diff --git a/apps/desktop/.gitignore b/apps/desktop/.gitignore
index e7ec8f6297f..34e4bd2053d 100644
--- a/apps/desktop/.gitignore
+++ b/apps/desktop/.gitignore
@@ -1,5 +1,6 @@
 dist/
 release/
 build/generated-icon.icon
+build/generated-icon.png
 playwright-report/
 test-results/
diff --git a/apps/desktop/README.md b/apps/desktop/README.md
index 309160f0339..c0dc2f721ab 100644
--- a/apps/desktop/README.md
+++ b/apps/desktop/README.md
@@ -1,4 +1,4 @@
-# Sim Desktop (macOS)
+# Sim Desktop (macOS, Windows)
 
 A thin Electron shell around the hosted Sim web app. The renderer loads the configured origin (default `https://www.sim.ai` — the origin the server actually serves; the apex 301s there) as a normal top-level page in a bundled, pinned Chromium — rendering is identical to Chrome of that version on every machine. No UI is re-implemented and no server stack is bundled.
 
@@ -102,6 +102,19 @@ Overall this is **within normal thin-wrapper coupling** — every item is either
 
 Local unsigned build: `bun run package:dir` (app in `release/mac-universal/`). Signed: `bun run package:mac` with `CSC_LINK`/`CSC_KEY_PASSWORD` exported.
 
+### Windows
+
+Build on a Windows host (electron-builder cross-compiles NSIS from macOS/Linux only with Wine, which is not supported here). Prerequisites: Bun ≥ 1.4.2, Node ≥ 20, and `tar` (built into Windows 10+). No C++ toolchain is needed: `scripts/build.ts` skips the AppKit Help-search addon off macOS, and node-pty ships ConPTY prebuilds (`@lydell/node-pty-win32-{x64,arm64}`, fetched by `scripts/ensure-pty-prebuilds.ts` the same way the macOS arches are).
+
+- `bun run package:win:dir` — unpacked app in `release/win-unpacked/` (x64; add `--arm64` for `release/win-arm64-unpacked/`).
+- `bun run package:win` — NSIS installer + zip per arch (`Sim-<version>-<arch>.exe`), from the same `electron-builder.yml`.
+- Signing: set `CSC_LINK`/`CSC_KEY_PASSWORD` to an Authenticode `.pfx`; unsigned builds trigger SmartScreen on first launch.
+- Bun does not run electron's `postinstall` on Windows; if `node_modules/electron/dist/electron.exe` is missing after `bun install`, run `node node_modules/electron/install.js` once.
+
+The agent terminal launches PowerShell (`pwsh`, else Windows PowerShell 5.1) with full shell integration: the hooks are passed as `-EncodedCommand` (a dot-sourced file would be blocked by the default execution policy), `prompt` is wrapped to report the directory, exit code and prompt start, and `PSConsoleHostReadLine` is wrapped to report each command line and its start — the arrangement Windows Terminal and VS Code use. Git for Windows' bash is offered under the app menu's **Terminal Shell** submenu when Git is installed; it uses the existing bash hooks, with `cygpath -w` translating the reported directory to a Windows path. The choice persists as `terminalShell` in `settings.json`. tmux does not exist on Windows; its first probe fails with ENOENT and marks it unavailable for the rest of the session, as on a Mac without tmux.
+
+Windows parity gaps (deliberate, see "Known caveats"): no auto-update (the updater is a no-op off macOS — the installer must be re-downloaded), no Help-menu docs search, no Chrome cookie/password import, and no Terminal.app/iTerm2 theme import.
+
 Local unsigned pre-release share: `SIM_DESKTOP_DEFAULT_ORIGIN=https://www.dev.sim.ai bun run package:share` builds a DMG whose fresh installs default to that origin (baked at build time; official builds leave it unset → prod) and skips per-file signature timestamps. Recipients must clear quarantine once: `xattr -cr /Applications/Sim.app`.
 
 The build also derives the app icon from `SIM_DESKTOP_DEFAULT_ORIGIN`. Every channel uses the exact production icon with its white background and black `sim` mark. Non-production channels add a thin outline using existing platform colors: dev uses orange, staging uses Loop blue, and localhost uses Workflow violet. The macOS menu-bar icon also carries a compact `D`, `S`, or `L` subscript for those environments; production remains unmarked. Native Icon Composer assets live in `build/`; `scripts/build.ts` copies the selected variant to the ignored `build/generated-icon.icon` path consumed by electron-builder. Electron-builder compiles it to `Assets.car` and derives the legacy `.icns` fallback from the same source. Matching 512px PNGs in `static/` provide the Dock icon for unpackaged runs.
@@ -216,6 +229,7 @@ Raw local file bytes are never exposed through the preload bridge and cannot be
 - Third-party web analytics (GTM/GA) are blocked at the network layer by default (`blockThirdPartyAnalytics`); first-party PostHog `/ingest` is untouched.
 - `Cmd+F` opens the native find overlay in built-in browser tabs. The hosted Sim workspace continues to use Monaco- and table-specific find surfaces.
 - Sign-in uses only the `127.0.0.1` loopback callback, which needs no OS registration — so it completes identically under `bun run dev` (unpackaged) and in a packaged build. There is no custom URL scheme.
+- Windows uses the native title bar (the `hiddenInset` traffic-light lane is macOS-only) and the tray's monochrome template icon is drawn as-is, so it is hard to see on a dark taskbar; the tray can be turned off in Desktop settings. Secure storage falls back to DPAPI via `safeStorage`, so remembered grants and credentials still work.
 
 ## Electron upgrades
 
diff --git a/apps/desktop/electron-builder.yml b/apps/desktop/electron-builder.yml
index 25856fb9dc8..2c24a95e6ba 100644
--- a/apps/desktop/electron-builder.yml
+++ b/apps/desktop/electron-builder.yml
@@ -71,6 +71,26 @@ mac:
   entitlementsInherit: build/entitlements.mac.plist
   notarize: true
 
+win:
+  target:
+    - target: nsis
+      arch: [x64, arm64]
+    - target: zip
+      arch: [x64, arm64]
+  # electron-builder derives the multi-size .ico from this PNG; scripts/build.ts
+  # copies the selected channel's 1024px logo here next to the .icon bundle.
+  icon: build/generated-icon.png
+  # Unsigned: SmartScreen warns on first launch until a code-signing
+  # certificate is configured (CSC_LINK / CSC_KEY_PASSWORD, as on macOS).
+  signAndEditExecutable: true
+
+nsis:
+  oneClick: false
+  perMachine: false
+  allowToChangeInstallationDirectory: true
+  deleteAppDataOnUninstall: false
+  shortcutName: ${productName}
+
 dmg:
   sign: false
   title: ${productName}
diff --git a/apps/desktop/package.json b/apps/desktop/package.json
index a4484720362..9b0da48dc93 100644
--- a/apps/desktop/package.json
+++ b/apps/desktop/package.json
@@ -3,7 +3,7 @@
   "version": "0.0.0",
   "private": true,
   "license": "Apache-2.0",
-  "description": "Sim desktop app for macOS \u2014 Electron shell around the hosted web app",
+  "description": "Sim desktop app for macOS and Windows \u2014 Electron shell around the hosted web app",
   "author": "Sim <support@sim.ai>",
   "homepage": "https://sim.ai",
   "type": "module",
@@ -18,6 +18,8 @@
     "start": "electron .",
     "package:dir": "bun run build && electron-builder --mac dir --publish never",
     "package:mac": "bun run build && electron-builder --mac --publish never",
+    "package:win:dir": "bun run build && electron-builder --win dir --publish never",
+    "package:win": "bun run build && electron-builder --win --publish never",
     "package:share": "bun run scripts/package-share.ts",
     "install:local": "bun run scripts/install-local.ts",
     "type-check": "tsc --noEmit",
@@ -31,8 +33,6 @@
   },
   "dependencies": {
     "@lydell/node-pty": "1.2.0-beta.12",
-    "@lydell/node-pty-darwin-arm64": "1.2.0-beta.12",
-    "@lydell/node-pty-darwin-x64": "1.2.0-beta.12",
     "@sim/browser-protocol": "workspace:*",
     "@sim/desktop-bridge": "workspace:*",
     "@sim/logger": "workspace:*",
@@ -45,6 +45,12 @@
     "safe-regex2": "5.1.0",
     "pdf-lib": "1.17.1"
   },
+  "optionalDependencies": {
+    "@lydell/node-pty-darwin-arm64": "1.2.0-beta.12",
+    "@lydell/node-pty-darwin-x64": "1.2.0-beta.12",
+    "@lydell/node-pty-win32-arm64": "1.2.0-beta.12",
+    "@lydell/node-pty-win32-x64": "1.2.0-beta.12"
+  },
   "devDependencies": {
     "@electron/fuses": "1.8.0",
     "@playwright/test": "1.61.1",
diff --git a/apps/desktop/scripts/build.ts b/apps/desktop/scripts/build.ts
index b15dc2fb354..e9b5e83d0e2 100644
--- a/apps/desktop/scripts/build.ts
+++ b/apps/desktop/scripts/build.ts
@@ -32,6 +32,11 @@ const appIcon = identityForOrigin(bakedDefaultOrigin).icon
 const generatedIcon = 'build/generated-icon.icon'
 rmSync(generatedIcon, { force: true, recursive: true })
 cpSync(appIcon, generatedIcon, { recursive: true })
+// Windows has no Icon Composer path; electron-builder builds the .ico from the
+// same 1024px logo the macOS bundle is composed from.
+const generatedWindowsIcon = 'build/generated-icon.png'
+rmSync(generatedWindowsIcon, { force: true })
+cpSync(join(appIcon, 'Assets', 'logo.png'), generatedWindowsIcon)
 console.log(`• Selecting desktop icon: ${appIcon}`)
 
