diff --git a/app/src/main/hl/engines/pathEnrich.ts b/app/src/main/hl/engines/pathEnrich.ts
index 6f47b2e8..e918afe9 100644
--- a/app/src/main/hl/engines/pathEnrich.ts
+++ b/app/src/main/hl/engines/pathEnrich.ts
@@ -246,14 +246,15 @@ function findOnWindowsPath(name: string, env: NodeJS.ProcessEnv): string | null
   // PATHEXT is the canonical search order. We always check `.exe` first so
   // a native binary wins over an npm shim with the same stem.
   const pathExt = (env.PATHEXT ?? '.COM;.EXE;.BAT;.CMD').split(';').map((e) => e.toLowerCase()).filter(Boolean);
-  // Always include .ps1 since npm-installed global CLIs may ship as PowerShell
-  // scripts on Windows (e.g. Claude Code's claude.ps1). Insert it before .bat/.cmd
-  // so native binaries still win, but working .ps1 shims take precedence over
-  // potentially broken/dummy .cmd stubs generated by older npm versions.
+  // npm-installed global CLIs typically ship .cmd, .ps1, AND a sh wrapper
+  // (e.g. claude.cmd + claude.ps1). When both .cmd and .ps1 are present we
+  // route through cmd.exe — it's already on COMSPEC, doesn't depend on
+  // env.Path-based powershell.exe lookup (which has been observed to fail
+  // with ENOENT inside Electron's main process), and avoids PowerShell's
+  // cold-start cost (~1-2s + Defender script scan). .ps1 stays as a
+  // fallback for packages that ship only PowerShell shims.
   if (!pathExt.includes('.ps1')) {
-    const batIdx = pathExt.findIndex((e) => e === '.bat' || e === '.cmd');
-    if (batIdx >= 0) pathExt.splice(batIdx, 0, '.ps1');
-    else pathExt.push('.ps1');
+    pathExt.push('.ps1');
   }
   const exts = name.includes('.') && pathExt.includes(path.win32.extname(name).toLowerCase())
     ? ['']
@@ -313,8 +314,16 @@ export function resolveCliSpawn(
   if (ext === '.ps1') {
     // PowerShell scripts: route through powershell.exe so execution policy
     // and profile loading don't block npm-installed CLIs like claude.ps1.
+    // Use the absolute path under %SystemRoot% rather than relying on
+    // env.Path / Path: Electron's main process has been observed to spawn
+    // with `spawn powershell.exe ENOENT` even when the WindowsPowerShell
+    // dir is on the system PATH, because libuv on Windows reads the env
+    // block's `Path` key (capitalized) and our enriched env may only
+    // expose `PATH`. The absolute path sidesteps that lookup entirely.
+    const systemRoot = env.SystemRoot ?? env.SYSTEMROOT ?? 'C:\\Windows';
+    const absPwsh = path.win32.join(systemRoot, 'System32', 'WindowsPowerShell', 'v1.0', 'powershell.exe');
     return {
-      command: 'powershell.exe',
+      command: absPwsh,
       args: ['-ExecutionPolicy', 'Bypass', '-NoProfile', '-File', resolved, ...args],
       viaCmdShell: false,
       spawnOptions: {},
diff --git a/app/src/main/hl/stock/browser-harness-js/sdk/browser-harness-js.cmd b/app/src/main/hl/stock/browser-harness-js/sdk/browser-harness-js.cmd
new file mode 100644
index 00000000..e91e699d
--- /dev/null
+++ b/app/src/main/hl/stock/browser-harness-js/sdk/browser-harness-js.cmd
@@ -0,0 +1,44 @@
+@echo off
+rem browser-harness-js Windows launcher — runs the bundled bash script under
+rem Git for Windows' bash.exe. The script is POSIX-only (curl, nohup, /tmp,
+rem bun bootstrap) so we delegate to bash rather than re-implement in cmd.exe.
+rem
+rem Discovery order:
+rem   1. %BROWSER_HARNESS_JS_BASH% (explicit env override)
+rem   2. %ProgramFiles%\Git\bin\bash.exe
+rem   3. %ProgramFiles(x86)%\Git\bin\bash.exe
+rem   4. %LocalAppData%\Programs\Git\bin\bash.exe   (per-user install)
+rem
+rem Without Git for Windows, exits 1 with a stderr hint so the agent sees a
+rem clean error instead of triggering Windows' "Open with..." association
+rem dialog on the extensionless bash script next to this file.
+
+setlocal
+
+set "SCRIPT_DIR=%~dp0"
+set "BASH_SCRIPT=%SCRIPT_DIR%browser-harness-js"
+
+rem `exit /b` (no arg) propagates the *current* ERRORLEVEL. Inside a
+rem parenthesized block, `exit /b %errorlevel%` would expand at parse time
+rem and silently report 0 even if bash failed.
+
+if defined BROWSER_HARNESS_JS_BASH (
+  if exist "%BROWSER_HARNESS_JS_BASH%" (
+    "%BROWSER_HARNESS_JS_BASH%" "%BASH_SCRIPT%" %*
+    exit /b
+  )
+)
+
+for %%P in (
+  "%ProgramFiles%\Git\bin\bash.exe"
+  "%ProgramFiles(x86)%\Git\bin\bash.exe"
+  "%LocalAppData%\Programs\Git\bin\bash.exe"
+) do (
+  if exist %%P (
+    %%P "%BASH_SCRIPT%" %*
+    exit /b
+  )
+)
+
+>&2 echo browser-harness-js: bash.exe not found. Install Git for Windows from https://gitforwindows.org/ or set BROWSER_HARNESS_JS_BASH to a bash.exe path.
+exit /b 1
diff --git a/app/src/renderer/hub/ConnectionsPane.tsx b/app/src/renderer/hub/ConnectionsPane.tsx
index 417cd7ec..881d0497 100644
--- a/app/src/renderer/hub/ConnectionsPane.tsx
+++ b/app/src/renderer/hub/ConnectionsPane.tsx
@@ -1181,6 +1181,15 @@ export function ConnectionsPane({
 
