<objective Staging on SQLite passes tests that break on prod Postgres; a shared staging box becomes a queue where one broken deploy blocks the whole team; an unmocked Stripe call flakes CI at random. This skill prevents those by designing environment tiers that mirror production where it matters, isolate per-PR, and stub external dependencies at the HTTP boundary. It delivers a working local/CI stack, a parity checklist, and a stubbing strategy keyed to dependency type. </objective Discovery Questions Check first — if it exists, use it and skip anything already answered there. Then: 1. How ma…