diff --git a/packages/web/server/index.js b/packages/web/server/index.js
index 1c386b3c..4eac3336 100644
--- a/packages/web/server/index.js
+++ b/packages/web/server/index.js
@@ -1079,6 +1079,19 @@ const openCodeLifecycleRuntime = createOpenCodeLifecycleRuntime({
     }
     return [...new Set(directories)];
   },
+  // A managed restart can move OpenCode to a NEW port (the old one may stay
+  // occupied by an orphaned process, e.g. killProcessOnPort is a no-op on
+  // Windows). Rebind the message-stream upstream readers to the current port
+  // so the UI keeps receiving events instead of staying pinned to the old
+  // process (#2638). The runtime is created later by the startup pipeline;
+  // by the time any restart runs, it is assigned.
+  onOpenCodeRestarted: () => {
+    try {
+      messageStreamRuntime?.rebindUpstream();
+    } catch (error) {
+      console.warn('Failed to rebind message stream after OpenCode restart:', error?.message ?? error);
+    }
+  },
   getManagedOpenCodeEnv: async () => {
     const settings = await readSettingsFromDiskMigrated().catch(() => null);
     const managedEnv = settings?.agentControlToolEnabled === false
diff --git a/packages/web/server/lib/event-stream/rebind.test.js b/packages/web/server/lib/event-stream/rebind.test.js
new file mode 100644
index 00000000..ebf821f2
--- /dev/null
+++ b/packages/web/server/lib/event-stream/rebind.test.js
@@ -0,0 +1,186 @@
+import { EventEmitter } from 'node:events';
+import { describe, expect, it, vi } from 'vitest';
+
+import { createGlobalMessageStreamHub } from './global-hub.js';
+import { createMessageStreamWsRuntime } from './runtime.js';
+
+class FakeSocket extends EventEmitter {
+  constructor() {
+    super();
+    this.readyState = 1;
+    this.sent = [];
+    this.closeCalls = [];
+  }
+
+  send(payload) {
+    this.sent.push(JSON.parse(payload));
+  }
+
+  ping() {
+    void 0;
+  }
+
+  close(code, reason) {
+    if (this.readyState === 3) {
+      return;
+    }
+    this.readyState = 3;
+    this.closeCalls.push({ code, reason });
+    this.emit('close');
+  }
+}
+
+function createSseResponse({ blocks = [], signal, holdOpen = false }) {
+  const encoder = new TextEncoder();
+  let index = 0;
+
+  return {
+    ok: true,
+    body: {
+      getReader() {
+        return {
+          async read() {
+            if (index < blocks.length) {
+              const next = blocks[index++];
+              return { value: encoder.encode(next), done: false };
+            }
+
+            if (!holdOpen) {
+              return { value: undefined, done: true };
+            }
+
+            return new Promise((resolve, reject) => {
+              const onAbort = () => {
+                signal.removeEventListener('abort', onAbort);
+                const error = new Error('Aborted');
+                error.name = 'AbortError';
+                reject(error);
+              };
+              signal.addEventListener('abort', onAbort, { once: true });
+            });
+          },
+        };
+      },
+    },
+  };
+}
+
+describe('rebindUpstream (#2638)', () => {
+  it('restarts the shared hub upstream so a connected client resumes receiving events on the new port', async () => {
+    const server = new EventEmitter();
+    const wsClients = new Set();
+    let port = 4096;
+    let fetchCalls = 0;
+
+    // Port changes after a managed restart: buildOpenCodeUrl resolves the
+    // CURRENT port on every attempt, exactly like production network-runtime.
+    const buildOpenCodeUrl = vi.fn(() => `http://127.0.0.1:${port}/global/event`);
+    const fetchImpl = vi.fn(async (_url, options) => {
+      fetchCalls += 1;
+      if (fetchCalls === 1) {
+        return createSseResponse({
+          signal: options.signal,
+          holdOpen: true,
+          blocks: ['id: evt-1\ndata: {"type":"server.connected","properties":{}}\n\n'],
+        });
+      }
+      return createSseResponse({
+        signal: options.signal,
+        holdOpen: true,
+        blocks: ['id: evt-2\ndata: {"type":"session.updated","properties":{"sessionID":"ses_1"}}\n\n'],
+      });
+    });
+
+    const globalHub = createGlobalMessageStreamHub({
+      buildOpenCodeUrl,
+      getOpenCodeAuthHeaders: () => ({}),
+      fetchImpl,
+      upstreamReconnectDelayMs: 0,
+    });
+
+    const runtime = createMessageStreamWsRuntime({
+      server,
+      uiAuthController: null,
+      isRequestOriginAllowed: async () => true,
+      rejectWebSocketUpgrade() {
+        throw new Error('upgrade should not be used in this test');
+      },
+      globalEventHub: globalHub,
+      buildOpenCodeUrl,
+      getOpenCodeAuthHeaders: () => ({}),
+      processForwardedEventPayload() {},
+      wsClients,
+      heartbeatIntervalMs: 5000,
+      upstreamReconnectDelayMs: 0,
+      fetchImpl,
+    });
+
+    const socket = new FakeSocket();
+    runtime.wsServer.emit('connection', socket, { url: '/api/global/event/ws' });
+    await new Promise((resolve) => setTimeout(resolve, 10));
+    expect(fetchCalls).toBe(1);
+    expect(socket.sent.some((frame) => frame.type === 'event' && frame.eventId === 'evt-1')).toBe(true);
+
+    // The managed process was restarted onto a new port while the old
+    // process's SSE stream stays open (orphaned survivor).
