feat(v0.3): H2 server — Claude Code hooks → live status side-channel

- types: ClaudeStatus + ServerMessage 'status'; Session.claudeStatus;
  SessionManager.handleHookEvent
- session: inject WEBTERM_SESSION + WEBTERM_HOOK_URL into the spawned shell env
  so hooks know which tab they belong to
- http/hook.ts: pure event→status mapper (PreToolUse→working, PermissionRequest/
  Notification:permission_prompt→waiting, Stop/idle_prompt→idle); 6 unit tests
- server: POST /hook (loopback-only, express.json 64kb) → manager pushes 'status'
- fix: closeIdleConnections() on shutdown so an idle hook keep-alive socket
  doesn't hang close()/SIGTERM
- integration ⑦ (real PTY): attach → POST /hook → ws receives status. 205 tests green.

src/http/hook.ts

@@ -0,0 +1,57 @@
+/**
+ * src/http/hook.ts (H2) — map a Claude Code hook POST to a session status update.
+ *
+ * Pure + never throws. The web-terminal sessionId arrives in the
+ * `X-Webterm-Session` header (injected as $WEBTERM_SESSION on spawn); the hook
+ * payload arrives as JSON in the body. We translate the event into a coarse
+ * ClaudeStatus the UI can show. The server is still a byte-shuttle for the
+ * terminal stream — this is an out-of-band side-channel.
+ */
+
+import type { ClaudeStatus } from '../types.js';
+
+export interface HookEvent {
+  sessionId: string;
+  status: ClaudeStatus;
+  detail?: string;
+}
+
+/**
+ * @param sessionId value of the `X-Webterm-Session` header
+ * @param body parsed JSON body of the hook POST (untrusted)
+ * @returns a status update, or null if the payload is unusable
+ */
+export function parseHookEvent(sessionId: string | undefined, body: unknown): HookEvent | null {
+  if (typeof sessionId !== 'string' || sessionId.length === 0) return null;
+  if (body === null || typeof body !== 'object') return null;
+
+  const b = body as Record<string, unknown>;
+  const event = typeof b['hook_event_name'] === 'string' ? b['hook_event_name'] : '';
+  const notif = typeof b['notification_type'] === 'string' ? b['notification_type'] : '';
+  const tool = typeof b['tool_name'] === 'string' ? b['tool_name'] : undefined;
+
+  let status: ClaudeStatus;
+  switch (event) {
+    case 'PreToolUse':
+    case 'PostToolUse':
+    case 'UserPromptSubmit':
+      status = 'working';
+      break;
+    case 'PermissionRequest':
+      status = 'waiting';
+      break;
+    case 'Stop':
+    case 'SessionEnd':
+      status = 'idle';
+      break;
+    case 'Notification':
+      status = notif === 'permission_prompt' ? 'waiting' : 'idle';
+      break;
+    default:
+      return null;
+  }
+
+  return status === 'waiting' && tool !== undefined
+    ? { sessionId, status, detail: tool }
+    : { sessionId, status };
+}

src/server.ts

@@ -35,6 +35,7 @@ import type { IncomingMessage } from 'node:http'
 import { loadConfig } from './config.js'
 import { parseClientMessage, serialize } from './protocol.js'
 import { isOriginAllowed } from './http/origin.js'
+import { parseHookEvent } from './http/hook.js'
 import { createSessionManager } from './session/manager.js'
 import { detachWs, writeInput, resize } from './session/session.js'
 import type { Config } from './types.js'
@@ -77,6 +78,25 @@ export function startServer(cfg: Config): { close(): Promise<void> } {
   const publicDir = path.join(__dirname, '..', 'public')
   app.use(express.static(publicDir))
 
+  // ── Claude Code hook side-channel (H2) ────────────────────────────────────
+  // Hooks running inside a spawned shell POST status here (loopback only — the
+  // shell runs on the host). sessionId arrives in the X-Webterm-Session header.
+  app.post('/hook', express.json({ limit: '64kb' }), (req, res) => {
+    const ip = req.socket.remoteAddress ?? ''
+    const isLoopback = ip === '127.0.0.1' || ip === '::1' || ip === '::ffff:127.0.0.1'
+    if (!isLoopback) {
+      res.status(403).end()
+      return
+    }
+    const ev = parseHookEvent(req.header('x-webterm-session'), req.body)
+    if (ev === null) {
+      res.status(400).end()
+      return
+    }
+    manager.handleHookEvent(ev.sessionId, ev.status, ev.detail)
+    res.status(204).end()
+  })
+
   // ── HTTP server ───────────────────────────────────────────────────────────
   const httpServer = createServer(app)
 
@@ -219,6 +239,7 @@ export function startServer(cfg: Config): { close(): Promise<void> } {
     console.error('[server] shutdown signal received — cleaning up')
     doShutdown()
     httpServer.close(() => process.exit(0))
+    httpServer.closeIdleConnections() // drop idle keep-alive (hook) sockets so close() drains
   }
 
   process.on('SIGINT', onSignal)
@@ -246,6 +267,9 @@ export function startServer(cfg: Config): { close(): Promise<void> } {
       return new Promise<void>((resolve) => {
         doShutdown()
         httpServer.close(() => resolve())
+        // Drop idle keep-alive sockets (e.g. an undici hook connection) so the
+        // close callback can fire instead of waiting for the keep-alive timeout.
+        httpServer.closeIdleConnections()
       })
     },
   }

src/session/manager.ts

@@ -22,7 +22,14 @@
  * Coding style: immutable-update preference, no console.log, errors explicit.
  */
 
