From 8b6af5d581130dd4d883623677d0e6d56e66ba6a Mon Sep 17 00:00:00 2001
From: Luyang Wang <luyang.wang@verizon.com>
Date: Fri, 9 Jan 2026 13:46:55 -0500
Subject: [PATCH 01/11] move session creation to runner level

---
 src/google/adk/runners.py                           | 5 +++--
 src/google/adk/sessions/database_session_service.py | 4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index 730216e0b0..d352b2f353 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -454,8 +454,9 @@ async def _run_with_trace(
             app_name=self.app_name, user_id=user_id, session_id=session_id
         )
         if not session:
-          message = self._format_session_not_found_message(session_id)
-          raise ValueError(message)
+          session = await self.session_service.create_session(
+              app_name=self.app_name, 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 '
diff --git a/src/google/adk/sessions/database_session_service.py b/src/google/adk/sessions/database_session_service.py
index 863bbfa861..8b7bda6d2a 100644
--- a/src/google/adk/sessions/database_session_service.py
+++ b/src/google/adk/sessions/database_session_service.py
@@ -436,8 +436,8 @@ async def append_event(self, session: Session, event: Event) -> Event:
       if storage_session.update_timestamp_tz > session.last_update_time:
         raise ValueError(
             "The last_update_time provided in the session object"
-            f" {datetime.fromtimestamp(session.last_update_time):'%Y-%m-%d %H:%M:%S'} is"
-            " earlier than the update_time in the storage_session"
+            f" {datetime.fromtimestamp(session.last_update_time):'%Y-%m-%d %H:%M:%S'}"
+            " is earlier than the update_time in the storage_session"
             f" {datetime.fromtimestamp(storage_session.update_timestamp_tz):'%Y-%m-%d %H:%M:%S'}."
             " Please check if it is a stale session."
         )

From ce2c649e1e2f5cd0dc821034082c20497203a603 Mon Sep 17 00:00:00 2001
From: Luyang Wang <luyang.wang@verizon.com>
Date: Fri, 9 Jan 2026 14:02:17 -0500
Subject: [PATCH 02/11] removed old test case

---
 tests/unittests/test_runners.py | 37 ---------------------------------
 1 file changed, 37 deletions(-)

diff --git a/tests/unittests/test_runners.py b/tests/unittests/test_runners.py
index c347a78931..359607d78b 100644
--- a/tests/unittests/test_runners.py
+++ b/tests/unittests/test_runners.py
@@ -200,43 +200,6 @@ def setup_method(self):
     )
 
 
-@pytest.mark.asyncio
-async def test_session_not_found_message_includes_alignment_hint():
-
-  class RunnerWithMismatch(Runner):
-
-    def _infer_agent_origin(
-        self, agent: BaseAgent
-    ) -> tuple[Optional[str], Optional[Path]]:
-      del agent
-      return "expected_app", Path("/workspace/agents/expected_app")
-
-  session_service = InMemorySessionService()
-  runner = RunnerWithMismatch(
-      app_name="configured_app",
-      agent=MockLlmAgent("root_agent"),
-      session_service=session_service,
-      artifact_service=InMemoryArtifactService(),
-  )
-
-  agen = runner.run_async(
-      user_id="user",
-      session_id="missing",
-      new_message=types.Content(role="user", parts=[]),
-  )
-
-  with pytest.raises(ValueError) as excinfo:
-    await agen.__anext__()
-
-  await agen.aclose()
-
-  message = str(excinfo.value)
-  assert "Session not found" in message
-  assert "configured_app" in message
-  assert "expected_app" in message
-  assert "Ensure the runner app_name matches" in message
-
-
 @pytest.mark.asyncio
 async def test_runner_allows_nested_agent_directories(tmp_path, monkeypatch):
   project_root = tmp_path / "workspace"

From 058922c3abf5ccbac33744d7caff97e170917f87 Mon Sep 17 00:00:00 2001
From: Luyang Wang <luyang.wang@verizon.com>
Date: Fri, 9 Jan 2026 14:13:18 -0500
Subject: [PATCH 03/11] update to all references

---
 src/google/adk/runners.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index d352b2f353..23ad5812f4 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -534,8 +534,9 @@ async def rewind_async(
         app_name=self.app_name, user_id=user_id, session_id=session_id
     )
     if not session:
-      raise ValueError(f'Session not found: {session_id}')
-
+        session = await self.session_service.create_session(
+            app_name=self.app_name, user_id=user_id, session_id=session_id
+        )
     rewind_event_index = -1
     for i, event in enumerate(session.events):
       if event.invocation_id == rewind_before_invocation_id:
@@ -967,9 +968,8 @@ async def run_live(
           app_name=self.app_name, user_id=user_id, session_id=session_id
       )
       if not session:
-        raise ValueError(
-            f'Session not found for user id: {user_id} and session id:'
-            f' {session_id}'
+        session = await self.session_service.create_session(
+            app_name=self.app_name, user_id=user_id, session_id=session_id
         )
     invocation_context = self._new_invocation_context_for_live(
         session,

From 5f465c1f530e8e2159a82a4041567a2b91ec7d34 Mon Sep 17 00:00:00 2001
From: Luyang Wang <luyang.wang@verizon.com>
Date: Fri, 9 Jan 2026 14:14:48 -0500
Subject: [PATCH 04/11] update pyink

---
 src/google/adk/runners.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index 23ad5812f4..8751455267 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -534,9 +534,9 @@ async def rewind_async(
         app_name=self.app_name, user_id=user_id, session_id=session_id
     )
     if not session:
-        session = await self.session_service.create_session(
-            app_name=self.app_name, user_id=user_id, session_id=session_id
-        )
+      session = await self.session_service.create_session(
+          app_name=self.app_name, user_id=user_id, session_id=session_id
+      )
     rewind_event_index = -1
     for i, event in enumerate(session.events):
       if event.invocation_id == rewind_before_invocation_id:

From 571bee587e4b30c1a59354af2aba24d345a7e5b5 Mon Sep 17 00:00:00 2001
From: Luyang Wang <luyang.wang@verizon.com>
Date: Fri, 9 Jan 2026 22:32:02 -0500
Subject: [PATCH 05/11] added test case

---
 tests/unittests/test_runners.py | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/tests/unittests/test_runners.py b/tests/unittests/test_runners.py
index 359607d78b..01ff06e245 100644
--- a/tests/unittests/test_runners.py
+++ b/tests/unittests/test_runners.py
@@ -200,6 +200,39 @@ def setup_method(self):
     )
 
 
+@pytest.mark.asyncio
+async def test_session_auto_creation():
+
+  class RunnerWithMismatch(Runner):
+
+    def _infer_agent_origin(
+        self, agent: BaseAgent
+    ) -> tuple[Optional[str], Optional[Path]]:
+      del agent
+      return "expected_app", Path("/workspace/agents/expected_app")
+
+  session_service = InMemorySessionService()
+  runner = RunnerWithMismatch(
+      app_name="expected_app",
+      agent=MockLlmAgent("test_agent"),
+      session_service=session_service,
+      artifact_service=InMemoryArtifactService(),
+  )
+
+  agen = runner.run_async(
+      user_id="user",
+      session_id="missing",
+      new_message=types.Content(role="user", parts=[types.Part(text="hi")]),
+  )
+
+  event = await agen.__anext__()
+  await agen.aclose()
+
+  # Verify that session_id="missing" doesn't error out - session is auto-created
+  assert event.author == "test_agent"
+  assert event.content.parts[0].text == "Test LLM response"
+
+
 @pytest.mark.asyncio
 async def test_runner_allows_nested_agent_directories(tmp_path, monkeypatch):
   project_root = tmp_path / "workspace"

From ef90f125efacdb171bdb64d28e4089b3f9c9b06e Mon Sep 17 00:00:00 2001
From: Luyang Wang <luyang.wang@verizon.com>
Date: Sat, 10 Jan 2026 20:11:06 -0500
Subject: [PATCH 06/11] add auto_create_session flag and default to false

---
 src/google/adk/runners.py       | 45 ++++++++++++++++++++++++---------
 tests/unittests/test_runners.py | 38 ++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+), 12 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index 4e88caf609..6d6e992771 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -149,6 +149,7 @@ def __init__(
       memory_service: Optional[BaseMemoryService] = None,
       credential_service: Optional[BaseCredentialService] = None,
       plugin_close_timeout: float = 5.0,
+      auto_create_session: bool = False,
   ):
     """Initializes the Runner.
 
@@ -175,6 +176,9 @@ def __init__(
         memory_service: The memory service for the runner.
         credential_service: The credential service for the runner.
         plugin_close_timeout: The timeout in seconds for plugin close methods.
+        auto_create_session: Whether to automatically create a session when
+          not found. Defaults to False. If False, a missing session raises
+          ValueError with a helpful message.
 
     Raises:
         ValueError: If `app` is provided along with `agent` or `plugins`, or if
@@ -195,6 +199,7 @@ def __init__(
     self.plugin_manager = PluginManager(
         plugins=plugins, close_timeout=plugin_close_timeout
     )
+    self.auto_create_session = auto_create_session
     (
         self._agent_origin_app_name,
         self._agent_origin_dir,
@@ -459,9 +464,13 @@ async def _run_with_trace(
             app_name=self.app_name, user_id=user_id, session_id=session_id
         )
         if not session:
-          session = await self.session_service.create_session(
-              app_name=self.app_name, user_id=user_id, session_id=session_id
-          )
+          if self.auto_create_session:
+            session = await self.session_service.create_session(
+                app_name=self.app_name, user_id=user_id, session_id=session_id
+            )
+          else:
+            message = self._format_session_not_found_message(session_id)
+            raise ValueError(message)
         if not invocation_id and not new_message:
           raise ValueError(
               'Running an agent requires either a new_message or an '
@@ -539,9 +548,13 @@ async def rewind_async(
         app_name=self.app_name, user_id=user_id, session_id=session_id
     )
     if not session:
-      session = await self.session_service.create_session(
-          app_name=self.app_name, user_id=user_id, session_id=session_id
-      )
+      if self.auto_create_session:
+        session = await self.session_service.create_session(
+            app_name=self.app_name, user_id=user_id, session_id=session_id
+        )
+      else:
+        message = self._format_session_not_found_message(session_id)
+        raise ValueError(message)
     rewind_event_index = -1
     for i, event in enumerate(session.events):
       if event.invocation_id == rewind_before_invocation_id:
@@ -973,9 +986,13 @@ async def run_live(
           app_name=self.app_name, user_id=user_id, session_id=session_id
       )
       if not session:
-        session = await self.session_service.create_session(
-            app_name=self.app_name, user_id=user_id, session_id=session_id
-        )
+        if self.auto_create_session:
+          session = await self.session_service.create_session(
+              app_name=self.app_name, user_id=user_id, session_id=session_id
+          )
+        else:
+          message = self._format_session_not_found_message(session_id)
+          raise ValueError(message)
     invocation_context = self._new_invocation_context_for_live(
         session,
         live_request_queue=live_request_queue,
@@ -1188,9 +1205,13 @@ async def run_debug(
         app_name=self.app_name, user_id=user_id, session_id=session_id
     )
     if not session:
-      session = await self.session_service.create_session(
-          app_name=self.app_name, user_id=user_id, session_id=session_id
-      )
+      if self.auto_create_session:
+        session = await self.session_service.create_session(
+            app_name=self.app_name, user_id=user_id, session_id=session_id
+        )
+      else:
+        message = self._format_session_not_found_message(session_id)
+        raise ValueError(message)
       if not quiet:
         print(f'\n ### Created new session: {session_id}')
     elif not quiet:
diff --git a/tests/unittests/test_runners.py b/tests/unittests/test_runners.py
index f70475b307..af85d6d21d 100644
--- a/tests/unittests/test_runners.py
+++ b/tests/unittests/test_runners.py
@@ -200,6 +200,43 @@ def setup_method(self):
     )
 