+    port = 5000;
+    runtime.rebindUpstream();
+    await new Promise((resolve) => setTimeout(resolve, 20));
+
+    // The hub dialed the new port and the connected client received events
+    // from the new upstream without reconnecting its own socket.
+    expect(fetchCalls).toBe(2);
+    expect(fetchImpl.mock.calls[1][0]).toContain(':5000/global/event');
+    expect(socket.sent.some((frame) => frame.type === 'event' && frame.eventId === 'evt-2')).toBe(true);
+
+    socket.close();
+    await runtime.close();
+  });
+
+  it('closes directory-scoped sockets so their pinned readers reconnect to the new port', async () => {
+    const server = new EventEmitter();
+    const wsClients = new Set();
+    let port = 4096;
+    let fetchCalls = 0;
+
+    const buildOpenCodeUrl = vi.fn(() => `http://127.0.0.1:${port}/event`);
+    const fetchImpl = vi.fn(async (_url, options) => {
+      fetchCalls += 1;
+      return createSseResponse({
+        signal: options.signal,
+        holdOpen: true,
+        blocks: ['id: evt-1\ndata: {"type":"server.connected","properties":{}}\n\n'],
+      });
+    });
+
+    const runtime = createMessageStreamWsRuntime({
+      server,
+      uiAuthController: null,
+      isRequestOriginAllowed: async () => true,
+      rejectWebSocketUpgrade() {
+        throw new Error('upgrade should not be used in this test');
+      },
+      buildOpenCodeUrl,
+      getOpenCodeAuthHeaders: () => ({}),
+      processForwardedEventPayload() {},
+      wsClients,
+      heartbeatIntervalMs: 5000,
+      upstreamReconnectDelayMs: 0,
+      fetchImpl,
+    });
+
+    const directorySocket = new FakeSocket();
+    runtime.wsServer.emit('connection', directorySocket, { url: '/api/event/ws?directory=%2Fproj' });
+    await new Promise((resolve) => setTimeout(resolve, 10));
+    expect(fetchCalls).toBe(1);
+
+    port = 5000;
+    runtime.rebindUpstream();
+
+    expect(directorySocket.readyState).toBe(3);
+    expect(directorySocket.closeCalls.length).toBeGreaterThan(0);
+
+    directorySocket.close();
+    await runtime.close();
+  });
+});
diff --git a/packages/web/server/lib/event-stream/runtime.js b/packages/web/server/lib/event-stream/runtime.js
index 72a28893..07b025dc 100644
--- a/packages/web/server/lib/event-stream/runtime.js
+++ b/packages/web/server/lib/event-stream/runtime.js
@@ -70,6 +70,12 @@ export function createMessageStreamWsRuntime({
     noServer: true,
   });
 
+  // Directory-scoped streams create one upstream reader per client
+  // connection. Track those sockets so a managed OpenCode restart can close
+  // them: each reader is pinned to the port it connected at and would
+  // otherwise keep streaming from an orphaned process on the old port (#2638).
+  const directorySockets = new Set();
+
   const ownsGlobalHub = !globalEventHub;
   const globalHub = globalEventHub ?? createGlobalMessageStreamHub({
     buildOpenCodeUrl,
@@ -103,6 +109,11 @@ export function createMessageStreamWsRuntime({
       return;
     }
 
+    directorySockets.add(socket);
+    socket.on('close', () => {
+      directorySockets.delete(socket);
+    });
+
     acceptDirectoryMessageStreamWsConnection({
       socket,
       requestedLastEventId,
@@ -156,6 +167,27 @@ export function createMessageStreamWsRuntime({
 
   return {
     wsServer,
+    /**
+     * Rebind all upstream readers to the current OpenCode port. Called after
+     * a managed process restart: the restart can land on a NEW port while
+     * the old process (or an orphaned survivor of it) still holds the
+     * previous one, and a healthy-but-pinned SSE connection never notices —
+     * so the UI would stop receiving events until the app restarts (#2638).
+     * Restarting the shared hub re-dials `buildOpenCodeUrl` (which reads the
+     * current port) on its next attempt; directory-scoped readers are
+     * rebuilt by closing their client sockets, which reconnect with
+     * `Last-Event-ID` and re-establish the stream against the new port.
