fix(windows): patch playwright-core processLauncher to pass windowsHide

chrome-headless-shell is a console-subsystem exe; launched by
playwright-core from the console-less browse daemon on Windows it
allocates a visible console window per browser launch, and the
launcher force-kill path shells out to taskkill (a cmd.exe window per
kill — the node_modules twin of the vendored-copy gap in #1989).
Upstream playwright sets no windowsHide and offers no knob, so this
cannot be fixed from gstack call sites the way #2153 fixed the
polyfill spawns.

Carry a bun patchedDependencies patch adding windowsHide: true to the
launcher spawnOptions and the taskkill spawnSync options. Applies
automatically on every bun install. Tripwire test reads the INSTALLED
node_modules file so a playwright version bump that orphans the
exact-version patch key fails CI instead of silently re-flashing
consoles.

Fixes #2160.

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

browse/test/playwright-launcher-patch.test.ts

@@ -0,0 +1,52 @@
+import { describe, test, expect } from 'bun:test';
+import * as fs from 'fs';
+import * as path from 'path';
+
+// Windows console-flash guard for the Playwright browser launcher (#2151
+// follow-up; siblings: #1835, #1989).
+//
+// On Windows the browse server runs console-less (node server-node.mjs,
+// detached from the CLI). chrome-headless-shell is a console-subsystem
+// exe, so playwright-core's processLauncher spawning it without
+// windowsHide allocates a visible console window per launch, and its
+// force-kill path shells out to `taskkill` (another window). Upstream
+// playwright doesn't set windowsHide, so we carry a bun
+// `patchedDependencies` patch. These tripwires pin:
+//   1. package.json declares the patch for the installed version — if a
+//      playwright bump orphans the patch key, test 3 catches the silent
+//      regression (bun applies patches per exact version).
+//   2. the patch file itself still contains both windowsHide sites.
+//   3. the INSTALLED node_modules file actually got patched.
+
+const ROOT = path.resolve(import.meta.dir, '..', '..');
+const INSTALLED_LAUNCHER = path.join(
+  ROOT, 'node_modules', 'playwright-core', 'lib', 'server', 'utils', 'processLauncher.js',
+);
+
+describe('playwright-core processLauncher windowsHide patch', () => {
+  test('1. package.json declares a patchedDependencies entry matching the installed playwright-core version', () => {
+    const pkg = JSON.parse(fs.readFileSync(path.join(ROOT, 'package.json'), 'utf-8'));
+    const installed = JSON.parse(fs.readFileSync(
+      path.join(ROOT, 'node_modules', 'playwright-core', 'package.json'), 'utf-8',
+    ));
+    const key = `playwright-core@${installed.version}`;
+    expect(pkg.patchedDependencies?.[key]).toBeDefined();
+    expect(fs.existsSync(path.join(ROOT, pkg.patchedDependencies[key]))).toBe(true);
+  });
+
+  test('2. the patch covers both spawn sites (browser launch + taskkill)', () => {
+    const pkg = JSON.parse(fs.readFileSync(path.join(ROOT, 'package.json'), 'utf-8'));
+    const patchRel = Object.entries(pkg.patchedDependencies ?? {})
+      .find(([k]) => k.startsWith('playwright-core@'))?.[1] as string;
+    const patch = fs.readFileSync(path.join(ROOT, patchRel), 'utf-8');
+    expect(patch).toContain('+    windowsHide: true,');
+    expect(patch).toContain('{ shell: true, windowsHide: true }');
+  });
+
+  test('3. the installed processLauncher.js is actually patched', () => {
+    const src = fs.readFileSync(INSTALLED_LAUNCHER, 'utf-8');
+    const launchBlock = src.slice(src.indexOf('async function launchProcess'), src.indexOf('const spawnedProcess'));
+    expect(launchBlock).toContain('windowsHide: true');
+    expect(src).toMatch(/taskkill[^\n]*\{ shell: true, windowsHide: true \}/);
+  });
+});

bun.lock

@@ -22,6 +22,9 @@
       },
     },
   },
+  "patchedDependencies": {
+    "playwright-core@1.58.2": "patches/playwright-core@1.58.2.patch",
+  },
   "packages": {
     "@anthropic-ai/claude-agent-sdk": ["@anthropic-ai/claude-agent-sdk@0.2.117", "", { "dependencies": { "@anthropic-ai/sdk": "^0.81.0", "@modelcontextprotocol/sdk": "^1.29.0" }, "optionalDependencies": { "@anthropic-ai/claude-agent-sdk-darwin-arm64": "0.2.117", "@anthropic-ai/claude-agent-sdk-darwin-x64": "0.2.117", "@anthropic-ai/claude-agent-sdk-linux-arm64": "0.2.117", "@anthropic-ai/claude-agent-sdk-linux-arm64-musl": "0.2.117", "@anthropic-ai/claude-agent-sdk-linux-x64": "0.2.117", "@anthropic-ai/claude-agent-sdk-linux-x64-musl": "0.2.117", "@anthropic-ai/claude-agent-sdk-win32-arm64": "0.2.117", "@anthropic-ai/claude-agent-sdk-win32-x64": "0.2.117" }, "peerDependencies": { "zod": "^4.0.0" } }, "sha512-pVBss1Vu0w87nKCBhWtjMggSgCh6GVUtdRmuE58ZvXv0E2q0JcnUCQHehmn92BAW0+VCwPY8q/k7uKWkgwz/gA=="],
 

package.json

@@ -76,5 +76,8 @@
     "@anthropic-ai/sdk": "^0.78.0",
     "xterm": "5",
     "xterm-addon-fit": "^0.8.0"
+  },
+  "patchedDependencies": {
+    "playwright-core@1.58.2": "patches/playwright-core@1.58.2.patch"
   }
 }

patches/playwright-core@1.58.2.patch

@@ -0,0 +1,24 @@
+diff --git a/lib/server/utils/processLauncher.js b/lib/server/utils/processLauncher.js
+index 954d5e6fbc527e640ccec5709263374101c6340b..6913f7e9cafe6bcc57ce5a501ce05edc01d36e0c 100644
+--- a/lib/server/utils/processLauncher.js
++++ b/lib/server/utils/processLauncher.js
+@@ -112,6 +112,10 @@ async function launchProcess(options) {
+     env: options.env,
+     cwd: options.cwd,
+     shell: options.shell,
++    // gstack patch (#2151 follow-up): chrome-headless-shell is a console-
++    // subsystem exe; launched from the console-less browse daemon on
++    // Windows it allocates a visible console window without CREATE_NO_WINDOW.
++    windowsHide: true,
+     stdio
+   };
+   const spawnedProcess = childProcess.spawn(options.command, options.args || [], spawnOptions);
+@@ -191,7 +195,7 @@ async function launchProcess(options) {
+       options.log(`[pid=${spawnedProcess.pid}] <will force kill>`);
+       try {
+         if (process.platform === "win32") {
+-          const taskkillProcess = childProcess.spawnSync(`taskkill /pid ${spawnedProcess.pid} /T /F`, { shell: true });
++          const taskkillProcess = childProcess.spawnSync(`taskkill /pid ${spawnedProcess.pid} /T /F`, { shell: true, windowsHide: true });
+           const [stdout2, stderr2] = [taskkillProcess.stdout.toString(), taskkillProcess.stderr.toString()];
+           if (stdout2)
+             options.log(`[pid=${spawnedProcess.pid}] taskkill stdout: ${stdout2}`);