 
+@pytest.mark.asyncio
+async def test_session_not_found_message_includes_alignment_hint():
+
+  class RunnerWithMismatch(Runner):
+
+    def _infer_agent_origin(
+        self, agent: BaseAgent
+    ) -> tuple[Optional[str], Optional[Path]]:
+      del agent
+      return "expected_app", Path("/workspace/agents/expected_app")
+
+  session_service = InMemorySessionService()
+  runner = RunnerWithMismatch(
+      app_name="configured_app",
+      agent=MockLlmAgent("root_agent"),
+      session_service=session_service,
+      artifact_service=InMemoryArtifactService(),
+  )
+
+  agen = runner.run_async(
+      user_id="user",
+      session_id="missing",
+      new_message=types.Content(role="user", parts=[]),
+  )
+
+  with pytest.raises(ValueError) as excinfo:
+    await agen.__anext__()
+
+  await agen.aclose()
+
+  message = str(excinfo.value)
+  assert "Session not found" in message
+  assert "configured_app" in message
+  assert "expected_app" in message
+  assert "Ensure the runner app_name matches" in message
+
+
 @pytest.mark.asyncio
 async def test_session_auto_creation():
 
@@ -217,6 +254,7 @@ def _infer_agent_origin(
       agent=MockLlmAgent("test_agent"),
       session_service=session_service,
       artifact_service=InMemoryArtifactService(),
+      auto_create_session=True,
   )
 
   agen = runner.run_async(

From 7df6afccd75e5e4c1959c373d3c200426b0547fb Mon Sep 17 00:00:00 2001
From: Luyang Wang <luyang.wang@verizon.com>
Date: Sat, 10 Jan 2026 20:19:44 -0500
Subject: [PATCH 07/11] keep run_debug intact

---
 src/google/adk/runners.py | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index 6d6e992771..3c39c276d5 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -1205,13 +1205,9 @@ async def run_debug(
         app_name=self.app_name, user_id=user_id, session_id=session_id
     )
     if not session:
-      if self.auto_create_session:
-        session = await self.session_service.create_session(
-            app_name=self.app_name, user_id=user_id, session_id=session_id
-        )
-      else:
-        message = self._format_session_not_found_message(session_id)
-        raise ValueError(message)
+      session = await self.session_service.create_session(
+          app_name=self.app_name, user_id=user_id, session_id=session_id
+      )
       if not quiet:
         print(f'\n ### Created new session: {session_id}')
     elif not quiet:

From 2fef4bcc4f20f2d02b0420db78d4856b00782628 Mon Sep 17 00:00:00 2001
From: Luyang Wang <luyang.wang@verizon.com>
Date: Sat, 10 Jan 2026 21:48:25 -0500
Subject: [PATCH 08/11] update session not found message

---
 src/google/adk/runners.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index 3c39c276d5..c1d9877d0f 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -348,7 +348,9 @@ def _format_session_not_found_message(self, session_id: str) -> str:
       return message
     return (
         f'{message}. {self._app_name_alignment_hint} '
-        'The mismatch prevents the runner from locating the session.'
+        'The mismatch prevents the runner from locating the session. '
+        'To automatically create a session when missing, set '
+        'auto_create_session=True when constructing the runner.'
     )
 
   def run(

From 57db5f1b5ef9b82adb27de960cfb02da35a7416e Mon Sep 17 00:00:00 2001
From: Luyang Wang <luyang.wang@verizon.com>
Date: Sun, 11 Jan 2026 20:11:32 -0500
Subject: [PATCH 09/11] added helper function and test cases

---
 src/google/adk/runners.py       | 97 ++++++++++++++++++++++-----------
 tests/unittests/test_runners.py | 87 +++++++++++++++++++++++++++++
 2 files changed, 151 insertions(+), 33 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index c1d9877d0f..f289b3cab4 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -353,6 +353,51 @@ def _format_session_not_found_message(self, session_id: str) -> str:
         'auto_create_session=True when constructing the runner.'
     )
 
