Add `drain_proof.py`: a machine-verifiable DrainProof artifact plus a
fail-closed verifier and the hard gate the sanctioned restart-apply path
must consult, so a restart can never proceed on a stale or false "ready"
claim (#655 umbrella, child of #658 coordinator / #659 drain / #660
checkpoints).
- DrainProof: HMAC-SHA256 keyed proof-id over a canonical body using a
per-process secret -> non-forgeable within the process; a proof minted in
a prior daemon process will not verify after restart. Short TTL (120s).
- build_drain_proof(): mints the proof from the #658 impact report + the
drain-mode outcomes. Checklist: no in-flight mutations, assignments
stopped, checkpoints complete, handoffs ok, leases handled, acks-or-
timeout. Every check fails closed on missing/ambiguous evidence; the
no-in-flight-mutations and leases-handled checks are derived from the
authoritative impact report, not self-reported.
- verify_drain_proof(): fail-closed — rejects missing, malformed, expired,
signature-mismatched (forged/tampered/prior-process), unclean, or
stale-fingerprint proofs; recomputes cleanliness from the checks rather
than trusting the flag.
- gate_apply_restart(): allow only on a valid clean proof; deny -> durable
incident descriptor; break-glass is the only bypass and is never silent.
- Checkpoint completeness is a supplied input, not a hard dependency on the
(still-unmerged #660) checkpoint schema.
Wire the gate into gitea_request_mcp_restart: dry_run=False now enforces the
hard gate (drain_proof_json required; break-glass via request_break_glass +
GITEA_BREAKGLASS_RESTART_AUTHORIZATION env). The tool still performs no
actual restart — execution remains a further child.
Tests: tests/test_drain_proof.py — 25 cases covering AC#1-4 (apply without
proof denied, successful drain verifiable, open unsafe mutation fails,
pass/fail/expired), forgery/tamper/wrong-secret/stale-fingerprint rejection,
break-glass bypass, and secret hygiene. 25/25 pass (coordinator suite
unaffected: 40/40 together).
Links #652#653#655#658#659#660.
Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01E7Fv9Bp2XWgvaWa4M1kdR7
(cherry picked from commit e7bcc952bb3e820fda95acbecefeaebfa5f8fcff)
