir}
+              placeholder="Documents\Audio (default)"
+              contentBefore={<FolderRegular />}
+            />
+            <Button icon={<FolderRegular />} onClick={() => chooseDir('audioDir')}>
+              Browse
+            </Button>
+            {audioDir && (
+              <Button appearance="subtle" onClick={() => clearDir('audioDir')}>
+                Reset
+              </Button>
+            )}
           </div>
         </Field>
 

src/renderer/src/components/Sidebar.tsx

@@ -1,11 +1,4 @@
-import {
-  Caption1,
-  Switch,
-  makeStyles,
-  mergeClasses,
-  tokens,
-  shorthands
-} from '@fluentui/react-components'
+import { Caption1, makeStyles, mergeClasses, tokens, shorthands } from '@fluentui/react-components'
 import {
   ArrowDownloadFilled,
   ArrowDownloadRegular,
@@ -13,8 +6,13 @@ import {
   LibraryRegular,
   SettingsRegular,
   WeatherMoonRegular,
-  WeatherSunnyRegular
+  WeatherSunnyRegular,
+  DesktopRegular,
+  PanelLeftContractRegular,
+  PanelLeftExpandRegular
 } from '@fluentui/react-icons'
+import type { ThemeMode } from '@shared/ipc'
+import { Hint } from './Hint'
 
 export type TabValue = 'downloads' | 'library' | 'history' | 'settings'
 
@@ -27,13 +25,48 @@ const useStyles = makeStyles({
     gap: '4px',
     padding: '16px 12px',
     backgroundColor: tokens.colorNeutralBackground1,
-    borderRight: `1px solid ${tokens.colorNeutralStroke2}`
+    borderRight: `1px solid ${tokens.colorNeutralStroke2}`,
+    transition: 'width 0.15s ease'
+  },
+  rootCollapsed: {
+    width: '60px',
+    alignItems: 'center'
+  },
+  topBar: {
+    display: 'flex',
+    justifyContent: 'flex-end',
+    paddingBottom: '2px'
+  },
+  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',
     gap: '11px',
-    padding: '6px 10px 14px'
+    padding: '0 10px 14px'
+  },
+  brandCollapsed: {
+    padding: '0 0 12px',
+    justifyContent: 'center'
   },
   mark: {
     width: '36px',
@@ -64,7 +97,8 @@ const useStyles = makeStyles({
   nav: {
     display: 'flex',
     flexDirection: 'column',
-    gap: '3px'
+    gap: '3px',
+    alignSelf: 'stretch'
   },
   navItem: {
     display: 'flex',
@@ -84,6 +118,10 @@ const useStyles = makeStyles({
       backgroundColor: tokens.colorNeutralBackground1Hover
     }
   },
+  navItemCollapsed: {
+    justifyContent: 'center',
+    padding: '9px 0'
+  },
   navItemActive: {
     backgroundColor: tokens.colorBrandBackground2,
     color: tokens.colorBrandForeground2,
@@ -94,22 +132,46 @@ const useStyles = makeStyles({
   },
   navIcon: {
     fontSize: '18px',
-    flexShrink: 0
+    flexShrink: 0,
+    display: 'flex'
   },
   spacer: {
     flexGrow: 1
   },
-  themeRow: {
+  // --- theme control (expanded): a 3-way Light / Dark / Auto segmented switch ---
+  themeGroup: {
+    alignSelf: 'stretch',
     display: 'flex',
-    alignItems: 'center',
-    justifyContent: 'space-between',
-    padding: '8px 12px',
-    color: tokens.colorNeutralForeground3
+    width: '100%',
+    border: `1px solid ${tokens.colorNeutralStroke1}`,
+    ...shorthands.borderRadius(tokens.borderRadiusMedium),
+    overflow: 'hidden'
   },
-  themeLabel: {
+  themeSeg: {
+    flex: 1,
+    appearance: 'none',
+    border: 'none',
+    backgroundColor: 'transparent',
+    color: tokens.colorNeutralForeground2,
     display: 'flex',
     alignItems: 'center',
-    gap: '9px'
+    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
+    }
   }
 })
 
@@ -120,67 +182,149 @@ const NAV: { value: TabValue; label: string; icon: React.JSX.Element }[] = [
   { value: 'settings', label: 'Settings', icon: <SettingsRegular /> }
 ]
 