+     */
+    rebindUpstream() {
+      globalHub.stop();
+      globalHub.start();
+      for (const socket of Array.from(directorySockets)) {
+        try {
+          socket.close(1012, 'OpenCode upstream restarted');
+        } catch {
+        }
+      }
+    },
     async close() {
       server.off('upgrade', upgradeHandler);
       globalBridge.close();
diff --git a/packages/web/server/lib/opencode/lifecycle.js b/packages/web/server/lib/opencode/lifecycle.js
index 172d88b2..bb13aab0 100644
--- a/packages/web/server/lib/opencode/lifecycle.js
+++ b/packages/web/server/lib/opencode/lifecycle.js
@@ -48,6 +48,7 @@ export const createOpenCodeLifecycleRuntime = (deps) => {
     getActiveSessionCount = () => 0,
     reapManagedOrphanedProcesses = reapOrphanedProcesses,
     getWarmupDirectories = async () => [],
+    onOpenCodeRestarted = null,
     now = Date.now,
   } = deps;
 
@@ -694,6 +695,17 @@ export const createOpenCodeLifecycleRuntime = (deps) => {
         setupProxy(state.expressApp);
         ensureOpenCodeApiPrefix();
       }
+
+      // The restart may have landed on a NEW port (the old one can remain
+      // occupied by an orphaned process, e.g. Windows killProcessOnPort is a
+      // no-op). Upstream event readers pinned to the old process would keep
+      // the UI silent forever, so rebind them to the current port. Best
+      // effort: a failure here must not fail the restart itself.
+      try {
+        onOpenCodeRestarted?.();
+      } catch (error) {
+        console.warn('Failed to rebind event stream after OpenCode restart:', error?.message ?? error);
+      }
     })();
 
     try {
diff --git a/packages/web/server/lib/opencode/lifecycle.test.js b/packages/web/server/lib/opencode/lifecycle.test.js
index fb57c3f2..04bf4c33 100644
--- a/packages/web/server/lib/opencode/lifecycle.test.js
+++ b/packages/web/server/lib/opencode/lifecycle.test.js
@@ -286,6 +286,70 @@ describe('OpenCode lifecycle', () => {
     expect(spawnMock).toHaveBeenCalledTimes(1);
   });
 
+  it('calls onOpenCodeRestarted after a successful managed restart', async () => {
+    const close = vi.fn(async () => {});
+    const replacement = createMockChild();
+    const onOpenCodeRestarted = vi.fn();
+    globalThis.fetch = vi.fn(async () => ({
+      ok: false,
+      json: async () => null,
+    }));
+    spawnMock.mockImplementationOnce(() => {
+      queueMicrotask(() => {
+        replacement.stdout.emit('data', 'opencode server listening on http://127.0.0.1:45678\n');
+      });
+      return replacement;
+    });
+    const runtime = createRuntime({ onOpenCodeRestarted }, {
+      openCodePort: 45678,
+      openCodeProcess: {
+        pid: null,
+        exitCode: 1,
+        signalCode: null,
+        close,
+      },
+    });
+
+    await runtime.triggerHealthCheck();
+
+    expect(close).toHaveBeenCalledTimes(1);
+    expect(spawnMock).toHaveBeenCalledTimes(1);
+    // The restart completed on a (possibly new) port — the event-stream
+    // upstreams must rebind so the UI keeps receiving events (#2638).
+    expect(onOpenCodeRestarted).toHaveBeenCalledTimes(1);
+  });
+
+  it('does not call onOpenCodeRestarted when a managed restart fails', async () => {
+    const close = vi.fn(async () => {});
+    const onOpenCodeRestarted = vi.fn();
+    globalThis.fetch = vi.fn(async () => ({
+      ok: false,
+      json: async () => null,
+    }));
+    spawnMock.mockImplementation(() => {
+      const child = createMockChild();
+      queueMicrotask(() => {
+        child.emit('error', new Error('spawn failed'));
+      });
+      return child;
+    });
+    const runtime = createRuntime({ onOpenCodeRestarted }, {
+      openCodePort: 45678,
+      openCodeProcess: {
+        pid: null,
+        exitCode: 1,
+        signalCode: null,
+        close,
+      },
+    });
+
+    // triggerHealthCheck logs instead of rethrowing; call restartOpenCode
+    // directly to observe the failure result.
+    await expect(runtime.restartOpenCode()).rejects.toThrow();
+
+    expect(onOpenCodeRestarted).not.toHaveBeenCalled();
+  });
+
   it('launches managed OpenCode with the managed PATH', async () => {
     delete process.env.OPENCODE_BINARY;
     const child = createMockChild();
diff --git a/scripts/repro/issue-2638/README.md b/scripts/repro/issue-2638/README.md
new file mode 100644
index 00000000..357ee8af
--- /dev/null
+++ b/scripts/repro/issue-2638/README.md
@@ -0,0 +1,47 @@
+# Reproduction: Chat UI stops updating until the desktop app is restarted (#2638)
+
+Reproduces https://github.com/openchamber/openchamber/issues/2638 using the
+real server modules (`lifecycle.js`, `global-hub.js`, `network-runtime.js`),
+real processes, and real ports — no mocks.
+
+## Run
+
+```sh
+# Windows-orphan scenario (the reported bug):
+node scripts/repro/issue-2638/reproduce-2638.mjs
+
+# Control: healthy restart on Linux (hub reconnects, UI keeps updating):
+node scripts/repro/issue-2638/reproduce-2638.mjs --baseline
+```
+
+Requires `lsof` (used only for cleanup). The default run simulates Windows
+(`process.platform` is temporarily overridden to `win32`) because the bug is
+specific to the Windows process-lifecycle path.
+
+## What it demonstrates
+
+1. A managed OpenCode process starts; the global message-stream hub connects to
+   its `/global/event` SSE stream and chat events flow to the UI.
+2. The managed process "exits" but the actual server process survives on the
+   old port (on Windows `killProcessOnPort` is a no-op and `taskkill` cannot
+   reach the orphaned tree — the report shows leftover `opencode.exe serve`
+   processes on historical ports).