 function compileNativeHelpSearch(): void {
diff --git a/apps/desktop/scripts/ensure-pty-prebuilds.ts b/apps/desktop/scripts/ensure-pty-prebuilds.ts
index a08856a51f2..52ac745440d 100644
--- a/apps/desktop/scripts/ensure-pty-prebuilds.ts
+++ b/apps/desktop/scripts/ensure-pty-prebuilds.ts
@@ -1,13 +1,16 @@
 /**
- * Fetches the node-pty prebuilt binaries for every architecture the macOS
- * universal build ships.
+ * Fetches the node-pty prebuilt binaries for every architecture the host
+ * platform's build ships: both halves of the macOS universal app, or x64 and
+ * arm64 on Windows.
  *
  * `@lydell/node-pty` selects its native binary at runtime from a per-arch
- * package (`@lydell/node-pty-darwin-arm64`, `-darwin-x64`), each declaring a
- * matching `cpu` field. Package managers honour that field, so installing on
- * an arm64 Mac leaves the x64 binary absent and the x64 half of the universal
- * app ships without a working PTY. Fetching the tarball directly is the only
- * way to get both without lying about the host architecture.
+ * package (`@lydell/node-pty-darwin-arm64`, `-win32-x64`, …), each declaring
+ * matching `os` and `cpu` fields. Package managers honour those fields, so
+ * installing on an arm64 Mac leaves the x64 binary absent and the x64 half of
+ * the universal app ships without a working PTY. Fetching the tarball directly
+ * is the only way to get both without lying about the host architecture. The
+ * per-arch packages are `optionalDependencies` so electron-builder's
+ * dependency walk skips the other platform's rather than failing the build.
  *
  * Both binaries live at distinct paths, so `@electron/universal` never has to
  * lipo them together — it sees byte-identical trees in both halves and keeps
@@ -32,7 +35,15 @@ import { getErrorMessage } from '@sim/utils/errors'
 
 const logger = createLogger('DesktopPtyPrebuilds')
 
-const REQUIRED_ARCHES = ['darwin-arm64', 'darwin-x64'] as const
+const REQUIRED_ARCHES_FOR_PLATFORM: Partial<Record<NodeJS.Platform, readonly string[]>> = {
+  darwin: ['darwin-arm64', 'darwin-x64'],
+  win32: ['win32-x64', 'win32-arm64'],
+}
+
+/** The addon each prebuild ships: a Unix pty, or the ConPTY bridge on Windows. */
+function prebuildBinary(arch: string): string {
+  return arch.startsWith('win32-') ? 'conpty.node' : 'pty.node'
+}
 
 const desktopDir = dirname(dirname(fileURLToPath(import.meta.url)))
 const workspaceRoot = dirname(dirname(desktopDir))
@@ -110,17 +121,22 @@ async function fetchPrebuild(arch: string, version: string): Promise<void> {
 }
 
 async function run(): Promise<void> {
+  const requiredArches = REQUIRED_ARCHES_FOR_PLATFORM[process.platform]
+  if (!requiredArches) {
+    throw new Error(`No desktop packaging target for platform "${process.platform}"`)
+  }
   const version = await pinnedVersion()
-  for (const arch of REQUIRED_ARCHES) {
+  for (const arch of requiredArches) {
     const dir = packageDir(arch)
-    if (existsSync(join(dir, 'prebuilds', arch, 'pty.node'))) {
+    const binary = prebuildBinary(arch)
+    if (existsSync(join(dir, 'prebuilds', arch, binary))) {
       logger.info('node-pty prebuild present', { arch })
       continue
     }
     logger.info('Fetching node-pty prebuild', { arch, version })
     await fetchPrebuild(arch, version)
-    if (!existsSync(join(dir, 'prebuilds', arch, 'pty.node'))) {
-      throw new Error(`Downloaded @lydell/node-pty-${arch} but pty.node is missing`)
+    if (!existsSync(join(dir, 'prebuilds', arch, binary))) {
+      throw new Error(`Downloaded @lydell/node-pty-${arch} but ${binary} is missing`)
     }
   }
 }
diff --git a/apps/desktop/src/main/browser-agent/file-transfer.test.ts b/apps/desktop/src/main/browser-agent/file-transfer.test.ts
index bc4569f37c6..1454fd715a7 100644
--- a/apps/desktop/src/main/browser-agent/file-transfer.test.ts
+++ b/apps/desktop/src/main/browser-agent/file-transfer.test.ts
@@ -1,7 +1,7 @@
 import { existsSync, mkdtempSync, readFileSync, writeFileSync } from 'node:fs'
 import { open, rename, rm, truncate } from 'node:fs/promises'
 import { tmpdir } from 'node:os'
-import { join } from 'node:path'
+import { basename, join } from 'node:path'
 import { BROWSER_FILE_TRANSFER_MAX_BYTES } from '@sim/browser-protocol'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
@@ -59,7 +59,7 @@ describe('stageUploadFiles', () => {
       body: JSON.stringify({ toolCallId: 'call-1', index: 0 }),
       signal,
     })
-    expect(staged.map((path) => path.split('/').pop())).toEqual(['Q3 plan.pdf', 'granted.txt'])
+    expect(staged.map((path) => basename(path))).toEqual(['Q3 plan.pdf', 'granted.txt'])
     expect(readFileSync(staged[0], 'utf8')).toBe('workspace bytes')
     expect(readFileSync(staged[1], 'utf8')).toBe('local bytes')
     expect(staged.every((path) => path.startsWith(join(temp, 'sim-browser-uploads')))).toBe(true)
@@ -83,7 +83,7 @@ describe('stageUploadFiles', () => {
     })
 
     expect(staged.startsWith(join(temp, 'sim-browser-uploads'))).toBe(true)
-    expect(staged.endsWith('/evil')).toBe(true)
+    expect(basename(staged)).toBe('evil')
   })
 
   it('refuses a workspace file over the transfer ceiling', async () => {
diff --git a/apps/desktop/src/main/browser-credentials/vault.test.ts b/apps/desktop/src/main/browser-credentials/vault.test.ts
index 264bbe7f799..aa16fa06909 100644
--- a/apps/desktop/src/main/browser-credentials/vault.test.ts
+++ b/apps/desktop/src/main/browser-credentials/vault.test.ts
@@ -86,7 +86,8 @@ describe('CredentialVault', () => {
     expect(JSON.parse(onDisk)).toMatchObject({ version: 1, ciphertext: expect.any(String) })
   })
 