       </section>
 
+      {/*
+        Cookie sync is unsupported on Windows: Chromium 127+ uses App-Bound
+        Encryption (v20) tied to the original user-data-dir, so a temp-copy
+        profile decrypts to nothing, and launching headless against the real
+        profile is blocked by the Chromium DevTools hardening that refuses
+        --remote-debugging-port for the default user-data-dir. Hide the
+        section entirely on win32 until we have a native v20 decryption path.
+      */}
+      {window.electronAPI?.shell?.platform !== 'win32' && (
       <section
         id={browserSyncSectionId}
         className={embedded ? 'settings-page__section' : 'conn-pane__group'}
@@ -1210,6 +1219,7 @@ export function ConnectionsPane({
         </div>
       )}
       </section>
+      )}
     </div>
   );
 }
diff --git a/app/src/renderer/hub/SettingsPane.tsx b/app/src/renderer/hub/SettingsPane.tsx
index 629f5307..8d1fe693 100644
--- a/app/src/renderer/hub/SettingsPane.tsx
+++ b/app/src/renderer/hub/SettingsPane.tsx
@@ -418,6 +418,11 @@ export function SettingsPane({ intent, keybindings, overrides, onUpdateBinding,
   const scrollerRef = useRef<HTMLDivElement>(null);
   const [activeSection, setActiveSection] = useState<SettingsSectionId>('settings-application');
   const platform = window.electronAPI?.shell?.platform ?? fallbackShortcutPlatform();
+  // Cookie sync is unsupported on Windows (Chromium ABE + DevTools hardening),
+  // so the Browser Sync tab + section are hidden on win32.
+  const tabs = platform === 'win32'
+    ? SETTINGS_TABS.filter((tab) => tab.id !== 'settings-browser-sync')
+    : SETTINGS_TABS;
 