+3. `restartOpenCode()` gives up after 5 s — logs
+   `Timed out waiting for OpenCode port <old> to be released` — and spawns a
+   fresh server on a NEW port, leaving the orphaned process running.
+4. HTTP/proxy traffic follows `state.openCodePort` to the new server, but the
+   hub's upstream SSE reader stays pinned to the OLD server's `/global/event`
+   stream (that connection never closed), so events emitted by the new server
+   never reach the UI: the chat UI goes stale while the new server keeps
+   persisting session data — visible only after restarting the app.
+
+The `--baseline` control proves the reconnect logic itself is fine: when the
+old process dies and the port is properly released, the hub reconnects to the
+new port and events are delivered.
+
+## Files
+
+- `reproduce-2638.mjs` — the reproduction driver (assertions + summary).
+- `fake-opencode-serve.mjs` — a fake `opencode serve` binary whose launcher
+  spawns a detached server core that survives the launcher's death
+  (Windows-style orphan), plus an in-process mode for the baseline control.
diff --git a/scripts/repro/issue-2638/fake-opencode-serve.mjs b/scripts/repro/issue-2638/fake-opencode-serve.mjs
new file mode 100755
index 00000000..0fc36dc0
--- /dev/null
+++ b/scripts/repro/issue-2638/fake-opencode-serve.mjs
@@ -0,0 +1,151 @@
+#!/usr/bin/env node
+// Fake `opencode serve` used to reproduce https://github.com/openchamber/openchamber/issues/2638
+//
+// Modes (controlled by env):
+//   FAKE_OPENCODE_CORE=1      – server-core mode: binds the port, serves
+//                               /global/health + SSE /global/event, ignores
+//                               SIGTERM so it survives its launcher's death
+//                               (Windows-style orphaned server process).
+//   FAKE_OPENCODE_BASELINE=1  – in-process mode: the server runs inside the
+//                               managed process and dies with it (normal
+//                               Linux behavior used as a control).
+//   default (launcher)        – spawns a detached core grandchild, waits for
+//                               it to bind, prints the `opencode server
+//                               listening on ...` line the lifecycle greps
+//                               for, stays alive, and on SIGTERM exits WITHOUT
+//                               killing the core (mimics opencode.exe dying
+//                               while its server child survives).
+import http from 'node:http';
+import net from 'node:net';
+import fs from 'node:fs';
+import path from 'node:path';
+import { spawn } from 'node:child_process';
+
+const args = process.argv.slice(2);
+const portIndex = args.indexOf('--port');
+const hostnameIndex = args.indexOf('--hostname');
+const port = portIndex >= 0 ? Number(args[portIndex + 1]) : 0;
+const hostname = hostnameIndex >= 0 ? args[hostnameIndex + 1] : '127.0.0.1';
+const pidDir = process.env.FAKE_OPENCODE_PID_DIR || null;
+
+function writePidFile(label) {
+  if (!pidDir) return;
+  try {
+    fs.mkdirSync(pidDir, { recursive: true });
+    fs.writeFileSync(path.join(pidDir, `${label}-${port}.pid`), String(process.pid));
+  } catch {
+    // best effort
+  }
+}
+
+function createServer() {
+  const clients = new Set();
+  const emitted = [];
+  const server = http.createServer((req, res) => {
+    const url = new URL(req.url, `http://${hostname}:${port}`);
+    if (url.pathname === '/global/health') {
+      res.writeHead(200, { 'content-type': 'application/json' });
+      res.end(JSON.stringify({ healthy: true }));
+      return;
+    }
+    if (url.pathname === '/global/event') {
+      res.writeHead(200, {
+        'content-type': 'text/event-stream',
+        'cache-control': 'no-cache',
+        connection: 'keep-alive',
+      });
+      clients.add(res);
+      req.on('close', () => clients.delete(res));
+      // SSE keep-alive comments — exactly what a real OpenCode server sends,
+      // which prevents the upstream reader's 20s stall timer from firing.
+      const keepalive = setInterval(() => {
+        res.write(': keepalive\n\n');
+      }, 1000);
+      req.on('close', () => clearInterval(keepalive));
+      return;
+    }
+    if (url.pathname === '/emit') {
+      const type = url.searchParams.get('type') || 'session.updated';
+      const id = url.searchParams.get('id') || `evt-${Date.now()}`;
+      emitted.push({ id, type });
+      const block = `id: ${id}\ndata: ${JSON.stringify({ type, id })}\n\n`;
+      for (const client of clients) client.write(block);
+      res.writeHead(200, { 'content-type': 'application/json' });
+      res.end(JSON.stringify({ ok: true, id }));
+      return;
+    }
+    if (url.pathname === '/events') {
+      res.writeHead(200, { 'content-type': 'application/json' });
+      res.end(JSON.stringify(emitted));
+      return;
+    }
+    res.writeHead(404);
+    res.end('not found');
+  });
+  return { server };
+}
+
+const runServer = (label) => {
+  createServer().server.listen(port, hostname, () => {
+    console.log(`opencode server listening on http://${hostname}:${port}`);
+  });
+  writePidFile(label);
+  setInterval(() => {}, 1 << 30);
+};
+
+const main = async () => {
+  // Server-core mode: the orphaned server. Survives its launcher's death.