+const THEMES: { value: ThemeMode; label: string; icon: React.JSX.Element }[] = [
+  { value: 'light', label: 'Light', icon: <WeatherSunnyRegular /> },
+  { value: 'dark', label: 'Dark', icon: <WeatherMoonRegular /> },
+  { value: 'system', label: 'Auto', icon: <DesktopRegular /> }
+]
+
 interface SidebarProps {
   tab: TabValue
   onTabChange: (t: TabValue) => void
+  /** the current theme preference: explicit light/dark, or 'system' to follow the OS */
+  theme: ThemeMode
+  /** whether the resolved theme is currently dark (drives the collapsed toggle icon) */
   isDark: boolean
-  /** true when theme is 'system' — the quick toggle still works (it sets an explicit mode) */
-  followingSystem: boolean
-  onToggleTheme: () => void
+  onSetTheme: (mode: ThemeMode) => void
+  /** AeroFetch version string, e.g. '0.3.2' ('' until loaded) */
+  version: string
+  collapsed: boolean
+  onToggleCollapsed: () => void
 }
 
 export function Sidebar({
   tab,
   onTabChange,
+  theme,
   isDark,
-  followingSystem,
-  onToggleTheme
+  onSetTheme,
+  version,
+  collapsed,
+  onToggleCollapsed
 }: SidebarProps): React.JSX.Element {
   const styles = useStyles()
+
+  // 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 themeIcon =
+    theme === 'system' ? (
+      <DesktopRegular fontSize={18} />
+    ) : isDark ? (
+      <WeatherMoonRegular fontSize={18} />
+    ) : (
+      <WeatherSunnyRegular fontSize={18} />
+    )
+  const themeLabel = theme === 'system' ? 'Auto (system)' : isDark ? 'Dark' : 'Light'
+
   return (
-    <nav className={styles.root}>
-      <div className={styles.brand}>
+    <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
+            type="button"
+            className={styles.iconBtn}
+            onClick={onToggleCollapsed}
+            aria-label={collapsed ? 'Expand sidebar' : 'Collapse sidebar'}
+            aria-pressed={collapsed}
+          >
+            {collapsed ? <PanelLeftExpandRegular /> : <PanelLeftContractRegular />}
+          </button>
+        </Hint>
+      </div>
+
+      <div className={mergeClasses(styles.brand, collapsed && styles.brandCollapsed)}>
         <div className={styles.mark}>
           <ArrowDownloadFilled />
         </div>
-        <div className={styles.brandText}>
-          <span className={styles.brandName}>AeroFetch</span>
-          <Caption1 className={styles.caption}>yt-dlp frontend</Caption1>
-        </div>
+        {!collapsed && (
+          <div className={styles.brandText}>
+            <span className={styles.brandName}>AeroFetch</span>
+            <Caption1 className={styles.caption}>{version ? `v${version}` : 'yt-dlp frontend'}</Caption1>
+          </div>
+        )}
       </div>
 
       <div className={styles.nav}>
         {NAV.map((n) => {
           const active = tab === n.value
-          return (
+          const btn = (
             <button
               key={n.value}
               type="button"
-              className={mergeClasses(styles.navItem, active && styles.navItemActive)}
+              className={mergeClasses(
+                styles.navItem,
+                collapsed && styles.navItemCollapsed,
+                active && styles.navItemActive
+              )}
               style={
-                active
+                active && !collapsed
                   ? { boxShadow: `inset 3px 0 0 0 ${tokens.colorCompoundBrandStroke}` }
                   : undefined
               }
               onClick={() => onTabChange(n.value)}
               aria-current={active ? 'page' : undefined}
+              aria-label={n.label}
             >
               <span className={styles.navIcon}>{n.icon}</span>
-              {n.label}
+              {!collapsed && n.label}
             </button>
           )
+          return collapsed ? (
+            <Hint key={n.value} label={n.label} placement="right">
+              {btn}
+            </Hint>
+          ) : (
+            btn
+          )
         })}
       </div>
 
       <div className={styles.spacer} />
 
-      <div className={styles.themeRow}>
-        <span className={styles.themeLabel}>
-          {isDark ? <WeatherMoonRegular fontSize={18} /> : <WeatherSunnyRegular fontSize={18} />}
-          {(isDark ? 'Dark' : 'Light') + (followingSystem ? ' · Auto' : '')}
-        </span>
-        <Switch checked={isDark} onChange={onToggleTheme} aria-label="Toggle dark mode" />
-      </div>
+      {collapsed ? (
+        <Hint label={`Theme: ${themeLabel}`} placement="right">
+          <button
+            type="button"
+            className={styles.iconBtn}
+            onClick={cycleTheme}
+            aria-label={`Theme: ${themeLabel}. Click to change.`}
+          >
+            {themeIcon}
+          </button>
+        </Hint>
+      ) : (
+        <div className={styles.themeGroup} role="radiogroup" aria-label="Theme">
+          {THEMES.map((t) => {
+            const on = theme === t.value
+            return (
+              <button
+                key={t.value}
+                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/main.tsx

