fix: replace assert with runtime guards in computer_use (browser_route, doctor)

tools/computer_use/browser_route.py

@@ -478,7 +478,11 @@ def mutate(
         )
         if refusal is not None:
             return refusal
-        assert selected_tab is not None and self.state.target_id is not None
+        if selected_tab is None or self.state.target_id is None:
+            return _refusal(
+                "browser_state_missing",
+                "Internal state error: no selected tab or target id after mutation check.",
+            )
 
         ref = call_args.get("ref")
         supports_trust_choice = tool in {"browser_click", "browser_pointer"}

tools/computer_use/doctor.py

@@ -223,7 +223,11 @@ def _open_mcp(binary: str) -> subprocess.Popen:
 
 def _mcp_rpc(proc: subprocess.Popen, msg_id: int, method: str, params: Any = None) -> Dict[str, Any]:
     """Write one JSON-RPC request and read one response line."""
-    assert proc.stdin is not None and proc.stdout is not None
+    if proc.stdin is None or proc.stdout is None:
+        raise RuntimeError(
+            "_mcp_rpc: subprocess stdin or stdout is None — "
+            "cannot communicate with MCP server"
+        )
     payload: Dict[str, Any] = {"jsonrpc": "2.0", "id": msg_id, "method": method}
     if params is not None:
         payload["params"] = params