Ai Migrations And Large Scale Changes

A library API change must be applied to 600 call sites across the repo. The Droid starts editing them one by one by hand.

For a mechanical change at scale, prefer a deterministic codemod / AST transform that applies uniformly and is reviewable as a rule, then verify by compile + tests — rather than 600 inconsistent hand edits. Reserve hand edits for the genuine exceptions the codemod cannot handle.

Migrating a date library, the Droid swaps in the new API but the new default timezone differs, silently shifting timestamps.

Migrations must preserve observable behavior unless a change is explicitly intended: audit defaults that differ between old and new APIs (timezone, locale, rounding) and pin them so behavior is unchanged. Characterization tests should catch silent shifts; add them where coverage is thin.

A multi-commit migration leaves the repo non-compiling on intermediate commits, breaking bisect and CI on the branch.

Order migration commits so each one leaves the tree compiling and tests passing where feasible; a chain of broken intermediate commits defeats bisect and blocks CI gating. If an atomic step is unavoidable, make it a single coherent commit, not a broken chain.