diff --git a/src/daemon/spawner.py b/src/daemon/spawner.py
index 64cb799..d8acc6a 100644
--- a/src/daemon/spawner.py
+++ b/src/daemon/spawner.py
@@ -1249,6 +1249,32 @@ curl -X POST http://{api_host}:{api_port}/api/projects/{project_id}/tasks/{task_
             pass
         return result
 
+    async def _probe_gateway(self, timeout: float = 3.0) -> bool:
+        """TCP + WebSocket Upgrade 握手探测 Gateway 存活
+
+        #08: Phase -1 — 在 spawn 前探测 Gateway 进程是否可达。
+        不可达 → AgentBusyError(reason="gateway_down") → 任务留 pending → ticker 30s 后重试。
+        """
+        try:
+            reader, writer = await asyncio.wait_for(
+                asyncio.open_connection(self.gateway_host, self.gateway_port),
+                timeout=timeout,
+            )
+            writer.write(
+                b'GET /ws HTTP/1.1\r\n'
+                b'Host: 127.0.0.1:%d\r\n'
+                b'Upgrade: websocket\r\n'
+                b'Connection: Upgrade\r\n'
+                b'Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==\r\n'
+                b'Sec-WebSocket-Version: 13\r\n\r\n' % self.gateway_port
+            )
+            await writer.drain()
+            resp = await asyncio.wait_for(reader.read(256), timeout=timeout)
+            writer.close()
+            return b'101' in resp
+        except Exception:
+            return False
+
     @staticmethod
     def _classify_outcome(exit_code: int, json_result: dict, stderr_text: str,
                           task_status: Optional[str], stdout_text: str = "") -> dict: