Sign-off: mergemaster#58 namespace signer verification candidate binding #5210

Source

compoundingtech/mergemaster#58

Merge SHA: 01a87dea048a14f1ceac378dd26c8021ab05bf80.

Status: post-merge review requested. Owner for follow-up answers: Mergemaster (agent/compoundingtech/mergemaster).

Stage 1a slice 2: namespace-signer-verification.

Question for Nathan

Is binding the merge-group candidate by run head_sha (Git-resolved tree) plus an exact gh-readonly-queue//pr-- name sufficient? The queue-name hash is not compared with the candidate, and the merge_group base_sha ancestry check lives in the gate, not in this verifier.

Risk

low today — Pure verification code. Nothing calls it in production, no key exists, and no gate trusts its output.

Risks start when a signer uses this code:

1. Before enabling any push signer, the owner must complete the preflight tracked in mergemaster#1. The preflight must refuse non-protected-branch pushes, fork PRs, branch dispatch, and renamed or copied payload workflows with event_not_allowed.
2. The caller must supply authenticated, attempt-specific API snapshots. The caller must recheck the current run immediately before signing.

This post-merge review does not authorize enabling a signer or trusting the verifier output in a gate.

Evidence

• feat: derive trusted signer expectations from BASE and API observations mergemaster#58
• CI Manager independent GO: message 6d453da63410e6bc, as reported by Compounding Manager.
• feat: derive trusted signer expectations from BASE and API observations mergemaster#58 (comment) — Janitor U04.
• feat: derive trusted signer expectations from BASE and API observations mergemaster#58 (comment) — merge record.
• Extract fractal self-attestation into mergemaster mergemaster#1 — push-event preflight prerequisite.

Completion rule

Compounding Manager records Nathan's answer or sign-off before this sub-issue closes. Agents do not wait for Nathan to self-merge, but all normal gates, exact-head GOs, checks, signing requirements and rulesets still apply. No --admin and no auto-merge. Merge alone does not close this sign-off request.