+  if (process.env.FAKE_OPENCODE_CORE === '1') {
+    runServer('core');
+    process.on('SIGTERM', () => {});
+    process.on('SIGINT', () => {});
+    return;
+  }
+
+  // Baseline in-process mode (control): dies with the managed process, so the
+  // port is properly released on restart.
+  if (process.env.FAKE_OPENCODE_BASELINE === '1') {
+    runServer('baseline');
+    return;
+  }
+
+  // Launcher mode: spawn a detached core grandchild, wait for it to bind,
+  // print the listening line, and on SIGTERM exit leaving the core running.
+  const core = spawn(process.execPath, [process.argv[1], ...args], {
+    detached: true,
+    stdio: ['ignore', 'ignore', 'ignore'],
+    env: { ...process.env, FAKE_OPENCODE_CORE: '1' },
+  });
+  core.unref();
+
+  for (let i = 0; i < 200; i += 1) {
+    if (core.exitCode !== null) throw new Error('core exited early');
+    const ok = await new Promise((resolve) => {
+      const socket = net.connect({ port, host: hostname });
+      const timer = setTimeout(() => {
+        socket.destroy();
+        resolve(false);
+      }, 200);
+      socket.once('connect', () => {
+        clearTimeout(timer);
+        socket.destroy();
+        resolve(true);
+      });
+      socket.once('error', () => {
+        clearTimeout(timer);
+        resolve(false);
+      });
+    });
+    if (ok) break;
+    await new Promise((r) => setTimeout(r, 50));
+  }
+
+  writePidFile('launcher');
+  console.log(`opencode server listening on http://${hostname}:${port}`);
+  // On SIGTERM exit ourselves, leaving the detached core running.
+  process.on('SIGTERM', () => process.exit(0));
+  process.on('SIGINT', () => process.exit(0));
+  setInterval(() => {}, 1 << 30);
+};
+
+await main();
diff --git a/scripts/repro/issue-2638/reproduce-2638.mjs b/scripts/repro/issue-2638/reproduce-2638.mjs
new file mode 100644
index 00000000..d4f99af4
--- /dev/null
+++ b/scripts/repro/issue-2638/reproduce-2638.mjs
@@ -0,0 +1,376 @@
+// Reproduction for https://github.com/openchamber/openchamber/issues/2638
+// "[Bug] Chat UI stops updating until the desktop app is restarted"
+//
+// Run with:  node reproduce-2638.mjs          (Windows-orphan scenario)
+//            node reproduce-2638.mjs --baseline (control: healthy restart)
+//
+// What it wires up (real repo modules, real processes, real ports):
+//   - createOpenCodeLifecycleRuntime (packages/web/server/lib/opencode/lifecycle.js)
+//   - createGlobalMessageStreamHub   (packages/web/server/lib/event-stream/global-hub.js)
+//   - createOpenCodeNetworkRuntime   (packages/web/server/lib/opencode/network-runtime.js)
+//   - a fake `opencode serve` binary (fake-opencode-serve.mjs)
+//
+// Scenario (issue #2638):
+//   1. OpenCode starts; the global message-stream hub connects to its
+//      /global/event SSE stream. Chat UI updates flow (baseline event e1
+//      reaches the hub).
+//   2. The managed OpenCode process "exits" but the actual server process
+//      survives on the old port (on Windows killProcessOnPort is a no-op and
+//      taskkill cannot reach the orphaned tree — the report shows leftover
+//      `opencode.exe serve` processes on historical ports).
+//   3. restartOpenCode() gives up after 5 s
+//      ("Timed out waiting for OpenCode port <old> to be released") and
+//      spawns a fresh server on a NEW port.
+//   4. HTTP/proxy traffic follows state.openCodePort to the NEW server, but
+//      the hub's upstream SSE reader is still pinned to the OLD server's
+//      /global/event stream (that connection never closed), so events from
+//      the new server never reach the UI. Chat UI goes stale while the new
+//      server keeps persisting session data — visible only after restarting
+//      the app, exactly as reported.
+
+import { spawnSync } from 'node:child_process';
+import net from 'node:net';
+import fs from 'node:fs';
+import path from 'node:path';
+import os from 'node:os';
+import { fileURLToPath } from 'node:url';
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+
+// Repository root (override with REPO=/path/to/openchamber if needed). Default:
+// walk up from this script until we find the repo root (AGENTS.md + package.json).
+const findRepoRoot = () => {
+  let dir = __dirname;
+  for (let i = 0; i < 8; i += 1) {
+    if (fs.existsSync(path.join(dir, 'AGENTS.md')) && fs.existsSync(path.join(dir, 'package.json'))) {
+      return dir;
+    }
+    const parent = path.dirname(dir);
+    if (parent === dir) break;
+    dir = parent;
+  }
+  return '/home/runner/work/openchamber/openchamber';
+};
+const REPO = process.env.REPO || findRepoRoot();
+
+const BASELINE = process.argv.includes('--baseline');
+
+// Simulate the Windows behavior reported in #2638 (process.platform is read
+// at call time inside lifecycle.js: killProcessOnPort no-ops on win32 and
+// terminateChildProcess takes the taskkill path, which cannot exist here).
