NoEligibleSpeaker: Custom speaker selection function returned None. Terminating conversation.

[thrishathi02]

This is the code that I'm using, and it gives me a error which says : "NoEligibleSpeaker: Custom speaker selection function returned None. Terminating conversation.". Please help.

def state_transition(last_speaker, groupchat):
messages = groupchat.messages
last_message = messages[-1] if messages else {}

if len(messages) == 1:
    log_agent_activity(f"1st Speaker Name: {last_speaker.name}. Start the agent now.")

else:
    log_agent_activity(f"Current Speaker Name: {last_speaker.name}. Proceeding with Execution.")

if last_speaker is user_proxy:
    if len(messages) == 1:
        log_agent_activity(f"Last Speaker Name: {last_speaker.name} :: Current Speaker Name: Planner Start")
        return planner
    else:
        log_agent_activity(f"Last Speaker Name: {last_speaker.name} :: Current Speaker Name: Retrieval Start")
        return retrieval

elif last_speaker is planner:
    if "terminate-flow" in last_message.get("content", "").lower():
        return terminator
    return retrieval

elif last_speaker is retrieval:
    if "terminate-agent" in last_message.get("content", "").lower():
        return answer_generator
    elif "terminate-flow" in last_message.get("content", "").lower():
        return terminator
    return retrieval  

elif last_speaker is answer_generator:
    if "terminate-agent" in last_message.get("content", "").lower():
        return critic
    elif "terminate-flow" in last_message.get("content", "").lower():
        return terminator
    return answer_generator  

elif last_speaker is critic:
    if "all-good" in last_message.get("content", "").lower():
        log_agent_activity(f"Last Speaker Name: {last_speaker.name} :: Current Speaker Name: Terminator Start")
        return terminator   
    else:
        return retrieval  

elif last_speaker is terminator:
    log_agent_activity(f"Last Speaker Name: {last_speaker.name} :: Conversation Ended")
    return None  

[thrishathi02]

I'm using V0.2 btw

[Reeyaku]

I'm facing similar problems

[thrishathi02]

Eric Zhu (@ekzhu), any idea on why this could be happening?

I'm using a similar method for state transition in another project, this error doesn't occur there at all.

[Eric Zhu (ekzhu)]

The custom speaker selection function returns None in the last if statement. Can you check?

[Eric Zhu (ekzhu)]

If you want to termination based on conversation history rather than relying on agent to terminate, please upgrade to v0.4 and use SourceMatchTermination for your scenario.

[thrishathi02]

According to this documentation : https://microsoft.github.io/autogen/0.2/blog/2024/02/29/StateFlow/

A None can be returned to end the workflow, has this changed?

[Eric Zhu (ekzhu)]

Yes it has been changed. Please see the SelectorGroupChat user guide regarding custom selector function: https://microsoft.github.io/autogen/dev/user-guide/agentchat-user-guide/selector-group-chat.html#custom-selector-function

and API doc: https://microsoft.github.io/autogen/dev/reference/python/autogen_agentchat.teams.html#autogen_agentchat.teams.SelectorGroupChat

[Julia Smith (pick7)]

That message means the speaker-selection function returned something AutoGen could not use as the next speaker. In your code there are two common ways that can happen.

First, the final branch returns None:

elif last_speaker is terminator:
    return None

If you want the conversation to end, it is better to end through a normal termination condition/message instead of relying on the custom speaker selector returning None. For example, have the terminator send a message that matches is_termination_msg, or stop before selecting another speaker after terminator has spoken.

Second, all your checks use identity comparisons:

if last_speaker is user_proxy:
elif last_speaker is planner:

That only works if the objects in the GroupChat(agents=[...]) list are the exact same Python objects referenced by those variables. If you recreated one agent or passed a different instance with the same name, none of the branches match, the function falls through, and Python returns None implicitly.

I would make the function fail loudly while debugging:

def state_transition(last_speaker, groupchat):
    print('last speaker:', last_speaker.name)

    if last_speaker.name == user_proxy.name:
        return planner if len(groupchat.messages) == 1 else retrieval

    if last_speaker.name == planner.name:
        content = groupchat.messages[-1].get('content', '').lower()
        return terminator if 'terminate-flow' in content else retrieval

    if last_speaker.name == retrieval.name:
        content = groupchat.messages[-1].get('content', '').lower()
        if 'terminate-flow' in content:
            return terminator
        if 'terminate-agent' in content:
            return answer_generator
        return retrieval

    if last_speaker.name == answer_generator.name:
        content = groupchat.messages[-1].get('content', '').lower()
        if 'terminate-flow' in content:
            return terminator
        if 'terminate-agent' in content:
            return critic
        return answer_generator

    if last_speaker.name == critic.name:
        content = groupchat.messages[-1].get('content', '').lower()
        return terminator if 'all-good' in content else retrieval

    if last_speaker.name == terminator.name:
        # Let your termination condition end the chat after this message.
        return user_proxy

    raise ValueError(f'Unhandled speaker: {last_speaker.name}')

The important part is the final raise. Once you see which speaker name is unhandled, either add that agent to your transition table or make sure the exact same agent instances are passed into GroupChat.