-  it('writes the vault file owner-only', async () => {
+  // Windows has no POSIX mode bits to assert on.
+  it.skipIf(process.platform === 'win32')('writes the vault file owner-only', async () => {
     const vault = new CredentialVault(vaultPath, encryption())
     await vault.importCredentials(CANDIDATES, 'keep-existing')
 
diff --git a/apps/desktop/src/main/browser-import/chromium-profiles.test.ts b/apps/desktop/src/main/browser-import/chromium-profiles.test.ts
index d39a737ea66..0ceb39fa1b0 100644
--- a/apps/desktop/src/main/browser-import/chromium-profiles.test.ts
+++ b/apps/desktop/src/main/browser-import/chromium-profiles.test.ts
@@ -48,6 +48,10 @@ async function writeLocalState(
   )
 }
 
+// Creating a symlink on Windows needs Developer Mode or elevation, which the
+// test runner cannot assume.
+const NO_SYMLINKS = process.platform === 'win32'
+
 describe('listBrowserProfiles', () => {
   it('returns display names, default profile first, with namespaced ids', async () => {
     await addProfile(CHROME, 'Profile 2')
@@ -81,7 +85,7 @@ describe('listBrowserProfiles', () => {
     expect(profiles.map(({ id }) => id)).toEqual(['chrome:Default'])
   })
 
-  it('refuses a profile directory redirected through a symlink', async () => {
+  it.skipIf(NO_SYMLINKS)('refuses a profile directory redirected through a symlink', async () => {
     const outsideProfile = join(home, 'outside-profile')
     await mkdir(outsideProfile, { recursive: true })
     await writeFile(join(outsideProfile, 'Login Data'), '')
@@ -93,20 +97,23 @@ describe('listBrowserProfiles', () => {
     await expect(listBrowserProfiles(CHROME, home)).resolves.toEqual([])
   })
 
-  it('refuses symlinked, hard-linked, and non-file password databases', async () => {
-    const outsideDatabase = join(home, 'outside-login-data')
-    await writeFile(outsideDatabase, '')
-
-    const userDataDir = userDataDirFor(CHROME, home)
-    for (const directory of ['Default', 'Profile 2', 'Profile 3']) {
-      await mkdir(join(userDataDir, directory), { recursive: true })
+  it.skipIf(NO_SYMLINKS)(
+    'refuses symlinked, hard-linked, and non-file password databases',
+    async () => {
+      const outsideDatabase = join(home, 'outside-login-data')
+      await writeFile(outsideDatabase, '')
+
+      const userDataDir = userDataDirFor(CHROME, home)
+      for (const directory of ['Default', 'Profile 2', 'Profile 3']) {
+        await mkdir(join(userDataDir, directory), { recursive: true })
+      }
+      await symlink(outsideDatabase, join(userDataDir, 'Default', 'Login Data For Account'))
+      await link(outsideDatabase, join(userDataDir, 'Profile 2', 'Login Data For Account'))
+      await mkdir(join(userDataDir, 'Profile 3', 'Login Data For Account'))
+
+      await expect(listBrowserProfiles(CHROME, home)).resolves.toEqual([])
     }
-    await symlink(outsideDatabase, join(userDataDir, 'Default', 'Login Data For Account'))
-    await link(outsideDatabase, join(userDataDir, 'Profile 2', 'Login Data For Account'))
-    await mkdir(join(userDataDir, 'Profile 3', 'Login Data For Account'))
-
-    await expect(listBrowserProfiles(CHROME, home)).resolves.toEqual([])
-  })
+  )
 })
 
 describe('listAllBrowserProfiles', () => {
diff --git a/apps/desktop/src/main/config.ts b/apps/desktop/src/main/config.ts
index 30c00528b10..cd77f93c5a1 100644
--- a/apps/desktop/src/main/config.ts
+++ b/apps/desktop/src/main/config.ts
@@ -3,6 +3,7 @@ import type { DesktopZoomPercent, TerminalAppearanceTheme } from '@sim/desktop-b
 import { createLogger } from '@sim/logger'
 import { isLoopbackHostname } from '@sim/security/ssrf'
 import { writeJsonFileAtomicallySync } from '@/main/atomic-json-file'
+import type { WindowsTerminalShell } from '@/main/terminal/default-shell'
 
 /** settings.json is meant to be readable when a user opens it. */
 const SETTINGS_INDENT = 2
@@ -114,6 +115,8 @@ export interface DesktopSettings {
   terminalTheme?: TerminalAppearanceTheme
   /** Device-wide default zoom for built-in terminal canvases. */
   terminalDefaultZoom?: DesktopZoomPercent
+  /** Windows only: which installed shell new terminals launch. */
+  terminalShell?: WindowsTerminalShell
   /**
    * Top-level sites visited in the dedicated agent-browser profile. This is
    * local inference metadata only; no cookies, credentials, or account data
diff --git a/apps/desktop/src/main/desktop-chat-session-store.test.ts b/apps/desktop/src/main/desktop-chat-session-store.test.ts
index cb49ee7f542..775f06d3d80 100644
--- a/apps/desktop/src/main/desktop-chat-session-store.test.ts
+++ b/apps/desktop/src/main/desktop-chat-session-store.test.ts
@@ -100,7 +100,7 @@ describe('DesktopChatSessionStore', () => {
     expect(restarted.getTerminal(ORIGIN, 'chat-a')).toEqual(TERMINAL)
   })
 
-  it('encrypts the complete descriptor payload and writes it owner-only', () => {
+  it('encrypts the complete descriptor payload', () => {
     const provider = encryption()
     const store = open(provider)
     store.setBrowser(ORIGIN, 'chat-secret', BROWSER)
@@ -115,6 +115,14 @@ describe('DesktopChatSessionStore', () => {
     expect(onDisk).not.toContain('report.csv')
     expect(JSON.parse(onDisk)).toEqual({ v: 1, ciphertext: expect.any(String) })
     expect(provider.encryptString).toHaveBeenCalledOnce()
+  })
+
+  // Windows has no POSIX mode bits to assert on.
+  it.skipIf(process.platform === 'win32')('writes the store file owner-only', () => {
+    const store = open(encryption())
+    store.setBrowser(ORIGIN, 'chat-secret', BROWSER)
+
+    expect(store.flush()).toBe(true)
     expect(statSync(filePath).mode & 0o077).toBe(0)
   })
 
diff --git a/apps/desktop/src/main/downloads.test.ts b/apps/desktop/src/main/downloads.test.ts
index 951bc151f6c..e3a9ec3a7b5 100644
--- a/apps/desktop/src/main/downloads.test.ts
+++ b/apps/desktop/src/main/downloads.test.ts
@@ -16,7 +16,8 @@ describe('sanitizeFilename', () => {
 })
 
 describe('uniqueDownloadPath', () => {
-  it('treats a dangling symlink as occupied', async () => {
+  // Creating a symlink on Windows needs Developer Mode or elevation.
+  it.skipIf(process.platform === 'win32')('treats a dangling symlink as occupied', async () => {
     const directory = mkdtempSync(join(tmpdir(), 'sim-download-path-'))
     symlinkSync(join(directory, 'missing-target'), join(directory, 'report.csv'))
 
@@ -45,7 +46,7 @@ describe('uniqueDownloadPath', () => {
     ])
 
     expect(new Set([first, second])).toEqual(
-      new Set(['/Downloads/report.csv', '/Downloads/report (copy-1).csv'])
+      new Set([join('/Downloads', 'report.csv'), join('/Downloads', 'report (copy-1).csv')])
     )
   })
 })
diff --git a/apps/desktop/src/main/index.ts b/apps/desktop/src/main/index.ts
index 990fa6724aa..8ba90ca529b 100644
--- a/apps/desktop/src/main/index.ts
+++ b/apps/desktop/src/main/index.ts
@@ -98,6 +98,12 @@ import {
 } from '@/main/session-lifecycle'
 import { setShellTheme } from '@/main/shell-theme'
 import { attachTelemetryPolicy } from '@/main/telemetry-policy'
+import {
+  findGitBash,
+  getPreferredWindowsShell,
+  isWindowsTerminalShell,
+  setPreferredWindowsShell,
+} from '@/main/terminal/default-shell'
 import { TerminalRegistry } from '@/main/terminal/registry'
 import { installTray, type TrayHandle } from '@/main/tray'
 import { checkForUpdatesInteractive, initUpdater, type UpdaterHandle } from '@/main/updater'
@@ -165,6 +171,10 @@ function main(): void {
     ),
   })
   const scopeEvents = new ScopedEventRouter()
+  if (process.platform === 'win32') {
+    const storedShell = config.get('terminalShell')
+    if (isWindowsTerminalShell(storedShell)) setPreferredWindowsShell(storedShell)
+  }
   const terminal = new TerminalRegistry({
     load: (scopeId) => desktopChatSessions.getTerminal(processOrigin, scopeId) ?? undefined,
     save: (scopeId, snapshot) => desktopChatSessions.setTerminal(processOrigin, scopeId, snapshot),
@@ -944,25 +954,39 @@ function main(): void {
       desktopExecutor.start()
     }
     await ensureMainWindow()
-    installApplicationMenu({
-      config,
-      getMainWindow,
-      isMainWindow: (win) => windows.has(win) && !win.isDestroyed(),
-      allowHttpLocalhost,
-      openSettings,
-      openServerSettings: () => serverWindow.open(),
-      newWindow: () => void createAndLoadAppWindow(),
-      newChat: () => void openMainWindowAt(newChatRoute(config.get('lastRoute'))),
-      handleFocusedResourceShortcut: (win, shortcut) =>
-        handleFocusedBrowserShortcut(shortcut, win) ||
-        terminal.handleFocusedShortcut(win, shortcut),
-      toggleSidebar: () => getMainWindow()?.webContents.send('desktop:command', 'toggle-sidebar'),
-      openSearch: () => getMainWindow()?.webContents.send('desktop:command', 'open-search'),
-      signOut: signOutFromMenu,
-      checkForUpdates: () =>
-        checkForUpdatesInteractive({ getWindow: getMainWindow, events, handle: updater }),
-      openDiagnostics: () => shell.showItemInFolder(events.filePath),
-    })
+    // Rebuilt after a shell choice so the radio reflects it; Electron menus
+    // are immutable once built.
+    const installMenu = () =>
+      installApplicationMenu({
+        config,
+        getMainWindow,
+        isMainWindow: (win) => windows.has(win) && !win.isDestroyed(),
+        allowHttpLocalhost,
+        openSettings,
+        openServerSettings: () => serverWindow.open(),
+        newWindow: () => void createAndLoadAppWindow(),
+        newChat: () => void openMainWindowAt(newChatRoute(config.get('lastRoute'))),
+        handleFocusedResourceShortcut: (win, shortcut) =>
+          handleFocusedBrowserShortcut(shortcut, win) ||
+          terminal.handleFocusedShortcut(win, shortcut),
+        toggleSidebar: () => getMainWindow()?.webContents.send('desktop:command', 'toggle-sidebar'),
+        openSearch: () => getMainWindow()?.webContents.send('desktop:command', 'open-search'),
+        signOut: signOutFromMenu,
+        checkForUpdates: () =>
+          checkForUpdatesInteractive({ getWindow: getMainWindow, events, handle: updater }),
+        openDiagnostics: () => shell.showItemInFolder(events.filePath),
+        terminalShell: {
+          current: getPreferredWindowsShell,
+          gitBashAvailable: () => findGitBash() !== null,
+          select: (choice) => {
+            setPreferredWindowsShell(choice)
+            config.set('terminalShell', choice)
+            config.flush()
+            installMenu()
+          },
+        },
+      })
+    installMenu()
     installDocumentationHelpSearch()
     setTrayEnabled(config.get('trayEnabled') ?? true)
     updater = initUpdater({
@@ -1001,7 +1025,17 @@ function main(): void {
 // The name follows the build's channel ("Sim", "Sim Dev", …) so one developer
 // can run one install per environment side by side — separate settings,
 // sessions, locks, and update feeds.
-app.setName(APP_NAME_FOR_CHANNEL[channelForOrigin(DEFAULT_ORIGIN)])
+const launchChannel = channelForOrigin(DEFAULT_ORIGIN)
+app.setName(APP_NAME_FOR_CHANNEL[launchChannel])
+// Windows groups taskbar buttons and attributes toast notifications by this
+// id; without it an unpackaged run shows up as a generic Electron app. Mirrors
+// the per-channel appId in scripts/channels.ts so the installed shortcut and
+// the running process agree.
+if (process.platform === 'win32') {
+  app.setAppUserModelId(
+    launchChannel === 'prod' ? 'ai.sim.desktop' : `ai.sim.desktop.${launchChannel}`
+  )
+}
 if (process.env.SIM_DESKTOP_USER_DATA) {
   app.setPath('userData', process.env.SIM_DESKTOP_USER_DATA)
 }
diff --git a/apps/desktop/src/main/ipc.test.ts b/apps/desktop/src/main/ipc.test.ts
index 4a596f77a65..aeb1c2e2a63 100644
--- a/apps/desktop/src/main/ipc.test.ts
+++ b/apps/desktop/src/main/ipc.test.ts
@@ -372,8 +372,10 @@ describe('registerIpcHandlers', () => {
 
     expect(await handler?.(evilEvent)).toBe(false)
     expect(await handler?.(appEvent)).toBe(false)
-    expect(await handler?.(activeAppEvent)).toBe(process.platform === 'darwin')
-    expect(shell.openExternal).toHaveBeenCalledTimes(process.platform === 'darwin' ? 1 : 0)
+    // Only macOS and Windows have a settings URL to open.
+    const hasSettingsPane = process.platform === 'darwin' || process.platform === 'win32'
+    expect(await handler?.(activeAppEvent)).toBe(hasSettingsPane)
+    expect(shell.openExternal).toHaveBeenCalledTimes(hasSettingsPane ? 1 : 0)
   })
 
   it('restricts the OAuth connect handoff to an activated app origin', async () => {
diff --git a/apps/desktop/src/main/local-files.test.ts b/apps/desktop/src/main/local-files.test.ts
index 1e01abebfd7..f243b7a97b3 100644
--- a/apps/desktop/src/main/local-files.test.ts
+++ b/apps/desktop/src/main/local-files.test.ts
@@ -12,13 +12,20 @@ afterEach(async () => {
   await rm(root, { recursive: true, force: true })
 })
 
-it('rejects missing paths and directory cycles with explicit errors before uploading', async () => {
+// Creating a symlink on Windows needs Developer Mode or elevation, which the
+// test runner cannot assume.
+const NO_SYMLINKS = process.platform === 'win32'
+
+it('rejects a missing path with an explicit error before uploading', async () => {
   expect(
     await executeLocalFileRequest(
       { operation: 'read' },
       { toolName: 'read_local_file', args: { path: join(root, 'missing') } }
     )
   ).toMatchObject({ ok: false })
+})
+
+it.skipIf(NO_SYMLINKS)('rejects a directory cycle with an explicit error', async () => {
   await symlink(root, join(root, 'cycle'))
   expect(
     await executeLocalFileRequest(
@@ -40,7 +47,7 @@ it('refuses oversized import files before any workspace mutation or bulk allocat
   ).toMatchObject({ ok: false, error: expect.stringContaining('64 MB') })
 })
 
