StreamingMode.SSE in Run Configs along with include_thoughts=True in ThinkingConfig prevents LLMAgent from making any function calls

[kaustav-purkait-unbxd]

Describe the bug
StreamingMode.SSE in Run Configs along with include_thoughts=True in ThinkingConfig prevents LLMAgent from making any function calls

To Reproduce
Steps to reproduce the behavior:

Run: Create LLM Agent with
planner=BuiltInPlanner(
thinking_config=genai_types.ThinkingConfig(
include_thoughts=True,
),
),
Execute run.async with run_config=RunConfig(streaming_mode=StreamingMode.SSE, max_llm_calls=200)

Error:
No function tools are called / executed if incude_thoughts = True and streaming_mode=StreamingMode.SSE

If the agent is forced to make a function call by specifying the tool to call, the following error occurs:

Unclosed client session
client_session: <aiohttp.client.ClientSession object at 0xffffb0733a60>
Unclosed connector
connections: ['deque([(<aiohttp.client_proto.ResponseHandler object at 0xffffb062fb80>, 63756.808505184)])']
connector: <aiohttp.connector.TCPConnector object at 0xffffb078c8b0>

Desktop (please complete the following information):

• OS: Ubuntu 22.04
• Python version(python -V): 3.10.12
• ADK version(pip show google-adk): 1.12.0

Model Information:
gemini-2.5-pro

[pashna]

Facing the same issue, the connection is very unstable, especially if combined with OPIK for observability. 1/5 concurrent sessions die.
Is there a workaround for this in the meantime?

[kotikkonstantin]

Guys, I have the same problem. Due to this bug, load tests are showing terrible results; my agent can only handle about five users sending requests simultaneously

[RKest]

@Jacksunwei please assign me to this issue, I'll take a look

[RKest]

@kaustav-purkait-unbxd @pashna @kotikkonstantin
Could you please take a look if this is still an issue, and if it still is give some more direction on how to replicate it?

I failed to reproduce it, by making the following changes to https://github.com/google/adk-python/tree/main/contributing/samples/hello_world:
SSE_and_thinking_setup.html

The output (a bit editorialized) as you can see is that both thinking and tool calls work with SSE
SSE_and_thinking_output.html