--- a/runner/core.py
+++ b/runner/core.py
@@ -107,12 +107,22 @@
         require(not event.get("error"), "Antigravity provider error")
         step = event.get("step_update")
         require(isinstance(step, dict), "Antigravity malformed step")
-        require(step.get("step_type") in ("tool", "agent_response", "checkpoint", "finish")
+        require(step.get("step_type") in ("user_input", "tool", "agent_response", "checkpoint", "finish")
                 and step.get("state") in ("ACTIVE", "DONE", "ERROR"), "Antigravity unknown step")
         require(not step.get("error"), "Antigravity provider error")
+        if step.get("step_type") == "user_input":
+            require(step.get("state") == "DONE" and "tool_info" not in step
+                    and "error" not in step and type(step.get("step_index")) is int
+                    and step["step_index"] == 0, "Antigravity malformed user input")
+            continue
         info = step.get("tool_info", {})
         require(isinstance(info, dict), "Antigravity malformed tool")
         error = info.get("error")
+        if info.get("name") == "run_command" and "output" in info:
+            output = info["output"]
+            require(isinstance(output, str), "Antigravity malformed shell output")
+            require(not re.search(r"(?im)^\s*(?:sandbox-exec: sandbox_apply: Operation not permitted|(?:error: )?(?:permission denied|operation not permitted|access denied))\s*$", output),
+                    "Antigravity shell permission denied")
         if error is None:
             require(step.get("state") not in ("ERROR", "FAILED", "CANCELLED"), "Antigravity failed step")
             continue