@@ -11,7 +11,8 @@ import App from './App'
 // In the real Electron app this branch is skipped — preload provides window.api.
 if (import.meta.env.DEV && !window.api) {
   const MOCK_SETTINGS: Settings = {
-    outputDir: 'C:\\Users\\you\\Downloads',
+    videoDir: 'C:\\Users\\you\\Documents\\Video',
+    audioDir: 'C:\\Users\\you\\Documents\\Audio',
     defaultKind: 'video',
     defaultVideoQuality: 'Best available',
     defaultAudioQuality: 'Best (MP3)',
@@ -44,6 +45,7 @@ if (import.meta.env.DEV && !window.api) {
   ]
 
   window.api = {
+    getAppVersion: async () => '0.3.2-preview',
     getYtdlpVersion: async () => ({ ok: true, version: '2025.06.01 (UI preview mock)' }),
     probe: async (url: string) => {
       await new Promise((r) => setTimeout(r, 700)) // simulate network latency
@@ -121,11 +123,11 @@ if (import.meta.env.DEV && !window.api) {
     previewCommand: async (opts) => {
       await new Promise((r) => setTimeout(r, 300)) // simulate the main-process round-trip
       const extra = opts.extraArgs ? ` ${opts.extraArgs}` : ''
+      const dir = opts.kind === 'audio' ? MOCK_SETTINGS.audioDir : MOCK_SETTINGS.videoDir
       return {
         ok: true,
         command:
-          `yt-dlp.exe -f "bv*+ba/b" -o "${MOCK_SETTINGS.outputDir}\\%(title)s.%(ext)s"` +
-          `${extra} -- ${opts.url}`
+          `yt-dlp.exe -f "bv*+ba/b" -o "${dir}\\%(title)s.%(ext)s"` + `${extra} -- ${opts.url}`
       }
     },
     updateYtdlp: async (channel) => {

src/renderer/src/store/downloads.ts

@@ -247,7 +247,8 @@ export const useDownloads = create<DownloadState>((set, get) => {
         url: item.url,
         kind: item.kind,
         quality: item.quality,
-        outputDir: useSettings.getState().outputDir || undefined,
+        // No outputDir here: main routes each download into the user's per-kind
+        // folder (Settings → Video/Audio folder), or the Documents\… default.
         formatId: item.formatId,
         formatHasAudio: item.formatHasAudio,
         options: item.options,

src/renderer/src/store/settings.ts

@@ -5,7 +5,8 @@ import { DEFAULT_DOWNLOAD_OPTIONS, type Settings } from '@shared/ipc'
 const PREVIEW = typeof window === 'undefined' || !window.electron
 
 const FALLBACK: Settings = {
-  outputDir: PREVIEW ? 'C:\\Users\\you\\Downloads' : '',
+  videoDir: PREVIEW ? 'C:\\Users\\you\\Documents\\Video' : '',
+  audioDir: PREVIEW ? 'C:\\Users\\you\\Documents\\Audio' : '',
   defaultKind: 'video',
   defaultVideoQuality: 'Best available',
   defaultAudioQuality: 'Best (MP3)',
@@ -35,7 +36,10 @@ interface SettingsState extends Settings {
   /** true once persisted settings have loaded (always true in preview) */
   loaded: boolean
   update: (partial: Partial<Settings>) => void
-  chooseOutputDir: () => void
+  /** open the OS folder picker and store the result as the video or audio folder */
+  chooseDir: (target: 'videoDir' | 'audioDir') => void
+  /** clear a per-kind folder override, restoring its Documents\… default */
+  clearDir: (target: 'videoDir' | 'audioDir') => void
 }
 
 export const useSettings = create<SettingsState>((set, get) => ({
@@ -47,12 +51,14 @@ export const useSettings = create<SettingsState>((set, get) => ({
     if (!PREVIEW) window.api.setSettings(partial).catch(() => {})
   },
 
-  chooseOutputDir: () => {
+  chooseDir: (target) => {
     if (PREVIEW) return
     window.api.chooseFolder().then((dir) => {
-      if (dir) get().update({ outputDir: dir })
+      if (dir) get().update({ [target]: dir })
     })
-  }
+  },
+
+  clearDir: (target) => get().update({ [target]: '' })
 }))
 
 // Load persisted settings on startup.

src/renderer/src/store/systemTheme.ts

@@ -1,5 +1,6 @@
 import { create } from 'zustand'
 import type { SystemThemeInfo } from '@shared/ipc'
+import { useSettings } from './settings'
 
