[Run Experiment] -> Dataset is missing required fields: messages

I added some runs from my rag agent into a new dataset. I did not change any schema from the trace, just multi-selected them and then add to dataset. The underlying agent’s graph state does have a ‘messages’ key.

But when I’m trying to run experiment with the very same agent from LangGraph studio and with the new dataset created, the ‘Start’ button is grey out saying ‘Dataset is missing required fields: messages’