Sentinel & Steward Loop — Ops Runbook (SCBE Edition)

Purpose

• Gate and verify every envelope with adaptive dwell + explainable risk signals.
• Steward lane handles review; Sentinel automates fast-path.

Daily Checklist

1. Review gcm_failures, nonce_reuse, replay_rejects, aad_mismatch.
2. p95/p99 envelope_create_ms and envelope_verify_ms within targets (<10ms / <25ms).
3. Phase skew p99 < 2000ms across providers.
4. Verify canary flags and circuit-breakers (no unintended trips).
5. Audit 5 random ALLOW decisions (attest reasonability).
6. Export yesterday’s metrics and lock/audit.

Escalations

• Sev2: review queue SLA breach or sustained review > 10% for 10m.
• Sev1: any nonce reuse or GCM auth failure rate > 0.5% for 5m.