   const scrollToSection = useCallback((id: SettingsSectionId, behavior: ScrollBehavior = 'smooth') => {
     const scroller = scrollerRef.current;
@@ -434,14 +439,14 @@ export function SettingsPane({ intent, keybindings, overrides, onUpdateBinding,
   const updateActiveFromScroll = useCallback(() => {
     const scroller = scrollerRef.current;
     if (!scroller) return;
-    let next = SETTINGS_TABS[0].id;
+    let next = tabs[0].id;
     const threshold = scroller.scrollTop + 112;
-    for (const tab of SETTINGS_TABS) {
+    for (const tab of tabs) {
       const section = scroller.querySelector<HTMLElement>(`#${tab.id}`);
       if (section && section.offsetTop <= threshold) next = tab.id;
     }
     setActiveSection(next);
-  }, []);
+  }, [tabs]);
 
   useEffect(() => {
     const sectionId = intent?.sectionId ?? (
@@ -467,7 +472,7 @@ export function SettingsPane({ intent, keybindings, overrides, onUpdateBinding,
           </header>
 
           <nav className="settings-page__tabs" aria-label="Settings sections">
-            {SETTINGS_TABS.map((tab) => (
+            {tabs.map((tab) => (
               <button
                 key={tab.id}
                 type="button"
diff --git a/app/src/renderer/onboarding/OnboardingApp.tsx b/app/src/renderer/onboarding/OnboardingApp.tsx
index 48acb25a..b1d14aec 100644
--- a/app/src/renderer/onboarding/OnboardingApp.tsx
+++ b/app/src/renderer/onboarding/OnboardingApp.tsx
@@ -252,6 +252,28 @@ function PreferencesStep({
 
 const VALID_STEPS: readonly Step[] = ['intro', 'profile', 'apikey', 'notifications', 'shortcut'];
 
+// Cookie sync is unsupported on Windows: Chromium 127+ uses App-Bound
+// Encryption (v20) keyed to the original user-data-dir, so a temp-copy
+// profile decrypts to nothing, and the alternative path of launching
+// headless against the real profile is blocked by the Chromium DevTools
+// hardening that refuses --remote-debugging-port for the default profile.
+// We hide the onboarding step + Settings card on Windows until we have a
+// native v20 decryption path.
+const COOKIE_SYNC_SUPPORTED = typeof window !== 'undefined'
+  && window.onboardingAPI?.platform !== 'win32';
+
+const IS_WINDOWS = typeof window !== 'undefined'
+  && window.onboardingAPI?.platform === 'win32';
+
+// On Windows we don't run the engine installers ourselves: the npm-install
+// scripts shell out through cmd.exe in ways that have been unreliable on
+// real user machines, so we instead copy the command to the user's
+// clipboard and poll detect-IPC until they finish running it manually.
+const ENGINE_INSTALL_COMMANDS: Record<InstallableOnboardingEngine, string> = {
+  'claude-code': 'npm install -g @anthropic-ai/claude-code',
+  codex: 'npm install -g @openai/codex',
+};
+
 export function OnboardingApp() {
   const [step, setStep] = useState<Step>('intro');
   const [hydrated, setHydrated] = useState(false);
@@ -265,7 +287,14 @@ export function OnboardingApp() {
       if (cancelled) return;
       const candidate = state?.lastStep;
       if (candidate && (VALID_STEPS as readonly string[]).includes(candidate)) {
-        setStep(candidate as Step);
+        // If a previous run persisted lastStep === 'profile' (e.g. on a
+        // different platform, or before cookie sync was disabled here),
+        // skip past it on win32 so the user doesn't land on a hidden step.
+        if (candidate === 'profile' && !COOKIE_SYNC_SUPPORTED) {
+          setStep('apikey');
+        } else {
+          setStep(candidate as Step);
+        }
       }
       setHydrated(true);
     }).catch(() => { setHydrated(true); });
@@ -557,6 +586,33 @@ export function OnboardingApp() {
     void handleInstallEngine('codex');
   }, [handleInstallEngine]);
 