 // True in the standalone browser preview (no Electron preload).
 const PREVIEW = typeof window === 'undefined' || !window.electron
@@ -24,3 +25,16 @@ if (!PREVIEW) {
     useSystemTheme.setState({ shouldUseDarkColors: e.matches })
   )
 }
+
+/**
+ * Whether the app is currently rendering in dark mode. Resolves the 'system'
+ * preference against the live OS signal, so a component never has to special-case
+ * it (the bug where a raw `theme === 'dark'` check left thumbnails light under
+ * Auto + a dark OS). The single source of truth for light/dark — used by App for
+ * the FluentProvider and by anything that needs theme-aware colors (thumbColors).
+ */
+export function useResolvedDark(): boolean {
+  const theme = useSettings((s) => s.theme)
+  const systemPrefersDark = useSystemTheme((s) => s.shouldUseDarkColors)
+  return theme === 'system' ? systemPrefersDark : theme === 'dark'
+}

src/renderer/src/thumb.ts

@@ -0,0 +1,47 @@
+/**
+ * Thumbnail helpers. A media "preview" thumbnail is either the explicit image URL
+ * yt-dlp handed us at probe time, or — for a YouTube video — one derived from the
+ * video id with no extra network probe. Anything non-YouTube without a probed
+ * thumbnail returns undefined, and the UI falls back to a kind icon.
+ */
+
+/**
+ * Pull the video id out of any YouTube watch / shorts / embed / live / youtu.be
+ * URL. Returns null for non-YouTube URLs or anything unparseable, so callers can
+ * cheaply ask "is there a thumbnail derivable from this link?".
+ */
+export function youtubeId(url: string | undefined): string | null {
+  if (!url) return null
+  let u: URL
+  try {
+    u = new URL(url)
+  } catch {
+    return null
+  }
+  const host = u.hostname.replace(/^www\./i, '').toLowerCase()
+  if (host === 'youtu.be') return u.pathname.slice(1).split('/')[0] || null
+  if (host === 'youtube.com' || host.endsWith('.youtube.com')) {
+    const v = u.searchParams.get('v')
+    if (v) return v
+    const m = u.pathname.match(/^\/(?:embed|shorts|v|live)\/([^/?#]+)/i)
+    if (m) return m[1]
+  }
+  return null
+}
+
+/**
+ * Resolve a preview thumbnail URL for a media item. Prefers an explicit thumbnail
+ * (from a probe), then a known videoId, then a YouTube URL it can derive an id
+ * from. Returns undefined when nothing usable is available.
+ */
+export function thumbUrl(opts: {
+  thumbnail?: string
+  videoId?: string
+  url?: string
+}): string | undefined {
+  if (opts.thumbnail) return opts.thumbnail
+  const id = opts.videoId || youtubeId(opts.url)
+  // mqdefault is 320×180 (16:9, no letterbox bars) and exists for every public
+  // video — a better fit for our 16:9 thumb boxes than the 4:3 hqdefault.
+  return id ? `https://i.ytimg.com/vi/${encodeURIComponent(id)}/mqdefault.jpg` : undefined
+}

src/shared/ipc.ts

@@ -4,6 +4,8 @@
  */
 
 export const IpcChannels = {
+  /** the AeroFetch app version (package.json / app.getVersion) */
+  appVersion: 'app:version',
   ytdlpVersion: 'ytdlp:version',
   probe: 'media:probe',
   downloadStart: 'download:start',
@@ -186,8 +188,23 @@ export interface YtdlpVersionResult {
   error?: string
 }
 
-/** yt-dlp's self-update release channel (`--update-to <channel>`). */
-export type YtdlpUpdateChannel = 'stable' | 'nightly'
+/**
+ * yt-dlp's self-update release channels (`--update-to <channel>`).
+ *
+ * SECURITY (audit F1): `--update-to` also accepts an `OWNER/REPO@TAG` spec, which
+ * makes yt-dlp download a release binary from an ARBITRARY GitHub repo and
+ * overwrite the running yt-dlp.exe — i.e. arbitrary, persistent code execution.
+ * The TypeScript type is erased at runtime and is no defence over IPC, so the
+ * value must be checked against this allowlist before it ever reaches the flag
+ * (see isYtdlpUpdateChannel; enforced in src/main/ytdlp.ts).
+ */
+export const YTDLP_UPDATE_CHANNELS = ['stable', 'nightly'] as const
+export type YtdlpUpdateChannel = (typeof YTDLP_UPDATE_CHANNELS)[number]
+
+/** Runtime guard for an untrusted update-channel value crossing the IPC boundary. */
+export function isYtdlpUpdateChannel(v: unknown): v is YtdlpUpdateChannel {
+  return typeof v === 'string' && (YTDLP_UPDATE_CHANNELS as readonly string[]).includes(v)
+}
 
 export interface YtdlpUpdateResult {
   ok: boolean
@@ -340,8 +357,10 @@ export type DownloadEvent =
 
