gstack/browse/src/server.ts

/**
 * gstack browse server — persistent Chromium daemon
 *
 * Architecture:
 *   Bun.serve HTTP on localhost → routes commands to Playwright
 *   Console/network/dialog buffers: CircularBuffer in-memory + async disk flush
 *   Chromium crash → server EXITS with clear error (CLI auto-restarts)
 *   Auto-shutdown after BROWSE_IDLE_TIMEOUT (default 30 min)
 *
 * State:
 *   State file: <project-root>/.gstack/browse.json (set via BROWSE_STATE_FILE env)
 *   Log files:  <project-root>/.gstack/browse-{console,network,dialog}.log
 *   Port:       random 10000-60000 (or BROWSE_PORT env for debug override)
 */

import { BrowserManager, markDaemonProcess } from './browser-manager';
import { handleReadCommand, hasOutArg } from './read-commands';
import { handleWriteCommand } from './write-commands';
import { handleMetaCommand } from './meta-commands';
import { hasActivePicker } from './cookie-picker-routes';
import { COMMAND_DESCRIPTIONS, PAGE_CONTENT_COMMANDS, DOM_CONTENT_COMMANDS, wrapUntrustedContent, canonicalizeCommand, buildUnknownCommandError, ALL_COMMANDS } from './commands';
import {
  wrapUntrustedPageContent, datamarkContent,
  runContentFilters, type ContentFilterResult,
  markHiddenElements, getCleanTextWithStripping, cleanupHiddenMarkers,
} from './content-security';
import { writeSecureFile, mkdirSecure, appendSecureFile } from './file-permissions';
import { handleSnapshot, SNAPSHOT_FLAGS } from './snapshot';
import {
  initRegistry, validateToken as validateScopedToken, checkScope, checkDomain,
  checkRate, recordCommand, isRootToken, type TokenInfo,
} from './token-registry';
import { resolveConfig, ensureStateDir, readVersionHash, resolveChromiumProfile, cleanSingletonLocks, isPairAgentEnabled } from './config';
import {
  isSessionPersistEnabled, persistSessionState, restoreSessionState,
  sessionPersistIntervalMs, SESSION_STATE_FILE,
} from './session-persist';
import { emitActivity } from './activity';
import { initAuditLog, writeAuditEntry } from './audit';
import { detachSession } from './cdp-inspector';
// Bun.spawn used instead of child_process.spawn (compiled bun binaries
// fail posix_spawn on all executables including /bin/bash)
import { safeUnlink, safeUnlinkQuiet, safeKill } from './error-handling';
import {
  findAvailablePort, formatExplicitPortUnavailableError, formatRandomPortUnavailableError,
} from './port-allocator';
import { acquireAgentStateLock, readAgentRecord, clearAgentRecord, isOurAgent, isAgentRecordLive, isAgentRecordGone, stopAgentByRecord, spawnTerminalAgent } from './terminal-agent-control';
import { isProcessAlive } from './error-handling';
import { allowedExtensionOrigin } from './extension-id';
import { sanitizeBody, stripLoneSurrogates } from './sanitize';
import { startSocksBridge, testUpstream, type BridgeHandle } from './socks-bridge';
import { parseProxyConfig, toUpstreamConfig, ProxyConfigError } from './proxy-config';
import { writeReceipt } from '../../lib/egress-receipt';
import { redactProxyUrl } from './proxy-redact';
import { type XvfbHandle } from './xvfb';
import { logTunnelDenial } from './tunnel-denial-log';
import { validateSseSessionToken, extractSseCookie } from './sse-session-cookie';
import { ROUTES } from './routes';
import { dispatchRoute, type RouteContext, type Surface } from './routes/table';
import { TUNNEL_COMMANDS, canDispatchOverTunnel } from './routes/commands';
import { getInspectorSubscriberCount, clearInspectorSubscribers } from './routes/inspector';
import * as fs from 'fs';
import * as net from 'net';
import * as path from 'path';
import * as crypto from 'crypto';

const SERVER_INSTANCE_ID = crypto.randomUUID();

function removeOwnedDaemonStateQuiet(): void {
  try {
    const release = acquireAgentStateLock(path.dirname(config.stateFile), 0);
    try {
      const state = JSON.parse(fs.readFileSync(config.stateFile, 'utf8'));
      if (state.pid === process.pid && state.instanceId === SERVER_INSTANCE_ID) safeUnlinkQuiet(config.stateFile);
    } finally { release(); }
  } catch {}
}

// ─── Unicode Sanitization ───────────────────────────────────────
// Unpaired UTF-16 surrogate halves (\uD800–\uDFFF) in page DOM text, OCR
// output, and other CDP-sourced strings are rejected by JSON consumers
// downstream (Anthropic API in particular: "no low surrogate in string").
// The sanitizers live in sanitize.ts (single source of truth, shared with
// sse-helpers.ts and the read/snapshot pipeline): `stripLoneSurrogates`
// replaces lone halves with U+FFFD (valid pairs like emoji survive), and
// `sanitizeReplacer` runs it on every string value inside JSON.stringify.
//
// INVARIANT: every server egress path that ships page-content strings MUST
// route through the sanitizer. handleCommandInternal wraps the final
// cr.result string (text/plain bodies carry lone surrogates verbatim;
// JSON.stringify already escapes them). The SSE producers stringify with
// `sanitizeReplacer` so payload string fields get cleaned BEFORE escaping.
// Plain post-stringify regex is a no-op there because JSON.stringify
// converts \uD800 → "\\ud800" — the regex can't see the surrogate after
// that point.

// ─── Config ─────────────────────────────────────────────────────
const config = resolveConfig();
ensureStateDir(config);
initAuditLog(config.auditLog);

// ─── Auth ───────────────────────────────────────────────────────
// activeShutdown points to the factory-scoped shutdown function once
// buildFetchHandler has been called. Module-level timers (idle check, parent
// watchdog) and signal handlers route through activeShutdown so they close
// the cfg-provided browserManager rather than a stale module-level reference.
// Null before the first buildFetchHandler call, which is correct: nothing to
// shut down yet.
let activeShutdown: ((code?: number) => Promise<void>) | null = null;

// AUTH_TOKEN is injectable via process.env.AUTH_TOKEN so embedders
// (gbrowser's gbd daemon spawn) can pre-allocate the token and hand it to
// the Bun child via env.
//
// Validation: require >= 16 chars after stripping ALL unicode whitespace
// (not just ASCII — .trim() misses U+200B / U+FEFF / U+00A0 / etc., which
// would otherwise let a misconfigured embedder ship a one-character BOM as
// the bearer secret). Reject tokens that are too short or contain only
// whitespace; fall back to randomUUID so the security boundary is never
// silently weakened by misconfiguration.
function sanitizeAuthToken(raw: string | undefined): string | null {
  if (!raw) return null;
  const stripped = raw.replace(/[\s ​-‍]/g, '');
  if (stripped.length < 16) return null;
  return stripped;
}
// AUTH_TOKEN const + module-level initRegistry call deleted in v1.35.0.0.
// buildFetchHandler now owns auth state end-to-end: cfg.authToken is the
// single source of truth, factory body calls initRegistry(cfg.authToken),
// and factory-scoped validateAuth closes over the same value. start() reads
// env once via resolveConfigFromEnv() and threads the result through.
const BROWSE_PORT = parseInt(process.env.BROWSE_PORT || '0', 10);
const IDLE_TIMEOUT_MS = parseInt(process.env.BROWSE_IDLE_TIMEOUT || '1800000', 10); // 30 min

/**
 * Port the local listener bound to. Set once the daemon picks a port.
 * Used by `$B skill run` to point spawned skill scripts at the daemon over
 * loopback. Module-level so handleCommandInternal can read it without threading
 * the port through every dispatch.
 */
let LOCAL_LISTEN_PORT: number = 0;
// Sidebar chat is always enabled in headed mode (ungated in v0.12.0)

// ─── Tunnel State ───────────────────────────────────────────────
//
// Dual-listener architecture: the daemon binds TWO HTTP listeners when a
// tunnel is active. The local listener serves bootstrap + CLI + sidebar
// (never exposed to ngrok). The tunnel listener serves only the pairing
// ceremony and scoped-token command endpoints (the ONLY port ngrok forwards).
//
// Security property comes from physical port separation: a tunnel caller
// cannot reach bootstrap endpoints because they live on a different TCP
// socket, not because of any per-request check.
let tunnelActive = false;
let tunnelUrl: string | null = null;
let tunnelListener: any = null;           // ngrok listener handle
let tunnelServer: ReturnType<typeof Bun.serve> | null = null; // tunnel HTTP listener

export type { Surface };

/**
 * Factory contract for embedders (gbrowser phoenix overlay).
 *
 * Today the CLI calls `start()` which reads env vars and binds Bun.serve
 * itself. Embedders building on this server as a submodule (gbrowser's
 * fd-passing gbd architecture) need to inject auth + ports + a
 * BrowserManager they pre-launched, and own the listener themselves.
 *
 * Status: v1 surfaces this type as documentation. AUTH_TOKEN env-injection
 * is already live (see ~L70). `start()` is exported and the kickoff /
 * signal-handler registration is gated on `import.meta.main`, so phoenix
 * can `import { start } from '.../server'` without auto-starting. Full
 * `buildFetchHandler` extraction lands in a follow-up; see plan
 * `/Users/garrytan/.claude/plans/system-instruction-you-are-working-swirling-fountain.md`
 * Part 1.
 */
export interface ServerConfig {
  /** Bearer token clients must present. Today injected via AUTH_TOKEN env. */
  authToken: string;
  /** Local listener port. Used in /welcome URL + state-file. */
  browsePort: number;
  /** Result of resolveConfig() — stateDir, auditLog, stateFile. */
  config: ReturnType<typeof resolveConfig>;
  /** Pre-launched BrowserManager. Caller owns lifecycle. */
  browserManager: BrowserManager;
  // NOTE: per-factory idleTimeoutMs and chromiumProfile were deleted — they
  // were documented but never read (the idle timer, activity state, and
  // shutdown target are module-global, so per-factory wiring would lie for
  // any embedder running >1 handler). Real support belongs to the deferred
  // server.ts singleton refactor. Until then: BROWSE_IDLE_TIMEOUT
  // and CHROMIUM_PROFILE env are the honest knobs.
  /** Caller-owned. shutdown() does NOT call xvfb.stop(); caller is responsible. */
  xvfb?: XvfbHandle | null;
  /** Caller-owned. shutdown() does NOT call proxyBridge.close(); caller is responsible. */
  proxyBridge?: BridgeHandle | null;
  startTime: number;
  /**
   * Overlay hook. Runs AFTER gstack resolves auth and BEFORE route dispatch.
   * Invalid tokens are auto-rejected at the gstack layer (401 returned
   * before hook fires), so the hook only ever sees valid TokenInfo or null
   * (no token presented). Returning a Response short-circuits gstack
   * dispatch; returning null falls through.
   */
  beforeRoute?: (req: Request, surface: Surface, auth: TokenInfo | null) => Promise<Response | null>;
  /**
   * Whether gstack owns the lifecycle of the terminal-agent process and its
   * discovery files (`<stateDir>/terminal-port`, `<stateDir>/terminal-internal-token`,
   * `<stateDir>/terminal-agent-pid`).
   *
   * When true (default), shutdown() runs four side effects:
   *   1. Identity-based kill via `killAgentByRecord(readAgentRecord(stateDir))`
   *      (v1.44+). Only signals the PID recorded by THIS daemon's agent.
   *      Replaced the historical `pkill -f terminal-agent\.ts` regex that
   *      matched sibling gstack sessions on the same host — see
   *      terminal-agent-control.ts for rationale.
   *   2. `safeUnlinkQuiet(<stateDir>/terminal-port)`
   *   3. `safeUnlinkQuiet(<stateDir>/terminal-internal-token)`
   *   4. `safeUnlinkQuiet(<stateDir>/terminal-agent-pid)` (the v1.44 record)
   *
   * This is correct for gstack's CLI path, which spawns `terminal-agent.ts` as
   * the producer of those files (see cli.ts:1037-1063).
   *
   * Embedders (gbrowser phoenix overlay, future hosts) that run their own PTY
   * server and write those files themselves should pass `false`. When `false`,
   * the embedder owns BOTH the agent process AND all three discovery files.
   * Note that terminal-agent.ts's own SIGTERM cleanup removes `terminal-port`
   * and `terminal-agent-pid` (the agent writes both at boot), so embedders
   * that pre-launch their own agent must ensure their cleanup matches.
   *
   * Polarity note: this differs from `xvfb?` and `proxyBridge?`, which gate by
   * the *presence* of a caller-owned handle (presence ⇒ don't close). This
   * field gates by an explicit boolean because there is no handle object —
   * the terminal-agent is started elsewhere (cli.ts), and shutdown's only
   * reference is the PID record + the file paths.
   */
  ownsTerminalAgent?: boolean;
}

