Fix WebCRT sessions killed by StrictMode ws_ticket reuse.

Allow short-lived tickets multiple uses, stop deleting PTY on transient websocket errors, and avoid marking connect complete after a dropped wait loop.

Co-authored-by: Cursor <cursoragent@cursor.com>

netx_api/webcrt_router.py

@@ -440,7 +440,8 @@ async def websocket_session(websocket: WebSocket, session_id: str) -> None:
                     }
                 )
             except Exception:
-                break
+                # Client dropped during connect wait (StrictMode remount etc.) — keep PTY.
+                return
             remaining = deadline - time.time()
             if remaining <= 0:
                 await websocket.send_json(
@@ -455,11 +456,19 @@ async def websocket_session(websocket: WebSocket, session_id: str) -> None:
                     lambda t=slice_timeout: wait_session_ready(session_id, timeout=t),
                 )
                 sess = get_session(session_id) or cur
+                if sess is None or sess.closed or sess.state == "closed":
+                    return
+                if sess.state == "connecting":
+                    # wait_session_ready should not return while still connecting.
+                    continue
                 break
             except HTTPException as exc:
                 if exc.status_code == 504:
                     # Slice timeout while still connecting — keep polling with progress.
                     continue
+                if exc.status_code == 404:
+                    # Session deleted while waiting.
+                    return
                 await websocket.send_json(
                     {"type": "status", "state": "error", "message": str(exc.detail)}
                 )
@@ -472,6 +481,21 @@ async def websocket_session(websocket: WebSocket, session_id: str) -> None:
                 await websocket.close(code=4502)
                 return
 
+    # Session may have been deleted while the previous wait loop was exiting.
+    if get_session(session_id) is None or sess.closed or sess.state in {"closed", "error"}:
+        if sess.state == "error":
+            try:
+                await websocket.send_json(
+                    {
+                        "type": "status",
+                        "state": "error",
+                        "message": sess.connect_error or "connect_failed",
+                    }
+                )
+            except Exception:
+                pass
+        return
+
     await websocket.send_json(
         {
             "type": "status",

netx_api/webcrt_session_registry.py

@@ -158,7 +158,8 @@ def find_ssh_session_for_ne(ne_id: str) -> WebcrtSession | None:
 
 def wait_session_ready(session_id: str, *, timeout: float = 120.0) -> WebcrtSession:
     """Block until async connect finishes (ready or error). Used by tests and WS."""
-    deadline = time.time() + max(1.0, float(timeout))
+    # Honor short slice timeouts from the WS wait loop (do not clamp to 1s).
+    deadline = time.time() + max(0.05, float(timeout))
     while time.time() < deadline:
         sess = get_session(session_id)
         if sess is None:
@@ -167,7 +168,9 @@ def wait_session_ready(session_id: str, *, timeout: float = 120.0) -> WebcrtSess
             return sess
         if sess.state == "error":
             raise HTTPException(status_code=502, detail=sess.connect_error or "connect_failed")
-        sess._ready_event.wait(timeout=0.25)
+        if sess.closed or sess.state == "closed":
+            raise HTTPException(status_code=404, detail="webcrt_session_not_found")
+        sess._ready_event.wait(timeout=min(0.25, max(0.01, deadline - time.time())))
     raise HTTPException(status_code=504, detail="connect_timeout")
 
 

netx_api/webcrt_tickets.py

@@ -1,4 +1,8 @@
-"""Short-lived WebCRT WebSocket tickets (avoid putting JWT in query strings)."""
+"""Short-lived WebCRT WebSocket tickets (avoid putting JWT in query strings).
+
+Tickets allow a small number of uses so React StrictMode remounts (dev) can
+open a second WebSocket with the same URL without racing a one-shot consume.
+"""
 
 from __future__ import annotations
 
@@ -8,8 +12,11 @@ import time
 from dataclasses import dataclass
 
 _TTL_SEC = 90
+# React 18 StrictMode mounts effects twice in DEV; keep a spare use.
+_MAX_USES = 3
 _lock = threading.Lock()
-_tickets: dict[str, tuple[float, str, frozenset[str]]] = {}
+# ticket -> (expires_at, user_id, scopes, uses_remaining)
+_tickets: dict[str, tuple[float, str, frozenset[str], int]] = {}
 
 
 @dataclass(frozen=True)
@@ -23,7 +30,7 @@ def issue_ws_ticket(*, user_id: str, scopes: frozenset[str], ttl_sec: int = _TTL
     exp = time.time() + max(15, int(ttl_sec))
     with _lock:
         _purge_locked()
-        _tickets[tid] = (exp, str(user_id), frozenset(scopes))
+        _tickets[tid] = (exp, str(user_id), frozenset(scopes), int(_MAX_USES))
     return tid, max(15, int(ttl_sec))
 
 
@@ -33,17 +40,23 @@ def consume_ws_ticket(ticket: str) -> TicketInfo | None:
         return None
     with _lock:
         _purge_locked()
-        row = _tickets.pop(raw, None)
-    if row is None:
-        return None
-    exp, user_id, scopes = row
-    if exp < time.time():
-        return None
+        row = _tickets.get(raw)
+        if row is None:
+            return None
+        exp, user_id, scopes, uses_left = row
+        if exp < time.time() or uses_left <= 0:
+            _tickets.pop(raw, None)
+            return None
+        uses_left -= 1
+        if uses_left <= 0:
+            _tickets.pop(raw, None)
+        else:
+            _tickets[raw] = (exp, user_id, scopes, uses_left)
     return TicketInfo(user_id=user_id, scopes=scopes)
 
 
 def _purge_locked() -> None:
     now = time.time()
-    dead = [k for k, (exp, _, _) in _tickets.items() if exp < now]
+    dead = [k for k, (exp, _, _, _) in _tickets.items() if exp < now]
     for k in dead:
         _tickets.pop(k, None)

web/src/pages/WebcrtPage.tsx

@@ -2341,14 +2341,19 @@ export function WebcrtPage() {
                               void openTarget(tab.target, { force: true });
                               return;
                             }
+                            // Transient browser WS failures (StrictMode remount / ticket race) must
+                            // NOT delete the device PTY — keep session_id for reconnect/reattach.
+                            const transientWs =
+                              /^(websocket_error|websocket_closed)/i.test(String(message || "")) ||
+                              String(message || "").toLowerCase().includes("websocket");
                             updateTab(tab.key, {
-                              status: "error",
-                              sessionId: "",
-                              wsUrl: "",
+                              status: transientWs ? "closed" : "error",
+                              sessionId: transientWs ? tab.sessionId : "",
+                              wsUrl: transientWs ? tab.wsUrl : "",
                               connectPhase: undefined,
                               errorMessage: webcrtErrorMessage(errMsg, t),
                             });
-                            if (sid) {
+                            if (sid && !transientWs) {
                               void closeWebcrtSession(sid).catch(() => undefined);
                             }
                             if (isInventoryTarget(tab.target) && isSshAuthFailure(errMsg)) {