-it.each(['file', 'directory'] as const)(
+it.skipIf(NO_SYMLINKS).each(['file', 'directory'] as const)(
   'rejects %s symlinks outside the import source during manifest and chunk reads',
   async (kind) => {
     const source = join(root, 'selected')
@@ -79,38 +86,41 @@ it.each(['file', 'directory'] as const)(
   }
 )
 
-it('supports internal symlinks and an explicitly selected symlink root, but rejects a retargeted child', async () => {
-  const source = join(root, 'selected')
-  await mkdir(source)
-  await writeFile(join(source, 'notes.txt'), 'inside')
-  await symlink(join(source, 'notes.txt'), join(source, 'alias.txt'))
-  const selectedAlias = join(root, 'selected-alias')
-  await symlink(source, selectedAlias)
-  const authorization = {
-    toolName: 'import_local_files',
-    args: { path: selectedAlias, targetWorkspaceId: 'target' },
-  }
-  const manifest = await executeLocalFileRequest({ operation: 'manifest' }, authorization)
-  if (!manifest.ok || manifest.data.kind !== 'manifest') throw new Error('Expected manifest')
-  const entry = manifest.data.entries.find((item) => item.relativePath === 'alias.txt')!
-  const request = {
-    operation: 'chunk',
-    relativePath: 'alias.txt',
-    revision: entry.revision,
-    offset: 0,
+it.skipIf(NO_SYMLINKS)(
+  'supports internal symlinks and an explicitly selected symlink root, but rejects a retargeted child',
+  async () => {
+    const source = join(root, 'selected')
+    await mkdir(source)
+    await writeFile(join(source, 'notes.txt'), 'inside')
+    await symlink(join(source, 'notes.txt'), join(source, 'alias.txt'))
+    const selectedAlias = join(root, 'selected-alias')
+    await symlink(source, selectedAlias)
+    const authorization = {
+      toolName: 'import_local_files',
+      args: { path: selectedAlias, targetWorkspaceId: 'target' },
+    }
+    const manifest = await executeLocalFileRequest({ operation: 'manifest' }, authorization)
+    if (!manifest.ok || manifest.data.kind !== 'manifest') throw new Error('Expected manifest')
+    const entry = manifest.data.entries.find((item) => item.relativePath === 'alias.txt')!
+    const request = {
+      operation: 'chunk',
+      relativePath: 'alias.txt',
+      revision: entry.revision,
+      offset: 0,
+    }
+    expect(await executeLocalFileRequest(request, authorization)).toEqual({
+      ok: true,
+      data: { kind: 'chunk', bytes: new Uint8Array(Buffer.from('inside')), eof: true },
+    })
+    await writeFile(join(root, 'outside.txt'), 'outside')
+    await rm(join(source, 'alias.txt'))
+    await symlink(join(root, 'outside.txt'), join(source, 'alias.txt'))
+    expect(await executeLocalFileRequest(request, authorization)).toMatchObject({
+      ok: false,
+      error: expect.stringContaining('outside this import source'),
+    })
   }
-  expect(await executeLocalFileRequest(request, authorization)).toEqual({
-    ok: true,
-    data: { kind: 'chunk', bytes: new Uint8Array(Buffer.from('inside')), eof: true },
-  })
-  await writeFile(join(root, 'outside.txt'), 'outside')
-  await rm(join(source, 'alias.txt'))
-  await symlink(join(root, 'outside.txt'), join(source, 'alias.txt'))
-  expect(await executeLocalFileRequest(request, authorization)).toMatchObject({
-    ok: false,
-    error: expect.stringContaining('outside this import source'),
-  })
-})
+)
 
 it('preserves a UTF-8 BOM and rejects split offsets and limits that cannot fit a character', async () => {
   const path = join(root, 'unicode.txt')
diff --git a/apps/desktop/src/main/local-filesystem.test.ts b/apps/desktop/src/main/local-filesystem.test.ts
index 2a98ddf8326..841f713ce89 100644
--- a/apps/desktop/src/main/local-filesystem.test.ts
+++ b/apps/desktop/src/main/local-filesystem.test.ts
@@ -55,6 +55,10 @@ async function mount(service: LocalFilesystemService): Promise<LocalFilesystemMo
   return data.mount
 }
 
+// Creating a symlink on Windows needs Developer Mode or elevation, which the
+// test runner cannot assume.
+const NO_SYMLINKS = process.platform === 'win32'
+
 describe('LocalFilesystemService', () => {
   let root: string
   let service: LocalFilesystemService
@@ -257,17 +261,21 @@ describe('LocalFilesystemService', () => {
     await expect(reading).resolves.toMatchObject({ ok: true })
   })
 
-  it('rejects unknown mounts and symlinks that escape the selected directory', async () => {
-    const granted = await mount(service)
-    const outside = await mkdtemp(join(tmpdir(), 'sim-localfs-outside-'))
-    await writeFile(join(outside, 'secret.txt'), 'secret')
-    await symlink(join(outside, 'secret.txt'), join(root, 'secret-link.txt'))
+  it('rejects unknown mounts', async () => {
+    await mount(service)
 
     const missingMount = await service.handle({
       operation: 'read',
       uri: 'localfs://not-granted/file.txt',
     })
     expect(missingMount).toMatchObject({ ok: false, code: 'MOUNT_NOT_FOUND' })
+  })
+
+  it.skipIf(NO_SYMLINKS)('rejects symlinks that escape the selected directory', async () => {
+    const granted = await mount(service)
+    const outside = await mkdtemp(join(tmpdir(), 'sim-localfs-outside-'))
+    await writeFile(join(outside, 'secret.txt'), 'secret')
+    await symlink(join(outside, 'secret.txt'), join(root, 'secret-link.txt'))
 
     const escaped = await service.handle({
       operation: 'read',
@@ -276,12 +284,9 @@ describe('LocalFilesystemService', () => {
     expect(escaped).toMatchObject({ ok: false, code: 'ACCESS_DENIED' })
   })
 
-  it('resolves a granted file for upload and refuses escapes, directories, and oversize files', async () => {
+  it('resolves a granted file for upload and refuses directories, oversize files, and unknown mounts', async () => {
     const granted = await mount(service)
     const vfsRoot = `user-local/${encodeURIComponent(granted.name)}--${granted.id}`
-    const outside = await mkdtemp(join(tmpdir(), 'sim-localfs-outside-'))
-    await writeFile(join(outside, 'secret.txt'), 'secret')
-    await symlink(join(outside, 'secret.txt'), join(root, 'secret-link.txt'))
 
     const file = await service.resolveGrantedFile(`${vfsRoot}/README.md`, 1024)
     try {
@@ -290,9 +295,6 @@ describe('LocalFilesystemService', () => {
     } finally {
       await file.handle.close()
     }
-    await expect(
-      service.resolveGrantedFile(`${vfsRoot}/secret-link.txt`, 1024)
-    ).rejects.toMatchObject({ code: 'ACCESS_DENIED' })
     await expect(service.resolveGrantedFile(`${vfsRoot}/src`, 1024)).rejects.toMatchObject({
       code: 'NOT_A_FILE',
     })
@@ -304,6 +306,18 @@ describe('LocalFilesystemService', () => {
     ).rejects.toMatchObject({ code: 'MOUNT_NOT_FOUND' })
   })
 
+  it.skipIf(NO_SYMLINKS)('refuses an upload through a symlink that escapes the grant', async () => {
+    const granted = await mount(service)
+    const vfsRoot = `user-local/${encodeURIComponent(granted.name)}--${granted.id}`
+    const outside = await mkdtemp(join(tmpdir(), 'sim-localfs-outside-'))
+    await writeFile(join(outside, 'secret.txt'), 'secret')
+    await symlink(join(outside, 'secret.txt'), join(root, 'secret-link.txt'))
+
+    await expect(
+      service.resolveGrantedFile(`${vfsRoot}/secret-link.txt`, 1024)
+    ).rejects.toMatchObject({ code: 'ACCESS_DENIED' })
+  })
+
   it.each(['..', '%2e%2e', 'src%2F..%2FREADME.md', 'README.md%00'])(
     'rejects unsafe upload path segment %s',
     async (segment) => {
@@ -318,7 +332,7 @@ describe('LocalFilesystemService', () => {
     }
   )
 
