Migration

Framework upgrades, major dep bumps, config migrations. The core challenge is proving zero regressions, which requires baselines captured on the TRUE pre-change state.

Rule Zero: Check Working Tree FIRST

Before planning, researching, or writing anything:

git status
git diff package.json

If package.json is already modified, deps may already be upgraded. Baselines taken now reflect post-upgrade state and are WORTHLESS for comparison. You must restore old deps before capturing baselines (see Phase 3a).

If package.json is clean, capture all baselines before touching it.

This is non-negotiable. Baselines on upgraded deps cannot prove zero regressions. Ask yourself: "What state was the code in BEFORE any migration work started?" That is the state you baseline against.