SkillValidated

Migration-check — verify the least reversible change first

A backend skill invoked on any schema or migration change: confirms reversibility or an explicit one-way call, checks defaults and nullability against live-row reality, and verifies a test exercises the new shape before it ships.

$cosq add migration-check

Free, works signed out. No CLI? Copy the file below into your repo — same result.

Why this one

Developers over-trust unverified AI output (METR RCT) — and a migration is the change you can least afford to verify in production.

How to use it

  1. 1Invoke on every migration before it merges
  2. 2Decide reversibility explicitly — 'probably fine' is not a rollback plan

What gets installed

Pick your tool to preview the exact file cosq add writes — byte-for-byte. Prefer copy-paste? Use the copy button on the file.

.claude/skills/migration-check/SKILL.md(created)
---
name: migration-check
description: Use on any database schema or migration change: check reversibility, defaults, nullability against existing rows, and that a test exercises the new shape.
---

For any schema or migration change, verify before it merges:

1. **Reversibility** — is there a down path, or is this explicitly one-way?
   State which, and what the rollback plan is if it ships broken.
2. **Existing rows** — do new NOT NULL columns have defaults or backfills?
   Would the migration lock a large table? Check against the real row shape,
   not the ORM model.
3. **Consumers** — which queries and endpoints read the changed shape? Flag
   any that would break mid-deploy (old code, new schema).
4. **Coverage** — point at the test that exercises the new shape. If none
   exists, draft it now; a migration without a test is unverified by
   definition.

Report each of the four with a pass / fail / not-applicable and one line of
evidence.