openclaw - 💡(How to fix) Fix systemEvent causes SWW when session conversation ends with assistant turn (Anthropic provider) [1 participants]

Error (from gateway.err.log)

error=LLM request rejected: This model does not support assistant message prefill. The conversation must end with a user message. rawError=400 {"type":"error","error":{"type":"invalid_request_error","message":"This model does not support assistant message prefill. The conversation must end with a user message."}}

• Failover chain exhausted: all fallback models hit billing cooldown after the format error on the primary model

TL;DR

Insert a placeholder user turn before the systemEvent injection to prevent Anthropic API rejection.

Guidance

• Check the conversation context before injecting the systemEvent to determine if the last turn is an assistant turn.
• If the last turn is an assistant turn, insert a placeholder user turn (e.g., [system event]) before the injected content to avoid Anthropic API rejection.
• Alternatively, consider restructuring the systemEvent as a new user turn rather than continuing the existing thread.
• Verify the fix by triggering the systemEvent cron job and checking the gateway logs for successful embedded agent runs.

Example

if last_turn_is_assistant:
    conversation_context.append("[system event]")
    # Proceed with systemEvent injection

Notes

This fix assumes that inserting a placeholder user turn or restructuring the systemEvent will resolve the Anthropic API rejection issue. However, the effectiveness of this fix may depend on the specific requirements of the Anthropic API and the OpenClaw implementation.

Recommendation

Apply the workaround by inserting a placeholder user turn before the systemEvent injection, as this is a straightforward and targeted solution to the identified issue.