+  async def _get_or_create_session(
+      self, *, user_id: str, session_id: str
+  ) -> Session:
+    """Gets the session or creates it if missing.
+
+    This helper first attempts to retrieve the session. If not found, it
+    creates a new session with the provided identifiers.
+
+    Args:
+      user_id: The user ID of the session.
+      session_id: The session ID of the session.
+
+    Returns:
+      The existing or newly created `Session`.
+    """
+    session = await self.session_service.get_session(
+        app_name=self.app_name, user_id=user_id, session_id=session_id
+    )
+    if session:
+      return session
+    return await self.session_service.create_session(
+        app_name=self.app_name, user_id=user_id, session_id=session_id
+    )
+
+  async def _get_session(self, *, user_id: str, session_id: str) -> Session:
+    """Gets a session or raises a helpful error if missing.
+
+    Args:
+      user_id: The user ID of the session.
+      session_id: The session ID of the session.
+
+    Returns:
+      The existing `Session`.
+
+    Raises:
+      ValueError: If the session cannot be found.
+    """
+    session = await self.session_service.get_session(
+        app_name=self.app_name, user_id=user_id, session_id=session_id
+    )
+    if not session:
+      message = self._format_session_not_found_message(session_id)
+      raise ValueError(message)
+    return session
+
   def run(
       self,
       *,
@@ -462,17 +507,14 @@ async def _run_with_trace(
         invocation_id: Optional[str] = None,
     ) -> AsyncGenerator[Event, None]:
       with tracer.start_as_current_span('invocation'):
-        session = await self.session_service.get_session(
-            app_name=self.app_name, user_id=user_id, session_id=session_id
-        )
-        if not session:
-          if self.auto_create_session:
-            session = await self.session_service.create_session(
-                app_name=self.app_name, user_id=user_id, session_id=session_id
-            )
-          else:
-            message = self._format_session_not_found_message(session_id)
-            raise ValueError(message)
+        if self.auto_create_session:
+          session = await self._get_or_create_session(
+              user_id=user_id, session_id=session_id
+          )
+        else:
+          session = await self._get_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 '
@@ -546,17 +588,12 @@ async def rewind_async(
       rewind_before_invocation_id: str,
   ) -> None:
     """Rewinds the session to before the specified invocation."""
-    session = await self.session_service.get_session(
-        app_name=self.app_name, user_id=user_id, session_id=session_id
-    )
-    if not session:
-      if self.auto_create_session:
-        session = await self.session_service.create_session(
-            app_name=self.app_name, user_id=user_id, session_id=session_id
-        )
-      else:
-        message = self._format_session_not_found_message(session_id)
-        raise ValueError(message)
+    if self.auto_create_session:
+      session = await self._get_or_create_session(
+          user_id=user_id, session_id=session_id
+      )
+    else:
+      session = await self._get_session(user_id=user_id, session_id=session_id)
     rewind_event_index = -1
     for i, event in enumerate(session.events):
       if event.invocation_id == rewind_before_invocation_id:
@@ -983,18 +1020,12 @@ async def run_live(
           DeprecationWarning,
           stacklevel=2,
       )
-    if not session:
-      session = await self.session_service.get_session(
-          app_name=self.app_name, user_id=user_id, session_id=session_id
+    if self.auto_create_session:
+      session = await self._get_or_create_session(
+          user_id=user_id, session_id=session_id
       )
-      if not session:
-        if self.auto_create_session:
-          session = await self.session_service.create_session(
-              app_name=self.app_name, user_id=user_id, session_id=session_id
-          )
-        else:
-          message = self._format_session_not_found_message(session_id)
-          raise ValueError(message)
+    else:
+      session = await self._get_session(user_id=user_id, session_id=session_id)
     invocation_context = self._new_invocation_context_for_live(
         session,
         live_request_queue=live_request_queue,
diff --git a/tests/unittests/test_runners.py b/tests/unittests/test_runners.py
index af85d6d21d..bb44ce73d6 100644
--- a/tests/unittests/test_runners.py
+++ b/tests/unittests/test_runners.py
@@ -68,6 +68,24 @@ async def _run_async_impl(
     )
 
 
+class MockLiveAgent(BaseAgent):
+  """Mock live agent for unit testing."""
+
+  def __init__(self, name: str):
+    super().__init__(name=name, sub_agents=[])
+
+  async def _run_live_impl(
+      self, invocation_context: InvocationContext
+  ) -> AsyncGenerator[Event, None]:
+    yield Event(
+        invocation_id=invocation_context.invocation_id,
+        author=self.name,
+        content=types.Content(
+            role="model", parts=[types.Part(text="live hello")]
+        ),
+    )
+
+
 class MockLlmAgent(LlmAgent):
   """Mock LLM agent for unit testing."""
 