/**
 * Return shape of buildFetchHandler() — fetch handlers + lifecycle helpers
 * embedders need to drive their own Bun.serve binding. See ServerConfig.
 */
export interface ServerHandle {
  fetchLocal: (req: Request, server: any) => Promise<Response>;
  fetchTunnel: (req: Request, server: any) => Promise<Response>;
  /**
   * Drains buffers, kills terminal-agent, closes browser, clears intervals,
   * removes state files. Does NOT stop bound Bun.Server listeners — call
   * stopListeners() for that. CLI relies on process.exit() to drop sockets.
   */
  shutdown: (exitCode?: number) => Promise<void>;
  /**
   * Graceful listener stop for embedders. Calls server.stop(true) on each
   * passed Bun.Server. CLI doesn't need this (process.exit handles it).
   */
  stopListeners: (local: any, tunnel?: any) => Promise<void>;
}

/**
 * Build a ServerConfig-shaped object from process.env. Used by gstack's
 * own CLI when running `bun run dev` or the compiled binary directly.
 * Embedders construct their own ServerConfig explicitly.
 *
 * Reads env, calls resolveConfig(). Does NOT bind a listener or call
 * initAuditLog/initRegistry — those happen inside the buildFetchHandler
 * lifecycle.
 */
export function resolveConfigFromEnv(): Omit<ServerConfig, 'browserManager' | 'startTime'> & {
  config: ReturnType<typeof resolveConfig>;
} {
  return {
    // Same sanitizer as the module-level AUTH_TOKEN: strips ALL unicode
    // whitespace and rejects tokens shorter than 16 chars so a misconfigured
    // embedder can't ship a BOM/zero-width as the bearer secret.
    authToken: sanitizeAuthToken(process.env.AUTH_TOKEN) || crypto.randomUUID(),
    browsePort: parseInt(process.env.BROWSE_PORT || '0', 10),
    config: resolveConfig(),
  };
}

/**
 * Paths reachable over the tunnel surface. Everything else returns 404.
 *
 * `/connect` is the only unauthenticated tunnel endpoint — POST for setup-key
 * exchange, GET for an `{alive: true}` probe used by /pair and /tunnel/start
 * to detect dead ngrok tunnels. Other paths in this set require a scoped
 * token via Authorization: Bearer.
 *
 * Updating this set is a deliberate security decision. Every addition widens
 * the tunnel attack surface. It must equal the paths of the route-table
 * entries that declare the 'tunnel' surface (browse/test/server-route-table.test.ts),
 * so widening the tunnel means editing this literal and the entry.
 */
const TUNNEL_PATHS = new Set<string>([
  '/connect',
  '/command',
]);

/**
 * POST /extension-token releases AUTH_TOKEN only to an Origin of exactly the
 * pinned extension, or the one set with `gstack-config set browse_extension_id`
 * (browse/src/extension-id.ts, shared with the terminal agent's /ws gate).
 */
export { GSTACK_EXTENSION_ID } from './extension-id';

/**
 * The extension-origin auth check (POST /extension-token): Origin is exactly
 * the pinned extension and Host is loopback. Defense-in-depth alongside the
 * 127.0.0.1 bind: a DNS-rebinding page can't present a localhost Host header.
 * Host arrives as '127.0.0.1:34567', so parse out the hostname — never compare
 * the raw header (which carries the port) against a literal.
 */
function isPinnedExtensionRequest(req: Request): boolean {
  let hostname: string | null = null;
  try {
    hostname = new URL(`http://${req.headers.get('host') ?? ''}`).hostname;
  } catch (err) {
    if (!(err instanceof TypeError)) throw err;  // TypeError = malformed Host
  }
  const originOk = req.headers.get('origin') === allowedExtensionOrigin();
  const hostOk = hostname === '127.0.0.1' || hostname === 'localhost';
  return originOk && hostOk;
}

export { TUNNEL_COMMANDS, canDispatchOverTunnel };

/**
 * Read ngrok authtoken from env var, ~/.gstack/ngrok.env, or ngrok's native
 * config files.  Returns null if nothing found.  Shared between the
 * /tunnel/start handler and the BROWSE_TUNNEL=1 auto-start flow.
 */
function resolveNgrokAuthtoken(): string | null {
  let authtoken = process.env.NGROK_AUTHTOKEN;
  if (authtoken) return authtoken;

  const home = process.env.HOME || '';
  const ngrokEnvPath = path.join(home, '.gstack', 'ngrok.env');
  if (fs.existsSync(ngrokEnvPath)) {
    try {
      const envContent = fs.readFileSync(ngrokEnvPath, 'utf-8');
      const match = envContent.match(/^NGROK_AUTHTOKEN=(.+)$/m);
      if (match) return match[1].trim();
    } catch {}
  }

  const ngrokConfigs = [
    path.join(home, 'Library', 'Application Support', 'ngrok', 'ngrok.yml'),
    path.join(home, '.config', 'ngrok', 'ngrok.yml'),
    path.join(home, '.ngrok2', 'ngrok.yml'),
  ];
  for (const conf of ngrokConfigs) {
    try {
      const content = fs.readFileSync(conf, 'utf-8');
      const match = content.match(/authtoken:\s*(.+)/);
      if (match) return match[1].trim();
    } catch {}
  }
  return null;
}

/**
 * Tear down the tunnel: close the ngrok listener and stop the tunnel-surface
 * Bun.serve listener.  Safe to call with nothing running.  Always clears
 * tunnel state regardless of individual close failures.
 */
async function closeTunnel(): Promise<void> {
  try { if (tunnelListener) await tunnelListener.close(); } catch {}
  try { if (tunnelServer) tunnelServer.stop(true); } catch {}
  tunnelListener = null;
  tunnelServer = null;
  tunnelUrl = null;
  tunnelActive = false;
}

/**
 * Result of startTunnel(). `stage` tells the caller which half failed so it
 * can keep its distinct error surface: 'bind' = the tunnel-surface Bun.serve
 * listener could not bind (nothing to clean up), 'ngrok' = anything after the
 * bind (ngrok forward, egress receipt, state-file write) — startTunnel has
 * already torn down both ngrok and the Bun listener by the time it returns.
 */
type StartTunnelResult =
  | { ok: true; url: string }
  | { ok: false; stage: 'bind' | 'ngrok'; error: Error };

/**
 * Start the ngrok tunnel using the dual-listener pattern: bind a dedicated
 * tunnel-surface listener on an ephemeral 127.0.0.1 port and point
 * ngrok.forward() at THAT port — the local listener (which serves
 * /extension-token, /cookie-picker, /inspector/*, welcome, etc.) is never
 * exposed to ngrok. Shared by the /tunnel/start route handler (which passes
 * its in-closure makeFetchHandler('tunnel')) and the BROWSE_TUNNEL=1
 * auto-start flow in start() (which passes handle.fetchTunnel from the
 * factory). The BROWSE_TUNNEL_LOCAL_ONLY=1 test path does NOT use this
 * helper — it binds the tunnel surface with no ngrok forwarding at all.
 *
 * Hard fail on listener bind (`stage: 'bind'`) — NEVER fall back to the
 * local port, which would silently defeat the whole security property.
 *
 * On success, sets the module tunnel state (tunnelListener / tunnelUrl /
 * tunnelServer / tunnelActive) and records the tunnel in the state file.
 */
async function startTunnel(opts: {
  fetchHandler: (req: Request, server: any) => Promise<Response>;
  authtoken: string;
  consent: string;
}): Promise<StartTunnelResult> {
  // Bind the tunnel listener on an ephemeral port.  HARD FAIL if this
  // errors — never fall back to the local port.
  let boundTunnel: ReturnType<typeof Bun.serve>;
  try {
    boundTunnel = Bun.serve({
      port: 0,
      hostname: '127.0.0.1',
      fetch: opts.fetchHandler,
    });
  } catch (err: any) {
    return { ok: false, stage: 'bind', error: err };
  }
  const tunnelPort = boundTunnel.port;

  // Point ngrok at the TUNNEL port (not the local port).  If this fails,
  // tear the listener back down so we don't leak sockets.
  try {
    const ngrok = await import('@ngrok/ngrok');
    const domain = process.env.NGROK_DOMAIN;
    const forwardOpts: any = { addr: tunnelPort, authtoken: opts.authtoken };
    if (domain) forwardOpts.domain = domain;

    // Egress receipt BEFORE the tunnel session opens, fail-closed: a
    // writeReceipt failure lands in this catch, which tears the tunnel
    // listener back down and refuses the start. One receipt per session
    // open; browse command behavior over the tunnel is unchanged.
    writeReceipt({
      sink: 'browse-tunnel',
      host: domain || 'connect.ngrok-agent.com',
      payloadClass: 'tunnel-session-open (scoped-token browser-command surface)',
      bytes: 0,
      sha256: null,
      consent: opts.consent,
    });

    tunnelListener = await ngrok.forward(forwardOpts);
    tunnelUrl = tunnelListener.url();
    tunnelServer = boundTunnel;
    tunnelActive = true;
    console.log(`[browse] Tunnel listener bound on 127.0.0.1:${tunnelPort}, ngrok → ${tunnelUrl}`);

    // Update state file
    const releaseStateLock = acquireAgentStateLock(config.stateDir);
    try {
      const stateContent = JSON.parse(fs.readFileSync(config.stateFile, 'utf-8'));
      if (stateContent.pid !== process.pid || stateContent.instanceId !== SERVER_INSTANCE_ID) throw new Error('daemon state was replaced');
      stateContent.tunnel = { url: tunnelUrl, domain: domain || null, startedAt: new Date().toISOString() };
      const tmpState = tmpStatePath();
      fs.writeFileSync(tmpState, JSON.stringify(stateContent, null, 2), { mode: 0o600 });
      fs.renameSync(tmpState, config.stateFile);
    } finally { releaseStateLock(); }

    return { ok: true, url: tunnelUrl! };
  } catch (err: any) {
    // Clean up BOTH ngrok and the Bun listener on failure.  If
    // ngrok.forward() succeeded but tunnelListener.url() or the
    // state-file write threw, we'd otherwise leak an active ngrok
    // session on the user's account.
    try { if (tunnelListener) await tunnelListener.close(); } catch {}
    try { boundTunnel.stop(true); } catch {}
    tunnelListener = null;
    return { ok: false, stage: 'ngrok', error: err };
  }
}

// Module-level validateAuth deleted in v1.35.0.0. Factory-scoped equivalent
// in buildFetchHandler closes over cfg.authToken so every internal auth check
// sees the same token the routes receive.

/**
 * Terminal-agent discovery. The non-compiled bun process at
 * `browse/src/terminal-agent.ts` writes its chosen port to
 * `<stateDir>/terminal-port` and the loopback handshake token to
 * `<stateDir>/terminal-internal-token` once it boots. Read on demand —
 * lazy so we don't break tests that don't spawn the agent.
 */
function readTerminalPort(): number | null {
  try {
    const f = path.join(path.dirname(config.stateFile), 'terminal-port');
    const v = parseInt(fs.readFileSync(f, 'utf-8').trim(), 10);
    return Number.isFinite(v) && v > 0 ? v : null;
  } catch { return null; }
}
function readTerminalInternalToken(): string | null {
  try {
    const f = path.join(path.dirname(config.stateFile), 'terminal-internal-token');
    const t = fs.readFileSync(f, 'utf-8').trim();
    return t.length > 16 ? t : null;
  } catch { return null; }
}

/**
 * Push a freshly-minted PTY cookie token to the terminal-agent so its
 * /ws upgrade can validate the cookie. v1.44+: also pushes the bound
 * sessionId so the agent can route /internal/restart and (Commit 3)
 * re-attach back to the same PtySession. Loopback POST authenticated
 * with the internal token written by the agent at startup. If the agent
 * isn't up yet, the extension just retries /pty-session.
 */
async function grantPtyToken(token: string, sessionId?: string): Promise<boolean> {
  const port = readTerminalPort();
  const internal = readTerminalInternalToken();
  if (!port || !internal) return false;
  try {
    const resp = await fetch(`http://127.0.0.1:${port}/internal/grant`, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'Authorization': `Bearer ${internal}`,
      },
      body: JSON.stringify(sessionId ? { token, sessionId } : { token }),
      signal: AbortSignal.timeout(2000),
    });
    return resp.ok;
  } catch { return false; }
}

/**
 * Ask the terminal-agent to dispose the PtySession bound to `sessionId`.
 * Scoped to one caller's session — sibling tabs/agents untouched. Used by
 * /pty-restart and /pty-dispose. Returns true on agent ack.
 */
async function restartPtySession(sessionId: string): Promise<boolean> {
  const port = readTerminalPort();
  const internal = readTerminalInternalToken();
  if (!port || !internal) return false;
  try {
    const resp = await fetch(`http://127.0.0.1:${port}/internal/restart`, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'Authorization': `Bearer ${internal}`,
      },
      body: JSON.stringify({ sessionId }),
      signal: AbortSignal.timeout(5000),
    });
    return resp.ok;
  } catch { return false; }
}

