[Bug]: Asyncio task created without holding a reference to it in astream_chat()

[andrewisplinghoff]

Bug Description

In the following two astream_chat() implementations, asyncio tasks are being created that are not awaited and also not being referenced after being created:

llama_index/llama-index-core/llama_index/core/chat_engine/simple.py

Line 205 in adc1beb

asyncio.create_task(chat_response.awrite_response_to_history(self._memory))

llama_index/llama-index-core/llama_index/core/chat_engine/condense_question.py

Line 362 in adc1beb

asyncio.create_task(response.awrite_response_to_history(self._memory))

To my current understanding, this leads to undefined behaviour as the Python Garbage Collector is free to remove these unreachable objects at any point in time:
https://textual.textualize.io/blog/2023/02/11/the-heisenbug-lurking-in-your-async-code/

Version

v0.12.16

Relevant Logs/Tracbacks

Some background info:
Started looking at this when I noticed messages such as the following when overloading the LLM behind the application, leading to connection errors:

ERROR:    asyncio [12-02-2025 14:07:13] Task exception was never retrieved
future: <Task finished name='Task-794' coro=<Dispatcher.span.<locals>.async_wrapper() done, defined at /usr/local/lib/python3.12/site-packages/llama_index/core/instrumentation/dispatcher.py:349> exception=APIConnectionError('Connection error.')>

This is also a sign that there was a task that never was awaited (not sure if this happened when running into the exception during the exact task linked above, though).

[logan-markewich]

imo I would really move to using AgentWorkflow for single agents [1] and multi agents [2] -- the implementation in these older agent classes is very janky due to needing to expose a generator return type

That being said, probably the fix here is to store the reference to the task on the StreamingAgentChatResponse object, and handle/clean up it appropriately in there

[andrewisplinghoff]

@logan-markewich As switching over to the workflow-based approach would be non-trivial for us, I've submitted a PR to fix this issue. Let me know what you think.