@@ -271,6 +289,75 @@ def _infer_agent_origin(
   assert event.content.parts[0].text == "Test LLM response"
 
 
+@pytest.mark.asyncio
+async def test_rewind_auto_create_session_on_missing_session():
+  """When auto_create_session=True, rewind should create session if missing.
+
+  The newly created session won't contain the target invocation, so
+  `rewind_async` should raise an Invocation ID not found error (rather than
+  a session not found error), demonstrating auto-creation occurred.
+  """
+  session_service = InMemorySessionService()
+  runner = Runner(
+      app_name="auto_create_app",
+      agent=MockLlmAgent("agent_for_rewind"),
+      session_service=session_service,
+      artifact_service=InMemoryArtifactService(),
+      auto_create_session=True,
+  )
+
+  with pytest.raises(ValueError, match=r"Invocation ID not found: inv_missing"):
+    await runner.rewind_async(
+        user_id="user",
+        session_id="missing",
+        rewind_before_invocation_id="inv_missing",
+    )
+
+  # Verify the session actually exists now due to auto-creation.
+  session = await session_service.get_session(
+      app_name="auto_create_app", user_id="user", session_id="missing"
+  )
+  assert session is not None
+  assert session.app_name == "auto_create_app"
+
+
+@pytest.mark.asyncio
+async def test_run_live_auto_create_session():
+  """run_live should auto-create session when missing and yield events."""
+  session_service = InMemorySessionService()
+  artifact_service = InMemoryArtifactService()
+  runner = Runner(
+      app_name="live_app",
+      agent=MockLiveAgent("live_agent"),
+      session_service=session_service,
+      artifact_service=artifact_service,
+      auto_create_session=True,
+  )
+
+  # An empty LiveRequestQueue is sufficient for our mock agent.
+  from google.adk.agents.live_request_queue import LiveRequestQueue
+
+  live_queue = LiveRequestQueue()
+
+  agen = runner.run_live(
+      user_id="user",
+      session_id="missing",
+      live_request_queue=live_queue,
+  )
+
+  event = await agen.__anext__()
+  await agen.aclose()
+
+  assert event.author == "live_agent"
+  assert event.content.parts[0].text == "live hello"
+
+  # Session should have been created automatically.
+  session = await session_service.get_session(
+      app_name="live_app", user_id="user", session_id="missing"
+  )
+  assert session is not None
+
+
 @pytest.mark.asyncio
 async def test_runner_allows_nested_agent_directories(tmp_path, monkeypatch):
   project_root = tmp_path / "workspace"

From 555293c79ae299b602aa2dc235c748daae1d8ae6 Mon Sep 17 00:00:00 2001
From: Luyang Wang <luyang.wang@verizon.com>
Date: Mon, 12 Jan 2026 14:04:36 -0500
Subject: [PATCH 10/11] combine helper function

---
 src/google/adk/runners.py | 61 ++++++++++++---------------------------
 1 file changed, 19 insertions(+), 42 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index f289b3cab4..97eb85dfdc 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -356,10 +356,11 @@ def _format_session_not_found_message(self, session_id: str) -> str:
   async def _get_or_create_session(
       self, *, user_id: str, session_id: str
   ) -> Session:
-    """Gets the session or creates it if missing.
+    """Gets the session or creates it if auto-creation is enabled.
 
-    This helper first attempts to retrieve the session. If not found, it
-    creates a new session with the provided identifiers.
+    This helper first attempts to retrieve the session. If not found and
+    auto_create_session is True, it creates a new session with the provided
+    identifiers. Otherwise, it raises a ValueError with a helpful message.
 