-  it.each([false, true])(
+  it.skipIf(NO_SYMLINKS).each([false, true])(
     'closes a file opened through a swapped ancestor (ancestor restored: %s)',
     async (restoreAncestor) => {
       const granted = await mount(service)
diff --git a/apps/desktop/src/main/menu.ts b/apps/desktop/src/main/menu.ts
index b2234f74d5b..373aa97f80d 100644
--- a/apps/desktop/src/main/menu.ts
+++ b/apps/desktop/src/main/menu.ts
@@ -8,6 +8,7 @@ import type {
   FocusedResourceShortcut,
   ResourceTabSelectionShortcut,
 } from '@/main/resource-shortcuts'
+import { WINDOWS_TERMINAL_SHELLS, type WindowsTerminalShell } from '@/main/terminal/default-shell'
 
 const ZOOM_STEP = 0.5
 
@@ -35,6 +36,38 @@ export interface MenuDeps {
   signOut: () => void
   checkForUpdates: () => void
   openDiagnostics: () => void
+  /**
+   * Windows only: the shell new terminals launch. macOS has one answer
+   * (`$SHELL`), so the submenu exists only where there is a choice to make.
+   */
+  terminalShell?: {
+    current: () => WindowsTerminalShell
+    gitBashAvailable: () => boolean
+    select: (shell: WindowsTerminalShell) => void
+  }
+}
+
+const TERMINAL_SHELL_LABELS: Record<WindowsTerminalShell, string> = {
+  powershell: 'PowerShell',
+  'git-bash': 'Git Bash',
+}
+
+function terminalShellSubmenu(deps: MenuDeps): MenuItemConstructorOptions[] {
+  const choice = deps.terminalShell
+  if (!choice || process.platform !== 'win32') return []
+  const current = choice.current()
+  return [
+    {
+      label: 'Terminal Shell',
+      submenu: WINDOWS_TERMINAL_SHELLS.map((shell) => ({
+        label: TERMINAL_SHELL_LABELS[shell],
+        type: 'radio' as const,
+        checked: shell === current,
+        enabled: shell !== 'git-bash' || choice.gitBashAvailable(),
+        click: () => choice.select(shell),
+      })),
+    },
+  ]
 }
 
 /**
@@ -199,13 +232,19 @@ export function buildMenuTemplate(deps: MenuDeps): MenuItemConstructorOptions[]
         },
         { label: 'Settings…', accelerator: 'CmdOrCtrl+,', click: deps.openSettings },
         { label: 'Server…', click: deps.openServerSettings },
+        ...terminalShellSubmenu(deps),
         { label: 'Check for Updates…', click: deps.checkForUpdates },
         { label: 'Sign Out', click: deps.signOut },
         { type: 'separator' },
-        { role: 'hide' },
-        { role: 'hideOthers' },
-        { role: 'unhide' },
-        { type: 'separator' },
+        // The hide roles are macOS-only; elsewhere they render as blank rows.
+        ...(process.platform === 'darwin'
+          ? ([
+              { role: 'hide' },
+              { role: 'hideOthers' },
+              { role: 'unhide' },
+              { type: 'separator' },
+            ] satisfies MenuItemConstructorOptions[])
+          : []),
         { role: 'quit' },
       ],
     },
diff --git a/apps/desktop/src/main/observability.test.ts b/apps/desktop/src/main/observability.test.ts
index 82fbfce631b..9fd4e656d63 100644
--- a/apps/desktop/src/main/observability.test.ts
+++ b/apps/desktop/src/main/observability.test.ts
@@ -25,8 +25,12 @@ describe('scrubUrl', () => {
   })
 })
 
+// Windows has no POSIX mode bits: there is nothing to assert, and a chmod that
+// fails there is reported differently.
+const NO_POSIX_MODES = process.platform === 'win32'
+
 describe('createEventLog', () => {
-  it('creates its directory and log with private permissions', () => {
+  it.skipIf(NO_POSIX_MODES)('creates its directory and log with private permissions', () => {
     const root = mkdtempSync(join(tmpdir(), 'sim-desktop-events-'))
     const dir = join(root, 'logs')
     const events = createEventLog(dir)
@@ -36,21 +40,24 @@ describe('createEventLog', () => {
     expect(statSync(events.filePath).mode & 0o777).toBe(0o600)
   })
 
-  it('reports permission failures without exposing local paths or OS errors', () => {
-    const root = mkdtempSync(join(tmpdir(), 'sim-desktop-events-'))
-    const overlongDir = join(root, 'x'.repeat(300))
+  it.skipIf(NO_POSIX_MODES)(
+    'reports permission failures without exposing local paths or OS errors',
+    () => {
+      const root = mkdtempSync(join(tmpdir(), 'sim-desktop-events-'))
+      const overlongDir = join(root, 'x'.repeat(300))
 
-    const events = createEventLog(overlongDir)
-    events.record('app_launch')
+      const events = createEventLog(overlongDir)
+      events.record('app_launch')
 
-    expect(mockLogger.warn.mock.calls).toEqual([
-      ['Could not apply private desktop event-log permissions', { target: 'directory' }],
-      ['Could not apply private desktop event-log permissions', { target: 'current-log' }],
-      ['Could not apply private desktop event-log permissions', { target: 'rotated-log' }],
-    ])
-    expect(JSON.stringify(mockLogger.warn.mock.calls)).not.toContain(root)
-    expect(JSON.stringify(mockLogger.warn.mock.calls)).not.toContain('ENAMETOOLONG')
-  })
+      expect(mockLogger.warn.mock.calls).toEqual([
+        ['Could not apply private desktop event-log permissions', { target: 'directory' }],
+        ['Could not apply private desktop event-log permissions', { target: 'current-log' }],
+        ['Could not apply private desktop event-log permissions', { target: 'rotated-log' }],
+      ])
+      expect(JSON.stringify(mockLogger.warn.mock.calls)).not.toContain(root)
+      expect(JSON.stringify(mockLogger.warn.mock.calls)).not.toContain('ENAMETOOLONG')
+    }
+  )
 })
 
