Reconnect dashboard PTY chat after socket drops

hermes_cli/web_server.py

@@ -167,6 +167,7 @@ def _resolve_restart_drain_timeout() -> float:
 async def _lifespan(app: "FastAPI"):
     app.state.event_channels = {}  # dict[str, set]
     app.state.event_lock = asyncio.Lock()
+    app.state.pty_active_session_files = {}  # dict[str, Path]
     # Serializes chat-argv resolution so concurrent /api/pty connections
     # don't trigger overlapping ``npm install`` / ``npm run build`` work.
     # On app.state (not a module global) so the Lock binds to the running
@@ -234,6 +235,15 @@ def _get_chat_argv_lock(app: "FastAPI") -> asyncio.Lock:
         return app.state.chat_argv_lock
 
 
+def _get_pty_active_session_files(app: "FastAPI") -> dict[str, Path]:
+    """Return channel -> active-session-file state for dashboard PTYs."""
+    try:
+        return app.state.pty_active_session_files
+    except AttributeError:
+        app.state.pty_active_session_files = {}
+        return app.state.pty_active_session_files
+
+
 app = FastAPI(title="Hermes Agent", version=__version__, lifespan=_lifespan)
 
 # Memory-provider OAuth connect routes live in the memory layer, not here.
@@ -11544,6 +11554,7 @@ def _resolve_chat_argv(
     resume: Optional[str] = None,
     sidecar_url: Optional[str] = None,
     profile: Optional[str] = None,
+    active_session_file: Optional[str] = None,
 ) -> tuple[list[str], Optional[str], Optional[dict]]:
     """Resolve the argv + cwd + env for the chat PTY.
 
@@ -11564,6 +11575,12 @@ def _resolve_chat_argv(
     the spawned ``tui_gateway.entry`` can mirror dispatcher emits to the
     dashboard's ``/api/pub`` endpoint (see :func:`pub_ws`).
 
+    `active_session_file` (when set) is forwarded as
+    ``HERMES_TUI_ACTIVE_SESSION_FILE``. The TUI writes the current session id
+    there whenever it creates/resumes/switches sessions, giving the dashboard a
+    small cross-process breadcrumb for reconnecting after an unexpected browser
+    WebSocket close.
+
     `profile` (when set) scopes the ENTIRE chat to that profile by pointing
     ``HERMES_HOME`` at the profile dir in the child env. Every spawned
     process (the TUI and the ``tui_gateway.entry`` it launches) resolves
@@ -11611,6 +11628,9 @@ def _resolve_chat_argv(
     if sidecar_url:
         env["HERMES_TUI_SIDECAR_URL"] = sidecar_url
 
+    if active_session_file:
+        env["HERMES_TUI_ACTIVE_SESSION_FILE"] = active_session_file
+
     # Profile-scoped chats must NOT attach to the dashboard's in-memory
     # gateway — it runs under the dashboard's own profile. Without the
     # attach URL, gatewayClient spawns its own `tui_gateway.entry`, which
@@ -11659,6 +11679,7 @@ async def _resolve_chat_argv_async(
     resume: Optional[str] = None,
     sidecar_url: Optional[str] = None,
     profile: Optional[str] = None,
+    active_session_file: Optional[str] = None,
 ) -> tuple[list[str], Optional[str], Optional[dict]]:
     """Resolve chat argv without blocking the dashboard event loop.
 
@@ -11670,12 +11691,18 @@ async def _resolve_chat_argv_async(
     multiple browser tabs connect at once without occupying worker threads
     while queued connections wait.
     """
+    kwargs = {
+        "resume": resume,
+        "sidecar_url": sidecar_url,
+        "profile": profile,
+    }
+    if active_session_file is not None:
+        kwargs["active_session_file"] = active_session_file
+
     async with _get_chat_argv_lock(app):
         return await asyncio.to_thread(
             _resolve_chat_argv,
-            resume=resume,
-            sidecar_url=sidecar_url,
-            profile=profile,
+            **kwargs,
         )
 
 
@@ -11737,6 +11764,37 @@ def _channel_or_close_code(ws: WebSocket) -> Optional[str]:
     return channel if _VALID_CHANNEL_RE.match(channel) else None
 
 
+def _active_session_file_for_channel(app: "FastAPI", channel: str) -> Path:
+    """Return the per-channel file where a dashboard TUI writes its active sid."""
+    files = _get_pty_active_session_files(app)
+    existing = files.get(channel)
+    if existing is not None:
+        return existing
+
+    fd, raw_path = tempfile.mkstemp(prefix="hermes-pty-active-", suffix=".json")
+    os.close(fd)
+    path = Path(raw_path)
+    files[channel] = path
+    return path
+
+
+def _read_active_session_file(path: Path) -> Optional[str]:
+    try:
+        data = json.loads(path.read_text(encoding="utf-8"))
+    except (OSError, json.JSONDecodeError):
+        return None
+
+    session_id = str(data.get("session_id") or "").strip()
+    return session_id or None
+
+
+def _forget_active_session_file(path: Path) -> None:
+    try:
+        path.unlink(missing_ok=True)
+    except OSError:
+        pass
+
+
 def _ws_close_reason(text: str) -> str:
     """Clamp a WS close reason to the protocol's 123-byte UTF-8 limit.
 
@@ -11807,11 +11865,32 @@ async def pty_ws(ws: WebSocket) -> None:
     profile = ws.query_params.get("profile") or None
     channel = _channel_or_close_code(ws)
     sidecar_url = _build_sidecar_url(channel) if channel else None
+    force_fresh = (ws.query_params.get("fresh") or "").strip().lower() in {
+        "1",
+        "true",
+        "yes",
+        "on",
+    }
+    active_session_file: Optional[Path] = None
+
+    if channel:
+        active_session_file = _active_session_file_for_channel(ws.app, channel)
+        if force_fresh:
+            resume = None
+            _forget_active_session_file(active_session_file)
+        elif not resume:
+            resume = _read_active_session_file(active_session_file)
+
+    resolve_kwargs = {
+        "resume": resume,
+        "sidecar_url": sidecar_url,
+        "profile": profile,
+    }
+    if active_session_file is not None:
+        resolve_kwargs["active_session_file"] = str(active_session_file)
 
     try:
-        argv, cwd, env = await _resolve_chat_argv_async(
-            resume=resume, sidecar_url=sidecar_url, profile=profile
-        )
+        argv, cwd, env = await _resolve_chat_argv_async(**resolve_kwargs)
     except HTTPException as exc:
         # Unknown/invalid profile from _resolve_profile_dir.
         await ws.send_text(f"\r\n\x1b[31mChat unavailable: {exc.detail}\x1b[0m\r\n")