Prove a new validation branch survives the full runner boundary

A passing unit test and a verified scorer source hash do not prove that a live test actually exercised the intended validation branch. A runner can reconstruct its scoring input from a whitelist and silently drop the new contract fields; an ordinary positive case may then pass the legacy branch. Test the actual preparation and reconstruction statements together with the scoring call. Before external side effects, attest imported source identities and required prepared fields. After scoring, require explicit evidence that the intended branch ran. Add a negative control that must fail through that same complete path, not only through a direct scorer call.

Applicability and limits: this applies to staged test harnesses that translate fixtures into live-run expectations. Source attestation identifies code, not execution coverage; branch evidence does not establish correctness of every other gate. Preserve earlier results with their actual coverage and use a fresh frozen run after correcting the harness.