diff --git a/client/js/app.js b/client/js/app.js
index 64b00dd..432fa35 100644
--- a/client/js/app.js
+++ b/client/js/app.js
@@ -483,8 +483,8 @@
 }
 
 function stopGeneration() {
-  ws.stop();
   btnSend.disabled = true;  // prevent double-click while waiting for stream_stopped
+  fetch(`/sessions/${currentId}/stop`, { method: 'POST' }).catch(console.error);
 }
 
 function onTextareaInput() {
diff --git a/client/js/ws.js b/client/js/ws.js
index 5940ad5..7c5f72c 100644
--- a/client/js/ws.js
+++ b/client/js/ws.js
@@ -23,12 +23,6 @@
     };
   }
 
-  stop() {
-    if (this.#ws?.readyState === WebSocket.OPEN) {
-      this.#ws.send(JSON.stringify({ type: 'stop' }));
-    }
-  }
-
   send(content, images = null, files = null) {
     if (this.#ws?.readyState === WebSocket.OPEN) {
       const payload = { type: 'message', content };
diff --git a/navi/api/websocket.py b/navi/api/websocket.py
index 34102ef..0f837fd 100644
--- a/navi/api/websocket.py
+++ b/navi/api/websocket.py
@@ -169,63 +169,17 @@
             client_alive = False
 
 
-async def _stream_recv(websocket: WebSocket, queue: asyncio.Queue, run: _AgentRun) -> bool:
-    """
-    Concurrently forward queue events to the WebSocket AND receive incoming
-    client messages (stop signals) during streaming.
+# ── Endpoints ─────────────────────────────────────────────────────────────────
 
-    Uses asyncio.wait to race between the stream finishing and the client
-    sending a message — no polling, no latency on stop.
+@router.post("/sessions/{session_id}/stop")
+async def stop_session(session_id: str) -> dict:
+    """Signal the running agent for this session to stop cooperatively."""
+    run = _runs.get(session_id)
+    if run is not None:
+        run.stop_event.set()
+        return {"ok": True}
+    return {"ok": False, "reason": "no active run"}
 
-    Returns True if client stayed connected throughout.
-    """
-    stream_task = asyncio.create_task(_stream_to_client(websocket, queue))
-    recv_task: asyncio.Task = asyncio.create_task(websocket.receive_text())
-
-    try:
-        while True:
-            done, _ = await asyncio.wait(
-                {stream_task, recv_task},
-                return_when=asyncio.FIRST_COMPLETED,
-            )
-
-            # Incoming message from client
-            if recv_task in done:
-                try:
-                    raw = recv_task.result()
-                    try:
-                        data = json.loads(raw)
-                    except json.JSONDecodeError:
-                        data = {}
-                    if data.get("type") == "stop":
-                        run.stop_event.set()
-                except Exception:
-                    # Receive failed — client disconnected; let stream_task drain
-                    stream_task.cancel()
-                    break
-
-                if stream_task.done():
-                    break
-                # Queue next receive
-                recv_task = asyncio.create_task(websocket.receive_text())
-
-            # Stream finished
-            if stream_task in done:
-                recv_task.cancel()
-                break
-
-    except Exception:
-        for t in (stream_task, recv_task):
-            if not t.done():
-                t.cancel()
-
-    try:
-        return stream_task.result()
-    except Exception:
-        return False
-
-
-# ── Endpoint ──────────────────────────────────────────────────────────────────
 
 @router.websocket("/ws/sessions/{session_id}")
 async def websocket_session(session_id: str, websocket: WebSocket) -> None:
@@ -257,7 +211,7 @@
             queue = existing.subscribe()
             log.info("ws.reattached", session_id=session_id)
             await websocket.send_json({"type": "stream_start"})
-            connected = await _stream_recv(websocket, queue, existing)
+            connected = await _stream_to_client(websocket, queue)
             existing.unsubscribe(queue)
             queue = None
             current_run = None
@@ -312,7 +266,7 @@
             )
 
             await websocket.send_json({"type": "stream_start"})
-            connected = await _stream_recv(websocket, queue, run)
+            connected = await _stream_to_client(websocket, queue)
             run.unsubscribe(queue)
             queue = None
             current_run = None