feat(sessions): add get_user_state(app_name, user_id) to BaseSessionService

src/google/adk/sessions/base_session_service.py

@@ -111,6 +111,46 @@ async def delete_session(
   ) -> None:
     """Deletes a session."""
 
+  async def get_user_state(
+      self, *, app_name: str, user_id: str
+  ) -> dict[str, Any]:
+    """Returns the user-scoped state for the given app and user.
+
+    User state is keyed by ``(app_name, user_id)`` and shared across all
+    sessions of the same user within the same app.  The returned dictionary
+    uses raw keys **without** the ``user:`` prefix (e.g. ``"my_key"`` rather
+    than ``"user:my_key"``).
+
+    This method exists so that callers can read user state without holding an
+    active ``session_id``.  A common use case is bootstrapping context at the
+    start of a new session before calling ``create_session``, which would
+    otherwise require an expensive ``list_sessions`` call just to access
+    user-scoped data.
+
+    Returns an empty dict when no user state has been stored for this
+    ``(app_name, user_id)`` combination.
+
+    Args:
+      app_name: The name of the app.
+      user_id: The ID of the user.
+
+    Returns:
+      A dictionary of raw (un-prefixed) user-scoped key/value pairs, or an
+      empty dict when no user state exists.
+
+    Raises:
+      NotImplementedError: When the concrete ``BaseSessionService``
+        implementation does not support reading user state independently of a
+        session.  Callers should catch this, then enumerate sessions via
+        ``list_sessions`` and call ``get_session`` on each result to access
+        the merged state, or accept that user state is unavailable.
+    """
+    raise NotImplementedError(
+        f'{type(self).__name__} does not support get_user_state. '
+        'To read user state, enumerate sessions via list_sessions and '
+        'call get_session on each result to access the merged state.'
+    )
+
   async def append_event(self, session: Session, event: Event) -> Event:
     """Appends an event to a session object."""
     if event.partial:

src/google/adk/sessions/database_session_service.py

@@ -616,6 +616,22 @@ async def delete_session(
       await sql_session.execute(stmt)
       await sql_session.commit()
 
+  @override
+  async def get_user_state(
+      self, *, app_name: str, user_id: str
+  ) -> dict[str, Any]:
+    await self._prepare_tables()
+    schema = self._get_schema_classes()
+    async with self._rollback_on_exception_session(
+        read_only=True
+    ) as sql_session:
+      storage_user_state = await sql_session.get(
+          schema.StorageUserState, (app_name, user_id)
+      )
+      if storage_user_state is None:
+        return {}
+      return dict(storage_user_state.state or {})
+
   @override
   async def append_event(self, session: Session, event: Event) -> Event:
     await self._prepare_tables()

src/google/adk/sessions/in_memory_session_service.py

@@ -312,6 +312,12 @@ def _delete_session_impl(
 
     self.sessions[app_name][user_id].pop(session_id)
 
+  @override
+  async def get_user_state(
+      self, *, app_name: str, user_id: str
+  ) -> dict[str, Any]:
+    return dict(self.user_state.get(app_name, {}).get(user_id, {}))
+
   @override
   async def append_event(self, session: Session, event: Event) -> Event:
     if event.partial:

src/google/adk/sessions/sqlite_session_service.py

@@ -359,6 +359,13 @@ async def delete_session(
       )
       await db.commit()
 
+  @override
+  async def get_user_state(
+      self, *, app_name: str, user_id: str
+  ) -> dict[str, Any]:
+    async with self._get_db_connection() as db:
+      return await self._get_user_state(db, app_name, user_id)
+
   @override
   async def append_event(self, session: Session, event: Event) -> Event:
     if event.partial:

src/google/adk/sessions/vertex_ai_session_service.py

@@ -269,6 +269,27 @@ async def delete_session(
         logger.error('Error deleting session %s: %s', session_id, e)
         raise
 
+  @override
+  async def get_user_state(
+      self, *, app_name: str, user_id: str
+  ) -> dict[str, Any]:
+    """Not supported by the Vertex AI Agent Engine backend.
+
+    The Vertex AI Agent Engine API does not expose user state independently of
+    a session.  To read user state, enumerate sessions via ``list_sessions``
+    and call ``get_session`` on each result to access the merged state.
+
+    Raises:
+      NotImplementedError: Always, because the Vertex AI Agent Engine API does
+        not provide a way to query user state without a session.
+    """
+    raise NotImplementedError(
+        'VertexAiSessionService does not support get_user_state. '
+        'The Vertex AI Agent Engine API does not expose user state '
+        'independently of a session. To read user state, enumerate sessions '
+        'via list_sessions and call get_session on each result.'
+    )
+
   @override
   async def append_event(self, session: Session, event: Event) -> Event:
     # Update the in-memory session.

