fix(browse): handoff() + launchHeaded() spread the shared STEALTH_LAUNCH_ARGS

handoff() built its launch args from only ['--hide-crash-restore-bubble',
...buildGStackLaunchArgs()], omitting STEALTH_LAUNCH_ARGS — so a handed-off
browser kept the --disable-blink-features=AutomationControlled tell that
launch() and launchHeaded() strip. launchHeaded() also hardcoded the flag as a
literal. Both now spread the shared constant, so the AutomationControlled flag
lives in one place across all three launch paths.

Tripwires: STEALTH_LAUNCH_ARGS spread into >= 3 sites (no inline literal) and
STEALTH_IGNORE_DEFAULT_ARGS wired into both persistent-context paths.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

browse/src/browser-manager.ts

@@ -437,12 +437,13 @@ export class BrowserManager {
 
     // Find the gstack extension directory for auto-loading
     const extensionPath = this.findExtensionPath();
-    const { buildGStackLaunchArgs } = await import('./stealth');
+    const { STEALTH_LAUNCH_ARGS, buildGStackLaunchArgs } = await import('./stealth');
     const launchArgs = [
       '--hide-crash-restore-bubble',
-      // Anti-bot-detection: remove the navigator.webdriver flag that Playwright sets.
-      // Sites like Google and NYTimes check this to block automation browsers.
-      '--disable-blink-features=AutomationControlled',
+      // Anti-bot-detection: --disable-blink-features=AutomationControlled (and any
+      // future blink-level tells) via the shared STEALTH_LAUNCH_ARGS constant — the
+      // same flag launch() and handoff() use, kept in one place instead of a literal.
+      ...STEALTH_LAUNCH_ARGS,
       // GStack Pack 1: per-install hardware/GPU/UA-CH overrides for the
       // C++ patches in gbrowser's Chromium build. Each switch is a no-op
       // on Chromium builds without the corresponding patch (the patch's
@@ -1541,8 +1542,11 @@ export class BrowserManager {
       const fs = require('fs');
       const path = require('path');
       const extensionPath = this.findExtensionPath();
-      const { buildGStackLaunchArgs } = await import('./stealth');
-      const launchArgs: string[] = ['--hide-crash-restore-bubble', ...buildGStackLaunchArgs()];
+      const { STEALTH_LAUNCH_ARGS, buildGStackLaunchArgs } = await import('./stealth');
+      // Same blink-level stealth flags as launch()/launchHeaded(). Without
+      // STEALTH_LAUNCH_ARGS the handed-off browser kept the AutomationControlled
+      // tell that the other two paths strip.
+      const launchArgs: string[] = ['--hide-crash-restore-bubble', ...STEALTH_LAUNCH_ARGS, ...buildGStackLaunchArgs()];
       if (extensionPath) {
         launchArgs.push(`--disable-extensions-except=${extensionPath}`);
         launchArgs.push(`--load-extension=${extensionPath}`);

browse/test/browser-manager-unit.test.ts

@@ -253,4 +253,40 @@ describe('stealth injected on every launch path', () => {
     const handoffBody = src.slice(handoffStart, resumeAnchor > 0 ? resumeAnchor : handoffStart + 4000);
     expect(handoffBody).toContain('applyStealth(');
   });
+
+  it('buildGStackLaunchArgs() is spread into all 3 launch sites', async () => {
+    // Same silent-drop regression class as applyStealth: a launch path that
+    // omits buildGStackLaunchArgs() loses the per-install GPU/UA/hardware
+    // cmdline spoof. launch(), launchHeaded(), and handoff() must all call it.
+    const { readFileSync } = await import('node:fs');
+    const { join } = await import('node:path');
+    const src = readFileSync(join(import.meta.dir, '..', 'src', 'browser-manager.ts'), 'utf-8');
+    const callSites = src.match(/buildGStackLaunchArgs\(\)/g) || [];
+    expect(callSites.length).toBeGreaterThanOrEqual(3);
+  });
+
+  it('STEALTH_LAUNCH_ARGS is spread into all 3 launch sites (no hardcoded literal)', async () => {
+    // The --disable-blink-features=AutomationControlled flag must come from the
+    // shared constant on launch(), launchHeaded(), AND handoff(). handoff()
+    // previously omitted it, leaving the AutomationControlled tell on the
+    // handed-off browser. No path may inline the literal instead.
+    const { readFileSync } = await import('node:fs');
+    const { join } = await import('node:path');
+    const src = readFileSync(join(import.meta.dir, '..', 'src', 'browser-manager.ts'), 'utf-8');
+    const spreads = src.match(/\.\.\.STEALTH_LAUNCH_ARGS/g) || [];
+    expect(spreads.length).toBeGreaterThanOrEqual(3);
+    // The literal must not be reintroduced in a launchArgs array (it belongs in
+    // the STEALTH_LAUNCH_ARGS constant in stealth.ts, not inline here).
+    expect(src).not.toContain("'--disable-blink-features=AutomationControlled'");
+  });
+
+  it('STEALTH_IGNORE_DEFAULT_ARGS is wired into both persistent-context paths', async () => {
+    // launchHeaded() and handoff() both launchPersistentContext and must strip
+    // Playwright's automation-tell defaults via the shared constant.
+    const { readFileSync } = await import('node:fs');
+    const { join } = await import('node:path');
+    const src = readFileSync(join(import.meta.dir, '..', 'src', 'browser-manager.ts'), 'utf-8');
+    const sites = src.match(/ignoreDefaultArgs:\s*STEALTH_IGNORE_DEFAULT_ARGS/g) || [];
+    expect(sites.length).toBeGreaterThanOrEqual(2);
+  });
 });