/** Extract bearer token from request. Returns the token string or null. */
function extractToken(req: Request): string | null {
  const header = req.headers.get('authorization');
  if (!header?.startsWith('Bearer ')) return null;
  return header.slice(7);
}

/** Validate token and return TokenInfo. Returns null if invalid/expired. */
function getTokenInfo(req: Request): TokenInfo | null {
  const token = extractToken(req);
  if (!token) return null;
  return validateScopedToken(token);
}

/** Check if request is from root token (local use). */
function isRootRequest(req: Request): boolean {
  const token = extractToken(req);
  return token !== null && isRootToken(token);
}

// ─── Help text (auto-generated from COMMAND_DESCRIPTIONS) ────────
function generateHelpText(): string {
  // Group commands by category
  const groups = new Map<string, string[]>();
  for (const [cmd, meta] of Object.entries(COMMAND_DESCRIPTIONS)) {
    const display = meta.usage || cmd;
    const list = groups.get(meta.category) || [];
    list.push(display);
    groups.set(meta.category, list);
  }

  const categoryOrder = [
    'Navigation', 'Reading', 'Interaction', 'Inspection',
    'Visual', 'Snapshot', 'Meta', 'Tabs', 'Server',
  ];

  const lines = ['gstack browse — headless browser for AI agents', '', 'Commands:'];
  for (const cat of categoryOrder) {
    const cmds = groups.get(cat);
    if (!cmds) continue;
    lines.push(`  ${(cat + ':').padEnd(15)}${cmds.join(', ')}`);
  }

  // Snapshot flags from source of truth
  lines.push('');
  lines.push('Snapshot flags:');
  const flagPairs: string[] = [];
  for (const flag of SNAPSHOT_FLAGS) {
    const label = flag.valueHint ? `${flag.short} ${flag.valueHint}` : flag.short;
    flagPairs.push(`${label}  ${flag.long}`);
  }
  // Print two flags per line for compact display
  for (let i = 0; i < flagPairs.length; i += 2) {
    const left = flagPairs[i].padEnd(28);
    const right = flagPairs[i + 1] || '';
    lines.push(`  ${left}${right}`);
  }

  return lines.join('\n');
}

// ─── Buffer (from buffers.ts) ────────────────────────────────────
import { consoleBuffer, networkBuffer, dialogBuffer, addConsoleEntry, addNetworkEntry, addDialogEntry, type LogEntry, type NetworkEntry, type DialogEntry } from './buffers';

export { consoleBuffer, networkBuffer, dialogBuffer, addConsoleEntry, addNetworkEntry, addDialogEntry, type LogEntry, type NetworkEntry, type DialogEntry };

const CONSOLE_LOG_PATH = config.consoleLog;
const NETWORK_LOG_PATH = config.networkLog;
const DIALOG_LOG_PATH = config.dialogLog;

/**
 * Per-process state-file temp path. The state-file write pattern is
 * `writeFileSync(tmp, ...) → renameSync(tmp, stateFile)` for atomicity,
 * but a shared `${stateFile}.tmp` filename means two concurrent writers
 * (cold-start race when N CLIs hit a fresh repo simultaneously, parallel
 * /tunnel/start handlers, or a combination) collide on the rename: the
 * first writer's renameSync moves the shared temp file out of the way,
 * the second writer's writeFileSync re-creates it, the second rename
 * then races with the first writer's already-renamed state. Worst case
 * the second renameSync throws ENOENT mid-air, killing one of the
 * spawning daemons during startup.
 *
 * Per-process suffix (pid + 4 random bytes) makes each writer's temp
 * path unique. The atomic rename still gives last-writer-wins semantics
 * for the final state.json content; the only behavior change is that
 * concurrent writers no longer kill each other on the rename.
 */
function tmpStatePath(stateFile: string = config.stateFile): string {
  return `${stateFile}.tmp.${process.pid}.${crypto.randomBytes(4).toString('hex')}`;
}


// ─── Sidebar agent / chat state ripped ──────────────────────────────
let lastConsoleFlushed = 0;
let lastNetworkFlushed = 0;
let lastDialogFlushed = 0;
let flushInProgress = false;

async function flushBuffers() {
  if (flushInProgress) return; // Guard against concurrent flush
  flushInProgress = true;

  try {
    // Console buffer
    const newConsoleCount = consoleBuffer.totalAdded - lastConsoleFlushed;
    if (newConsoleCount > 0) {
      const entries = consoleBuffer.last(Math.min(newConsoleCount, consoleBuffer.length));
      const lines = entries.map(e =>
        `[${new Date(e.timestamp).toISOString()}] [${e.level}] ${e.text}`
      ).join('\n') + '\n';
      appendSecureFile(CONSOLE_LOG_PATH, lines);
      lastConsoleFlushed = consoleBuffer.totalAdded;
    }

    // Network buffer
    const newNetworkCount = networkBuffer.totalAdded - lastNetworkFlushed;
    if (newNetworkCount > 0) {
      const entries = networkBuffer.last(Math.min(newNetworkCount, networkBuffer.length));
      const lines = entries.map(e =>
        `[${new Date(e.timestamp).toISOString()}] ${e.method} ${e.url} → ${e.status || 'pending'} (${e.duration || '?'}ms, ${e.size || '?'}B)`
      ).join('\n') + '\n';
      appendSecureFile(NETWORK_LOG_PATH, lines);
      lastNetworkFlushed = networkBuffer.totalAdded;
    }

    // Dialog buffer
    const newDialogCount = dialogBuffer.totalAdded - lastDialogFlushed;
    if (newDialogCount > 0) {
      const entries = dialogBuffer.last(Math.min(newDialogCount, dialogBuffer.length));
      const lines = entries.map(e =>
        `[${new Date(e.timestamp).toISOString()}] [${e.type}] "${e.message}" → ${e.action}${e.response ? ` "${e.response}"` : ''}`
      ).join('\n') + '\n';
      appendSecureFile(DIALOG_LOG_PATH, lines);
      lastDialogFlushed = dialogBuffer.totalAdded;
    }
  } catch (err: any) {
    console.error('[browse] Buffer flush failed:', err.message);
  } finally {
    flushInProgress = false;
  }
}

// Flush every 1 second
const flushInterval = setInterval(flushBuffers, 1000);

// ─── Idle Timer ────────────────────────────────────────────────
let lastActivity = Date.now();

function resetIdleTimer() {
  lastActivity = Date.now();
}

// Named for behavioral testing via __testInternals__. The factory tests in
// server-factory.test.ts call this directly so the idle-shutdown path can be
// exercised without waiting 60s for the interval to fire.
function idleCheckTick() {
  // Headed mode: the user is looking at the browser. Never auto-die.
  // Only shut down when the user explicitly disconnects or closes the window.
  // Reads via the activeBrowserManager indirection so embedders that pass
  // their own BrowserManager into buildFetchHandler hit the right instance.
  if (activeBrowserManager.getConnectionMode() === 'headed') return;
  // Tunnel mode: remote agents may send commands sporadically. Never auto-die.
  if (tunnelActive) return;
  if (Date.now() - lastActivity > IDLE_TIMEOUT_MS) {
    console.log(`[browse] Idle for ${IDLE_TIMEOUT_MS / 1000}s, shutting down`);
    activeShutdown?.();
  }
}
const idleCheckInterval = setInterval(idleCheckTick, 60_000);

// Test-only surface for server-factory.test.ts. Lets the dual-instance
// idle-timer behavior be exercised deterministically without mutating
// Date.now (which would interact with the leaked module-level setInterval).
// Production code must never import this — see `idle timer + onDisconnect
// dual-instance fix` describe block for usage.
export const __testInternals__ = {
  serverInstanceId: SERVER_INSTANCE_ID,
  tunnelPaths: TUNNEL_PATHS as ReadonlySet<string>,
  idleCheckTick,
  // Watchdog seams (watchdog.test.ts): drive the 15s poll against an
  // arbitrary (dead) PID, trigger the handoff-promotion suppression exactly
  // as onHeadedPromotion does, and reset the latches between tests.
  parentWatchdogTick,
  suppressHeadedParentShutdown,
  resetParentWatchdogState: () => { headedParentShutdownSuppressed = false; parentGone = false; },
  setTunnelActive: (v: boolean) => { tunnelActive = v; },
  setLastActivity: (t: number) => { lastActivity = t; },
  formatExplicitPortUnavailableError,
  formatRandomPortUnavailableError,
  // Reset the module-level shutdown latch so tests that drive shutdown to
  // completion (process.exit-stubbed) can be followed by tests that also
  // need shutdown to fire. Without this, the second test's shutdown
  // returns early at the `if (isShuttingDown) return;` guard.
  resetShutdownState: () => { isShuttingDown = false; },
};

// ─── Parent-Process Watchdog ────────────────────────────────────────
// When the spawning CLI process (e.g. a Claude Code session) exits, this
// server can become an orphan — keeping chrome-headless-shell alive and
// causing console-window flicker on Windows. Poll the parent PID every 15s
// and self-terminate if it is gone.
//
// Headed mode (BROWSE_HEADED=1 or BROWSE_PARENT_PID=0): The user controls
// the browser window lifecycle. The CLI exits immediately after connect,
// so the watchdog would kill the server prematurely. Disabled in both cases
// as defense-in-depth — the CLI sets PID=0 for headed mode, and the server
// also checks BROWSE_HEADED in case a future launcher forgets.
// Cleanup happens via browser disconnect event or $B disconnect.
const BROWSE_PARENT_PID = parseInt(process.env.BROWSE_PARENT_PID || '0', 10);
// Outer gate: if the spawner explicitly marks this as headed (env var set at
// launch time), skip registering the watchdog entirely. Cheaper than entering
// the closure every 15s. The CLI's connect path sets BROWSE_HEADED=1 + PID=0,
// so this branch is the normal path for /open-gstack-browser.
const IS_HEADED_WATCHDOG = process.env.BROWSE_HEADED === '1';
// Runtime promotion to headed (`handoff`) must NOT clear this interval — the
// same tick is the tunnel-orphan reaper, and idle timeout is disabled in
// tunnel mode, so parent death is the ONLY thing that reaps an
// internet-exposed daemon after handoff → resume → /pair-agent. Promotion
// sets this suppress flag instead; the tick re-reads it (and tunnelActive)
// every pass. See suppressHeadedParentShutdown() below.
let headedParentShutdownSuppressed = false;
// Latch for the one-time "parent exited, staying alive" log line.
let parentGone = false;
// Named + parameterized (default: the boot-time env PID) so watchdog.test.ts
// can drive the tick deterministically via __testInternals__, mirroring
// idleCheckTick above. setInterval invokes it with no args in production.
function parentWatchdogTick(parentPid: number = BROWSE_PARENT_PID): void {
  try {
    process.kill(parentPid, 0); // signal 0 = existence check only, no signal sent
  } catch {
    // Parent exited. Resolution order:
    // 1. Active cookie picker (one-time code or session live)? Stay alive
    //    regardless of mode — tearing down the server mid-import leaves the
    //    picker UI with a stale "Failed to fetch" error.
    // 2. Headed (unless suppressed by a runtime promotion) / tunnel mode?
    //    Shutdown. The idle timeout doesn't apply in these modes (see
    //    idleCheckInterval above — both early-return), so ignoring parent
    //    death here would leak orphan daemons after /pair-agent or
    //    /open-gstack-browser sessions.
    // 3. Normal (headless) mode, or headed-by-promotion? Stay alive. Claude
    //    Code's Bash tool kills the parent shell between invocations, and a
    //    promoted daemon's user owns the window lifecycle. The idle timeout
    //    (30 min) handles eventual cleanup.
    if (hasActivePicker()) return;
    const headed = activeBrowserManager.getConnectionMode() === 'headed'
      && !headedParentShutdownSuppressed;
    if (headed || tunnelActive) {
      console.log(`[browse] Parent process ${parentPid} exited in ${headed ? 'headed' : 'tunnel'} mode, shutting down`);
      activeShutdown?.();
    } else if (!parentGone) {
      parentGone = true;
      console.log(`[browse] Parent process ${parentPid} exited (server stays alive, idle timeout will clean up)`);
    }
  }
}
// Poll cadence. Env-overridable as a test seam: watchdog.test.ts shrinks it
// (250ms) so a free-tier test can observe a real tick deciding on a dead
// parent instead of sleeping through the 15s production cadence. Production
// launchers never set this; unparsable or non-positive values fall back to 15s.
const rawWatchdogIntervalMs = parseInt(process.env.BROWSE_PARENT_WATCHDOG_INTERVAL_MS || '', 10);
const PARENT_WATCHDOG_INTERVAL_MS =
  Number.isFinite(rawWatchdogIntervalMs) && rawWatchdogIntervalMs > 0
    ? rawWatchdogIntervalMs
    : 15_000;
if (BROWSE_PARENT_PID > 0 && !IS_HEADED_WATCHDOG) {
  setInterval(parentWatchdogTick, PARENT_WATCHDOG_INTERVAL_MS);
} else if (IS_HEADED_WATCHDOG) {
  console.log('[browse] Parent-process watchdog disabled (headed mode)');
} else if (BROWSE_PARENT_PID === 0) {
  console.log('[browse] Parent-process watchdog disabled (BROWSE_PARENT_PID=0)');
}

