fix(agent): close interrupted early-persisted user turns

Track text-only user messages that were flushed before the turn loop completes, then materialize an interrupted assistant placeholder on the next request so session history stays legal and later turns do not skip their own assistant reply.

Made-with: Cursor

tests/agent/test_loop_save_turn.py

@@ -229,6 +229,7 @@ async def test_process_message_persists_user_message_before_turn_completes(tmp_p
     persisted = loop.sessions.get_or_create("feishu:c1")
     assert [m["role"] for m in persisted.messages] == ["user"]
     assert persisted.messages[0]["content"] == "persist me"
+    assert persisted.metadata.get(AgentLoop._PENDING_USER_TURN_KEY) is True
     assert persisted.updated_at >= persisted.created_at
 
 
@@ -262,3 +263,48 @@ async def test_process_message_does_not_duplicate_early_persisted_user_message(t
         {"role": "user", "content": "hello"},
         {"role": "assistant", "content": "done"},
     ]
+    assert AgentLoop._PENDING_USER_TURN_KEY not in session.metadata
+
+
+@pytest.mark.asyncio
+async def test_next_turn_after_crash_closes_pending_user_turn_before_new_input(tmp_path: Path) -> None:
+    loop = _make_full_loop(tmp_path)
+    loop.consolidator.maybe_consolidate_by_tokens = AsyncMock(return_value=False)  # type: ignore[method-assign]
+    loop.provider.chat_with_retry = AsyncMock(return_value=MagicMock())  # unused because _run_agent_loop is stubbed
+
+    session = loop.sessions.get_or_create("feishu:c3")
+    session.add_message("user", "old question")
+    session.metadata[AgentLoop._PENDING_USER_TURN_KEY] = True
+    loop.sessions.save(session)
+
+    loop._run_agent_loop = AsyncMock(return_value=(
+        "new answer",
+        None,
+        [
+            {"role": "system", "content": "system"},
+            {"role": "user", "content": "old question"},
+            {"role": "assistant", "content": "Error: Task interrupted before a response was generated."},
+            {"role": "user", "content": "new question"},
+            {"role": "assistant", "content": "new answer"},
+        ],
+        "stop",
+        False,
+    ))  # type: ignore[method-assign]
+
+    result = await loop._process_message(
+        InboundMessage(channel="feishu", sender_id="u1", chat_id="c3", content="new question")
+    )
+
+    assert result is not None
+    assert result.content == "new answer"
+    session = loop.sessions.get_or_create("feishu:c3")
+    assert [
+        {k: v for k, v in m.items() if k in {"role", "content"}}
+        for m in session.messages
+    ] == [
+        {"role": "user", "content": "old question"},
+        {"role": "assistant", "content": "Error: Task interrupted before a response was generated."},
+        {"role": "user", "content": "new question"},
+        {"role": "assistant", "content": "new answer"},
+    ]
+    assert AgentLoop._PENDING_USER_TURN_KEY not in session.metadata