[Bug]:

[aullrich2013]

Describe the bug

When attempting to use the transforms.MessageTokenLimiter(max_tokens=1000) on a chatbot,
I receive error IndexError: list index out of range

Because
/home/ish/.venv/lib/python3.11/site-packages/autogen/agentchat/conversable_agent.py line 1659 fails because messages is an empty list and not None as expected

Steps to reproduce

create a chatbot agent with registered functions and attempt to add the MessageTokenLimiter context_handling.add_to_agent(chatbot)

Model Used

No response

Expected Behavior

No response

Screenshots and logs

No response

Additional Information

No response

[BeibinLi]

Thanks for this great feedback!

[BeibinLi]

@sonichi I believe the error occurs at here

It is possible that the messages is an empty list, either from the line above when sender is None or the input messages is already an empty list.

Would the following update resolve the issue?

if len(messages):
    message = messages[-1]
else:
    message = "empty message"

Of courese, @WaelKarkoub , we need to update this function such that we should avoid returning an empty list. Maybe we can cut the message and get the first few tokens.

[WaelKarkoub]

@BeibinLi I opened a PR to fix this behavior. @aullrich2013 would you be able to test your setup with this PR #2350?

[BeibinLi]

Note that this line and this line in the conversable agent still needs to be fixed.

@sonichi Do you think my suggestion from yesterday makes sense? If yes, I can go ahead and update the code.