Admit onboard camera preview only after its acquisition producer is ready

src/k1link/device_plugins/xgrids_k1/camera.py

@@ -970,7 +970,9 @@ class XgridsK1CameraGateway:
             )
             return self.snapshot()
 
-    def open_delivery(self, generation: int) -> CameraProcessLease:
+    def open_delivery(
+        self, generation: int, *, require_recording: bool = False
+    ) -> CameraProcessLease:
         with self._lifecycle_lock:
             with self._lock:
                 self._require_open_locked()
@@ -978,6 +980,8 @@ class XgridsK1CameraGateway:
                     raise ValueError("camera preview generation не активно")
                 producer = self._producer
                 recording_active = self._recording_root is not None
+                if require_recording and (not recording_active or producer is None):
+                    raise RuntimeError("camera acquisition producer is not ready")
             if producer is None:
                 # An acquisition owns its producer lifecycle.  Once an epoch is
                 # sealed, a disposable browser reconnect must not resurrect the

src/k1link/viewer/node_media.py

@@ -133,8 +133,23 @@ class NodeMediaPeers:
         while identifier in self.items and time.monotonic() < deadline:
             state = self.camera.snapshot()
             delivery = state.get("delivery") or {}
-            if state.get("generation") is not None and delivery.get("media_type"):
-                lease = await asyncio.to_thread(self.camera.open_delivery, state["generation"])
+            recording = state.get("recording") or {}
+            if recording.get("source_end_expected"):
+                break
+            if (state.get("generation") is not None and delivery.get("media_type")
+                    and recording.get("active") is True
+                    and recording.get("producer_alive") is True
+                    and recording.get("media_ready") is True
+                    and recording.get("active_epoch") == state["generation"]):
+                try:
+                    lease = await asyncio.to_thread(
+                        self.camera.open_delivery, state["generation"], require_recording=True
+                    )
+                except (ValueError, RuntimeError):
+                    # The acquisition owner may replace an epoch between this
+                    # snapshot and lease admission. Observe its next ready epoch.
+                    await asyncio.sleep(0.25)
+                    continue
                 try:
                     channel.send(json.dumps({
                         "type": "camera-ready", "mime": delivery["media_type"],
@@ -143,8 +158,6 @@ class NodeMediaPeers:
                     self.camera.release_delivery(lease, client_closed=True)
                     raise
                 return lease
-            if state.get("phase") == "error":
-                break
             await asyncio.sleep(0.25)
         return None