An agent trace is not one record. It is three records that never fully agree: the log line, the tool call, and the diff. The log says what the program believed was happening. The tool record says what the runtime actually dispatched. The diff says what the filesystem finally accepted.

When those three disagree, you get a bug class that no single source can show you. A green log with a red diff is an unlogged write. A dispatched call with an empty diff is a lie about work done. A log that announces a retry the runtime never issued is an incident note that will mislead the next reader. Reconcile the three before you read anything else in the trace.

The fixture first, because a harness you cannot reproduce is a rumor

Start with a trace you can hand to a colleague.…