Issue 5, Sep 24, 2026
The History Corruption Trap
Senior AI Engineer interview at Anthropic, and the interviewer asks:
“Your long-running agent crashes mid-task. You resume from the saved history, and the API rejects the entire conversation. Nothing looks malformed. What invariant did you break, and how do you guarantee a crash can never put you here again?”
Don’t say: “The history got corrupted, so I’d wrap the API call in retries.”
When retries fail on a resumed agent, your state isn't corrupted, it's incomplete. Here is the subtle invariant that breaks long-running tasks and how atomic turn commits fix it.
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The full answer, with the mechanism and the arithmetic, is for paid subscribers on Substack.