 describe('installMainProcessFailureObservers', () => {
diff --git a/apps/desktop/src/main/terminal/default-shell.ts b/apps/desktop/src/main/terminal/default-shell.ts
new file mode 100644
index 00000000000..d4cf857a09e
--- /dev/null
+++ b/apps/desktop/src/main/terminal/default-shell.ts
@@ -0,0 +1,98 @@
+/**
+ * Picks the shell a new terminal tab launches.
+ *
+ * POSIX hosts publish the user's login shell in `$SHELL`. Windows has no such
+ * convention: `COMSPEC` names cmd.exe, which is the shell of last resort, so
+ * PowerShell is preferred when it is installed — pwsh (PowerShell 7) first,
+ * then the Windows PowerShell 5.1 that ships with every supported Windows.
+ * Git for Windows' bash is offered as an alternative when it is installed,
+ * because the bash shell-integration hooks work in it unchanged.
+ */
+import { existsSync } from 'node:fs'
+import { delimiter, dirname, join } from 'node:path'
+
+export type WindowsTerminalShell = 'powershell' | 'git-bash'
+
+export const WINDOWS_TERMINAL_SHELLS: readonly WindowsTerminalShell[] = ['powershell', 'git-bash']
+
+export function isWindowsTerminalShell(value: unknown): value is WindowsTerminalShell {
+  return value === 'powershell' || value === 'git-bash'
+}
+
+const WINDOWS_POWERSHELL_CANDIDATES = ['pwsh.exe', 'powershell.exe'] as const
+
+/**
+ * The shell the next Windows terminal launches. Process-wide rather than
+ * threaded through every service because the choice is a device preference,
+ * like the terminal theme, and every chat scope's shells share it.
+ */
+let preferredWindowsShell: WindowsTerminalShell = 'powershell'
+
+export function setPreferredWindowsShell(shell: WindowsTerminalShell): void {
+  preferredWindowsShell = shell
+}
+
+export function getPreferredWindowsShell(): WindowsTerminalShell {
+  return preferredWindowsShell
+}
+
+function findOnPath(executable: string, env: NodeJS.ProcessEnv): string | null {
+  for (const directory of (env.PATH ?? env.Path ?? '').split(delimiter)) {
+    if (!directory) continue
+    const candidate = join(directory, executable)
+    if (existsSync(candidate)) return candidate
+  }
+  return null
+}
+
+/**
+ * Git for Windows' bash, or null when Git is not installed.
+ *
+ * Only Git's own install locations are checked. A bare `bash.exe` on PATH is
+ * not trusted: `C:\Windows\System32\bash.exe` is the WSL launcher, which runs
+ * a Linux VM rather than a shell on this machine.
+ */
+export function findGitBash(env: NodeJS.ProcessEnv = process.env): string | null {
+  const roots = [
+    env.ProgramFiles,
+    env['ProgramFiles(x86)'],
+    env.ProgramW6432,
+    env.LOCALAPPDATA ? join(env.LOCALAPPDATA, 'Programs') : undefined,
+  ]
+  for (const root of roots) {
+    if (!root) continue
+    const candidate = join(root, 'Git', 'bin', 'bash.exe')
+    if (existsSync(candidate)) return candidate
+  }
+  // A Git installed elsewhere still puts `cmd\git.exe` on PATH; bash sits
+  // beside it in the install's `bin`.
+  const git = findOnPath('git.exe', env)
+  if (git) {
+    const candidate = join(dirname(dirname(git)), 'bin', 'bash.exe')
+    if (existsSync(candidate)) return candidate
+  }
+  return null
+}
+
+function findPowerShell(env: NodeJS.ProcessEnv): string | null {
+  for (const executable of WINDOWS_POWERSHELL_CANDIDATES) {
+    const found = findOnPath(executable, env)
+    if (found) return found
+  }
+  return null
+}
+
+export function defaultShellPath(
+  env: NodeJS.ProcessEnv = process.env,
+  platform: NodeJS.Platform = process.platform,
+  preference: WindowsTerminalShell = preferredWindowsShell
+): string {
+  if (platform !== 'win32') {
+    return env.SHELL || '/bin/zsh'
+  }
+  if (preference === 'git-bash') {
+    const gitBash = findGitBash(env)
+    if (gitBash) return gitBash
+  }
+  return findPowerShell(env) ?? env.COMSPEC ?? 'cmd.exe'
+}
diff --git a/apps/desktop/src/main/terminal/session.ts b/apps/desktop/src/main/terminal/session.ts
index 4dd33ad7f43..f9031f9144b 100644
--- a/apps/desktop/src/main/terminal/session.ts
+++ b/apps/desktop/src/main/terminal/session.ts
@@ -30,6 +30,7 @@ import {
   type IBufferCell,
   type IBufferLine,
 } from '@xterm/headless'
+import { defaultShellPath } from '@/main/terminal/default-shell'
 import { readProcessCwd } from '@/main/terminal/process-cwd'
 import {
   buildShellLaunch,
@@ -351,7 +352,7 @@ export class TerminalSession {
   }
 
   static create(options: TerminalSessionOptions): TerminalSession {
-    const shellPath = process.env.SHELL || '/bin/zsh'
+    const shellPath = defaultShellPath()
     const shell = detectShell(shellPath)
     const nonce = createNonce()
     const integrationDir = mkdtempSync(join(tmpdir(), 'sim-terminal-'))
@@ -363,10 +364,11 @@ export class TerminalSession {
     const { ELECTRON_RUN_AS_NODE: _runAsNode, ...env } = process.env as Record<string, string>
 
     // A shell we cannot instrument still gives the user a working terminal;
-    // the agent is refused separately via NO_SHELL_INTEGRATION.
+    // the agent is refused separately via NO_SHELL_INTEGRATION. `-l` is the
+    // POSIX login flag; Windows shells reject it.
     const launch = shell
       ? buildShellLaunch(shell, integrationDir, nonce, env)
-      : { args: ['-l'], env: {} }
+      : { args: process.platform === 'win32' ? [] : ['-l'], env: {} }
 
     const shellEnv = { ...env, ...launch.env, TERM: 'xterm-256color', TERM_PROGRAM: 'Sim' }
     const pty = spawn(shellPath, launch.args, {
@@ -457,7 +459,7 @@ export class TerminalSession {
    * at a glance.
    */
   tabState(active: boolean): TerminalTabState {
-    const directory = this.cwd ? (this.cwd.split('/').filter(Boolean).pop() ?? '/') : null
+    const directory = this.cwd ? (this.cwd.split(/[\\/]/).filter(Boolean).pop() ?? '/') : null
     return {
       terminalId: this.terminalId,
       // The directory, always: whether to show the running command instead is
diff --git a/apps/desktop/src/main/terminal/shell-integration.test.ts b/apps/desktop/src/main/terminal/shell-integration.test.ts
index ab47bf5a8ab..b6548771de5 100644
--- a/apps/desktop/src/main/terminal/shell-integration.test.ts
+++ b/apps/desktop/src/main/terminal/shell-integration.test.ts
@@ -86,6 +86,11 @@ describe('detectShell', () => {
   it('recognises the shells we can instrument', () => {
     expect(detectShell('/bin/zsh')).toBe('zsh')
     expect(detectShell('/usr/local/bin/bash')).toBe('bash')
+    expect(detectShell('C:\\Program Files\\Git\\bin\\bash.exe')).toBe('bash')
+    expect(detectShell('C:\\WINDOWS\\System32\\WindowsPowerShell\\v1.0\\powershell.exe')).toBe(
+      'powershell'
+    )
+    expect(detectShell('C:\\Program Files\\PowerShell\\7\\pwsh.exe')).toBe('powershell')
   })
 
   it('returns null for shells without hooks, leaving the terminal uninstrumented', () => {
diff --git a/apps/desktop/src/main/terminal/shell-integration.ts b/apps/desktop/src/main/terminal/shell-integration.ts
index f69e86e1d2d..75f94d567f8 100644
--- a/apps/desktop/src/main/terminal/shell-integration.ts
+++ b/apps/desktop/src/main/terminal/shell-integration.ts
@@ -17,15 +17,18 @@
  */
 import { randomBytes } from 'node:crypto'
 import { mkdirSync, writeFileSync } from 'node:fs'
-import { basename, join } from 'node:path'
+import { join } from 'node:path'
 
 /** Shells we can install prompt hooks into. */
-export type SupportedShell = 'zsh' | 'bash'
+export type SupportedShell = 'zsh' | 'bash' | 'powershell'
 
 export function detectShell(shellPath: string): SupportedShell | null {
-  const name = basename(shellPath)
+  // Split on both separators rather than basename(): a Windows path must
+  // resolve the same way on the macOS machines that run the test suite.
+  const name = (shellPath.split(/[\\/]/).pop() ?? '').toLowerCase().replace(/\.exe$/, '')
   if (name === 'zsh' || name === '-zsh') return 'zsh'
   if (name === 'bash' || name === '-bash') return 'bash'
+  if (name === 'pwsh' || name === 'powershell') return 'powershell'
   return null
 }
 
@@ -51,10 +54,14 @@ export interface ParseResult {
   markers: ShellMarker[]
 }
 
-/** Undoes the escaping applied by the shell hooks. */
+/**
+ * Undoes the escaping applied by the shell hooks: `\\` for a backslash and
+ * `\xHH` for separators. One pass, so an escaped backslash followed by `x3b`
+ * is not mistaken for an escaped semicolon.
+ */
 function unescapeValue(value: string): string {
-  return value.replace(/\\x([0-9a-fA-F]{2})/g, (_match, hex: string) =>
-    String.fromCharCode(Number.parseInt(hex, 16))
+  return value.replace(/\\\\|\\x([0-9a-fA-F]{2})/g, (_match, hex: string | undefined) =>
+    hex === undefined ? '\\' : String.fromCharCode(Number.parseInt(hex, 16))
   )
 }
 
