What problem does it solve? Backend TypeScript edits often drift into unplanned rewrites, silently change contracts or persisted behavior, or add proof that does not match the real risk. This Skill keeps implementation work inside the existing seams of a repository so changes stay small, safe, and honest. ## Core Features & Use Cases - Seam-aware implementation: Names the active seam (TypeScript modeling, API contract, Fastify runtime, Prisma/PostgreSQL, Redis, or Vitest testing) and activates only the references the change actually crosses. - Design preservation: Checklists enforce that architecture boundaries, request/response shapes, error envelopes, and persisted data stay stable unless the task explicitly changes them. - Proof-slice selection: Guides choosing the smallest honest test or verification step for the touched risk instead of broad, low-signal test suites. - Use Case: When asked to refactor a Fastify handler that parses request bodies and writes to Postgres, the Skill keeps boundary parsing explicit, reuses existing error constants, preserves the transaction owner, and adds one focused test for the changed branch. ## Quick Start Ask the agent to implement a specific backend TypeScript change, such as refactoring a handler or wiring a new boundary, while preserving the existing design and adding a narrow test.
