Blind Replay Before Merge: Keep Only the Agent Diff a Clean Environment Recreates

An agent-written patch that lives only inside one long chat session is not a reviewable change for merge. Hidden constraints from that conversation never reach the repository, the failing tests, or the next reviewer. A pairing session that wants a durable result should keep only the diff a second memory-free environment can recreate. The brief, not the transcript, becomes the source of truth for that recreation before anyone discusses merge. Chat windows quietly store rejected files, private service names, and half-stated architecture that later readers will never see. A senior pairing partner should treat that hidden context as contamination rather than as extra helpful memory for the model. The protocol below is a worked example of that stance, not a report of a named production incident. The two roles are a driver chasing an agent-assisted patch and a senior who refuses to merge from chat history alone. Pairing setup for a known failing test The shared codebase is a sma