fix(delegate): handle content-block tool results

tests/tools/test_delegate.py

@@ -554,6 +554,37 @@ class TestDelegateObservability(unittest.TestCase):
             self.assertIn("result_bytes", entry["tool_trace"][0])
             self.assertEqual(entry["tool_trace"][0]["status"], "ok")
 
+    def test_tool_trace_handles_list_content_blocks(self):
+        """Tool-result content blocks should not crash observability metadata."""
+        parent = _make_mock_parent(depth=0)
+
+        with patch("run_agent.AIAgent") as MockAgent:
+            mock_child = MagicMock()
+            mock_child.model = "claude-sonnet-4-6"
+            mock_child.session_prompt_tokens = 0
+            mock_child.session_completion_tokens = 0
+            mock_child.run_conversation.return_value = {
+                "final_response": "done",
+                "completed": True,
+                "interrupted": False,
+                "api_calls": 1,
+                "messages": [
+                    {"role": "assistant", "tool_calls": [
+                        {"id": "tc_1", "function": {"name": "image_generate", "arguments": '{"prompt": "x"}'}}
+                    ]},
+                    {"role": "tool", "tool_call_id": "tc_1", "content": [
+                        {"type": "text", "text": '{"success": true}'},
+                    ]},
+                ],
+            }
+            MockAgent.return_value = mock_child
+
+            result = json.loads(delegate_task(goal="Test list content", parent_agent=parent))
+            trace = result["results"][0]["tool_trace"]
+            self.assertEqual(trace[0]["tool"], "image_generate")
+            self.assertEqual(trace[0]["status"], "ok")
+            self.assertGreater(trace[0]["result_bytes"], 0)
+
     def test_tool_trace_detects_error(self):
         """Tool results containing 'error' should be marked as error status."""
         parent = _make_mock_parent(depth=0)