 /** Persisted user settings (electron-store). */
 export interface Settings {
-  /** absolute output directory (empty string resolves to the OS Downloads folder) */
-  outputDir: string
+  /** where video downloads are saved; empty string = the default Documents\Video folder */
+  videoDir: string
+  /** where audio downloads are saved; empty string = the default Documents\Audio folder */
+  audioDir: string
   defaultKind: MediaKind
   defaultVideoQuality: string
   defaultAudioQuality: string

test/buildArgs.test.ts

@@ -2,6 +2,7 @@ import { describe, it, expect } from 'vitest'
 import {
   buildArgs,
   parseExtraArgs,
+  selectExtraArgs,
   formatCommandLine,
   sanitizeDirSegment,
   collectionOutputTemplate,
@@ -328,6 +329,80 @@ describe('parseExtraArgs', () => {
   })
 })
 
+describe('selectExtraArgs — custom-command consent gate (audit F2)', () => {
+  const templates = [
+    { id: 'thumb', args: '--write-thumbnail' },
+    { id: 'danger', args: '--exec "calc.exe"' }
+  ]
+
+  it('returns [] when custom commands are disabled, even with a per-download override', () => {
+    // The core fix: a renderer-supplied extraArgs must NOT run while the gate is off.
+    expect(
+      selectExtraArgs({
+        customCommandEnabled: false,
+        perDownloadExtraArgs: '--exec "calc.exe"',
+        defaultTemplateId: 'danger',
+        templates
+      })
+    ).toEqual([])
+  })
+
+  it('returns [] when disabled even if a default template id is set', () => {
+    expect(
+      selectExtraArgs({
+        customCommandEnabled: false,
+        perDownloadExtraArgs: undefined,
+        defaultTemplateId: 'thumb',
+        templates
+      })
+    ).toEqual([])
+  })
+
+  it('parses a per-download override when enabled', () => {
+    expect(
+      selectExtraArgs({
+        customCommandEnabled: true,
+        perDownloadExtraArgs: '--write-thumbnail --no-mtime',
+        defaultTemplateId: null,
+        templates
+      })
+    ).toEqual(['--write-thumbnail', '--no-mtime'])
+  })
+
+  it('an explicit empty override yields [] even with a default template set', () => {
+    expect(
+      selectExtraArgs({
+        customCommandEnabled: true,
+        perDownloadExtraArgs: '',
+        defaultTemplateId: 'thumb',
+        templates
+      })
+    ).toEqual([])
+  })
+
+  it('falls back to the default template when no per-download override is given', () => {
+    expect(
+      selectExtraArgs({
+        customCommandEnabled: true,
+        perDownloadExtraArgs: undefined,
+        defaultTemplateId: 'thumb',
+        templates
+      })
+    ).toEqual(['--write-thumbnail'])
+  })
+
+  it('returns [] when the default template id matches nothing', () => {
+    expect(
+      selectExtraArgs({
+        customCommandEnabled: true,
+        perDownloadExtraArgs: undefined,
+        defaultTemplateId: 'missing',
+        templates
+      })
+    ).toEqual([])
+  })
+})
+
 describe('formatCommandLine', () => {
   it('joins the exe and args with spaces when nothing needs quoting', () => {
     expect(formatCommandLine('yt-dlp.exe', ['-f', 'best', '--', 'https://x.test/v'])).toBe(
@@ -410,6 +485,14 @@ describe('sanitizeDirSegment', () => {
     expect(sanitizeDirSegment('com1')).toBe('_com1')
   })
 
+  it('prefixes a reserved device name even when it carries an extension (audit T3)', () => {
+    expect(sanitizeDirSegment('CON.txt')).toBe('_CON.txt')
+    expect(sanitizeDirSegment('nul.mp4')).toBe('_nul.mp4')
+    expect(sanitizeDirSegment('LPT1.foo.bar')).toBe('_LPT1.foo.bar')
+    // a non-reserved name that merely starts with similar letters is left alone
+    expect(sanitizeDirSegment('console.log')).toBe('console.log')
+  })
+
   it('falls back to Untitled for empty / all-illegal input', () => {
     expect(sanitizeDirSegment('')).toBe('Untitled')
     expect(sanitizeDirSegment('???')).toBe('Untitled')