+if (!BASELINE) {
+  Object.defineProperty(process, 'platform', { value: 'win32' });
+}
+
+const { createOpenCodeLifecycleRuntime } = await import(
+  path.join(REPO, 'packages/web/server/lib/opencode/lifecycle.js')
+);
+
+// --- shared state + real network runtime -----------------------------------
+const state = {
+  openCodeWorkingDirectory: '/tmp',
+  openCodeProcess: null,
+  openCodePort: null,
+  openCodeBaseUrl: null,
+  currentRestartPromise: null,
+  isRestartingOpenCode: false,
+  openCodeApiPrefix: '',
+  openCodeApiPrefixDetected: false,
+  openCodeApiDetectionTimer: null,
+  lastOpenCodeError: null,
+  isOpenCodeReady: false,
+  openCodeNotReadySince: 0,
+  isExternalOpenCode: false,
+  isShuttingDown: false,
+  healthCheckInterval: null,
+  expressApp: null,
+  useWslForOpencode: false,
+  resolvedWslBinary: null,
+  resolvedWslOpencodePath: null,
+  resolvedWslDistro: null,
+  lastOpenCodeLaunchDiagnostics: null,
+};
+
+const { createOpenCodeNetworkRuntime } = await import(
+  path.join(REPO, 'packages/web/server/lib/opencode/network-runtime.js')
+);
+const networkRuntime = createOpenCodeNetworkRuntime({
+  state,
+  getOpenCodeAuthHeaders: () => ({}),
+  configuredOpenCodeHostname: '127.0.0.1',
+});
+
+const fakeBinary = path.join(__dirname, 'fake-opencode-serve.mjs');
+const pidDir = fs.mkdtempSync(path.join(os.tmpdir(), 'oc-repro-2638-'));
+process.env.OPENCODE_BINARY = fakeBinary;
+process.env.FAKE_OPENCODE_PID_DIR = pidDir;
+if (BASELINE) process.env.FAKE_OPENCODE_BASELINE = '1';
+
+const lifecycle = createOpenCodeLifecycleRuntime({
+  state,
+  env: {
+    ENV_CONFIGURED_OPENCODE_PORT: 0,
+    ENV_CONFIGURED_OPENCODE_HOST: null,
+    ENV_EFFECTIVE_PORT: 0,
+    ENV_CONFIGURED_OPENCODE_HOSTNAME: '127.0.0.1',
+    ENV_SKIP_OPENCODE_START: false,
+  },
+  syncToHmrState: () => {},
+  syncFromHmrState: () => {},
+  getOpenCodeAuthHeaders: () => ({}),
+  buildOpenCodeUrl: (...args) => networkRuntime.buildOpenCodeUrl(...args),
+  waitForReady: (...args) => networkRuntime.waitForReady(...args),
+  normalizeApiPrefix: (...args) => networkRuntime.normalizeApiPrefix(...args),
+  applyOpencodeBinaryFromSettings: async () => {},
+  ensureOpencodeCliEnv: () => {},
+  ensureLocalOpenCodeServerPassword: async () => 'password',
+  resolveManagedOpenCodeLaunchSpec: (binary) => ({ binary, args: [], wrapperType: null }),
+  setOpenCodePort: (port) => { state.openCodePort = port; },
+  setDetectedOpenCodeApiPrefix: () => {},
+  setupProxy: () => {},
+  ensureOpenCodeApiPrefix: () => {},
+  clearResolvedOpenCodeBinary: () => {},
+  buildAugmentedPath: () => process.env.PATH,
+  buildManagedOpenCodePath: () => process.env.PATH,
+  getManagedOpenCodeShellEnvSnapshot: async () => ({}),
+  getManagedOpenCodeEnv: async () => ({}),
+  reapManagedOrphanedProcesses: async () => ({ reaped: 0 }),
+  getWarmupDirectories: async () => [],
+  // Production index.js wires this to the message-stream runtime's
+  // rebindUpstream(); mirror it here so the harness exercises the fix.
+  onOpenCodeRestarted: () => {
+    try {
+      rebindHub?.();
+    } catch {
+    }
+  },
+});
+
+const { createGlobalMessageStreamHub } = await import(
+  path.join(REPO, 'packages/web/server/lib/event-stream/global-hub.js')
+);
+
+// The hub represents the server→OpenCode SSE push pipeline that feeds the
+// renderer (both the server-side PushWatcher and the browser WS bridge).