tests/unittests/sessions/test_get_user_state.py

@@ -0,0 +1,175 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Tests for BaseSessionService.get_user_state across concrete implementations."""
+
+import enum
+
+from google.adk.events.event import Event
+from google.adk.events.event_actions import EventActions
+from google.adk.sessions.base_session_service import BaseSessionService
+from google.adk.sessions.database_session_service import DatabaseSessionService
+from google.adk.sessions.in_memory_session_service import InMemorySessionService
+from google.adk.sessions.sqlite_session_service import SqliteSessionService
+from google.adk.sessions.vertex_ai_session_service import VertexAiSessionService
+import pytest
+
+_APP = 'test-app'
+_OTHER_APP = 'other-app'
+_USER = 'user-42'
+_OTHER_USER = 'user-99'
+
+
+class SessionServiceType(enum.Enum):
+  IN_MEMORY = 'IN_MEMORY'
+  DATABASE = 'DATABASE'
+  SQLITE = 'SQLITE'
+
+
+def _make_service(
+    service_type: SessionServiceType, tmp_path=None
+) -> BaseSessionService:
+  if service_type == SessionServiceType.DATABASE:
+    return DatabaseSessionService('sqlite+aiosqlite:///:memory:')
+  if service_type == SessionServiceType.SQLITE:
+    return SqliteSessionService(str(tmp_path / 'sqlite.db'))
+  return InMemorySessionService()
+
+
+@pytest.fixture(
+    params=[
+        SessionServiceType.IN_MEMORY,
+        SessionServiceType.DATABASE,
+        SessionServiceType.SQLITE,
+    ]
+)
+async def session_service(request, tmp_path):
+  """Provides a session service and closes database backends on teardown."""
+  service = _make_service(request.param, tmp_path)
+  yield service
+  if isinstance(service, DatabaseSessionService):
+    await service.close()
+
+
+async def test_get_user_state_returns_empty_dict_when_no_state_exists(
+    session_service,
+):
+  """Returns {} when (app_name, user_id) has never had state written."""
+  state = await session_service.get_user_state(app_name=_APP, user_id=_USER)
+  assert state == {}
+
+
+async def test_get_user_state_returns_state_written_via_append_event(
+    session_service,
+):
+  """State written with the user: prefix is returned without the prefix."""
+  session = await session_service.create_session(app_name=_APP, user_id=_USER)
+  await session_service.append_event(
+      session,
+      Event(
+          author='system',
+          actions=EventActions(
+              state_delta={'user:profile': {'name': 'Alice'}, 'session_key': 1}
+          ),
+      ),
+  )
+
+  state = await session_service.get_user_state(app_name=_APP, user_id=_USER)
+
+  assert state == {'profile': {'name': 'Alice'}}
+  assert 'session_key' not in state
+
+
+async def test_get_user_state_is_not_visible_across_users(session_service):
+  """User state is scoped to (app_name, user_id) — other users see {}."""
+  session = await session_service.create_session(app_name=_APP, user_id=_USER)
+  await session_service.append_event(
+      session,
+      Event(
+          author='system',
+          actions=EventActions(state_delta={'user:secret': 'only-for-user-42'}),
+      ),
+  )
+
+  other_state = await session_service.get_user_state(
+      app_name=_APP, user_id=_OTHER_USER
+  )
+  assert other_state == {}
+
+
+async def test_get_user_state_is_not_visible_across_apps(session_service):
+  """User state is scoped to (app_name, user_id) — other apps see {}."""
+  session = await session_service.create_session(app_name=_APP, user_id=_USER)
+  await session_service.append_event(
+      session,
+      Event(
+          author='system',
+          actions=EventActions(state_delta={'user:data': 'only-app-a'}),
+      ),
+  )
+
+  other_state = await session_service.get_user_state(
+      app_name=_OTHER_APP, user_id=_USER
+  )
+  assert other_state == {}
+
+
+async def test_get_user_state_available_before_session_is_created(
+    session_service,
+):
+  """Core use case: user state is readable without an active session_id."""
+  first_session = await session_service.create_session(
+      app_name=_APP, user_id=_USER
+  )
+  await session_service.append_event(
+      first_session,
+      Event(
+          author='system',
+          actions=EventActions(state_delta={'user:ctx': {'v': 1}}),
+      ),
+  )
+
+  # Simulate a brand-new session_id (not yet created) — get_user_state must
+  # still return the persisted user state.
+  state = await session_service.get_user_state(app_name=_APP, user_id=_USER)
+  assert state == {'ctx': {'v': 1}}
+
+
+async def test_get_user_state_reflects_latest_write(session_service):
+  """Subsequent writes overwrite earlier values under the same key."""
+  session = await session_service.create_session(app_name=_APP, user_id=_USER)
+  await session_service.append_event(
+      session,
+      Event(
+          author='system',
+          actions=EventActions(state_delta={'user:counter': 1}),
+      ),
+  )
+  await session_service.append_event(
+      session,
+      Event(
+          author='system',
+          actions=EventActions(state_delta={'user:counter': 2}),
+      ),
+  )
+
+  state = await session_service.get_user_state(app_name=_APP, user_id=_USER)
+  assert state['counter'] == 2
+
+
+async def test_vertex_ai_session_service_raises_not_implemented():
+  """VertexAiSessionService raises NotImplementedError for get_user_state."""
+  service = VertexAiSessionService(project='proj', location='us-central1')
+  with pytest.raises(NotImplementedError):
+    await service.get_user_state(app_name=_APP, user_id=_USER)