fix(session): avoid blocking large chat cleanup

tests/test_loop_consolidation_tokens.py

@@ -1,9 +1,10 @@
+import asyncio
 from unittest.mock import AsyncMock, MagicMock
 
 import pytest
 
-from nanobot.agent.loop import AgentLoop
 import nanobot.agent.memory as memory_module
+from nanobot.agent.loop import AgentLoop
 from nanobot.bus.queue import MessageBus
 from nanobot.providers.base import LLMResponse
 
@@ -188,3 +189,36 @@ async def test_preflight_consolidation_before_llm_call(tmp_path, monkeypatch) ->
     assert "consolidate" in order
     assert "llm" in order
     assert order.index("consolidate") < order.index("llm")
+
+
+@pytest.mark.asyncio
+async def test_slow_preflight_consolidation_continues_in_background(tmp_path, monkeypatch) -> None:
+    order: list[str] = []
+
+    loop = _make_loop(tmp_path, estimated_tokens=0, context_window_tokens=200)
+    monkeypatch.setattr(loop, "_PREFLIGHT_CONSOLIDATION_BUDGET_SECONDS", 0.01)
+
+    release = asyncio.Event()
+
+    async def slow_consolidation(_session):
+        order.append("consolidate-start")
+        await release.wait()
+        order.append("consolidate-end")
+
+    async def track_llm(*args, **kwargs):
+        order.append("llm")
+        return LLMResponse(content="ok", tool_calls=[])
+
+    loop.memory_consolidator.maybe_consolidate_by_tokens = slow_consolidation  # type: ignore[method-assign]
+    loop.provider.chat_with_retry = track_llm
+
+    await loop.process_direct("hello", session_key="cli:test")
+
+    assert "consolidate-start" in order
+    assert "llm" in order
+    assert "consolidate-end" not in order
+
+    release.set()
+    await loop.close_mcp()
+
+    assert "consolidate-end" in order

tests/test_session_manager_persistence.py

@@ -0,0 +1,104 @@
+from __future__ import annotations
+
+import json
+import os
+import time
+from datetime import datetime
+from pathlib import Path
+
+from nanobot.session.manager import SessionManager
+
+
+def _read_jsonl(path: Path) -> list[dict]:
+    return [
+        json.loads(line)
+        for line in path.read_text(encoding="utf-8").splitlines()
+        if line.strip()
+    ]
+
+
+def test_save_appends_only_new_messages(tmp_path: Path) -> None:
+    manager = SessionManager(tmp_path)
+    session = manager.get_or_create("qq:test")
+    session.add_message("user", "hello")
+    session.add_message("assistant", "hi")
+    manager.save(session)
+
+    path = manager._get_session_path(session.key)
+    original_text = path.read_text(encoding="utf-8")
+
+    session.add_message("user", "next")
+    manager.save(session)
+
+    lines = _read_jsonl(path)
+    assert path.read_text(encoding="utf-8").startswith(original_text)
+    assert sum(1 for line in lines if line.get("_type") == "metadata") == 1
+    assert [line["content"] for line in lines if line.get("role")] == ["hello", "hi", "next"]
+
+
+def test_save_appends_metadata_checkpoint_without_rewriting_history(tmp_path: Path) -> None:
+    manager = SessionManager(tmp_path)
+    session = manager.get_or_create("qq:test")
+    session.add_message("user", "hello")
+    session.add_message("assistant", "hi")
+    manager.save(session)
+
+    path = manager._get_session_path(session.key)
+    original_text = path.read_text(encoding="utf-8")
+
+    session.last_consolidated = 2
+    manager.save(session)
+
+    lines = _read_jsonl(path)
+    assert path.read_text(encoding="utf-8").startswith(original_text)
+    assert sum(1 for line in lines if line.get("_type") == "metadata") == 2
+    assert lines[-1]["_type"] == "metadata"
+    assert lines[-1]["last_consolidated"] == 2
+
+    manager.invalidate(session.key)
+    reloaded = manager.get_or_create("qq:test")
+    assert reloaded.last_consolidated == 2
+    assert [message["content"] for message in reloaded.messages] == ["hello", "hi"]
+
+
+def test_clear_rewrites_session_file(tmp_path: Path) -> None:
+    manager = SessionManager(tmp_path)
+    session = manager.get_or_create("qq:test")
+    session.add_message("user", "hello")
+    session.add_message("assistant", "hi")
+    manager.save(session)
+
+    path = manager._get_session_path(session.key)
+    session.clear()
+    manager.save(session)
+
+    lines = _read_jsonl(path)
+    assert len(lines) == 1
+    assert lines[0]["_type"] == "metadata"
+    assert lines[0]["last_consolidated"] == 0
+
+    manager.invalidate(session.key)
+    reloaded = manager.get_or_create("qq:test")
+    assert reloaded.messages == []
+    assert reloaded.last_consolidated == 0
+
+
+def test_list_sessions_uses_file_mtime_for_append_only_updates(tmp_path: Path) -> None:
+    manager = SessionManager(tmp_path)
+    session = manager.get_or_create("qq:test")
+    session.add_message("user", "hello")
+    manager.save(session)
+
+    path = manager._get_session_path(session.key)
+    stale_time = time.time() - 3600
+    os.utime(path, (stale_time, stale_time))
+
+    before = datetime.fromisoformat(manager.list_sessions()[0]["updated_at"])
+    assert before.timestamp() < time.time() - 3000
+
+    session.add_message("assistant", "hi")
+    manager.save(session)
+
+    after = datetime.fromisoformat(manager.list_sessions()[0]["updated_at"])
+    assert after > before
+