+const received = [];
+const statuses = [];
+let rebindHub = null;
+const hub = createGlobalMessageStreamHub({
+  buildOpenCodeUrl: (p) => networkRuntime.buildOpenCodeUrl(p, ''),
+  getOpenCodeAuthHeaders: () => ({}),
+  upstreamStallTimeoutMs: 20000,
+  upstreamReconnectDelayMs: 250,
+});
+hub.subscribeEvent(({ eventId, payload }) => {
+  received.push({ eventId, type: payload?.type, id: payload?.id });
+});
+hub.subscribeStatus((status) => statuses.push(status));
+rebindHub = () => {
+  hub.stop();
+  hub.start();
+};
+
+// --- helpers ----------------------------------------------------------------
+const warnLog = [];
+const origWarn = console.warn;
+console.warn = (...args) => {
+  warnLog.push(args.map(String).join(' '));
+  origWarn(...args);
+};
+
+const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
+
+async function waitFor(fn, timeoutMs, what) {
+  const deadline = Date.now() + timeoutMs;
+  while (Date.now() < deadline) {
+    if (await fn()) return true;
+    await sleep(50);
+  }
+  throw new Error(`timeout waiting for ${what}`);
+}
+
+const emitEvent = async (port, id, type = 'session.updated') => {
+  const res = await fetch(`http://127.0.0.1:${port}/emit?type=${type}&id=${id}`);
+  if (!res.ok) throw new Error(`emit ${id} failed on port ${port}`);
+  return res.json();
+};
+
+const persistedEvents = async (port) => {
+  const res = await fetch(`http://127.0.0.1:${port}/events`);
+  return res.ok ? res.json() : [];
+};
+
+const portOpen = (port) => new Promise((resolve) => {
+  const socket = net.connect({ port, host: '127.0.0.1' });
+  const timer = setTimeout(() => { socket.destroy(); resolve(false); }, 300);
+  socket.once('connect', () => { clearTimeout(timer); socket.destroy(); resolve(true); });
+  socket.once('error', () => { clearTimeout(timer); resolve(false); });
+});
+
+const pidFilePids = () => {
+  const out = [];
+  for (const file of fs.readdirSync(pidDir)) {
+    if (!file.endsWith('.pid')) continue;
+    try {
+      out.push({ label: file.replace(/\.pid$/, ''), pid: Number(fs.readFileSync(path.join(pidDir, file), 'utf8')) });
+    } catch {
+      // ignore
+    }
+  }
+  return out;
+};
+
+const killPortPids = (port) => {
+  try {
+    const result = spawnSync('lsof', ['-ti', `:${port}`], { encoding: 'utf8' });
+    const pids = String(result.stdout || '').trim().split(/\s+/).map(Number).filter(Boolean);
+    for (const pid of pids) {
+      if (pid === process.pid) continue; // never kill ourselves (TIME_WAIT client sockets)
+      try { process.kill(pid, 'SIGKILL'); } catch { /* already gone */ }
+    }
+  } catch { /* lsof unavailable */ }
+};
+
+const cleanup = async () => {
+  for (const { label, pid } of pidFilePids()) {
+    if (label.startsWith('launcher') || label.startsWith('baseline')) {
+      try { process.kill(pid, 'SIGTERM'); } catch { /* gone */ }
+    } else {
+      try { process.kill(pid, 'SIGKILL'); } catch { /* gone */ }
+    }
+  }
+  if (state.openCodePort) killPortPids(state.openCodePort);
+  // Belt and braces: kill any surviving fake-opencode processes from this run.
+  try {
+    const result = spawnSync('pgrep', ['-f', 'fake-opencode-serve.mjs'], { encoding: 'utf8' });
+    const pids = String(result.stdout || '').trim().split(/\s+/).map(Number).filter(Boolean);
+    for (const pid of pids) {
+      if (pid === process.pid) continue;
+      try { process.kill(pid, 'SIGKILL'); } catch { /* gone */ }
+    }
+  } catch { /* pgrep unavailable */ }
+  await sleep(300);
+  try { fs.rmSync(pidDir, { recursive: true, force: true }); } catch { /* ignore */ }
+  console.warn = origWarn;
+};
+
+// --- run ---------------------------------------------------------------------
+console.log(`\n=== reproduce-2638 (${BASELINE ? 'BASELINE control' : 'Windows-orphan scenario'}) ===\n`);
+let failures = 0;
+const check = (label, ok, detail = '') => {
+  console.log(`  ${ok ? 'PASS' : 'FAIL'}  ${label}${detail ? ` — ${detail}` : ''}`);
+  if (!ok) failures += 1;
+};
+
+try {
+  // 1. Bootstrapping starts the managed OpenCode (launcher + server core) on P1.
+  await lifecycle.bootstrapOpenCodeAtStartup();
+  const p1 = state.openCodePort;
+  console.log(`[1] bootstrap OK — managed OpenCode listening on port ${p1} (pid ${state.openCodeProcess?.pid})`);
+
+  // 2. Connect the message-stream hub (server→OpenCode SSE push pipeline).
+  hub.start();
+  await waitFor(() => statuses.some((s) => s.type === 'connect'), 10000, 'hub connect to P1');
+  console.log('[2] message-stream hub connected to /global/event');
+
+  // 3. Baseline delivery: an event emitted by P1 reaches the UI pipeline.
+  await emitEvent(p1, 'evt-before-restart');
+  await waitFor(() => received.some((r) => r.eventId === 'evt-before-restart'), 5000, 'event delivery');
+  check('events flow to the UI before the restart (baseline)', received.some((r) => r.eventId === 'evt-before-restart'));
+
+  // 4. The managed process "exits" while the actual server survives on P1
+  //    (simulates the Windows orphan: launcher dies, server core keeps the
+  //    port and the SSE stream). In baseline mode the server runs in-process
+  //    and dies with the managed process instead.