/**
 * Suppress the headed-mode parent-death shutdown after a runtime promotion.
 *
 * The watchdog's contract is "headless daemons outlive their parent, headed ones
 * do not" — reasonable at boot, when mode is fixed by env. `handoff` breaks that
 * assumption: it swaps in a headed context on a RUNNING daemon
 * (browser-manager.ts, connectionMode = 'headed') without a restart, so a daemon
 * that legitimately registered a watchdog is suddenly on the fatal side of the
 * branch. The parent is typically a short-lived shell — Claude Code's Bash tool
 * kills one after every invocation — so the next 15s poll shuts the daemon down,
 * discarding whatever the user was handed off to do, such as a login.
 *
 * Once promoted, the user owns the window lifecycle exactly as if the daemon had
 * been started headed, which is the case the env guards already exempt.
 *
 * A flag, NOT clearInterval: the tick doubles as the tunnel-orphan reaper
 * (its `tunnelActive` branch), and idle timeout is disabled in tunnel mode —
 * clearing the whole interval here left handoff → resume → /pair-agent with
 * an internet-exposed daemon nothing could ever reap. After promotion, parent
 * death no longer kills the daemon for BEING HEADED, but still kills it when
 * a tunnel is active.
 */
function suppressHeadedParentShutdown(stateConfig: ServerConfig['config'] = config, manager: BrowserManager = activeBrowserManager): void {
  if (headedParentShutdownSuppressed) return;
  headedParentShutdownSuppressed = true;
  try {
    const release = acquireAgentStateLock(stateConfig.stateDir);
    try {
      const state = JSON.parse(fs.readFileSync(stateConfig.stateFile, 'utf8'));
      if (state.pid === process.pid && state.instanceId === SERVER_INSTANCE_ID) {
        const xvfb = manager.getXvfbHandle();
        state.mode = 'headed';
        delete state.chromiumPid;
        delete state.chromiumStartTime;
        if (xvfb) Object.assign(state, { xvfbPid: xvfb.pid, xvfbStartTime: xvfb.startTime, xvfbDisplay: xvfb.display });
        const tmpFile = tmpStatePath(stateConfig.stateFile);
        try {
          fs.writeFileSync(tmpFile, JSON.stringify(state, null, 2), { mode: 0o600 });
          fs.renameSync(tmpFile, stateConfig.stateFile);
        } finally { safeUnlinkQuiet(tmpFile); }
      }
    } finally { release(); }
  } catch (err) {
    console.warn('[browse] Could not persist headed promotion:', err instanceof Error ? err.message : String(err));
  }
  console.log('[browse] Parent-death headed shutdown suppressed (promoted to headed at runtime); watchdog stays armed as the tunnel-orphan reaper');
}

// ─── Command Sets (from commands.ts — single source of truth) ───
import { READ_COMMANDS, WRITE_COMMANDS, META_COMMANDS } from './commands';

export { READ_COMMANDS, WRITE_COMMANDS, META_COMMANDS };

/**
 * Whether an invocation should be treated as a WRITE for capability gating
 * (scope, watch-mode block, tab ownership, tunnel). A command is a write if it
 * mutates state (`WRITE_COMMANDS`) OR it carries an `--out` flag — `js`/`eval
 * --out` writes the evaluate result to local disk, so the capability is
 * per-invocation, not per-command-name. This deliberately does NOT change
 * dispatch routing: `js`/`eval` still route to `handleReadCommand`; only the
 * security gates consult this.
 */
function isWriteInvocation(command: string, args: string[]): boolean {
  return WRITE_COMMANDS.has(command) || hasOutArg(args);
}

export { getInspectorSubscriberCount };

// ─── Server ────────────────────────────────────────────────────
const browserManager = new BrowserManager();
// Declared here rather than beside suppressHeadedParentShutdown: that function
// sits with the watchdog it gates, which is above this line, and binding it up
// there would touch `browserManager` in its temporal dead zone — aborting
// module evaluation and leaving every later const uninitialized.
browserManager.onHeadedPromotion = suppressHeadedParentShutdown;
// Indirection for embedders. Module-level handlers (idleCheckTick, parent
// watchdog, SIGTERM) read activeBrowserManager so that buildFetchHandler can
// retarget them at a caller-supplied BrowserManager. Symmetric with the
// existing `let activeShutdown` pattern at module scope (line ~113).
// Without this, embedders like gbrowser hit the dead module-level instance
// whose connectionMode never leaves 'launched' — and headed mode never
// short-circuits idle-shutdown.
let activeBrowserManager: BrowserManager = browserManager;
// When the user closes the headed browser window, run full cleanup
// (kill terminal agent, save session, remove profile locks, delete state file)
// before exiting. Exit code 0 means user-initiated clean quit (Cmd+Q on
// macOS) so process supervisors like gbrowser's gbd skip the restart loop;
// 2 means a real crash that should respawn. The fallback `?? 2` preserves
// legacy crash semantics for any caller that invokes onDisconnect without
// an explicit code. This is the safety-net default for the CLI flow before
// any buildFetchHandler call rebinds onDisconnect onto the cfg instance.
browserManager.onDisconnect = (code) => activeShutdown?.(code ?? 2);
let isShuttingDown = false;
// Session-persist ticker handle. Registered in start() (module scope so the
// factory's shutdown() can reach it), cleared by shutdown() BEFORE the final
// snapshot — a tick landing during browser teardown would otherwise overwrite
// the good final snapshot with a degraded one (zero tabs).
let sessionPersistInterval: ReturnType<typeof setInterval> | null = null;

// Port allocation lives in port-allocator.ts (#2314, decision 8) so the
// terminal-agent shares the SAME fixed 10000-60000 scan range instead of
// binding port:0 into the OS ephemeral range. The imports at the top of
// this file re-expose the pieces __testInternals__ pins.

// Find port: explicit BROWSE_PORT, or random in 10000-60000
function findPort(): Promise<number> {
  return findAvailablePort(BROWSE_PORT);
}

/**
 * Translate Playwright errors into actionable messages for AI agents.
 */
function wrapError(err: any): string {
  const msg = err.message || String(err);
  // Timeout errors
  if (err.name === 'TimeoutError' || msg.includes('Timeout') || msg.includes('timeout')) {
    if (msg.includes('locator.click') || msg.includes('locator.fill') || msg.includes('locator.hover')) {
      return `Element not found or not interactable within timeout. Check your selector or run 'snapshot' for fresh refs.`;
    }
    if (msg.includes('page.goto') || msg.includes('Navigation')) {
      return `Page navigation timed out. The URL may be unreachable or the page may be loading slowly.`;
    }
    return `Operation timed out: ${msg.split('\n')[0]}`;
  }
  // Multiple elements matched
  if (msg.includes('resolved to') && msg.includes('elements')) {
    return `Selector matched multiple elements. Be more specific or use @refs from 'snapshot'.`;
  }
  // Pass through other errors
  return msg;
}

/** Internal command result — used by handleCommand and chain subcommand routing */
interface CommandResult {
  status: number;
  result: string;
  headers?: Record<string, string>;
  json?: boolean; // true if result is JSON (errors), false for text/plain
}

/**
 * Core command execution logic. Returns a structured result instead of HTTP Response.
 * Used by both the HTTP handler (handleCommand) and chain subcommand routing.
 *
 * Options:
 *   skipRateCheck: true when called from chain (chain counts as 1 request)
 *   skipActivity: true when called from chain (chain emits 1 event for all subcommands)
 *   chainDepth: recursion guard — reject nested chains (depth > 0 means inside a chain)
 */
async function handleCommandInternalImpl(
  body: { command: string; args?: string[]; tabId?: number },
  tokenInfo?: TokenInfo | null,
  opts?: { skipRateCheck?: boolean; skipActivity?: boolean; chainDepth?: number },
): Promise<CommandResult> {
  const { args = [], tabId } = body;
  const rawCommand = body.command;

  if (!rawCommand) {
    return { status: 400, result: JSON.stringify({ error: 'Missing "command" field' }), json: true };
  }

  // ─── Alias canonicalization (before scope, watch, tab-ownership, dispatch) ─
  // Agent-friendly names like 'setcontent' route to canonical 'load-html'. Must
  // happen BEFORE scope check so a read-scoped token calling 'setcontent' is still
  // rejected (load-html lives in SCOPE_WRITE). Audit logging preserves rawCommand
  // so the trail records what the agent actually typed.
  const command = canonicalizeCommand(rawCommand);
  const isAliased = command !== rawCommand;

  // ─── Recursion guard: reject nested chains ──────────────────
  if (command === 'chain' && (opts?.chainDepth ?? 0) > 0) {
    return { status: 400, result: JSON.stringify({ error: 'Nested chain commands are not allowed' }), json: true };
  }

  // ─── Scope check (for scoped tokens) ──────────────────────────
  if (tokenInfo && tokenInfo.clientId !== 'root') {
    if (!checkScope(tokenInfo, command)) {
      return {
        status: 403, json: true,
        result: JSON.stringify({
          error: `Command "${command}" not allowed by your token scope`,
          hint: `Your scopes: ${tokenInfo.scopes.join(', ')}. Ask the user to re-pair without --restrict for full page access, or with --control for browser control commands.`,
        }),
      };
    }

    // `--out` writes the evaluate result to local disk, which is a WRITE
    // capability distinct from the JS-exec (admin) capability js/eval need.
    // Require write scope so an admin-but-not-write token can't write files.
    if (hasOutArg(args) && !tokenInfo.scopes.includes('write')) {
      return {
        status: 403, json: true,
        result: JSON.stringify({
          error: `"--out" writes to disk and requires the "write" scope`,
          hint: `Your scopes: ${tokenInfo.scopes.join(', ')}. Re-pair with write access to use --out.`,
        }),
      };
    }

    // Domain check for navigation commands
    if ((command === 'goto' || command === 'newtab') && args[0]) {
      if (!checkDomain(tokenInfo, args[0])) {
        return {
          status: 403, json: true,
          result: JSON.stringify({
            error: `Domain not allowed by your token scope`,
            hint: `Allowed domains: ${tokenInfo.domains?.join(', ') || 'none configured'}`,
          }),
        };
      }
    }

    // Rate check (skipped for chain subcommands — chain counts as 1 request)
    if (!opts?.skipRateCheck) {
      const rateResult = checkRate(tokenInfo);
      if (!rateResult.allowed) {
        return {
          status: 429, json: true,
          result: JSON.stringify({
            error: 'Rate limit exceeded',
            hint: `Max ${tokenInfo.rateLimit} requests/second. Retry after ${rateResult.retryAfterMs}ms.`,
          }),
          headers: { 'Retry-After': String(Math.ceil((rateResult.retryAfterMs || 1000) / 1000)) },
        };
      }
    }

    // Record command execution for idempotent key exchange tracking
    if (!opts?.skipRateCheck && tokenInfo.token) recordCommand(tokenInfo.token);
  }

  // Pin to a specific tab if requested (set by BROWSE_TAB env var, e.g. per-tab agent contexts).
  // This prevents parallel agents from interfering with each other's tab context.
  // Safe because Bun's event loop is single-threaded — no concurrent handleCommand.
  let savedTabId: number | null = null;
  if (tabId !== undefined && tabId !== null) {
    savedTabId = browserManager.getActiveTabId();
    // bringToFront: false — internal tab pinning must NOT steal window focus
    try { browserManager.switchTab(tabId, { bringToFront: false }); } catch (err: any) {
      console.warn('[browse] Failed to pin tab', tabId, ':', err.message);
    }
  }

  // ─── Tab ownership check (own-only tokens / pair-agent isolation) ──
  //
  // Only `own-only` tokens (pair-agent over tunnel) are bound to their own
  // tabs. `shared` tokens — the default for skill spawns and local scoped
  // clients — can drive any tab; the capability gate (scope checks above)
  // and rate limits already constrain what they can do.
  //
  // Skip for `newtab` — it creates a tab rather than accessing one.
  if (command !== 'newtab' && tokenInfo && tokenInfo.clientId !== 'root' && tokenInfo.tabPolicy === 'own-only') {
    const targetTab = tabId ?? browserManager.getActiveTabId();
    if (!browserManager.checkTabAccess(targetTab, tokenInfo.clientId, { isWrite: isWriteInvocation(command, args), ownOnly: true })) {
      return {
        status: 403, json: true,
        result: JSON.stringify({
          error: 'Tab not owned by your agent. Use newtab to create your own tab.',
          hint: `Tab ${targetTab} is owned by ${browserManager.getTabOwner(targetTab) || 'root'}. Your agent: ${tokenInfo.clientId}.`,
        }),
      };
    }
  }

