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feat: add state_delta - optional state changes to apply to the session #4192

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feat: add state_delta - optional state changes to apply to the session #4192

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1e6c85e
feat: add state_delta - optional state changes to apply to the session
yingyinggu-dev Jan 18, 2026
f2b99ac
add unit tests for state_delta in run_live
yingyinggu-dev Jan 18, 2026
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12 changes: 12 additions & 0 deletions src/google/adk/runners.py
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Original file line number Diff line number Diff line change
Expand Up @@ -926,6 +926,7 @@ async def run_live(
session_id: Optional[str] = None,
live_request_queue: LiveRequestQueue,
run_config: Optional[RunConfig] = None,
state_delta: Optional[dict[str, Any]] = None,
session: Optional[Session] = None,
) -> AsyncGenerator[Event, None]:
"""Runs the agent in live mode (experimental feature).
Expand Down Expand Up @@ -966,6 +967,7 @@ async def run_live(
None.
live_request_queue: The queue for live requests.
run_config: The run config for the agent.
state_delta: Optional state changes to apply to the session.
session: The session to use. This parameter is deprecated, please use
`user_id` and `session_id` instead.

Expand Down Expand Up @@ -1009,6 +1011,16 @@ async def run_live(
run_config=run_config,
)

# Apply state_delta if provided
if state_delta:
state_event = Event(
invocation_id=invocation_context.invocation_id,
author='user',
actions=EventActions(state_delta=state_delta),
)
_apply_run_config_custom_metadata(state_event, run_config)
await self.session_service.append_event(session=session, event=state_event)
Comment on lines +1015 to +1022
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@gemini-code-assist gemini-code-assist bot Jan 18, 2026

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medium

The logic to create and append a state change event is similar to logic in other methods like _append_new_message_to_session and rewind_async. To improve maintainability and reduce code duplication, consider extracting this into a private helper method in a follow-up change. A shared helper would centralize the creation of these control events.

For example, a helper could look like this:

async def _append_control_event(self, session: Session, invocation_context: InvocationContext, actions: EventActions, run_config: Optional[RunConfig]):
    event = Event(
        invocation_id=invocation_context.invocation_id,
        author='user',
        actions=actions,
    )
    _apply_run_config_custom_metadata(event, run_config)
    await self.session_service.append_event(session=session, event=event)


root_agent = self.agent
invocation_context.agent = self._find_agent_to_run(session, root_agent)

Expand Down
44 changes: 44 additions & 0 deletions tests/unittests/test_runners.py
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Original file line number Diff line number Diff line change
Expand Up @@ -442,6 +442,50 @@ async def _run_live_impl(
assert "non_streaming_tool" not in active_tools


@pytest.mark.asyncio
async def test_run_live_state_delta_applied_to_session():
"""run_live should apply state_delta to the session at the start."""
session_service = InMemorySessionService()
artifact_service = InMemoryArtifactService()
runner = Runner(
app_name="run_live_app",
agent=MockLiveAgent("live_agent"),
session_service=session_service,
artifact_service=artifact_service,
auto_create_session=True,
)

live_queue = LiveRequestQueue()
state_delta = {"useCase": "voice_assistant"}

agen = runner.run_live(
user_id="user",
session_id="test_session",
live_request_queue=live_queue,
state_delta=state_delta,
)

event = await agen.__anext__()
await agen.aclose()

assert event.author == "live_agent"

# Verify state_delta was applied to the session
session = await session_service.get_session(
app_name="run_live_app", user_id="user", session_id="test_session"
)
assert session is not None
assert session.state.get("useCase") == "voice_assistant"

# Verify the state_delta event was appended to the session
state_delta_events = [
e for e in session.events
if e.actions.state_delta and e.author == "user"
]
assert len(state_delta_events) == 1
assert state_delta_events[0].actions.state_delta == state_delta


@pytest.mark.asyncio
async def test_runner_allows_nested_agent_directories(tmp_path, monkeypatch):
project_root = tmp_path / "workspace"
Expand Down