Don't Merge on Green: A Fixture Contract, a Pre-Push Hook, and a Merge Packet

A green required check is not a merge decision. It is a signal that one job graph finished without a red X. If a pre-push hook was skipped, or a snapshot fixture was regenerated without a reason, you can still ship a lie. This article walks through a merge packet: a small JSON artifact your CI publishes next to the check. The packet records hook results, fixture drift, and required-job status. A model may write the eight-line brief. It does not get a vote. Why green still lies CI dashboards collapse many facts into one glyph. You see green. You click merge. You miss three common failures. First, someone pushed with --no-verify and skipped the hook that keeps fixture hashes honest. Second, a test helper rewrote golden files because a serializer added a field. Third, a retry job went green on the second attempt and nobody recorded that the first attempt failed. You do not need a platform rewrite to catch this. You need a contract the merge button cannot ignore. Cheap code generation makes the second failure more common. When it is easy to regenerate tests, it is easy to regenerate the fixtures those tests pin. The pin becomes a moving target. Treat unexplained fixture diffs as merge blockers, the same way you treat a failed unit job. What the merge packet contains Keep the packet boring. One file. One schema. Commit it as a CI artifact, not as a comment that can be edited after the fact. { "commit" : "REPLACE_WITH_SHA" , "generated_at" : "2026-09-03T00:00:00Z" , "hooks" : { "pre_push_fixture_guard" : "passed" }, "fixtures" : { "manifest_path" : "tests/fixtures.sha256" , "changed_paths" : [], "unexplained_paths" : [] }, "required_jobs" : [ { "name" : "unit" , "conclusion" : "success" }, { "name" : "contract" , "conclusion" : "success" } ], "merge_ready" : false , "brief" : null } merge_ready is computed by a script you own. Not by a prompt. The brief is optional prose for humans who will not open the JSON. Step 1: Pin fixtures with a manifest Pick a directory you alrea