test/deeplink.test.ts

@@ -42,6 +42,20 @@ describe('extractIncomingUrl — aerofetch:// protocol', () => {
   it('returns null when there is no url= param', () => {
     expect(extractIncomingUrl(['AeroFetch.exe', 'aerofetch://download'])).toBeNull()
   })
+
+  it('normalises the target, stripping embedded control chars (audit T3 / F5)', () => {
+    // A tab spliced into the inner URL must not survive to the renderer banner.
+    const raw = 'https://www.youtube.com/watch?v=abc\tdef'
+    const arg = `aerofetch://download?url=${encodeURIComponent(raw)}`
+    expect(extractIncomingUrl(['AeroFetch.exe', arg])).toBe(
+      'https://www.youtube.com/watch?v=abcdef'
+    )
+  })
+
+  it('matches the aerofetch:// scheme case-insensitively (audit T5)', () => {
+    const arg = `AEROFETCH://download?url=${encodeURIComponent(TARGET)}`
+    expect(extractIncomingUrl(['AeroFetch.exe', arg])).toBe(TARGET)
+  })
 })
 
 describe('extractIncomingUrl — .url Internet Shortcut (Explorer "Send to")', () => {
@@ -62,6 +76,18 @@ describe('extractIncomingUrl — .url Internet Shortcut (Explorer "Send to")', (
   it('ignores files that merely end in .url-like text but are not real paths', () => {
     expect(extractIncomingUrl(['AeroFetch.exe', 'not-a-real-path.url'])).toBeNull()
   })
+
+  it('reads a URL= line that falls within the 64 KB size cap (audit T5)', () => {
+    const junk = '; padding\r\n'.repeat(100) // ~1 KB of leading content
+    const path = urlFile('Small.url', `[InternetShortcut]\r\n${junk}URL=${TARGET}\r\n`)
+    expect(extractIncomingUrl(['AeroFetch.exe', path])).toBe(TARGET)
+  })
+
+  it('ignores a URL= line that falls past the 64 KB size cap (audit T5)', () => {
+    const junk = '; padding\r\n'.repeat(8000) // ~88 KB, beyond the read window
+    const path = urlFile('Huge.url', `[InternetShortcut]\r\n${junk}URL=${TARGET}\r\n`)
+    expect(extractIncomingUrl(['AeroFetch.exe', path])).toBeNull()
+  })
 })
 
 describe('extractIncomingUrl — no match', () => {

test/indexer.test.ts

@@ -4,6 +4,7 @@ import {
   buildMediaItems,
   mergeItemsPreservingState,
   buildFeedUrl,
+  isYouTubeFeedUrl,
   parseRssVideoIds,
   entryUrl,
   fmtDuration,
@@ -57,6 +58,10 @@ describe('entryUrl', () => {
     expect(entryUrl({ url: 'javascript:alert(1)' })).toBeNull()
     expect(entryUrl({})).toBeNull()
   })
+  it('percent-encodes an untrusted id rather than splicing it raw (audit T2)', () => {
+    expect(entryUrl({ id: 'ab cd&x=1' })).toBe('https://www.youtube.com/watch?v=ab%20cd%26x%3D1')
+    expect(entryUrl({ id: 'vid123' })).toBe('https://www.youtube.com/watch?v=vid123') // unchanged
+  })
 })
 
 describe('fmtDuration', () => {
@@ -189,6 +194,26 @@ describe('buildFeedUrl', () => {
   })
 })
 
+describe('isYouTubeFeedUrl (audit T7 — SSRF guard)', () => {
+  it('accepts a youtube feeds URL (www optional) and what buildFeedUrl produces', () => {
+    expect(isYouTubeFeedUrl('https://www.youtube.com/feeds/videos.xml?channel_id=UCabc')).toBe(true)
+    expect(isYouTubeFeedUrl('https://youtube.com/feeds/videos.xml?playlist_id=PLxyz')).toBe(true)
+    expect(isYouTubeFeedUrl(buildFeedUrl('channel', 'UCabc')!)).toBe(true)
+    expect(isYouTubeFeedUrl(buildFeedUrl('playlist', 'PLxyz')!)).toBe(true)
+  })
+
+  it('rejects internal/arbitrary hosts, wrong scheme, and wrong path (SSRF vectors)', () => {
+    expect(isYouTubeFeedUrl('http://169.254.169.254/latest/meta-data/')).toBe(false) // cloud metadata
+    expect(isYouTubeFeedUrl('http://localhost:8080/admin')).toBe(false)
+    expect(isYouTubeFeedUrl('https://evil.com/feeds/videos.xml')).toBe(false)
+    expect(isYouTubeFeedUrl('https://notyoutube.com.evil.com/feeds/videos.xml')).toBe(false)
+    expect(isYouTubeFeedUrl('http://www.youtube.com/feeds/videos.xml')).toBe(false) // not https
+    expect(isYouTubeFeedUrl('https://www.youtube.com/watch?v=x')).toBe(false) // wrong path
+    expect(isYouTubeFeedUrl('file:///etc/passwd')).toBe(false)
+    expect(isYouTubeFeedUrl('not a url')).toBe(false)
+  })
+})
+
 describe('parseRssVideoIds', () => {
   it('extracts every <yt:videoId> from a feed body, in order', () => {
     const xml = `

