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feat: expose live_session_resumption_update in events for cross-connection resumption #4358

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feat: expose live_session_resumption_update in events for cross-connection resumption #4358

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2f77fbb
feat: expose live_session_resumption_update in events for cross-conne…
AshleyMaloney Feb 2, 2026
3cb4a66
refactor: consolidate live_session_resumption_update handling in _pos…
AshleyMaloney Feb 2, 2026
ecfc3a1
test: add unit tests for _postprocess_live session resumption
AshleyMaloney Feb 5, 2026
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27 changes: 19 additions & 8 deletions src/google/adk/flows/llm_flows/base_llm_flow.py
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Original file line number Diff line number Diff line change
Expand Up @@ -369,14 +369,6 @@ def get_author_for_event(llm_response):
while True:
async with Aclosing(llm_connection.receive()) as agen:
async for llm_response in agen:
if llm_response.live_session_resumption_update:
logger.info(
'Update session resumption handle:'
f' {llm_response.live_session_resumption_update}.'
)
invocation_context.live_session_resumption_handle = (
llm_response.live_session_resumption_update.new_handle
)
model_response_event = Event(
id=Event.new_id(),
invocation_id=invocation_context.invocation_id,
Expand Down Expand Up @@ -739,6 +731,25 @@ async def _postprocess_live(
async for event in agen:
yield event

# Handle session resumption updates for cross-connection resumption.
# Must be before skip condition - resumption updates have no content.
if llm_response.live_session_resumption_update:
# Update internal handle for auto-resumption within run_live()
logger.info(
'Update session resumption handle: %s',
llm_response.live_session_resumption_update,
)
invocation_context.live_session_resumption_handle = (
llm_response.live_session_resumption_update.new_handle
)

# Expose update in event for application-level cross-connection resumption
model_response_event.live_session_resumption_update = (
llm_response.live_session_resumption_update
)
yield model_response_event
return
Comment on lines +736 to +751
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@gemini-code-assist gemini-code-assist bot Feb 5, 2026

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medium

This new logic is a great addition for enabling cross-connection session resumption. To ensure this feature remains robust and to prevent future regressions, it would be beneficial to add a unit test for this new code path in _postprocess_live. A test could verify that when an llm_response contains a live_session_resumption_update, the invocation_context is updated correctly and the corresponding event is yielded.

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@ryanaiagent ryanaiagent Feb 5, 2026

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can you please add a unit test.


# Skip the model response event if there is no content and no error code.
# This is needed for the code executor to trigger another loop.
# But don't skip control events like turn_complete or transcription events.
Expand Down
114 changes: 114 additions & 0 deletions tests/unittests/flows/llm_flows/test_base_llm_flow_session_resumption.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,114 @@
# 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.

from google.adk.agents.llm_agent import Agent
from google.adk.events.event import Event
from google.adk.flows.llm_flows.base_llm_flow import BaseLlmFlow
from google.adk.models.llm_request import LlmRequest
from google.adk.models.llm_response import LlmResponse
from google.genai import types
import pytest

from ... import testing_utils


class BaseLlmFlowForTesting(BaseLlmFlow):
"""Test implementation of BaseLlmFlow for testing purposes."""

pass


@pytest.mark.asyncio
async def test_postprocess_live_yields_session_resumption_event():
"""Test _postprocess_live yields event for session resumption update."""
# Create a resumption update as received from Gemini Live API
resumption_update = types.LiveServerSessionResumptionUpdate(
new_handle='test-handle-abc123',
resumable=True,
)

# Create LlmResponse with only a resumption update (no content)
llm_response = LlmResponse(live_session_resumption_update=resumption_update)

# Set up invocation context
agent = Agent(name='test_agent', model='mock')
invocation_context = await testing_utils.create_invocation_context(
agent=agent, user_content=''
)

# Create the mutable event that _postprocess_live populates
model_response_event = Event(
id=Event.new_id(),
invocation_id=invocation_context.invocation_id,
author=agent.name,
)

flow = BaseLlmFlowForTesting()
llm_request = LlmRequest()
events = []

# Collect events from _postprocess_live
async for event in flow._postprocess_live(
invocation_context, llm_request, llm_response, model_response_event
):
events.append(event)

# Verify event is yielded with resumption update
assert len(events) == 1
assert events[0].live_session_resumption_update == resumption_update
assert (
events[0].live_session_resumption_update.new_handle
== 'test-handle-abc123'
)
assert events[0].live_session_resumption_update.resumable is True

# Verify invocation context handle is updated for auto-resumption
assert (
invocation_context.live_session_resumption_handle == 'test-handle-abc123'
)


@pytest.mark.asyncio
async def test_postprocess_live_skips_empty_response():
"""Test _postprocess_live skips response with no content or resumption."""
# Create LlmResponse with no content and no resumption update
llm_response = LlmResponse()

# Set up invocation context
agent = Agent(name='test_agent', model='mock')
invocation_context = await testing_utils.create_invocation_context(
agent=agent, user_content=''
)

model_response_event = Event(
id=Event.new_id(),
invocation_id=invocation_context.invocation_id,
author=agent.name,
)

flow = BaseLlmFlowForTesting()
llm_request = LlmRequest()
events = []

# Collect events from _postprocess_live
async for event in flow._postprocess_live(
invocation_context, llm_request, llm_response, model_response_event
):
events.append(event)

# Verify no event is yielded for empty response
assert len(events) == 0

# Verify handle remains unset
assert invocation_context.live_session_resumption_handle is None