+  // Windows-only: copy the npm install command to the clipboard, then poll
+  // the detect-IPC until the user has run it themselves. We don't spawn the
+  // installer ourselves on win32 because the cmd.exe path-out has been
+  // unreliable. The polling reuses `waitForInstalledStatus` (~2 min window).
+  const handleManualInstallEngine = useCallback(async (engineId: InstallableOnboardingEngine) => {
+    if (installingEnginesRef.current[engineId]) return;
+    try {
+      await navigator.clipboard.writeText(ENGINE_INSTALL_COMMANDS[engineId]);
+    } catch (err) {
+      console.warn('[onboarding] manual install: clipboard write failed', err);
+    }
+    setEngineInstalling(engineId, true);
+    try {
+      await waitForInstalledStatus(engineId);
+    } finally {
+      setEngineInstalling(engineId, false);
+    }
+  }, [setEngineInstalling, waitForInstalledStatus]);
+
+  const handleManualInstallClaudeCode = useCallback(() => {
+    void handleManualInstallEngine('claude-code');
+  }, [handleManualInstallEngine]);
+
+  const handleManualInstallCodex = useCallback(() => {
+    void handleManualInstallEngine('codex');
+  }, [handleManualInstallEngine]);
+
   const claudeCodeReady = Boolean(claudeCode?.installed && claudeCode.authed);
   const codexReady = Boolean(codex?.installed && codex.authed);
   const hasUsableAnthropicKey = Boolean(claudeCode?.installed && apiKey.trim());
@@ -830,7 +886,9 @@ export function OnboardingApp() {
 