  // ─── newtab with ownership for scoped tokens ──────────────
  if (command === 'newtab' && tokenInfo && tokenInfo.clientId !== 'root') {
    const newId = await browserManager.newTab(args[0] || undefined, tokenInfo.clientId);
    return {
      status: 200, json: true,
      result: JSON.stringify({
        tabId: newId,
        owner: tokenInfo.clientId,
        hint: 'Include "tabId": ' + newId + ' in subsequent commands to target this tab.',
      }),
    };
  }

  // Block mutation commands while watching (read-only observation mode).
  // `--out` invocations count as mutations (they write the result to disk).
  if (browserManager.isWatching() && isWriteInvocation(command, args)) {
    return {
      status: 400, json: true,
      result: JSON.stringify({ error: 'Cannot run mutation commands while watching. Run `$B watch stop` first.' }),
    };
  }

  // Activity: emit command_start (skipped for chain subcommands)
  const startTime = Date.now();
  if (!opts?.skipActivity) {
    emitActivity({
      type: 'command_start',
      command,
      args,
      url: browserManager.getCurrentUrl(),
      tabs: browserManager.getTabCount(),
      mode: browserManager.getConnectionMode(),
      clientId: tokenInfo?.clientId,
    });
  }

  try {
    let result: string;

    const session = browserManager.getActiveSession();

    // Per-request warnings collected during hidden-element detection,
    // surfaced into the envelope the LLM sees. Carries across the read
    // phase into the centralized wrap block below.
    let hiddenContentWarnings: string[] = [];

    if (READ_COMMANDS.has(command)) {
      const isScoped = tokenInfo && tokenInfo.clientId !== 'root';
      // Hidden-element / ARIA-injection detection for every scoped
      // DOM-reading channel (text, html, links, forms, accessibility,
      // attrs, data, media, ux-audit). Previously only `text` received
      // stripping; other channels let hidden injection payloads reach
      // the LLM despite the envelope wrap. Detections become CONTENT
      // WARNINGS on the outgoing envelope so the model can see what it
      // would have otherwise trusted silently.
      if (isScoped && DOM_CONTENT_COMMANDS.has(command)) {
        const page = session.getPage();
        try {
          const strippedDescs = await markHiddenElements(page);
          if (strippedDescs.length > 0) {
            console.warn(`[browse] Content security: ${strippedDescs.length} hidden elements flagged on ${command} for ${tokenInfo.clientId}`);
            hiddenContentWarnings = strippedDescs.slice(0, 8).map(d =>
              `hidden content: ${d.slice(0, 120)}`,
            );
            if (strippedDescs.length > 8) {
              hiddenContentWarnings.push(`hidden content: +${strippedDescs.length - 8} more flagged elements`);
            }
          }
          if (command === 'text') {
            const target = session.getActiveFrameOrPage();
            result = await getCleanTextWithStripping(target);
          } else {
            result = await handleReadCommand(command, args, session, browserManager);
          }
        } finally {
          await cleanupHiddenMarkers(page);
        }
      } else {
        result = await handleReadCommand(command, args, session, browserManager);
      }
    } else if (WRITE_COMMANDS.has(command)) {
      result = await browserManager.failIfNavigationBlocked(session.getPage(), handleWriteCommand(command, args, session, browserManager));
    } else if (META_COMMANDS.has(command)) {
      // Pass chain depth + executeCommand callback so chain routes subcommands
      // through the full security pipeline (scope, domain, tab, wrapping).
      const chainDepth = (opts?.chainDepth ?? 0);
      // shutdown is factory-scoped (deleted from module scope in v1.35.0.0);
      // route the call through activeShutdown which buildFetchHandler assigns.
      const shutdownFn = () => activeShutdown ? activeShutdown() : Promise.resolve();
      result = await handleMetaCommand(command, args, browserManager, shutdownFn, tokenInfo, {
        chainDepth,
        daemonPort: LOCAL_LISTEN_PORT,
        executeCommand: (body, ti) => handleCommandInternal(body, ti, {
          skipRateCheck: true,    // chain counts as 1 request
          skipActivity: true,     // chain emits 1 event for all subcommands
          chainDepth: chainDepth + 1,  // recursion guard
        }),
      });
      // Start periodic snapshot interval when watch mode begins
      if (command === 'watch' && args[0] !== 'stop' && browserManager.isWatching()) {
        const watchInterval = setInterval(async () => {
          if (!browserManager.isWatching()) {
            clearInterval(watchInterval);
            return;
          }
          try {
            const snapshot = await handleSnapshot(['-i'], browserManager.getActiveSession());
            browserManager.addWatchSnapshot(snapshot);
          } catch {
            // Page may be navigating — skip this snapshot
          }
        }, 5000);
        browserManager.watchInterval = watchInterval;
      }
    } else if (command === 'help') {
      const helpText = generateHelpText();
      return { status: 200, result: helpText };
    } else {
      // Use the rich unknown-command helper: names the input, suggests the closest
      // match via Levenshtein (≤ 2 distance, ≥ 4 chars input), and appends an upgrade
      // hint if the command is listed in NEW_IN_VERSION.
      return {
        status: 400, json: true,
        result: JSON.stringify({
          error: buildUnknownCommandError(rawCommand, ALL_COMMANDS),
          hint: `Available commands: ${[...READ_COMMANDS, ...WRITE_COMMANDS, ...META_COMMANDS].sort().join(', ')}`,
        }),
      };
    }

    // ─── Centralized content wrapping (single location for all commands) ───
    // Scoped tokens: content filter + enhanced envelope + datamarking
    // Root tokens: basic untrusted content wrapper (backward compat)
    // Chain exempt from top-level wrapping (each subcommand wrapped individually)
    if (PAGE_CONTENT_COMMANDS.has(command) && command !== 'chain') {
      const isScoped = tokenInfo && tokenInfo.clientId !== 'root';
      if (isScoped) {
        // Run content filters
        const filterResult: ContentFilterResult = runContentFilters(
          result, browserManager.getCurrentUrl(), command,
        );
        if (filterResult.blocked) {
          return { status: 403, json: true, result: JSON.stringify({ error: filterResult.message }) };
        }
        // Datamark text command output only (not html, forms, or structured data)
        if (command === 'text') {
          result = datamarkContent(result);
        }
        // Enhanced envelope wrapping for scoped tokens.
        // Merge per-request hidden-element warnings with content-filter
        // warnings so both reach the LLM through the same CONTENT
        // WARNINGS header.
        const combinedWarnings = [...filterResult.warnings, ...hiddenContentWarnings];
        result = wrapUntrustedPageContent(
          result, command,
          combinedWarnings.length > 0 ? combinedWarnings : undefined,
        );
      } else {
        // Root token: basic wrapping (backward compat, Decision 2)
        result = wrapUntrustedContent(result, browserManager.getCurrentUrl());
      }
    }

    // Activity: emit command_end (skipped for chain subcommands)
    const successDuration = Date.now() - startTime;
    if (!opts?.skipActivity) {
      emitActivity({
        type: 'command_end',
        command,
        args,
        url: browserManager.getCurrentUrl(),
        duration: successDuration,
        status: 'ok',
        result: result,
        tabs: browserManager.getTabCount(),
        mode: browserManager.getConnectionMode(),
        clientId: tokenInfo?.clientId,
      });
    }

    writeAuditEntry({
      ts: new Date().toISOString(),
      cmd: command,
      aliasOf: isAliased ? rawCommand : undefined,
      args: args.join(' '),
      origin: browserManager.getCurrentUrl(),
      durationMs: successDuration,
      status: 'ok',
      hasCookies: browserManager.hasCookieImports(),
      mode: browserManager.getConnectionMode(),
    });

    browserManager.resetFailures();
    // Restore original active tab if we pinned to a specific one
    if (savedTabId !== null) {
      try { browserManager.switchTab(savedTabId, { bringToFront: false }); } catch (restoreErr: any) {
        console.warn('[browse] Failed to restore tab after command:', restoreErr.message);
      }
    }
    return { status: 200, result };
  } catch (err: any) {
    // Restore original active tab even on error
    if (savedTabId !== null) {
      try { browserManager.switchTab(savedTabId, { bringToFront: false }); } catch (restoreErr: any) {
        console.warn('[browse] Failed to restore tab after error:', restoreErr.message);
      }
    }

    // Activity: emit command_end (error) — skipped for chain subcommands
    const errorDuration = Date.now() - startTime;
    if (!opts?.skipActivity) {
      emitActivity({
        type: 'command_end',
        command,
        args,
        url: browserManager.getCurrentUrl(),
        duration: errorDuration,
        status: 'error',
        error: err.message,
        tabs: browserManager.getTabCount(),
        mode: browserManager.getConnectionMode(),
        clientId: tokenInfo?.clientId,
      });
    }

    writeAuditEntry({
      ts: new Date().toISOString(),
      cmd: command,
      aliasOf: isAliased ? rawCommand : undefined,
      args: args.join(' '),
      origin: browserManager.getCurrentUrl(),
      durationMs: errorDuration,
      status: 'error',
      error: err.message,
      hasCookies: browserManager.hasCookieImports(),
      mode: browserManager.getConnectionMode(),
    });

    browserManager.incrementFailures();
    let errorMsg = wrapError(err);
    const hint = browserManager.getFailureHint();
    if (hint) errorMsg += '\n' + hint;
    return { status: 500, result: JSON.stringify({ error: errorMsg }), json: true };
  }
}

/**
 * Sanitizing wrapper around handleCommandInternalImpl. ALL callers (single-command
 * HTTP, batch loop, scoped-token dispatch) go through this so the lone-surrogate
 * sanitization happens once at the architectural choke point, not per-leaf.
 * Do not bypass this by calling handleCommandInternalImpl directly.
 */
async function handleCommandInternal(
  body: { command: string; args?: string[]; tabId?: number },
  tokenInfo?: TokenInfo | null,
  opts?: { skipRateCheck?: boolean; skipActivity?: boolean; chainDepth?: number },
): Promise<CommandResult> {
  const cr = await handleCommandInternalImpl(body, tokenInfo, opts);
  return { ...cr, result: stripLoneSurrogates(cr.result) };
}

/**
 * Build the HTTP response from a CommandResult. Pure function so it can be
 * unit-tested without spinning up the server (#1440). Defense in depth on top
 * of handleCommandInternal's choke-point sanitization: this catches any
 * \uXXXX JSON-escape surrogate forms that the raw-codepoint regex above
 * misses when the body has already been JSON-stringified.
 */
export function buildCommandResponse(cr: CommandResult): Response {
  const contentType = cr.json ? 'application/json' : 'text/plain';
  const safeBody = typeof cr.result === 'string' ? sanitizeBody(cr.result, !!cr.json) : cr.result;
  return new Response(safeBody, {
    status: cr.status,
    headers: { 'Content-Type': contentType, ...cr.headers },
  });
}

/** HTTP wrapper — converts CommandResult to Response. Used by the /command
 * route (routes/commands.ts, via RouteContext). The wrapper layer exists so
 * `buildCommandResponse` is independently unit-testable (v1.38.1.0).
 */
async function handleCommand(body: any, tokenInfo?: TokenInfo | null): Promise<Response> {
  const cr = await handleCommandInternal(body, tokenInfo);
  return buildCommandResponse(cr);
}

// Module-level shutdown function deleted in v1.39.0.0; it now lives inside
// the buildFetchHandler closure so it closes the cfg-provided browserManager.
// Signal handlers below call activeShutdown which buildFetchHandler assigns.

