fix(open-gstack-browser): pre-flight cleanup never killed the stale daemon

Step 0 read the old pid with `grep -o '"pid":[0-9]*'` and Step 2 read the port
the same way. Neither can match. Every writer of that file in
browse/src/server.ts serializes with `JSON.stringify(state, null, 2)`, so the
bytes on disk are `"pid": 12060` — colon, space, digits.

The failure was silent in the worst way. `_OLD_PID` came back empty, the kill
never ran, browse.json was deleted anyway, and the next `connect` died with
"existing daemon has different config (proxy/headed mismatch)" — an error
pointing at proxy/headed flags rather than at the cleanup that no-opped. Caught
against a daemon left over from a reboot: the operator was told to check flags
they had never passed.

Both patterns now accept optional whitespace. The new tripwire does not match
strings — it RUNS the snippets the skill hands the agent, against a state file
written exactly the way the server writes one, and asserts pid and port come
back out. A third case pins the coupling to `JSON.stringify(state, null, 2)`,
so a switch to compact JSON surfaces as a failing expectation rather than as
silence.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0111Mq3JGwZDcstn5wYcbhSw

open-gstack-browser/SKILL.md

@@ -210,7 +210,7 @@ positives and Chromium profile lock conflicts.
 ```bash
 # Kill any existing browse server
 if [ -f "$(git rev-parse --show-toplevel 2>/dev/null)/.gstack/browse.json" ]; then
-  _OLD_PID=$(cat "$(git rev-parse --show-toplevel)/.gstack/browse.json" 2>/dev/null | grep -o '"pid":[0-9]*' | grep -o '[0-9]*')
+  _OLD_PID=$(cat "$(git rev-parse --show-toplevel)/.gstack/browse.json" 2>/dev/null | grep -o '"pid":[[:space:]]*[0-9]*' | grep -o '[0-9]*')
   [ -n "$_OLD_PID" ] && kill "$_OLD_PID" 2>/dev/null || true
   sleep 1
   [ -n "$_OLD_PID" ] && kill -9 "$_OLD_PID" 2>/dev/null || true
@@ -255,7 +255,7 @@ $B status
 Confirm the output shows `Mode: headed`. Read the port from the state file:
 
 ```bash
-cat "$(git rev-parse --show-toplevel 2>/dev/null)/.gstack/browse.json" 2>/dev/null | grep -o '"port":[0-9]*' | grep -o '[0-9]*'
+cat "$(git rev-parse --show-toplevel 2>/dev/null)/.gstack/browse.json" 2>/dev/null | grep -o '"port":[[:space:]]*[0-9]*' | grep -o '[0-9]*'
 ```
 
 The port should be **34567**. If it's different, note it — the user may need it

open-gstack-browser/SKILL.md.tmpl

@@ -39,7 +39,7 @@ positives and Chromium profile lock conflicts.
 ```bash
 # Kill any existing browse server
 if [ -f "$(git rev-parse --show-toplevel 2>/dev/null)/.gstack/browse.json" ]; then
-  _OLD_PID=$(cat "$(git rev-parse --show-toplevel)/.gstack/browse.json" 2>/dev/null | grep -o '"pid":[0-9]*' | grep -o '[0-9]*')
+  _OLD_PID=$(cat "$(git rev-parse --show-toplevel)/.gstack/browse.json" 2>/dev/null | grep -o '"pid":[[:space:]]*[0-9]*' | grep -o '[0-9]*')
   [ -n "$_OLD_PID" ] && kill "$_OLD_PID" 2>/dev/null || true
   sleep 1
   [ -n "$_OLD_PID" ] && kill -9 "$_OLD_PID" 2>/dev/null || true
@@ -84,7 +84,7 @@ $B status
 Confirm the output shows `Mode: headed`. Read the port from the state file:
 
 ```bash
-cat "$(git rev-parse --show-toplevel 2>/dev/null)/.gstack/browse.json" 2>/dev/null | grep -o '"port":[0-9]*' | grep -o '[0-9]*'
+cat "$(git rev-parse --show-toplevel 2>/dev/null)/.gstack/browse.json" 2>/dev/null | grep -o '"port":[[:space:]]*[0-9]*' | grep -o '[0-9]*'
 ```
 