       <div className={`onboarding-content ${step === 'intro' ? 'onboarding-content-wide' : ''}`}>
         <div className="step-indicator">
-          {(['intro', 'profile', 'apikey', 'notifications', 'shortcut'] as Step[]).map((s, i, all) => {
+          {((COOKIE_SYNC_SUPPORTED
+            ? ['intro', 'profile', 'apikey', 'notifications', 'shortcut']
+            : ['intro', 'apikey', 'notifications', 'shortcut']) as Step[]).map((s, i, all) => {
             const currentIdx = all.indexOf(step);
             const thisIdx = i;
             const cls = thisIdx < currentIdx ? 'done' : thisIdx === currentIdx ? 'active' : '';
@@ -851,7 +909,10 @@ export function OnboardingApp() {
                 <p className="intro-subtitle">
                   Run AI agents that browse the web, complete tasks, and report back — all from your desktop.
                 </p>
-                <button className="btn btn-primary intro-cta" onClick={() => setStep('profile')}>
+                <button
+                  className="btn btn-primary intro-cta"
+                  onClick={() => setStep(COOKIE_SYNC_SUPPORTED ? 'profile' : 'apikey')}
+                >
                   Get started
                 </button>
               </div>
@@ -1083,7 +1144,7 @@ export function OnboardingApp() {
                     <button
                       type="button"
                       className="provider-card__action"
-                      onClick={handleInstallClaudeCode}
+                      onClick={IS_WINDOWS ? handleManualInstallClaudeCode : handleInstallClaudeCode}
                       disabled={installingClaudeCode}
                     >
                       <div className="claude-code-card__icon">
@@ -1091,10 +1152,16 @@ export function OnboardingApp() {
                       </div>
                       <div className="claude-code-card__text">
                         <div className="claude-code-card__title">
-                          {installingClaudeCode ? 'Installing Claude Code…' : 'Install Claude Code'}
+                          {installingClaudeCode
+                            ? (IS_WINDOWS ? 'Waiting for Claude Code…' : 'Installing Claude Code…')
+                            : (IS_WINDOWS ? 'Copy install command' : 'Install Claude Code')}
                         </div>
                         <div className="claude-code-card__sub">
-                          Runs the installer in the background. We’ll detect it when it finishes.
+                          {IS_WINDOWS
+                            ? (installingClaudeCode
+                              ? `Run ${ENGINE_INSTALL_COMMANDS['claude-code']} in your terminal — we’ll detect it when it finishes.`
+                              : `Click to copy ${ENGINE_INSTALL_COMMANDS['claude-code']}. Paste it into PowerShell, and we’ll detect when it finishes.`)
+                            : 'Runs the installer in the background. We’ll detect it when it finishes.'}
                         </div>
                       </div>
                       <div className="claude-code-card__chevron">{installingClaudeCode ? '\u2026' : '\u203A'}</div>
@@ -1174,7 +1241,7 @@ export function OnboardingApp() {
                     <button
                       type="button"
                       className="provider-card__action"
-                      onClick={handleInstallCodex}
+                      onClick={IS_WINDOWS ? handleManualInstallCodex : handleInstallCodex}
                       disabled={installingCodex}
                     >
                       <div className="claude-code-card__icon">
@@ -1182,10 +1249,16 @@ export function OnboardingApp() {
                       </div>
                       <div className="claude-code-card__text">
                         <div className="claude-code-card__title">
-                          {installingCodex ? 'Installing Codex…' : 'Install Codex CLI'}
+                          {installingCodex
+                            ? (IS_WINDOWS ? 'Waiting for Codex…' : 'Installing Codex…')
+                            : (IS_WINDOWS ? 'Copy install command' : 'Install Codex CLI')}
                         </div>
                         <div className="claude-code-card__sub">
-                          Runs the installer in the background. We’ll detect it when it finishes.
+                          {IS_WINDOWS
+                            ? (installingCodex
+                              ? `Run ${ENGINE_INSTALL_COMMANDS.codex} in your terminal — we’ll detect it when it finishes.`
+                              : `Click to copy ${ENGINE_INSTALL_COMMANDS.codex}. Paste it into PowerShell, and we’ll detect when it finishes.`)
+                            : 'Runs the installer in the background. We’ll detect it when it finishes.'}
                         </div>
                       </div>
                       <div className="claude-code-card__chevron">{installingCodex ? '\u2026' : '\u203A'}</div>
@@ -1280,7 +1353,10 @@ export function OnboardingApp() {
               </button>
             </div>
 
-            <button className="back-btn" onClick={() => setStep('profile')}>
+            <button
+              className="back-btn"
+              onClick={() => setStep(COOKIE_SYNC_SUPPORTED ? 'profile' : 'intro')}
+            >
               Back
             </button>
           </div>
diff --git a/app/tests/unit/hl/codexStdinWindows.test.ts b/app/tests/unit/hl/codexStdinWindows.test.ts
index fb6f9c1a..265b99a5 100644
--- a/app/tests/unit/hl/codexStdinWindows.test.ts
+++ b/app/tests/unit/hl/codexStdinWindows.test.ts
@@ -16,7 +16,12 @@ const MULTILINE_PROMPT = [
 ].join('\n');
 
 describe.skipIf(!onWindows)('codex stdin path on Windows', () => {
-  it('resolves bcode PowerShell shims before cmd/bat shims', () => {
+  it('prefers cmd shims over PowerShell shims when both exist', () => {
+    // npm-installed CLIs typically ship both .cmd and .ps1 (e.g. codex.cmd +
+    // codex.ps1). We pick .cmd as the tiebreaker because cmd.exe is always
+    // on COMSPEC and avoids powershell.exe's cold-start cost (and its
+    // observed `spawn powershell.exe ENOENT` failures from Electron's main
+    // process). The .ps1-only fallback is exercised by the next test.
     const tmpRaw = fs.mkdtempSync(path.join(os.tmpdir(), 'bcode-shim-'));
     const tmp = fs.realpathSync.native(tmpRaw);
     const ps1 = path.join(tmp, 'bcode.ps1');
@@ -31,7 +36,28 @@ describe.skipIf(!onWindows)('codex stdin path on Windows', () => {
     };
     const resolved = resolveCliSpawn('bcode', ['--version'], { env, platform: 'win32' });
 
