fix(agent): avoid persisting empty-response recovery scaffolding

tests/run_agent/test_empty_response_recovery_persistence.py

@@ -0,0 +1,66 @@
+"""Regression tests for empty-response recovery transcript persistence."""
+
+from run_agent import AIAgent
+
+
+def _agent_with_stubbed_persistence():
+    agent = AIAgent.__new__(AIAgent)
+    agent._persist_user_message_idx = None
+    agent._persist_user_message_override = None
+    agent._session_db = None
+    agent._session_messages = []
+    agent.saved_session_logs = []
+    agent.flushed_session_db_messages = []
+    agent._save_session_log = lambda messages: agent.saved_session_logs.append(
+        [m.copy() for m in messages]
+    )
+    agent._flush_messages_to_session_db = lambda messages, conversation_history=None: (
+        agent.flushed_session_db_messages.append([m.copy() for m in messages])
+    )
+    return agent
+
+
+def test_persist_session_strips_trailing_empty_recovery_scaffolding():
+    agent = _agent_with_stubbed_persistence()
+    messages = [
+        {"role": "user", "content": "run the task"},
+        {"role": "tool", "content": "{}", "tool_call_id": "call_1"},
+        {
+            "role": "assistant",
+            "content": "(empty)",
+            "_empty_recovery_synthetic": True,
+        },
+        {
+            "role": "user",
+            "content": (
+                "You just executed tool calls but returned an empty response. "
+                "Please process the tool results above and continue with the task."
+            ),
+            "_empty_recovery_synthetic": True,
+        },
+    ]
+
+    AIAgent._persist_session(agent, messages, conversation_history=[])
+
+    assert messages == [
+        {"role": "user", "content": "run the task"},
+        {"role": "tool", "content": "{}", "tool_call_id": "call_1"},
+    ]
+    assert agent.saved_session_logs[-1] == messages
+    assert all(not msg.get("_empty_recovery_synthetic") for msg in messages)
+
+
+def test_persist_session_keeps_real_terminal_empty_response():
+    agent = _agent_with_stubbed_persistence()
+    messages = [
+        {"role": "user", "content": "run the task"},
+        {"role": "assistant", "content": "(empty)"},
+    ]
+
+    AIAgent._persist_session(agent, messages, conversation_history=[])
+
+    assert messages == [
+        {"role": "user", "content": "run the task"},
+        {"role": "assistant", "content": "(empty)"},
+    ]
+    assert agent.saved_session_logs[-1] == messages