@@ -245,11 +252,18 @@ __sim_preexec() {
   builtin printf '\\e]633;C;%s\\a' "$__sim_nonce"
 }
 
+# Git for Windows' bash reports /c/Users/... paths; the host, and the rest of
+# the app, speak C:\\Users\\..., so the directory is translated when cygpath
+# is there to do it.
+__sim_cwd() {
+  if command -v cygpath >/dev/null 2>&1; then cygpath -w "$PWD"; else builtin printf '%s' "$PWD"; fi
+}
+
 __sim_precmd() {
   local st=$?
   # Cwd is reported before the finish marker so a \`cd\` is already visible by
   # the time the command's result is resolved.
-  builtin printf '\\e]633;P;Cwd=%s;%s\\a' "$(__sim_esc "$PWD")" "$__sim_nonce"
+  builtin printf '\\e]633;P;Cwd=%s;%s\\a' "$(__sim_esc "$(__sim_cwd)")" "$__sim_nonce"
   if [ -n "$__sim_in_cmd" ]; then
     builtin printf '\\e]633;D;%s;%s\\a' "$st" "$__sim_nonce"
   fi
@@ -265,6 +279,75 @@ PROMPT_COMMAND="__sim_precmd\${PROMPT_COMMAND:+; $PROMPT_COMMAND}"
   return rcPath
 }
 
+/**
+ * PowerShell has no preexec hook either, and its `prompt` is a plain function
+ * the host calls. The host also calls `PSConsoleHostReadLine` to read each
+ * line, so wrapping that yields the exact command text (E) and the moment it
+ * starts (C), while `prompt` reports the directory (P), the result of the
+ * previous command (D) and the new prompt (A). This is the arrangement
+ * Windows Terminal and VS Code use.
+ *
+ * The script is handed over as `-EncodedCommand` rather than a file: dot
+ * sourcing a file is subject to the machine's execution policy, which blocks
+ * scripts outright on a stock Windows client, and lowering that policy for
+ * the shell would loosen it for everything the user runs there too.
+ */
+function powerShellScript(nonce: string): string {
+  return `
+$global:__simNonce = '${nonce}'
+$global:__simInCmd = $false
+$global:__simOriginalPrompt = $function:prompt
+
+function global:__simEscape([string]$Value) {
+  return $Value.Replace('\\', '\\\\').Replace(';', '\\x3b').Replace([string][char]13, '').Replace([string][char]10, '\\x0a')
+}
+
+function global:__simMarker([string]$Body) {
+  return [string][char]27 + ']633;' + $Body + ';' + $global:__simNonce + [string][char]7
+}
+
+function global:prompt {
+  $succeeded = $?
+  $code = if ($succeeded) { 0 } elseif ($global:LASTEXITCODE) { [int]$global:LASTEXITCODE } else { 1 }
+  $location = $ExecutionContext.SessionState.Path.CurrentFileSystemLocation.ProviderPath
+  $out = __simMarker ('P;Cwd=' + (__simEscape $location))
+  if ($global:__simInCmd) {
+    $out += __simMarker ('D;' + $code)
+    $global:__simInCmd = $false
+  }
+  $original = $null
+  if ($global:__simOriginalPrompt) {
+    try { $original = [string](& $global:__simOriginalPrompt) } catch { $original = $null }
+  }
+  if (-not $original) { $original = 'PS ' + $location + '> ' }
+  return $out + (__simMarker 'A') + $original
+}
+
+function global:PSConsoleHostReadLine {
+  $line = $null
+  if (Get-Module PSReadLine) {
+    # The two-argument overload only: in PSReadLine 2.0 (Windows PowerShell
+    # 5.1) the third parameter is a CancellationToken, and a bool coerces to
+    # a cancelled one, so that call returns at once and the prompt loops.
+    $line = [Microsoft.PowerShell.PSConsoleReadLine]::ReadLine($Host.Runspace, $ExecutionContext)
+  } else {
+    $line = $Host.UI.ReadLine()
+  }
+  if ($line -and $line.Trim()) {
+    $global:__simInCmd = $true
+    [Console]::Write((__simMarker ('E;' + (__simEscape $line))) + (__simMarker 'C'))
+  }
+  return $line
+}
+
+# The agent clears a half-typed line with Ctrl-U before each command, which
+# PSReadLine's default Windows key map leaves unbound.
+if (Get-Module PSReadLine) {
+  Set-PSReadLineKeyHandler -Chord Ctrl+u -Function BackwardDeleteLine -ErrorAction SilentlyContinue
+}
+`
+}
+
 export interface ShellLaunch {
   args: string[]
   env: Record<string, string>
@@ -282,6 +365,13 @@ export function buildShellLaunch(
 ): ShellLaunch {
   mkdirSync(dir, { recursive: true })
 
+  if (shell === 'powershell') {
+    // Profiles still load (no -NoProfile), so the user's aliases and prompt
+    // come first and ours wraps theirs.
+    const encoded = Buffer.from(powerShellScript(nonce), 'utf16le').toString('base64')
+    return { args: ['-NoLogo', '-NoExit', '-EncodedCommand', encoded], env: {} }
+  }
+
   if (shell === 'zsh') {
     writeZshFiles(dir, nonce, env.ZDOTDIR || env.HOME || '')
     return {
diff --git a/bun.lock b/bun.lock
index 1b2e0623614..c48c656be77 100644
--- a/bun.lock
+++ b/bun.lock
@@ -47,8 +47,6 @@
       "version": "0.0.0",
       "dependencies": {
         "@lydell/node-pty": "1.2.0-beta.12",
-        "@lydell/node-pty-darwin-arm64": "1.2.0-beta.12",
-        "@lydell/node-pty-darwin-x64": "1.2.0-beta.12",
         "@sim/browser-protocol": "workspace:*",
         "@sim/desktop-bridge": "workspace:*",
         "@sim/logger": "workspace:*",
@@ -81,6 +79,12 @@
         "typescript": "^7.0.2",
         "vitest": "^5.0.1",
       },
+      "optionalDependencies": {
+        "@lydell/node-pty-darwin-arm64": "1.2.0-beta.12",
+        "@lydell/node-pty-darwin-x64": "1.2.0-beta.12",
+        "@lydell/node-pty-win32-arm64": "1.2.0-beta.12",
+        "@lydell/node-pty-win32-x64": "1.2.0-beta.12",
+      },
     },
     "apps/docs": {
       "name": "docs",
@@ -4786,7 +4790,7 @@
 
     "wsl-utils": ["wsl-utils@0.4.0", "", { "dependencies": { "is-wsl": "^3.1.0", "powershell-utils": "^0.1.0" } }, "sha512-9YmF+2sFEd+T7TkwlmE337F0IVzfDvDknhtpBQxxXzEOfgPphGlFYpyx0cTuCIFj8/p+sqwBYAeGxOMNSzPPDA=="],
 
-    "xlsx": ["xlsx@https://cdn.sheetjs.com/xlsx-0.20.3/xlsx-0.20.3.tgz", { "bin": { "xlsx": "./bin/xlsx.njs" } }],
+    "xlsx": ["xlsx@https://cdn.sheetjs.com/xlsx-0.20.3/xlsx-0.20.3.tgz", { "bin": { "xlsx": "./bin/xlsx.njs" } }, "sha512-oLDq3jw7AcLqKWH2AhCpVTZl8mf6X2YReP+Neh0SJUzV/BdZYjth94tG5toiMB1PPrYtxOCfaoUCkvtuH+3AJA=="],
 
     "xml": ["xml@1.0.1", "", {}, "sha512-huCv9IH9Tcf95zuYCsQraZtWnJvBtLVE0QHMOs8bWyZAFZNDcYjsPq1nEx8jKA9y+Beo9v+7OBPRisQTjinQMw=="],