// Handle signals
//
// Node passes the signal name (e.g. 'SIGTERM') as the first arg to listeners.
// Wrap calls so activeShutdown receives no args — otherwise the string gets
// passed as exitCode and process.exit() coerces it to NaN, exiting with code 1
// instead of 0. (Caught in v0.18.1.0 #1025.)
//
// Gated on `import.meta.main` so embedders (gbrowser phoenix) that import
// server.ts as a submodule can register their own signal handlers without
// fighting with gstack's. CLI path is unchanged.
if (import.meta.main) {
  // Standalone daemon: a Chromium crash must exit THIS process (its
  // supervisor/user notices); embedders and in-process test launches must
  // never be exited by browser-manager's disconnect handler.
  markDaemonProcess();
  // SIGINT (Ctrl+C): user intentionally stopping → shutdown.
  process.on('SIGINT', () => activeShutdown?.());
  // SIGHUP (terminal hangup): with handleSIGHUP:false at the three launch
  // sites (#2220), Playwright no longer closes Chromium when this process
  // gets hung up on — this handler is now the ONLY Chromium cleanup on
  // SIGHUP (ENG-OV4). Route to the same shutdown path as SIGINT:
  // activeShutdown closes the browser, releases ports, and removes the
  // state file. Without it, a hangup would leak a live Chromium.
  process.on('SIGHUP', () => activeShutdown?.());
  // SIGTERM behavior depends on mode:
  // - Normal (headless) mode: Claude Code's Bash sandbox fires SIGTERM when the
  //   parent shell exits between tool invocations. Ignoring it keeps the server
  //   alive across $B calls. Idle timeout (30 min) handles eventual cleanup.
  // - Headed / tunnel mode: idle timeout doesn't apply in these modes. Respect
  //   SIGTERM so external tooling (systemd, supervisord, CI) can shut cleanly
  //   without waiting forever. Ctrl+C and /stop still work either way.
  // - Active cookie picker: never tear down mid-import regardless of mode —
  //   would strand the picker UI with "Failed to fetch."
  process.on('SIGTERM', () => {
    if (hasActivePicker()) {
      console.log('[browse] Received SIGTERM but cookie picker is active, ignoring to avoid stranding the picker UI');
      return;
    }
    const headed = activeBrowserManager.getConnectionMode() === 'headed';
    if (headed || tunnelActive) {
      console.log(`[browse] Received SIGTERM in ${headed ? 'headed' : 'tunnel'} mode, shutting down`);
      activeShutdown?.();
    } else {
      console.log('[browse] Received SIGTERM (ignoring — use /stop or Ctrl+C for intentional shutdown)');
    }
  });
  // Windows: taskkill /F bypasses SIGTERM, but 'exit' fires for some shutdown paths.
  // Defense-in-depth — primary cleanup is the CLI's stale-state detection via health check.
  if (process.platform === 'win32') {
    process.on('exit', removeOwnedDaemonStateQuiet);
  }
}

// Emergency cleanup for crashes (OOM, uncaught exceptions, browser disconnect)
function emergencyCleanup() {
  if (isShuttingDown) return;
  isShuttingDown = true;
  // Xvfb cleanup MUST happen before state-file deletion. spawnXvfb detaches
  // the child, so without this, an uncaught exception leaves the Xvfb
  // running with no PID record — orphan accumulates and eventually
  // exhausts the :99-:120 display range. Read the state file FIRST,
  // call cleanupXvfb (validates cmdline + start-time before kill), THEN
  // delete the state file.
  try {
    if (fs.existsSync(config.stateFile)) {
      const raw = fs.readFileSync(config.stateFile, 'utf-8');
      const state = JSON.parse(raw);
      if (state.pid !== process.pid || state.instanceId !== SERVER_INSTANCE_ID) return;
      if (state.xvfbPid && state.xvfbStartTime) {
        // Lazy import — emergencyCleanup may run on platforms where
        // ./xvfb's Linux-specific helpers fail to load. Best effort.
        try {
          const { cleanupXvfb } = require('./xvfb');
          cleanupXvfb({
            pid: state.xvfbPid,
            startTime: state.xvfbStartTime,
            display: state.xvfbDisplay || ':99',
          });
        } catch { /* best effort */ }
      }
    }
  } catch { /* state file unparseable — fall through to lock + state cleanup */ }

  // Clean Chromium profile locks via the shared helper (defensive guard
  // refuses to operate on unrecognized profile dirs).
  if (activeBrowserManager.getConnectionMode() === 'headed' || process.env.BROWSE_HEADED === '1') {
    cleanSingletonLocks(resolveChromiumProfile());
  }
  removeOwnedDaemonStateQuiet();
}
// Same import.meta.main gate as SIGINT/SIGTERM — embedders register their
// own crash handlers.
if (import.meta.main) {
  process.on('uncaughtException', (err) => {
    console.error('[browse] FATAL uncaught exception:', err.message);
    emergencyCleanup();
    process.exit(1);
  });
  process.on('unhandledRejection', (err: any) => {
    console.error('[browse] FATAL unhandled rejection:', err?.message || err);
    emergencyCleanup();
    process.exit(1);
  });
}

// ─── Start ─────────────────────────────────────────────────────
/**
 * Entry point for `bun run dev` and the compiled binary.
 *
 * Exported so embedders (gbrowser phoenix overlay) can call it
 * directly with env vars set, bypassing the module-level `import.meta.main`
 * gate. Phoenix's eventual fd-passing path will use `buildFetchHandler`
 * directly; until that lands, calling `start()` from a non-main entry is
 * supported via env (AUTH_TOKEN, BROWSE_PORT, BROWSE_OWN_SIGNALS).
 */
/**
 * Build a request handler set for the browse daemon. Embedders (gbrowser
 * phoenix overlay) call this directly with their own cfg to compose overlay
 * routes via cfg.beforeRoute, pass a pre-launched cfg.browserManager, and
 * opt out of terminal-agent teardown via cfg.ownsTerminalAgent (default
 * true, set to false when the embedder runs its own PTY server). The CLI
 * path calls this through start() with env-derived defaults and explicit
 * cfg.ownsTerminalAgent: true — externally-observable behavior is identical.
 *
 * Auth state lives ENTIRELY inside the factory closure: cfg.authToken is the
 * single source of truth for the bearer secret, factory-scoped validateAuth
 * closes over it, and factory-scoped shutdown closes the cfg-provided
 * browserManager. Module-level lifecycle singletons (LOCAL_LISTEN_PORT,
 * tunnelActive, inspector state) intentionally STAY at module scope; see
 * the v1.35.0.0 CHANGELOG entry for the architectural rationale.
 *
 * The returned ServerHandle is callable directly. Bun.serve is the caller's
 * responsibility — embedders may fd-pass; CLI uses Bun.serve normally.
 */
export function buildFetchHandler(cfg: ServerConfig): ServerHandle {
  if (!cfg.authToken || cfg.authToken.length < 16) {
    throw new Error('buildFetchHandler: cfg.authToken must be a non-empty string >= 16 chars');
  }
  if (!cfg.browserManager) {
    throw new Error('buildFetchHandler: cfg.browserManager is required');
  }

  // Re-run init with cfg-provided values. ensureStateDir is idempotent
  // (mkdir -p); initAuditLog is idempotent (sets a module string);
  // initRegistry is idempotent for same-token, throws for different-token.
  // Owning init here (instead of at module load) means cfg.authToken is the
  // single source of truth for the registry root token.
  ensureStateDir(cfg.config);
  initAuditLog(cfg.config.auditLog);
  initRegistry(cfg.authToken);

  const { authToken, browserManager: cfgBrowserManager, startTime, beforeRoute, browsePort } = cfg;
  // Strict opt-out: only explicit `false` flips the gate. Any other value
  // (undefined, truthy non-bool from a JS caller bypassing TS, etc.) defaults
  // to gstack-owns. Matches the "default-true preserves CLI bit-for-bit"
  // premise even under malformed cfg.
  const ownsTerminalAgent = cfg.ownsTerminalAgent === false ? false : true;

  // ─── Terminal-Agent Watchdog (v1.44+) ─────────────────────────────
  //
  // The terminal-agent process can die independently of the server: SIGKILL
  // from the OS OOM killer, an uncaught exception under load, an external
  // `pkill` from a sibling debugging session. Pre-v1.44 the sidebar would
  // see the broken connection and stay broken until the user reloaded.
  // Now: 60s ticker checks the recorded agent PID, respawns via the shared
  // spawnTerminalAgent helper if dead.
  //
  // Identity-based — uses readAgentRecord + isProcessAlive, NOT a process
  // name probe. Critical: prevents respawning around a slow-but-alive agent
  // (which would create split-brain — two agents writing the port file,
  // tokens diverging between them, mystery PTY upgrade failures).
  //
  // Crash-loop guard: 3 respawn attempts inside 60s → stop trying and emit
  // a one-line error. Manual `forceRestart` from the sidebar clears the
  // history (the user is the explicit signal to retry).
  //
  // Only active when ownsTerminalAgent === true. Embedders that pre-launch
  // their own PTY server (gbrowser phoenix overlay) must not be auto-respawned
  // by us — their lifecycle is their concern.
  let agentWatchdogInterval: ReturnType<typeof setInterval> | null = null;
  const respawnHistory: number[] = [];
  const AGENT_WATCHDOG_TICK_MS = parseInt(
    process.env.GSTACK_AGENT_WATCHDOG_TICK_MS || '60000',
    10,
  );
  const RESPAWN_GUARD_MAX = 3;
  // The guard window MUST span enough ticks for RESPAWN_GUARD_MAX respawns to
  // land inside it. This was a fixed 60_000 against a 60_000 tick, so at most
  // ONE respawn could ever be in the window and `respawnHistory.length >= 3`
  // was unreachable — the guard could not fire at the default tick rate, and a
  // steady one-per-tick leak ran unbounded instead of stopping after 3. Scale
  // with the tick so the intent ("3 crashes in quick succession → stop") holds
  // at any tick value: 3 respawns within 5 ticks trips it.
  const RESPAWN_GUARD_WINDOW_MS = Math.max(
    60_000,
    AGENT_WATCHDOG_TICK_MS * (RESPAWN_GUARD_MAX + 2),
  );
  let agentRespawnGuardTripped = false;
  let consecutiveSpawnFailures = 0;

  if (ownsTerminalAgent) {
    agentWatchdogInterval = setInterval(() => {
      if (isShuttingDown) return;
      if (agentRespawnGuardTripped) return;
      const stateDir = path.dirname(cfg.config.stateFile);
      const record = readAgentRecord(stateDir);
      // If the record exists and the PID is alive, the agent is healthy
      // (or at least still answering signal 0). Slow-but-alive agents
      // intentionally fall through here — split-brain is worse than
      // unresponsiveness, and slow recovery is handled by the user via
      // restart.
      if (record && !isAgentRecordGone(record)) return;
      // Either no record (never spawned, or cleaned up after crash) or
      // PID is dead. Try to respawn.
      const now = Date.now();
      while (respawnHistory.length && now - respawnHistory[0] > RESPAWN_GUARD_WINDOW_MS) {
        respawnHistory.shift();
      }
      if (respawnHistory.length >= RESPAWN_GUARD_MAX) {
        agentRespawnGuardTripped = true;
        console.error(
          `[browse] terminal-agent respawn guard tripped (${RESPAWN_GUARD_MAX} crashes in ${RESPAWN_GUARD_WINDOW_MS / 1000}s) — manual restart required`,
        );
        return;
      }
      respawnHistory.push(now);
      try {
        const pid = spawnTerminalAgent({
          stateFile: cfg.config.stateFile,
          serverPort: cfg.browsePort,
          ownerPid: process.pid,
          cwd: cfg.config.projectDir,
        });
        if (pid) {
          consecutiveSpawnFailures = 0;
          console.log(`[browse] terminal-agent respawned by watchdog (PID: ${pid})`);
        } else {
          consecutiveSpawnFailures++;
          console.warn('[browse] terminal-agent respawn skipped — script not found on disk');
        }
      } catch (err: any) {
        consecutiveSpawnFailures++;
        console.warn('[browse] terminal-agent respawn failed:', err?.message || err);
      }
      if (consecutiveSpawnFailures >= RESPAWN_GUARD_MAX) {
        agentRespawnGuardTripped = true;
        console.error('[browse] terminal-agent respawn guard tripped after repeated failed starts — manual restart required');
      }
    }, AGENT_WATCHDOG_TICK_MS);
    // Detach the watchdog timer from Node's event-loop ref count so a
    // healthy idle process can still exit cleanly if everything else is
    // also unref'd. Bun's setInterval returns a Timer with unref().
    (agentWatchdogInterval as any)?.unref?.();
  }

  // Factory-scoped validateAuth. Closes over cfg.authToken so every internal
  // auth check sees the same token the routes receive. Module-level
  // validateAuth was deleted in v1.35.0.0.
  function validateAuth(req: Request): boolean {
    const header = req.headers.get('authorization');
    if (header === null) return false;
    // Constant-time compare so a byte-by-byte early-exit can't leak the token
    // prefix via response timing. timingSafeEqual requires equal-length inputs,
    // so the length check gates it (the length itself is not secret).
    const got = Buffer.from(header);
    const want = Buffer.from(`Bearer ${authToken}`);
    return got.length === want.length && crypto.timingSafeEqual(got, want);
  }

