Today I started receiving the following error when running a workflow in the “preview” and ChatKit:
Agent Builder Error code: 400 - {‘error’: {‘message’: “Item ‘msg_0xxxxxxxxxxxxxx’ of type ‘message’ was provided without its required ‘reasoning’ item: ‘rs_0xxxxxxxxxxxxx’.”, ‘type’: ‘invalid_request_error’, ‘param’: ‘input’, ‘code’: None}}
When this happens, no errors or output is reported to ChatKit. How can I avoid this?
edit: Ive narrowed this down to conversation length. It looks like the serialization is getting chopped off when the thread is trimmed to fit the max token output. This is my guess anyway after receiving this error with nothing but GPT5 models. I also tried using nothing but 4.1 models and with the same result (although the conversation did last longer).