-import type { Config, Dims, Session, SessionManager, WebSocketLike } from '../types.js';
+import type {
+  ClaudeStatus,
+  Config,
+  Dims,
+  Session,
+  SessionManager,
+  WebSocketLike,
+} from '../types.js';
 import { WS_OPEN } from '../types.js';
 import { serialize } from '../protocol.js';
 import { createSession, attachWs, kill } from './session.js';
@@ -119,6 +126,20 @@ export function createSessionManager(cfg: Config): SessionManager {
     return sessions.get(id);
   }
 
+  /**
+   * H2: a Claude Code hook reported activity for `sessionId`. Record it and push
+   * a `status` frame to the attached ws (no-op if the session is gone/detached).
+   */
+  function handleHookEvent(sessionId: string, status: ClaudeStatus, detail?: string): void {
+    const session = sessions.get(sessionId);
+    if (session === undefined) return;
+    session.claudeStatus = status;
+    sendIfOpen(
+      session.attachedWs,
+      detail !== undefined ? { type: 'status', status, detail } : { type: 'status', status },
+    );
+  }
+
   /**
    * Reclaim detached sessions whose liveness window has expired (M3).
    *
@@ -159,5 +180,5 @@ export function createSessionManager(cfg: Config): SessionManager {
     sessions = new Map();
   }
 
-  return { handleAttach, get, reapIdle, shutdown };
+  return { handleAttach, get, handleHookEvent, reapIdle, shutdown };
 }

src/session/session.ts

@@ -58,17 +58,26 @@ export function createSession(
   now: number,
   onExit: (session: Session) => void,
 ): Session {
+  // Generate the id first so it can be injected into the shell env: Claude Code
+  // hooks running inside this shell read $WEBTERM_SESSION to tell us which tab
+  // an event belongs to, and POST to $WEBTERM_HOOK_URL (H2).
+  const id = randomUUID();
+
   // M4: let a spawn failure (e.g. missing shell) propagate synchronously.
   const pty: IPty = spawn(cfg.shellPath, [], {
     name: 'xterm-256color',
     cols: dims.cols,
     rows: dims.rows,
     cwd: cfg.homeDir,
-    env: process.env,
+    env: {
+      ...process.env,
+      WEBTERM_SESSION: id,
+      WEBTERM_HOOK_URL: `http://127.0.0.1:${cfg.port}/hook`,
+    },
   });
 
   const meta: SessionMeta = {
-    id: randomUUID(),
+    id,
     createdAt: now,
     shellPath: cfg.shellPath,
   };
@@ -81,6 +90,7 @@ export function createSession(
     lastOutputAt: now,
     exitedAt: null,
     exitCode: null,
+    claudeStatus: 'unknown',
     pty,
   };
 

src/types.ts

@@ -44,12 +44,17 @@ export type ClientMessage =
   | { type: 'input'; data: string }
   | { type: 'resize'; cols: number; rows: number };
 
+/** Claude Code activity, derived from hooks (H2). 'unknown' = no hook signal yet. */
+export type ClaudeStatus = 'working' | 'waiting' | 'idle' | 'unknown';
+
 /** server → client. exit.code = shell code; -1 when spawn never succeeded (M4).
- *  exit.reason optional normally, REQUIRED on spawn failure / abnormal exit. */
+ *  exit.reason optional normally, REQUIRED on spawn failure / abnormal exit.
+ *  status (H2) = Claude Code activity pushed from a hook side-channel. */
 export type ServerMessage =
   | { type: 'attached'; sessionId: string }
   | { type: 'output'; data: string }
-  | { type: 'exit'; code: number; reason?: string };
+  | { type: 'exit'; code: number; reason?: string }
+  | { type: 'status'; status: ClaudeStatus; detail?: string };
 
 /** parseClientMessage result — never throws; errors flow here (§5.3). */
 export type ParseResult =
@@ -139,6 +144,8 @@ export interface Session {
    *  and attach replays the buffer then re-sends `exit` (L1). */
   exitedAt: number | null;
   exitCode: number | null;
+  /** Claude Code activity from hooks (H2); updated by manager.handleHookEvent. */
+  claudeStatus: ClaudeStatus;
   readonly pty: IPty;
 }
 
@@ -156,6 +163,8 @@ export interface Session {
 export interface SessionManager {
   handleAttach(ws: WebSocketLike, sessionId: string | null, dims: Dims, now: number): Session;
   get(id: string): Session | undefined;
+  /** Set a session's Claude status (from a hook) and push it to the attached ws (H2). */
+  handleHookEvent(sessionId: string, status: ClaudeStatus, detail?: string): void;
   /** reclaim when now - max(detachedAt, lastOutputAt) > idleTtlMs (M3). Returns count. */
   reapIdle(now: number): number;
   shutdown(): void;