     Args:
       user_id: The user ID of the session.
@@ -367,35 +368,21 @@ async def _get_or_create_session(
 
     Returns:
       The existing or newly created `Session`.
-    """
-    session = await self.session_service.get_session(
-        app_name=self.app_name, user_id=user_id, session_id=session_id
-    )
-    if session:
-      return session
-    return await self.session_service.create_session(
-        app_name=self.app_name, user_id=user_id, session_id=session_id
-    )
-
-  async def _get_session(self, *, user_id: str, session_id: str) -> Session:
-    """Gets a session or raises a helpful error if missing.
-
-    Args:
-      user_id: The user ID of the session.
-      session_id: The session ID of the session.
-
-    Returns:
-      The existing `Session`.
 
     Raises:
-      ValueError: If the session cannot be found.
+      ValueError: If the session is not found and auto_create_session is False.
     """
     session = await self.session_service.get_session(
         app_name=self.app_name, user_id=user_id, session_id=session_id
     )
     if not session:
-      message = self._format_session_not_found_message(session_id)
-      raise ValueError(message)
+      if self.auto_create_session:
+        session = await self.session_service.create_session(
+            app_name=self.app_name, user_id=user_id, session_id=session_id
+        )
+      else:
+        message = self._format_session_not_found_message(session_id)
+        raise ValueError(message)
     return session
 
   def run(
@@ -507,14 +494,9 @@ async def _run_with_trace(
         invocation_id: Optional[str] = None,
     ) -> AsyncGenerator[Event, None]:
       with tracer.start_as_current_span('invocation'):
-        if self.auto_create_session:
-          session = await self._get_or_create_session(
-              user_id=user_id, session_id=session_id
-          )
-        else:
-          session = await self._get_session(
-              user_id=user_id, session_id=session_id
-          )
+        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 '
@@ -588,12 +570,9 @@ async def rewind_async(
       rewind_before_invocation_id: str,
   ) -> None:
     """Rewinds the session to before the specified invocation."""
-    if self.auto_create_session:
-      session = await self._get_or_create_session(
-          user_id=user_id, session_id=session_id
-      )
-    else:
-      session = await self._get_session(user_id=user_id, session_id=session_id)
+    session = await self._get_or_create_session(
+        user_id=user_id, session_id=session_id
+    )
     rewind_event_index = -1
     for i, event in enumerate(session.events):
       if event.invocation_id == rewind_before_invocation_id:
@@ -1020,12 +999,10 @@ async def run_live(
           DeprecationWarning,
           stacklevel=2,
       )
-    if self.auto_create_session:
+    if not session:
       session = await self._get_or_create_session(
           user_id=user_id, session_id=session_id
       )
-    else:
-      session = await self._get_session(user_id=user_id, session_id=session_id)
     invocation_context = self._new_invocation_context_for_live(
         session,
         live_request_queue=live_request_queue,

From 2221386a5344a3b0e7de6dacb60b87b3212b95d6 Mon Sep 17 00:00:00 2001
From: Luyang Wang <luyang.wang@verizon.com>
Date: Mon, 12 Jan 2026 14:36:31 -0500
Subject: [PATCH 11/11] fix linting error

---
 src/google/adk/sessions/database_session_service.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/google/adk/sessions/database_session_service.py b/src/google/adk/sessions/database_session_service.py
index 8b7bda6d2a..863bbfa861 100644
--- a/src/google/adk/sessions/database_session_service.py
+++ b/src/google/adk/sessions/database_session_service.py
@@ -436,8 +436,8 @@ async def append_event(self, session: Session, event: Event) -> Event:
       if storage_session.update_timestamp_tz > session.last_update_time:
         raise ValueError(
             "The last_update_time provided in the session object"
-            f" {datetime.fromtimestamp(session.last_update_time):'%Y-%m-%d %H:%M:%S'}"
-            " is earlier than the update_time in the storage_session"
+            f" {datetime.fromtimestamp(session.last_update_time):'%Y-%m-%d %H:%M:%S'} is"
+            " earlier than the update_time in the storage_session"
             f" {datetime.fromtimestamp(storage_session.update_timestamp_tz):'%Y-%m-%d %H:%M:%S'}."
             " Please check if it is a stale session."
         )