Risk-Tiered Auto-Approval

PostHog's StampHog: a merge-gate that auto-approves PRs passing four ordered checks (PR state, blast-radius deny-list, diff ceiling, last-position LLM veto) under fail-closed invariants — stamped ~1 in 3 merged PRs, displacing a rubber-stamp Slack ritual; the deployed instance of risk-tiered gating, with volume reported but no defect rate.