test/security-guards.test.ts

@@ -0,0 +1,94 @@
+import { describe, it, expect } from 'vitest'
+import { assertHttpUrl } from '../src/main/url'
+import { isAllowedLoginUrl } from '../src/main/cookies'
+import { isYtdlpUpdateChannel } from '@shared/ipc'
+
+// --- F5: assertHttpUrl — argument-injection guard + normalisation -----------
+
+describe('assertHttpUrl (audit F5)', () => {
+  it('accepts http(s) URLs and returns the normalised href', () => {
+    expect(assertHttpUrl('https://www.youtube.com/watch?v=abc')).toBe(
+      'https://www.youtube.com/watch?v=abc'
+    )
+    // http with a bare host normalises to a trailing slash
+    expect(assertHttpUrl('http://example.com')).toBe('http://example.com/')
+  })
+
+  it('trims surrounding whitespace', () => {
+    expect(assertHttpUrl('  https://example.com/v  ')).toBe('https://example.com/v')
+  })
+
+  it('strips interior tabs/newlines the URL parser tolerates (normalised output)', () => {
+    // Returning the raw input would leak these through to argv / loadURL.
+    expect(assertHttpUrl('https://exa\nmple.com/v')).toBe('https://example.com/v')
+    const out = assertHttpUrl('https://example.com/a\tb')
+    expect(out).not.toContain('\t')
+    expect(out).not.toContain('\n')
+  })
+
+  it('rejects non-http(s) protocols', () => {
+    expect(() => assertHttpUrl('file:///C:/Windows/system32')).toThrow()
+    expect(() => assertHttpUrl('javascript:alert(1)')).toThrow()
+    expect(() => assertHttpUrl('ftp://example.com/x')).toThrow()
+    expect(() => assertHttpUrl('aerofetch://download?url=x')).toThrow()
+  })
+
+  it('rejects unparseable input', () => {
+    expect(() => assertHttpUrl('not a url')).toThrow()
+    expect(() => assertHttpUrl('')).toThrow()
+  })
+
+  it('can never return a value that begins with "-" (would read as a yt-dlp flag)', () => {
+    // A leading '-' cannot start a valid URL scheme, so it always throws —
+    // the returned value therefore never opens with a dash.
+    expect(() => assertHttpUrl('-https://example.com')).toThrow()
+  })
+})
+
+// --- T4: isAllowedLoginUrl — sign-in window navigation confinement ----------
+
+describe('isAllowedLoginUrl (audit T4)', () => {
+  it('allows http(s) and about:blank', () => {
+    expect(isAllowedLoginUrl('https://accounts.google.com/signin')).toBe(true)
+    expect(isAllowedLoginUrl('http://example.com/login')).toBe(true)
+    expect(isAllowedLoginUrl('about:blank')).toBe(true)
+  })
+
+  it('blocks file://, the app protocol, and other external URI schemes', () => {
+    expect(isAllowedLoginUrl('file:///C:/Windows/System32/calc.exe')).toBe(false)
+    expect(isAllowedLoginUrl('aerofetch://download?url=https://evil.test')).toBe(false)
+    expect(isAllowedLoginUrl('ms-settings:')).toBe(false)
+    expect(isAllowedLoginUrl('mailto:x@y.z')).toBe(false)
+    expect(isAllowedLoginUrl('javascript:alert(1)')).toBe(false)
+  })
+
+  it('blocks unparseable input', () => {
+    expect(isAllowedLoginUrl('not a url')).toBe(false)
+    expect(isAllowedLoginUrl('')).toBe(false)
+  })
+})
+
+// --- F1: isYtdlpUpdateChannel — --update-to allowlist -----------------------
+
+describe('isYtdlpUpdateChannel (audit F1)', () => {
+  it('accepts the two supported channels', () => {
+    expect(isYtdlpUpdateChannel('stable')).toBe(true)
+    expect(isYtdlpUpdateChannel('nightly')).toBe(true)
+  })
+
+  it('rejects an arbitrary repository spec (the --update-to RCE vector)', () => {
+    expect(isYtdlpUpdateChannel('evil/yt-dlp@latest')).toBe(false)
+    expect(isYtdlpUpdateChannel('owner/repo')).toBe(false)
+  })
+
+  it('rejects other yt-dlp channels not on AeroFetch’s allowlist', () => {
+    expect(isYtdlpUpdateChannel('master')).toBe(false)
+  })
+
+  it('rejects non-string / empty values', () => {
+    expect(isYtdlpUpdateChannel('')).toBe(false)
+    expect(isYtdlpUpdateChannel(undefined)).toBe(false)
+    expect(isYtdlpUpdateChannel(null)).toBe(false)
+    expect(isYtdlpUpdateChannel(42)).toBe(false)
+  })
+})

