feat: add sqlite checkpoint fallback switch

offline-backend-20260512/backend/config.yaml

@@ -220,7 +220,11 @@ database:
 
 checkpointer:
   type: postgres
+  # true: 新 checkpoint 写入 Postgres；false: 保留 PG 配置但继续使用 SQLite。
+  # 也可临时用环境变量 DEER_FLOW_USE_PG_CHECKPOINTER=0 覆盖。
+  use_postgres: true
   connection_string: postgresql://postgres:postgres123@47.88.25.99:8432/deerflow
+  sqlite_connection_string: .deer-flow/data/deerflow.db
   dual_read_enabled: true
   dual_read_sqlite_paths:
     - .deer-flow/data/deerflow.db

offline-backend-20260512/backend/packages/harness/deerflow/config/checkpointer_config.py

@@ -20,9 +20,23 @@ class CheckpointerConfig(BaseModel):
         default=None,
         description="Connection string for sqlite (file path) or postgres (DSN). "
         "Required for sqlite and postgres types. "
-        "For sqlite, use a file path like '.deer-flow/checkpoints.db' or ':memory:' for in-memory. "
+        "For sqlite, use a file path like '.deer-flow/checkpoints.db' or ':memory:' for in-memory. "
         "For postgres, use a DSN like 'postgresql://user:pass@localhost:5432/db'.",
     )
+    use_postgres: bool = Field(
+        default=True,
+        description=(
+            "When type='postgres', set false to keep the Postgres DSN in config "
+            "but run the checkpointer on SQLite instead."
+        ),
+    )
+    sqlite_connection_string: str | None = Field(
+        default=None,
+        description=(
+            "SQLite file used when type='postgres' and use_postgres=false. "
+            "Defaults to the first dual_read_sqlite_paths entry or 'store.db'."
+        ),
+    )
     dual_read_enabled: bool = Field(
         default=False,
         description=(

offline-backend-20260512/backend/packages/harness/deerflow/runtime/checkpointer/async_provider.py

@@ -48,6 +48,13 @@ def _dual_read_enabled(config) -> bool:
     return os.getenv("DEER_FLOW_CHECKPOINT_DUAL_READ", "").strip().lower() in {"1", "true", "yes", "on"}
 
 
+def _use_postgres_enabled(config) -> bool:
+    raw = os.getenv("DEER_FLOW_USE_PG_CHECKPOINTER")
+    if raw:
+        return raw.strip().lower() not in {"0", "false", "no", "off"}
+    return bool(getattr(config, "use_postgres", True))
+
+
 def _dual_read_paths(config) -> list[str]:
     paths = list(getattr(config, "dual_read_sqlite_paths", []) or [])
     paths.extend(_csv_env("DEER_FLOW_CHECKPOINT_SQLITE_PATHS"))
@@ -63,10 +70,32 @@ def _dual_read_paths(config) -> list[str]:
             seen.add(conn_str)
     return resolved
 
-
-# ---------------------------------------------------------------------------
-# Async factory
-# ---------------------------------------------------------------------------
+
+def _sqlite_conn_str_for_postgres_fallback(config) -> str:
+    configured = getattr(config, "sqlite_connection_string", None)
+    if configured:
+        return configured
+    paths = _dual_read_paths(config)
+    return paths[0] if paths else "store.db"
+
+
+@contextlib.asynccontextmanager
+async def _sqlite_checkpointer_from_conn_str(raw: str) -> AsyncIterator[Checkpointer]:
+    try:
+        from langgraph.checkpoint.sqlite.aio import AsyncSqliteSaver
+    except ImportError as exc:
+        raise ImportError(SQLITE_INSTALL) from exc
+
+    conn_str = resolve_sqlite_conn_str(raw)
+    await asyncio.to_thread(ensure_sqlite_parent_dir, conn_str)
+    async with AsyncSqliteSaver.from_conn_string(conn_str) as saver:
+        await saver.setup()
+        yield saver
+
+
+# ---------------------------------------------------------------------------
+# Async factory
+# ---------------------------------------------------------------------------
 
 
 @contextlib.asynccontextmanager
@@ -78,20 +107,19 @@ async def _async_checkpointer(config) -> AsyncIterator[Checkpointer]:
         yield InMemorySaver()
         return
 
-    if config.type == "sqlite":
-        try:
-            from langgraph.checkpoint.sqlite.aio import AsyncSqliteSaver
-        except ImportError as exc:
-            raise ImportError(SQLITE_INSTALL) from exc
-
-        conn_str = resolve_sqlite_conn_str(config.connection_string or "store.db")
-        await asyncio.to_thread(ensure_sqlite_parent_dir, conn_str)
-        async with AsyncSqliteSaver.from_conn_string(conn_str) as saver:
-            await saver.setup()
-            yield saver
-        return
-
+    if config.type == "sqlite":
+        async with _sqlite_checkpointer_from_conn_str(config.connection_string or "store.db") as saver:
+            yield saver
+        return
+
     if config.type == "postgres":
+        if not _use_postgres_enabled(config):
+            conn_str = _sqlite_conn_str_for_postgres_fallback(config)
+            logger.info("Checkpointer: use_postgres=false; using SQLite fallback (%s)", conn_str)
+            async with _sqlite_checkpointer_from_conn_str(conn_str) as saver:
+                yield saver
+            return
+
         try:
             from langgraph.checkpoint.postgres.aio import AsyncPostgresSaver
         except ImportError as exc:

offline-backend-20260512/config.yaml

@@ -188,7 +188,11 @@ checkpointer:
   # 这里同时被「主 agent」和「AI 写作 graph」共用 —— LangGraph 用
   # (thread_id, checkpoint_ns) 做隔离，session_id 是 uuid，不会撞。
   type: postgres
+  # true: 新 checkpoint 写入 Postgres；false: 保留 PG 配置但继续使用 SQLite。
+  # 也可临时用环境变量 DEER_FLOW_USE_PG_CHECKPOINTER=0 覆盖。
+  use_postgres: true
   connection_string: postgresql://postgres:postgres123@47.88.25.99:8432/deerflow
+  sqlite_connection_string: backend/.deer-flow/data/deerflow.db
   dual_read_enabled: true
   dual_read_sqlite_paths:
     - backend/.deer-flow/data/deerflow.db