bostonaholic Pre-image First
Before mutation, capture the untouched baseline and a recovery anchor or pre-image; No pre-image, no destructive write.
- Run checks BEFORE the operation so later failures classify as pre-existing or introduced.
- Capture the recovery anchor before rewrites and report it on success and failure; preserve
git reset --hard <sha>recovery where applicable. - Cache bodies before composing replacements for rewrite, close, or overwrite operations.
- Compare the target with its pre-image at write time; skip and report drift.
- Apply
principle-idempotent-rerunsto this comparison on re-run. - A baseline that could not run is UNKNOWN and never proves preservation.