fix(web): allow session resume without new message (#4100)

src/google/adk/cli/adk_web_server.py

@@ -202,7 +202,7 @@ class RunAgentRequest(common.BaseModel):
   app_name: str
   user_id: str
   session_id: str
-  new_message: types.Content
+  new_message: Optional[types.Content] = None
   streaming: bool = False
   state_delta: Optional[dict[str, Any]] = None
   # for resume long-running functions
@@ -369,7 +369,7 @@ def _otel_env_vars_enabled() -> bool:
 
 
 def _setup_gcp_telemetry(
-    internal_exporters: list[SpanProcessor] = None,
+    internal_exporters: list[SpanProcessor] | None = None,
 ):
   if typing.TYPE_CHECKING:
     from ..telemetry.setup import OTelHooks
@@ -411,7 +411,7 @@ def _setup_gcp_telemetry(
 
 
 def _setup_telemetry_from_env(
-    internal_exporters: list[SpanProcessor] = None,
+    internal_exporters: list[SpanProcessor] | None = None,
 ):
   from ..telemetry.setup import maybe_set_otel_providers
 
@@ -507,7 +507,7 @@ def __init__(
     # Internal properties we want to allow being modified from callbacks.
     self.runners_to_clean: set[str] = set()
     self.current_app_name_ref: SharedValue[str] = SharedValue(value="")
-    self.runner_dict = {}
+    self.runner_dict: dict[str, Runner] = {}
     self.url_prefix = url_prefix
 
   async def get_runner_async(self, app_name: str) -> Runner:
@@ -707,8 +707,8 @@ def get_fast_api_app(
       A FastAPI app instance.
     """
     # Properties we don't need to modify from callbacks
-    trace_dict = {}
-    session_trace_dict = {}
+    trace_dict: dict[str, Any] = {}
+    session_trace_dict: dict[str, list[int]] = {}
     # Set up a file system watcher to detect changes in the agents directory.
     observer = Observer()
     setup_observer(observer, self)
@@ -1413,6 +1413,7 @@ async def run_agent(req: RunAgentRequest) -> list[Event]:
               session_id=req.session_id,
               new_message=req.new_message,
               state_delta=req.state_delta,
+              invocation_id=req.invocation_id,
           )
       ) as agen:
         events = [event async for event in agen]

src/google/adk/runners.py

@@ -23,6 +23,7 @@
 from typing import Any
 from typing import AsyncGenerator
 from typing import Callable
+from typing import cast
 from typing import Generator
 from typing import List
 from typing import Optional
@@ -414,7 +415,7 @@ def run(
       The events generated by the agent.
     """
     run_config = run_config or RunConfig()
-    event_queue = queue.Queue()
+    event_queue: queue.Queue[Optional[Event]] = queue.Queue()
 
     async def _invoke_run_async():
       try:
@@ -481,8 +482,8 @@ async def run_async(
       The events generated by the agent.
 
     Raises:
-      ValueError: If the session is not found; If both invocation_id and
-        new_message are None.
+      ValueError: If the session is not found and `auto_create_session` is False,
+        or if both `invocation_id` and `new_message` are `None`.
     """
     run_config = run_config or RunConfig()
 
@@ -497,6 +498,7 @@ async def _run_with_trace(
         session = await self._get_or_create_session(
             user_id=user_id, session_id=session_id
         )
+
         if not invocation_id and not new_message:
           raise ValueError(
               'Running an agent requires either a new_message or an '
@@ -1002,7 +1004,7 @@ async def run_live(
       )
     if not session:
       session = await self._get_or_create_session(
-          user_id=user_id, session_id=session_id
+          user_id=cast(str, user_id), session_id=cast(str, session_id)
       )
     invocation_context = self._new_invocation_context_for_live(
         session,
@@ -1321,7 +1323,7 @@ async def _setup_context_for_resumed_invocation(
 
     # Step 1: Maybe retrieve a previous user message for the invocation.
     user_message = new_message or self._find_user_message_for_invocation(
-        session.events, invocation_id
+        session.events, cast(str, invocation_id)
     )
     if not user_message:
       raise ValueError(
@@ -1537,12 +1539,7 @@ async def close(self):
 
     logger.info('Runner closed.')
 
-  if sys.version_info < (3, 11):
-    Self = 'Runner'  # pylint: disable=invalid-name
-  else:
-    from typing import Self  # pylint: disable=g-import-not-at-top
-
-  async def __aenter__(self) -> Self:
+  async def __aenter__(self) -> 'Runner':
     """Async context manager entry."""
     return self
 

tests/unittests/cli/test_fast_api.py

@@ -48,6 +48,7 @@
 from google.adk.sessions.state import State
 from google.genai import types
 from pydantic import BaseModel
+from pydantic import Field
 import pytest
 
 # Configure logging to help diagnose server startup issues
@@ -132,6 +133,7 @@ async def dummy_run_async(
     run_config: Optional[RunConfig] = None,
     invocation_id: Optional[str] = None,
 ):
+
   run_config = run_config or RunConfig()
   yield _event_1()
   await asyncio.sleep(0)
@@ -154,9 +156,9 @@ class _MockEvalCaseResult(BaseModel):
   user_id: str
   session_id: str
   eval_set_file: str
-  eval_metric_results: list = {}
-  overall_eval_metric_results: list = ({},)
-  eval_metric_result_per_invocation: list = {}
+  eval_metric_results: list = Field(default_factory=list)
+  overall_eval_metric_results: list = Field(default_factory=list)
+  eval_metric_result_per_invocation: list = Field(default_factory=list)
 
 
 #################################################
@@ -1336,5 +1338,31 @@ def test_builder_save_rejects_traversal(builder_test_client, tmp_path):
   assert not (tmp_path / "app" / "tmp" / "escape.yaml").exists()
 
 
+@pytest.mark.parametrize(
+    "extra_payload",
+    [
+        {},
+        {"state_delta": {"some_key": "some_value"}},
+    ],
+    ids=["no_state_delta", "with_state_delta"],
+)
+def test_agent_run_resume_without_message_success(
+    test_app, create_test_session, extra_payload
+):
+  """Test that /run allows resuming a session with only an invocation_id."""
+  info = create_test_session
+  url = "/run"
+  payload = {
+      "app_name": info["app_name"],
+      "user_id": info["user_id"],
+      "session_id": info["session_id"],
+      "invocation_id": "test_invocation_id",
+      "streaming": False,
+      **extra_payload,
+  }
+  response = test_app.post(url, json=payload)
+  assert response.status_code == 200
+
+
 if __name__ == "__main__":
   pytest.main(["-xvs", __file__])