 The port should be **34567**. If it's different, note it — the user may need it

test/skill-browse-state-extraction.test.ts

@@ -0,0 +1,77 @@
+import { describe, test, expect } from 'bun:test';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { execFileSync } from 'child_process';
+
+// Tripwire for the pid/port extraction snippets in /open-gstack-browser.
+//
+// Step 0 (pre-flight cleanup) reads the stale daemon's pid out of
+// .gstack/browse.json to kill it; Step 2 reads the port back to tell the user
+// which one the Side Panel needs. Both used `grep -o '"pid":[0-9]*'`, which
+// cannot match: every writer of that file in browse/src/server.ts serializes
+// with `JSON.stringify(state, null, 2)`, so the real bytes are `"pid": 12060`
+// — colon, SPACE, digits.
+//
+// The failure was silent in the worst way. `_OLD_PID` came back empty, the
+// `kill` never ran, browse.json was deleted anyway, and the next `connect`
+// died with "existing daemon has different config (proxy/headed mismatch)"
+// — an error that points at proxy/headed flags, not at the cleanup that
+// no-opped. Observed 2026-08-28 against a daemon left over from a reboot.
+//
+// So this test does not match strings; it RUNS the snippets the skill tells
+// the agent to run, against a state file written exactly the way the server
+// writes one, and asserts the values come back out.
+
+const ROOT = path.resolve(import.meta.dir, '..');
+const SKILL = path.join(ROOT, 'open-gstack-browser', 'SKILL.md');
+const TMPL = path.join(ROOT, 'open-gstack-browser', 'SKILL.md.tmpl');
+
+/** The exact shape browse/src/server.ts writes (JSON.stringify(state, null, 2)). */
+function writeStateFile(dir: string, pid: number, port: number): string {
+  const file = path.join(dir, 'browse.json');
+  fs.writeFileSync(
+    file,
+    JSON.stringify({ pid, port, token: 'not-a-real-token', mode: 'headed' }, null, 2),
+  );
+  return file;
+}
+
+/** Pull the grep pipeline for `field` out of the skill prose and run it. */
+function extractViaSkill(source: string, field: 'pid' | 'port', stateFile: string): string {
+  const line = source
+    .split('\n')
+    .find((l) => l.includes(`grep -o '"${field}":`));
+  expect(line, `no ${field} extraction line found in the skill`).toBeDefined();
+
+  // Keep only the pipeline itself: everything from the first `grep` on, so the
+  // surrounding shell (cat of a git-root path, variable assignment) does not
+  // have to be reproduced here.
+  const pipeline = line!.slice(line!.indexOf('grep -o'));
+  const script = `cat ${JSON.stringify(stateFile)} | ${pipeline.replace(/\)$/, '')}`;
+  return execFileSync('bash', ['-c', script], { encoding: 'utf-8' }).trim();
+}
+
+describe('/open-gstack-browser state-file extraction', () => {
+  for (const [label, file] of [['generated', SKILL], ['template', TMPL]] as const) {
+    test(`${label}: pid and port survive the pretty-printed state file`, () => {
+      const source = fs.readFileSync(file, 'utf-8');
+      const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'browse-state-'));
+      try {
+        const stateFile = writeStateFile(dir, 12060, 34567);
+        expect(extractViaSkill(source, 'pid', stateFile)).toBe('12060');
+        expect(extractViaSkill(source, 'port', stateFile)).toBe('34567');
+      } finally {
+        fs.rmSync(dir, { recursive: true, force: true });
+      }
+    });
+  }
+
+  test('server.ts still writes the state file pretty-printed', () => {
+    // If a refactor ever switches to compact JSON, the snippets above keep
+    // working (the pattern tolerates zero spaces too) — but the reason this
+    // test exists changes, so make the coupling visible instead of implicit.
+    const server = fs.readFileSync(path.join(ROOT, 'browse', 'src', 'server.ts'), 'utf-8');
+    expect(server).toContain('JSON.stringify(state, null, 2)');
+  });
+});