-    expect(resolved.command).toBe('powershell.exe');
+    expect(resolved.command.toLowerCase()).toMatch(/cmd\.exe$/);
+    expect(resolved.viaCmdShell).toBe(true);
+    expect(resolved.spawnOptions).toEqual({ windowsVerbatimArguments: true });
+    expect(resolved.args[3]).toContain(cmd);
+  });
+
+  it('falls back to PowerShell when only a .ps1 shim exists', () => {
+    const tmpRaw = fs.mkdtempSync(path.join(os.tmpdir(), 'bcode-ps1-only-'));
+    const tmp = fs.realpathSync.native(tmpRaw);
+    const ps1 = path.join(tmp, 'bcode.ps1');
+    fs.writeFileSync(ps1, 'Write-Output "bcode ps1"', 'utf-8');
+
+    const env = {
+      ...process.env,
+      Path: `${tmp};${process.env.Path ?? ''}`,
+      PATHEXT: '.COM;.EXE;.BAT;.CMD',
+    };
+    const resolved = resolveCliSpawn('bcode', ['--version'], { env, platform: 'win32' });
+
+    // Absolute path to powershell.exe under %SystemRoot%, not bare
+    // 'powershell.exe' — main-process spawns have ENOENTed on the bare name.
+    expect(resolved.command.toLowerCase()).toMatch(/system32[\\/]+windowspowershell[\\/]+v1\.0[\\/]+powershell\.exe$/);
     expect(resolved.args).toEqual(['-ExecutionPolicy', 'Bypass', '-NoProfile', '-File', ps1, '--version']);
     expect(resolved.spawnOptions).toEqual({});
   });
diff --git a/app/tests/unit/hl/harnessBootstrap.test.ts b/app/tests/unit/hl/harnessBootstrap.test.ts
index 71521101..bb0d0e96 100644
--- a/app/tests/unit/hl/harnessBootstrap.test.ts
+++ b/app/tests/unit/hl/harnessBootstrap.test.ts
@@ -42,11 +42,21 @@ describe('bootstrapHarness browser-harness-js materialization', () => {
     bootstrapHarness();
 
     const cli = path.join(browserHarnessJsDir(), 'sdk', 'browser-harness-js');
+    const cliCmd = path.join(browserHarnessJsDir(), 'sdk', 'browser-harness-js.cmd');
     expect(fs.existsSync(helpersPath())).toBe(true);
     expect(fs.readFileSync(skillPath(), 'utf-8')).toContain('Browser Harness JS');
     expect(fs.existsSync(toolsPath())).toBe(false);
     expect(fs.existsSync(cli)).toBe(true);
-    expect(fs.statSync(cli).mode & 0o111).not.toBe(0);
+    // Windows launcher ships alongside the bash script so Codex can find it
+    // via PATHEXT (.CMD) instead of hitting the no-handler popup on the
+    // extensionless bash file.
+    expect(fs.existsSync(cliCmd)).toBe(true);
+    expect(fs.readFileSync(cliCmd, 'utf-8')).toContain('bash.exe');
     expect(fs.existsSync(path.join(interactionSkillsDir(), 'screenshots.md'))).toBe(true);
+    // Executable-bit assert: skipped on Windows because NTFS permission
+    // mapping doesn't expose POSIX exec bits the way the test asserts.
+    if (process.platform !== 'win32') {
+      expect(fs.statSync(cli).mode & 0o111).not.toBe(0);
+    }
   });
 });