  // Factory-scoped shutdown. Closes the cfg-provided browserManager so
  // embedders that pass their own BrowserManager get correct teardown.
  // Module-level shutdown was deleted in v1.35.0.0.
  async function shutdown(exitCode: number = 0) {
    if (isShuttingDown) return;
    isShuttingDown = true;
    // State and terminal files belong to this instance, including embedders
    // whose cfg differs from the standalone daemon's module-level config.
    const config = cfg.config;
    const stateOwner = (() => {
      try { return JSON.parse(fs.readFileSync(config.stateFile, 'utf8')); } catch { return null; }
    })();
    const foreignState = Number.isSafeInteger(stateOwner?.pid) && stateOwner.pid > 0
      && (stateOwner.pid !== process.pid || (stateOwner.instanceId && stateOwner.instanceId !== SERVER_INSTANCE_ID));

    console.log('[browse] Shutting down...');
    if (ownsTerminalAgent && !foreignState) {
      // Identity-based kill (v1.44+). Replaces the v1.43- `pkill -f
      // terminal-agent\.ts` regex teardown which matched sibling gstack
      // sessions on the same host. Only the PID recorded in
      // `<stateDir>/terminal-agent-pid` by THIS daemon's agent is signaled.
      try {
        const stateDir = path.dirname(config.stateFile);
        const releaseAgentLock = acquireAgentStateLock(stateDir);
        try {
          let currentState: { pid?: number; instanceId?: string } | null = null;
          try { currentState = JSON.parse(fs.readFileSync(config.stateFile, 'utf8')); } catch {}
          if (currentState?.pid && (currentState.pid !== process.pid
            || (currentState.instanceId && currentState.instanceId !== SERVER_INSTANCE_ID))) {
            console.warn('[browse] terminal-agent state now belongs to a successor; retaining its files');
          } else {
            const record = readAgentRecord(stateDir);
            const agentStopped = !record || (record.pid !== 0
              && (!isAgentRecordLive(record) || (isOurAgent(record, process.pid) && stopAgentByRecord(record))));
            const current = readAgentRecord(stateDir);
            if (agentStopped && (!record || (current?.pid === record.pid && current.gen === record.gen))) {
              safeUnlinkQuiet(path.join(stateDir, 'terminal-port'));
              safeUnlinkQuiet(path.join(stateDir, 'terminal-internal-token'));
              if (record) clearAgentRecord(stateDir, record);
            } else if (!agentStopped) {
              console.warn('[browse] terminal-agent identity or exit could not be confirmed; retaining its record');
            }
          }
        } finally { releaseAgentLock(); }
      } catch (err: any) {
        console.warn('[browse] Failed to stop terminal-agent; retaining its state:', err.message);
      }
    }
    try { detachSession(); } catch (err: any) {
      console.warn('[browse] Failed to detach CDP session:', err.message);
    }
    clearInspectorSubscribers();
    if (cfgBrowserManager.isWatching()) cfgBrowserManager.stopWatch();
    clearInterval(flushInterval);
    clearInterval(idleCheckInterval);
    if (agentWatchdogInterval) clearInterval(agentWatchdogInterval);
    // Stop the session-persist ticker BEFORE the final snapshot below —
    // paired with the isShuttingDown gate inside the tick, this guarantees
    // no interval snapshot can race the final one during teardown.
    if (sessionPersistInterval) {
      clearInterval(sessionPersistInterval);
      sessionPersistInterval = null;
    }
    await flushBuffers();

    // Final session snapshot before the browser goes away (#778). Best
    // effort with a hard 2s deadline: shutdown must never hang on a wedged
    // page.evaluate — after the deadline we proceed to browser close and let
    // the previous interval snapshot stand (atomic writes guarantee it's
    // intact). The .catch is attached to the persist promise itself so a
    // late rejection after losing the race can't become an unhandled
    // rejection.
    if (isSessionPersistEnabled()) {
      const finalSnapshot = persistSessionState(cfgBrowserManager, path.join(config.stateDir, SESSION_STATE_FILE))
        .catch((err: any) => {
          console.warn(`[browse] SESSION_PERSIST_FAILED at shutdown: ${err?.message ?? err}`);
        });
      await Promise.race([
        finalSnapshot,
        new Promise<void>((resolve) => setTimeout(resolve, 2_000)),
      ]);
    }

    await cfgBrowserManager.close();

    if (cfgBrowserManager.getConnectionMode() === 'headed') {
      cleanSingletonLocks(resolveChromiumProfile());
    }
    if (!foreignState) {
      try {
        const releaseStateLock = acquireAgentStateLock(path.dirname(config.stateFile));
        try {
          const currentState = JSON.parse(fs.readFileSync(config.stateFile, 'utf8'));
          if (currentState.pid === process.pid && currentState.instanceId === SERVER_INSTANCE_ID) safeUnlinkQuiet(config.stateFile);
        } finally { releaseStateLock(); }
      } catch (err: any) {
        if (fs.existsSync(config.stateFile)) console.warn('[browse] Daemon state cleanup could not confirm ownership:', err?.message || err);
      }
    }
    process.exit(exitCode);
  }

  // Named lifecycle helper (matches closeTunnel style). Logs failures so
  // future debugging isn't blind to a stuck listener.
  async function stopListeners(local: any, tunnel?: any) {
    try { if (local?.stop) local.stop(true); }
    catch (err: any) { console.warn('[browse] local listener stop failed:', err?.message || err); }
    try { if (tunnel?.stop) tunnel.stop(true); }
    catch (err: any) { console.warn('[browse] tunnel listener stop failed:', err?.message || err); }
  }

  // Register this handle's shutdown as the active one. Module-level
  // handlers (idleCheckInterval, parent watchdog, onDisconnect, signal
  // handlers) call activeShutdown so they reach THIS shutdown, not a stale
  // module reference. Critical for embedders whose cfg.browserManager
  // differs from the module-level instance.
  activeShutdown = shutdown;

  // Retarget the BrowserManager indirection at the cfg-instance so the
  // module-level idleCheckTick + parent watchdog + SIGTERM handler all read
  // the right connectionMode. Without this, headed embedders auto-shutdown
  // after 30 min of HTTP idle because the dead module-level instance still
  // reports connectionMode === 'launched'.
  activeBrowserManager = cfgBrowserManager;
  // Same reason as above: the watchdog reads activeBrowserManager, so the
  // instance that can promote itself to headed must be the one that can
  // suppress the headed parent-death branch. An embedder-supplied manager
  // otherwise promotes silently and the watchdog keeps shutting down on a
  // promotion it can no longer see.
  cfgBrowserManager.onHeadedPromotion = () => suppressHeadedParentShutdown(cfg.config, cfgBrowserManager);

  // Wire the cfg-instance's onDisconnect to run shutdown when the user
  // closes the headed browser window. CHAIN any caller-provided handler
  // instead of overwriting it: gbrowser may have set its own onDisconnect
  // before calling buildFetchHandler (e.g. for snapshot/log work that needs
  // to run before the process exits). Caller errors are logged but never
  // block gstack shutdown — defensive symmetry with the safeUnlinkQuiet /
  // safeKill philosophy in error-handling.ts.
  const callerOnDisconnect = cfgBrowserManager.onDisconnect;
  cfgBrowserManager.onDisconnect = async (code) => {
    if (callerOnDisconnect) {
      try { await callerOnDisconnect(code); }
      catch (err: any) {
        console.warn('[browse] caller onDisconnect threw:', err?.message ?? err);
      }
    }
    await activeShutdown?.(code ?? 2);
  };

  // Everything a route handler may use. Handlers get the cfg-provided
  // BrowserManager and auth checks as functions; the raw token reaches only
  // the two bootstrap routes that hand it on (see RouteContext).
  const routeCtx: RouteContext = {
    browserManager: cfgBrowserManager,
    startTime,
    browsePort,
    validateAuth,
    isRootRequest,
    getTokenInfo,
    hasSseCookie: (req) => validateSseSessionToken(extractSseCookie(req)),
    isPinnedExtensionRequest,
    isRootTokenValue: (token) => token !== null && token === authToken,
    bootstrapRootToken: authToken,
    resetIdleTimer,
    terminal: { readPort: readTerminalPort, grantToken: grantPtyToken, restartSession: restartPtySession },
    tunnel: {
      state: () => ({ active: tunnelActive, url: tunnelUrl, hasListener: tunnelServer !== null }),
      close: closeTunnel,
      resolveAuthtoken: resolveNgrokAuthtoken,
      start: (authtoken) => startTunnel({
        fetchHandler: makeFetchHandler('tunnel'),
        authtoken,
        consent: 'pair_agent=on (isPairAgentEnabled gate at /tunnel/start)',
      }),
    },
    commands: {
      handle: handleCommand,
      handleInternal: (body, tokenInfo, opts) => handleCommandInternal(body, tokenInfo, opts),
    },
  };

  const makeFetchHandler = (surface: Surface) => async (req: Request): Promise<Response> => {
    const url = new URL(req.url);

    // ─── Tunnel surface filter (runs before any route dispatch) ──
    if (surface === 'tunnel') {
      const isGetConnect = req.method === 'GET' && url.pathname === '/connect';
      const allowed = TUNNEL_PATHS.has(url.pathname);
      if (!allowed && !isGetConnect) {
        logTunnelDenial(req, url, 'path_not_on_tunnel');
        return new Response(JSON.stringify({ error: 'Not found' }), {
          status: 404, headers: { 'Content-Type': 'application/json' },
        });
      }
      if (isRootRequest(req)) {
        logTunnelDenial(req, url, 'root_token_on_tunnel');
        return new Response(JSON.stringify({
          error: 'Root token rejected on tunnel surface',
          hint: 'Remote agents must pair via /connect to receive a scoped token.',
        }), { status: 403, headers: { 'Content-Type': 'application/json' } });
      }
      if (url.pathname !== '/connect' && !getTokenInfo(req)) {
        logTunnelDenial(req, url, 'missing_scoped_token');
        return new Response(JSON.stringify({ error: 'Unauthorized' }), {
          status: 401, headers: { 'Content-Type': 'application/json' },
        });
      }
    }

    // beforeRoute overlay hook (v1.35.0.0). Runs AFTER the tunnel surface
    // filter and BEFORE per-route dispatch. Pre-resolves bearer auth once
    // so the hook receives TokenInfo | null. Note: getTokenInfo returns null
    // for both missing AND invalid bearer — see the ServerConfig.beforeRoute
    // JSDoc for the security implications.
    if (beforeRoute) {
      const auth = getTokenInfo(req);
      const overlayResp = await beforeRoute(req, surface, auth);
      if (overlayResp) return overlayResp;
    }

    return dispatchRoute(ROUTES, req, url, surface, routeCtx);
  };

  return {
    fetchLocal: makeFetchHandler('local'),
    fetchTunnel: makeFetchHandler('tunnel'),
    shutdown,
    stopListeners,
  };
}

export async function start() {
  // Clear old log files
  safeUnlink(CONSOLE_LOG_PATH);
  safeUnlink(NETWORK_LOG_PATH);
  safeUnlink(DIALOG_LOG_PATH);

  const port = await findPort();
  LOCAL_LISTEN_PORT = port;

  // ─── Proxy config (D8 + codex F5) ──────────────────────────────
  // BROWSE_PROXY_URL is set by the CLI when --proxy was passed. For SOCKS5
  // with auth, we run a local 127.0.0.1 bridge that relays to the
  // authenticated upstream (Chromium can't do SOCKS5 auth itself). For
  // HTTP/HTTPS or unauthenticated SOCKS5, we pass the URL directly to
  // Chromium's proxy.server option.
  let proxyBridge: BridgeHandle | null = null;
  const proxyUrl = process.env.BROWSE_PROXY_URL;
  if (proxyUrl) {
    let parsed;
    try {
      parsed = parseProxyConfig({
        proxyUrl,
        envUser: process.env.BROWSE_PROXY_USER,
        envPass: process.env.BROWSE_PROXY_PASS,
      });
    } catch (err) {
      if (err instanceof ProxyConfigError) {
        console.error(`[browse] error: ${err.message} (${err.hint})`);
        process.exit(1);
      }
      throw err;
    }

    if (parsed.scheme === 'socks5' && parsed.hasAuth) {
      // Pre-flight: verify upstream accepts our creds before launching
      // Chromium. 5s budget, 3 retries with 500ms backoff (D4: handles VPN
      // warm-up race). On failure, exit with redacted error.
      console.log(`[browse] Testing SOCKS5 upstream ${redactProxyUrl(proxyUrl)}...`);
      try {
        const test = await testUpstream({
          upstream: toUpstreamConfig(parsed),
          budgetMs: 5000,
          retries: 3,
          backoffMs: 500,
        });
        console.log(`[browse] [proxy] upstream test ok in ${test.ms}ms (${test.attempts} attempt${test.attempts === 1 ? '' : 's'})`);
      } catch (err) {
        const msg = err instanceof Error ? err.message : String(err);
        console.error(`[browse] [proxy] FAIL upstream ${redactProxyUrl(proxyUrl)}: ${msg}`);
        process.exit(1);
      }

      proxyBridge = await startSocksBridge({ upstream: toUpstreamConfig(parsed) });
      console.log(`[browse] [proxy] bridge listening on 127.0.0.1:${proxyBridge.port}`);
      browserManager.setProxyConfig({ server: `socks5://127.0.0.1:${proxyBridge.port}` });
    } else {
      // HTTP/HTTPS or unauth SOCKS5 — pass through to Chromium directly.
      browserManager.setProxyConfig({
        server: `${parsed.scheme}://${parsed.host}:${parsed.port}`,
        ...(parsed.userId ? { username: parsed.userId } : {}),
        ...(parsed.password ? { password: parsed.password } : {}),
      });
      console.log(`[browse] [proxy] using ${redactProxyUrl(proxyUrl)} (pass-through to Chromium)`);
    }

    // Tear down bridge on shutdown.
    process.on('exit', () => {
      if (proxyBridge) {
        proxyBridge.close().catch(() => { /* shutting down anyway */ });
      }
    });
  }

  process.on('exit', () => { browserManager.closeOwnedDisplay(); });

