fix

.gitignore

@@ -9,4 +9,5 @@ src/lilith_agent/__pycache__/
 submission.jsonl
 anatomy.pdf
 anatomy_full.pdf
-*.csv
+*.csv
+.pycache/*

requirements.txt

@@ -2,7 +2,8 @@ gradio
 requests
 httpx
 pandas
-langgraph>=0.2.0
+langgraph>=1.0,<2.0
+langgraph-checkpoint-sqlite
 langmem>=0.0.1
 langchain-core>=0.3.0
 langchain-anthropic>=0.2.0

src/lilith_agent/app.py

@@ -9,8 +9,6 @@ from typing import Callable
 
 from langchain_core.messages import AIMessage, HumanMessage, ToolMessage
 from langchain_core.tools import BaseTool
-from langgraph.checkpoint.sqlite import SqliteSaver
-import sqlite3
 import os
 from pathlib import Path
 from langgraph.graph import END, StateGraph
@@ -24,6 +22,7 @@ class AgentState(TypedDict):
 
 
 from lilith_agent.config import Config
+from lilith_agent.checkpointing import build_checkpointer
 from lilith_agent.models import get_cheap_model, get_extra_strong_model
 
 log = logging.getLogger(__name__)
@@ -646,13 +645,8 @@ def build_react_agent(cfg: Config):
     graph.add_edge("fail_safe", "extract_memory")
     graph.add_edge("extract_memory", END)
 
-    # Setup SQLite Saver
     lilith_home = Path(os.getenv("LILITH_HOME", ".lilith"))
-    lilith_home.mkdir(parents=True, exist_ok=True)
-    db_path = lilith_home / "threads.sqlite"
-    
-    conn = sqlite3.connect(str(db_path), check_same_thread=False)
-    memory_saver = SqliteSaver(conn)
+    memory_saver = build_checkpointer(lilith_home)
 
     compiled = graph.compile(checkpointer=memory_saver)
     return compiled.with_config({"recursion_limit": cfg.recursion_limit})

src/lilith_agent/checkpointing.py

@@ -0,0 +1,32 @@
+from __future__ import annotations
+
+import importlib
+import logging
+import sqlite3
+from pathlib import Path
+from typing import Any
+
+log = logging.getLogger(__name__)
+
+
+def build_checkpointer(lilith_home: Path) -> Any:
+    """Create the graph checkpointer, preferring SQLite persistence when available."""
+    lilith_home.mkdir(parents=True, exist_ok=True)
+    db_path = lilith_home / "threads.sqlite"
+
+    try:
+        sqlite_module = importlib.import_module("langgraph.checkpoint.sqlite")
+        sqlite_saver_cls = sqlite_module.SqliteSaver
+    except ModuleNotFoundError as exc:
+        memory_module = importlib.import_module("langgraph.checkpoint.memory")
+        in_memory_saver_cls = memory_module.InMemorySaver
+        log.warning(
+            "langgraph-checkpoint-sqlite missing; using InMemorySaver instead. "
+            "Install langgraph-checkpoint-sqlite to restore persistent thread checkpoints. "
+            "Original import error: %s",
+            exc,
+        )
+        return in_memory_saver_cls()
+
+    conn = sqlite3.connect(str(db_path), check_same_thread=False)
+    return sqlite_saver_cls(conn)

tests/test_checkpointing.py

@@ -0,0 +1,57 @@
+from __future__ import annotations
+
+import importlib
+import types
+import unittest
+from pathlib import Path
+from unittest.mock import patch
+
+from lilith_agent.checkpointing import build_checkpointer
+
+
+class CheckpointingTests(unittest.TestCase):
+    def test_build_checkpointer_uses_sqlite_when_available(self) -> None:
+        tmp_path = Path(self._testMethodName)
+
+        class FakeSqliteSaver:
+            def __init__(self, conn) -> None:
+                self.conn = conn
+
+        def fake_import_module(name: str):
+            if name == "langgraph.checkpoint.sqlite":
+                return types.SimpleNamespace(SqliteSaver=FakeSqliteSaver)
+            raise AssertionError(f"unexpected import: {name}")
+
+        with patch.object(importlib, "import_module", side_effect=fake_import_module):
+            saver = build_checkpointer(tmp_path)
+
+        self.assertIsInstance(saver, FakeSqliteSaver)
+        self.assertTrue((tmp_path / "threads.sqlite").exists())
+
+    def test_build_checkpointer_falls_back_to_in_memory_when_sqlite_package_missing(self) -> None:
+        tmp_path = Path(self._testMethodName)
+
+        class FakeInMemorySaver:
+            pass
+
+        def fake_import_module(name: str):
+            if name == "langgraph.checkpoint.sqlite":
+                raise ModuleNotFoundError("No module named 'langgraph.checkpoint.sqlite'")
+            if name == "langgraph.checkpoint.memory":
+                return types.SimpleNamespace(InMemorySaver=FakeInMemorySaver)
+            raise AssertionError(f"unexpected import: {name}")
+
+        with patch.object(importlib, "import_module", side_effect=fake_import_module):
+            with self.assertLogs("lilith_agent.checkpointing", level="WARNING") as captured:
+                saver = build_checkpointer(tmp_path)
+
+        self.assertIsInstance(saver, FakeInMemorySaver)
+        self.assertIn("langgraph-checkpoint-sqlite missing", "\n".join(captured.output))
+
+    def test_requirements_include_langgraph_checkpoint_sqlite(self) -> None:
+        requirements = Path("requirements.txt").read_text().splitlines()
+        self.assertIn("langgraph-checkpoint-sqlite", requirements)
+
+
+if __name__ == "__main__":
+    unittest.main()