+  const launcherPid = state.openCodeProcess.pid;
+  process.kill(launcherPid, 'SIGTERM');
+  await waitFor(async () => {
+    try { process.kill(launcherPid, 0); return false; } catch { return true; }
+  }, 5000, 'launcher exit');
+  console.log(`[4] managed process (pid ${launcherPid}) exited; ${BASELINE ? 'server process died with it' : `orphaned server core still listening on ${p1}`}`);
+
+  // 5. Trigger the reported restart path ("Refreshing OpenCode after manual
+  //    configuration reload" / periodic health check).
+  console.log('[5] triggering restart (refreshOpenCodeAfterConfigChange)...');
+  await lifecycle.refreshOpenCodeAfterConfigChange('manual configuration reload');
+  const p2 = state.openCodePort;
+  console.log(`[5] restarted — new managed OpenCode listening on port ${p2}`);
+
+  // 6. Assert the reported log line: the old port was never released. In the
+  //    baseline control the port IS released, so the warning must be absent.
+  const timeoutWarn = warnLog.find((line) => line.includes('Timed out waiting for OpenCode port') && line.includes(String(p1)));
+  if (BASELINE) {
+    check(`no "Timed out waiting for OpenCode port ${p1}" warning in baseline control`, !timeoutWarn);
+  } else {
+    check(`"Timed out waiting for OpenCode port ${p1} to be released" is logged`, Boolean(timeoutWarn), timeoutWarn || '');
+  }
+  check('new port differs from old port (leaked process pinned the old one)', p2 !== p1, `p1=${p1} p2=${p2}`);
+
+  // 7. Assert the orphaned old server is still running (process pile-up from
+  //    the report: "six opencode.exe serve processes were still running").
+  //    In baseline mode we instead expect the port to be properly released.
+  const oldCoreStillUp = await portOpen(p1);
+  const pids = pidFilePids();
+  const orphanPids = pids.filter(({ label }) => label.startsWith('core')).map(({ pid }) => pid);
+  const orphanAlive = orphanPids.length > 0 && orphanPids.every((pid) => {
+    try { process.kill(pid, 0); return true; } catch { return false; }
+  });
+  if (BASELINE) {
+    check('old port properly released (no orphan in baseline control)', !oldCoreStillUp,
+      `old port ${p1} ${oldCoreStillUp ? 'still open' : 'released'}`);
+  } else {
+    check('orphaned server process still running on the old port', oldCoreStillUp && orphanAlive,
+      `old port ${p1} still open; orphan core pids ${orphanPids.join(', ')}`);
+  }
+
+  // 8. The stale-UI reproduction: the new server persists events, but in the
+  //    orphan scenario they never reach the UI because the hub is still pinned
+  //    to the old SSE stream. In baseline mode the hub must reconnect to the
+  //    new port and deliver them (wait for the reconnect before emitting —
+  //    the upstream reader only learns about the new port on its next attempt).
+  const connectsBefore = statuses.filter((s) => s.type === 'connect').length;
+  if (!BASELINE) {
+    await sleep(1000);
+  } else {
+    await waitFor(() => statuses.filter((s) => s.type === 'connect').length >= connectsBefore + 1, 15000, 'hub reconnect to new port');
+  }
+  await emitEvent(p2, 'evt-after-restart');
+  console.log(`[8] emitted evt-after-restart on new port ${p2} — waiting to see if the UI receives it...`);
+  await sleep(2500);
+  const deliveredAfter = received.filter((r) => r.eventId === 'evt-after-restart').length;
+  if (BASELINE) {
+    check('NEW server event IS delivered to the UI (hub reconnected in baseline)', deliveredAfter === 1,
+      `delivered=${deliveredAfter}, total hub events=${received.length}`);
+  } else {
+    // Fixed: the lifecycle hook rebinds the hub after the managed restart,
+    // so the UI receives events from the new port even when the old port is
+    // orphaned. The wait mirrors the baseline branch (the reader re-dials on
+    // its next attempt after the rebind).
+    await waitFor(() => statuses.filter((s) => s.type === 'connect').length >= connectsBefore + 1, 15000, 'hub reconnect to new port after rebind');
+    check('NEW server event IS delivered to the UI (rebound after restart)', deliveredAfter === 1,
+      `delivered=${deliveredAfter}, total hub events=${received.length}`);
+  }
+
+  const persistedOnNew = await persistedEvents(p2);
+  check('NEW server persisted the event (data survives, UI does not show it)', persistedOnNew.some((e) => e.id === 'evt-after-restart'),
+    `persisted on port ${p2}: ${JSON.stringify(persistedOnNew)}`);
+
+  // 9. Orphan scenario: with the rebind the hub is no longer pinned to the
+  //    old server — events emitted by the old (zombie) server must NOT reach
+  //    the UI anymore (it left the previous upstream behind).
+  if (!BASELINE) {
+    await emitEvent(p1, 'evt-zombie-old-server');
+    await sleep(2000);
+    check('OLD zombie server events no longer reach the UI (hub rebound to new upstream)', !received.some((r) => r.eventId === 'evt-zombie-old-server'));
+  }
+
+  console.log(`\n=== ${failures === 0 ? 'REPRODUCED (all checks passed)' : `${failures} check(s) FAILED`} ===\n`);
+  console.log(`hub statuses observed: ${JSON.stringify(statuses)}`);
+} catch (error) {
+  console.error('\nReproduction script error:', error);
+  failures += 1;
+} finally {
+  await cleanup();
+}
+
+process.exit(failures === 0 ? 0 : 1);