test/validation.test.ts

@@ -4,9 +4,10 @@ import {
   isSafeOutputDir,
   isValidHistoryEntry,
   isValidErrorLogEntry,
-  isTemplateLike
+  isTemplateLike,
+  isValidSource
 } from '../src/main/validation'
-import type { HistoryEntry, ErrorLogEntry } from '@shared/ipc'
+import type { HistoryEntry, ErrorLogEntry, Source } from '@shared/ipc'
 
 // --- S4: filename template path-traversal -----------------------------------
 
@@ -40,6 +41,24 @@ describe('isSafeFilenameTemplate', () => {
   it('allows .. only when embedded in a longer segment (not a real traversal)', () => {
     // '..foo' / 'foo..bar' are filenames, not parent-dir references.
     expect(isSafeFilenameTemplate('my..video.%(ext)s')).toBe(true)
+    expect(isSafeFilenameTemplate('.%(title)s.%(ext)s')).toBe(true) // leading dot = hidden file
+  })
+
+  // --- T1: Windows-specific bypasses --------------------------------------
+
+  it('rejects a drive-relative prefix that path.isAbsolute misses', () => {
+    // 'C:foo' is NOT absolute per Node, but still escapes the output dir.
+    expect(isSafeFilenameTemplate('C:foo\\%(title)s.%(ext)s')).toBe(false)
+    expect(isSafeFilenameTemplate('c:%(title)s')).toBe(false)
+  })
+
+  it('rejects a .. segment dressed up with trailing/leading dots or spaces', () => {
+    // Windows trims trailing dots/spaces, so these all resolve to '..'.
+    expect(isSafeFilenameTemplate('%(title)s/.. /x')).toBe(false)
+    expect(isSafeFilenameTemplate('%(title)s/.. ./x')).toBe(false)
+    expect(isSafeFilenameTemplate('%(title)s/ ../x')).toBe(false)
+    expect(isSafeFilenameTemplate('%(title)s\\..  \\x')).toBe(false)
+    expect(isSafeFilenameTemplate('...')).toBe(false)
   })
 })
 
@@ -144,3 +163,48 @@ describe('isTemplateLike', () => {
     expect(isTemplateLike('str')).toBe(false)
   })
 })
+
+// --- T7: source row validation (feedUrl drives a network fetch) --------------
+
+const validSource: Source = {
+  id: 's1',
+  url: 'https://www.youtube.com/@x',
+  kind: 'channel',
+  title: 'X',
+  addedAt: 1700000000000,
+  itemCount: 5
+}
+
+describe('isValidSource', () => {
+  it('accepts a well-formed source and its optional fields', () => {
+    expect(isValidSource(validSource)).toBe(true)
+    expect(
+      isValidSource({
+        ...validSource,
+        channel: 'X',
+        watched: true,
+        feedUrl: 'https://www.youtube.com/feeds/videos.xml?channel_id=UC',
+        lastIndexedAt: 1700000000001
+      })
+    ).toBe(true)
+  })
+
+  it('rejects a non-string feedUrl (audit T7)', () => {
+    expect(isValidSource({ ...validSource, feedUrl: 123 })).toBe(false)
+  })
+
+  it('rejects a non-boolean watched (audit T7)', () => {
+    expect(isValidSource({ ...validSource, watched: 'yes' })).toBe(false)
+  })
+
+  it('rejects a wrong kind or a missing required field', () => {
+    expect(isValidSource({ ...validSource, kind: 'video' })).toBe(false)
+    const { id: _id, ...noId } = validSource
+    expect(isValidSource(noId)).toBe(false)
+  })
+
+  it('rejects non-objects', () => {
+    expect(isValidSource(null)).toBe(false)
+    expect(isValidSource('nope')).toBe(false)
+  })
+})