  // Read env once — single source of truth for authToken (and other env).
  // Threaded through launchHeaded, buildFetchHandler, and the state file
  // write so all consumers see the same value. v1.34.x's module-level
  // AUTH_TOKEN const was deleted in v1.35.0.0.
  const envCfg = resolveConfigFromEnv();

  // Launch browser (headless or headed with extension)
  // BROWSE_HEADLESS_SKIP=1 skips browser launch entirely (for HTTP-only testing)
  const skipBrowser = process.env.BROWSE_HEADLESS_SKIP === '1';
  if (!skipBrowser) {
    const headed = process.env.BROWSE_HEADED === '1';
    if (headed) {
      await browserManager.launchHeaded(envCfg.authToken);
      console.log(`[browse] Launched headed Chromium with extension`);
    } else {
      await browserManager.launch();
    }
  }

  const startTime = Date.now();

  // ─── Build the request handlers via buildFetchHandler factory ───
  // CLI path passes env-derived values; no beforeRoute hook. Phoenix uses
  // the same factory with its own cfg + overlay hook.
  const handle = buildFetchHandler({
    ...envCfg,
    browsePort: port,        // actual bound port (resolveConfigFromEnv default is 0)
    browserManager,          // module-level instance, same as today
    proxyBridge,
    startTime,
    ownsTerminalAgent: true, // CLI spawns terminal-agent.ts itself (see cli.ts:1037-1063)
  });

  const server = Bun.serve({
    port,
    hostname: '127.0.0.1',
    fetch: handle.fetchLocal,
  });

  browserManager.serverPort = port;

  // Navigate to welcome page if in headed mode and still on about:blank
  if (browserManager.getConnectionMode() === 'headed') {
    try {
      const currentUrl = browserManager.getCurrentUrl();
      if (currentUrl === 'about:blank' || currentUrl === '') {
        const page = browserManager.getPage();
        await page.goto(`http://127.0.0.1:${port}/welcome`, { timeout: 3000 }).catch((err: any) => {
          console.warn('[browse] Failed to navigate to welcome page:', err.message);
        });
      }
    } catch (err: any) {
      console.warn('[browse] Welcome page navigation setup failed:', err.message);
    }
  }

  if (isShuttingDown) return;

  // Write state file (atomic: write .tmp then rename)
  const xvfb = browserManager.getXvfbHandle();
  const state: Record<string, unknown> = {
    pid: process.pid,
    instanceId: SERVER_INSTANCE_ID,
    port,
    token: envCfg.authToken,
    startedAt: new Date().toISOString(),
    serverPath: path.resolve(import.meta.dir, 'server.ts'),
    binaryVersion: readVersionHash() || undefined,
    mode: browserManager.getConnectionMode(),
    // D2 daemon-mismatch detection: CLI computes the same hash from its
    // resolved flags and refuses if it differs from this stored value.
    ...(process.env.BROWSE_CONFIG_HASH ? { configHash: process.env.BROWSE_CONFIG_HASH } : {}),
    // Xvfb child PID + start-time + display so disconnect (or a future
    // daemon launch on this state file) can validate-then-cleanup orphans
    // without clobbering a recycled PID.
    ...(xvfb ? { xvfbPid: xvfb.pid, xvfbStartTime: xvfb.startTime, xvfbDisplay: xvfb.display } : {}),
    // #2709: launched-Chromium identity (pid + start time) so `browse stop`
    // can reap a survivor — the headless launch has no SingletonLock for
    // killOrphanChromium to walk, and on macOS 26 the orphaned GPU process
    // kept spinning at ~800% CPU after the daemon exited.
    ...(() => {
      const info = browserManager.getChromiumProcInfo();
      return info ? { chromiumPid: info.pid, chromiumStartTime: info.startTime } : {};
    })(),
  };
  const tmpFile = tmpStatePath();
  fs.writeFileSync(tmpFile, JSON.stringify(state, null, 2), { mode: 0o600 });
  try {
    const releaseStateLock = acquireAgentStateLock(config.stateDir);
    try { fs.renameSync(tmpFile, config.stateFile); } finally { releaseStateLock(); }
  } catch (err) {
    safeUnlinkQuiet(tmpFile);
    throw err;
  }

  const stateWatchMs = parseInt(process.env.GSTACK_STATE_WATCH_MS || '60000', 10);
  if (stateWatchMs > 0) {
    let missed = 0;
    const stateWatch = setInterval(() => {
      let owner: { pid?: number; instanceId?: string } | null = null;
      try { owner = JSON.parse(fs.readFileSync(config.stateFile, 'utf8')); } catch {}
      if (owner?.pid === process.pid && owner.instanceId === SERVER_INSTANCE_ID) { missed = 0; return; }
      if (++missed < 2) return;
      clearInterval(stateWatch);
      console.warn('[browse] daemon state is no longer reachable; shutting down this instance');
      handle.shutdown();
    }, stateWatchMs);
    (stateWatch as any).unref?.();
  }

  // ─── Opt-in session persistence (#778 class) ─────────────────
  // BROWSE_PERSIST_STATE=1: restore cookies/storage/tabs from the last
  // snapshot, then keep snapshotting on an interval. Launched mode only —
  // the headed persistent profile owns its own state. The final snapshot at
  // clean shutdown lives in buildFetchHandler's shutdown().
  //
  // Runs AFTER Bun.serve() + the state-file write, in the BACKGROUND:
  // restore re-creates tabs sequentially with up-to-15s goto timeouts while
  // the CLI's readiness probe gives up at 8s — one slow/unreachable saved
  // URL must never make every `$B` command report "Server failed to start".
  // Fire-and-forget: a restore failure is logged and never affects the
  // daemon.
  if (!skipBrowser && isSessionPersistEnabled() && browserManager.getConnectionMode() === 'launched') {
    const sessionStatePath = path.join(config.stateDir, SESSION_STATE_FILE);
    restoreSessionState(browserManager, sessionStatePath)
      .then((restored) => {
        if (restored) {
          // Counts come from the deserialized snapshot itself — no extra
          // saveState() round-trip against pages that may still be loading.
          console.log(`[browse] Session state restored: ${restored.cookies.length} cookies / ${restored.pages.length} tabs (BROWSE_PERSIST_STATE=1)`);
        } else {
          console.log('[browse] Session persistence on; no prior state — fresh session (BROWSE_PERSIST_STATE=1)');
        }
      })
      .catch((err: any) => {
        console.warn(`[browse] SESSION_RESTORE_FAILED: ${err?.message ?? err}`);
      });
    let persistWarned = false;
    // In-flight guard: never start a new snapshot while the previous one is
    // still pending (a slow page.evaluate would otherwise pile up ticks).
    let persistInFlight = false;
    sessionPersistInterval = setInterval(() => {
      // Shutdown gate (belt; shutdown()'s clearInterval is the suspenders):
      // a tick that fires during browser teardown snapshots a degraded state
      // (zero tabs) over the good final snapshot.
      if (isShuttingDown) return;
      if (persistInFlight) return; // skip the tick
      persistInFlight = true;
      persistSessionState(browserManager, sessionStatePath)
        .catch((err: any) => {
          // Warn once — a full disk must not spam the log every 30s, and a
          // snapshot failure must never kill the daemon (R3).
          if (!persistWarned) {
            persistWarned = true;
            console.warn(`[browse] SESSION_PERSIST_FAILED: ${err?.message ?? err} (further failures suppressed)`);
          }
        })
        .finally(() => { persistInFlight = false; });
    }, sessionPersistIntervalMs());
    (sessionPersistInterval as any)?.unref?.();
  }

  // Clean up stale state files (older than 7 days)
  try {
    const stateDir = path.join(config.stateDir, 'browse-states');
    if (fs.existsSync(stateDir)) {
      const SEVEN_DAYS = 7 * 24 * 60 * 60 * 1000;
      for (const file of fs.readdirSync(stateDir)) {
        const filePath = path.join(stateDir, file);
        const stat = fs.statSync(filePath);
        if (Date.now() - stat.mtimeMs > SEVEN_DAYS) {
          fs.unlinkSync(filePath);
          console.log(`[browse] Deleted stale state file: ${file}`);
        }
      }
    }
  } catch (err: any) {
    console.warn('[browse] Failed to clean stale state files:', err.message);
  }

  console.log(`[browse] Server running on http://127.0.0.1:${port} (PID: ${process.pid})`);
  console.log(`[browse] State file: ${config.stateFile}`);
  console.log(`[browse] Idle timeout: ${IDLE_TIMEOUT_MS / 1000}s`);

  // ─── Tunnel startup (optional) ────────────────────────────────
  // Start ngrok tunnel if BROWSE_TUNNEL=1 is set.  Uses the dual-listener
  // pattern: bind a dedicated tunnel listener on an ephemeral port and
  // point ngrok.forward() at IT, not the local daemon port.
  if (process.env.BROWSE_TUNNEL === '1' && !isPairAgentEnabled()) {
    console.error('[browse] BROWSE_TUNNEL=1 ignored: pair-agent is off. Enable once with: gstack-config set pair_agent on');
  } else if (process.env.BROWSE_TUNNEL === '1') {
    const authtoken = resolveNgrokAuthtoken();
    if (!authtoken) {
      console.error('[browse] BROWSE_TUNNEL=1 but no NGROK_AUTHTOKEN found. Set it via env var or ~/.gstack/ngrok.env');
    } else {
      // Shared startTunnel helper: binds the tunnel listener, opens ngrok,
      // and on any failure tears down BOTH ngrok and the Bun listener so we
      // don't leak an ngrok session if the error happened after
      // ngrok.forward() resolved.
      const started = await startTunnel({
        fetchHandler: handle.fetchTunnel,
        authtoken,
        consent: 'pair_agent=on (isPairAgentEnabled gate, BROWSE_TUNNEL=1)',
      });
      if (!started.ok) {
        console.error(`[browse] Failed to start tunnel: ${started.error.message}`);
      }
    }
  } else if (process.env.BROWSE_TUNNEL_LOCAL_ONLY === '1') {
    // Test-only: bind the dual-listener tunnel surface on 127.0.0.1 with NO
    // ngrok forwarding. Lets paid evals exercise the surface==='tunnel' gate
    // without an ngrok authtoken or live network. Production tunneling still
    // requires BROWSE_TUNNEL=1 + a valid authtoken above.
    try {
      const boundTunnel = Bun.serve({
        port: 0,
        hostname: '127.0.0.1',
        fetch: handle.fetchTunnel,
      });
      tunnelServer = boundTunnel;
      tunnelActive = true;
      const tunnelPort = boundTunnel.port;
      console.log(`[browse] Tunnel listener bound (local-only test mode) on 127.0.0.1:${tunnelPort}`);
      const releaseStateLock = acquireAgentStateLock(config.stateDir);
      try {
        const stateContent = JSON.parse(fs.readFileSync(config.stateFile, 'utf-8'));
        if (stateContent.pid !== process.pid || stateContent.instanceId !== SERVER_INSTANCE_ID) throw new Error('daemon state was replaced');
        stateContent.tunnelLocalPort = tunnelPort;
        const tmpState = tmpStatePath();
        fs.writeFileSync(tmpState, JSON.stringify(stateContent, null, 2), { mode: 0o600 });
        fs.renameSync(tmpState, config.stateFile);
      } finally { releaseStateLock(); }
    } catch (err: any) {
      console.error(`[browse] BROWSE_TUNNEL_LOCAL_ONLY=1 listener bind failed: ${err.message}`);
    }
  }
}

/**
 * Test-only. Resets the module-level shutdown latch so a second test case
 * can exercise shutdown() in the same process. Mirrors __resetRegistry in
 * token-registry.ts. shutdown() short-circuits when isShuttingDown is true
 * (see line near the start of shutdown), so without this, tests that call
 * shutdown() more than once silently no-op after the first call.
 *
 * DO NOT call from production code. Defeats the shutdown re-entry guard,
 * which can race process.exit with cfgBrowserManager.close() and the pkill /
 * safeUnlinkQuiet side effects. The `__` prefix is the convention; nothing
 * enforces it. If you find yourself reaching for this outside a test file,
 * the right fix is to make isShuttingDown factory-scoped instead.
 */
export function __resetShuttingDown(): void {
  isShuttingDown = false;
}

// Auto-kickoff only when this module is the entry point. Embedders
// (gbrowser phoenix overlay) import { start, buildFetchHandler, ... }
// without triggering the listener-binding side effects.
if (import.meta.main) {
  start().catch((err) => {
    console.error(`[browse] Failed to start: ${err.message}`);
    // Write error to disk for the CLI to read — on Windows, the CLI can't capture
    // stderr because the server is launched with detached: true, stdio: 'ignore'.
    try {
      const errorLogPath = path.join(config.stateDir, 'browse-startup-error.log');
      mkdirSecure(config.stateDir);
      writeSecureFile(errorLogPath, `${new Date().toISOString()} ${err.message}\n${err.stack || ''}\n`);
    } catch {
      // stateDir may not exist — nothing more we can do
    }
    process.exit(1);
  });
}