diff --git a/backend/packages/harness/deerflow/runtime/events/store/db.py b/backend/packages/harness/deerflow/runtime/events/store/db.py
index 6d55f2b84d..cc46014160 100644
--- a/backend/packages/harness/deerflow/runtime/events/store/db.py
+++ b/backend/packages/harness/deerflow/runtime/events/store/db.py
@@ -424,7 +424,7 @@ class DbRunEventStore(RunEventStore):
         stmt = select(RunEventRow).where(RunEventRow.thread_id == thread_id, RunEventRow.run_id == run_id)
         if resolved_user_id is not None:
             stmt = stmt.where(RunEventRow.user_id == resolved_user_id)
-        if event_types:
+        if event_types is not None:
             stmt = stmt.where(RunEventRow.event_type.in_(event_types))
         if task_id is not None:
             # Filter on metadata["task_id"] in SQL (before LIMIT) so cursor
diff --git a/backend/tests/test_db_run_event_empty_filter.py b/backend/tests/test_db_run_event_empty_filter.py
new file mode 100644
index 0000000000..ece87ee68c
--- /dev/null
+++ b/backend/tests/test_db_run_event_empty_filter.py
@@ -0,0 +1,49 @@
+"""Regression tests for explicit empty event-type filters across backends."""
+
+import pytest
+
+from deerflow.persistence.engine import close_engine, get_session_factory, init_engine
+from deerflow.runtime.events.store.db import DbRunEventStore
+from deerflow.runtime.events.store.jsonl import JsonlRunEventStore
+from deerflow.runtime.events.store.memory import MemoryRunEventStore
+
+
+@pytest.mark.anyio
+@pytest.mark.parametrize("backend", ["memory", "jsonl", "db"])
+async def test_empty_event_types_is_an_empty_filter_across_backends(tmp_path, backend):
+    if backend == "db":
+        await init_engine(
+            "sqlite",
+            url=f"sqlite+aiosqlite:///{tmp_path / 'run-events.db'}",
+            sqlite_dir=str(tmp_path),
+        )
+        event_store = DbRunEventStore(get_session_factory())
+    elif backend == "jsonl":
+        event_store = JsonlRunEventStore(base_dir=tmp_path / "jsonl")
+    else:
+        event_store = MemoryRunEventStore()
+
+    try:
+        await event_store.put(
+            thread_id="t1",
+            run_id="r1",
+            event_type="llm_end",
+            category="trace",
+        )
+        await event_store.put(
+            thread_id="t1",
+            run_id="r1",
+            event_type="tool_start",
+            category="trace",
+        )
+
+        unfiltered = await event_store.list_events("t1", "r1", event_types=None)
+        assert [event["event_type"] for event in unfiltered] == ["llm_end", "tool_start"]
+
+        filtered = await event_store.list_events("t1", "r1", event_types=["llm_end"])
+        assert [event["event_type"] for event in filtered] == ["llm_end"]
+
+        assert await event_store.list_events("t1", "r1", event_types=[]) == []
+    finally:
+        if backend == "db":
+            await close_engine()