principle-sequence-verifiable-units

Sequence work into verifiable units

Order work as a sequence of small units, each ending in a state you can check, and don't advance until the current one is green.

Why: A break caught at the unit that caused it is cheap to localize. A break caught after a batch is buried, and you have already built further on a broken base. Sequencing those same units into a delivery a reviewer can replay turns "trust me" into "watch it go red, then green."

Execution. In a sweep, migration, or any run of similar edits, verify each change before starting the next. Each unit is a before/after bracket: known-good state, one change, run the check, then proceed. Rebase onto clean trunk first so every check measures against the real baseline. When a lever does the edits, the per-unit check is nearly free. Run it anyway.

Scaffold first. If something helps every later phase, do it first. Ask "does every subsequent phase benefit from this existing?" CI, linting, test infrastructure, and shared types are scaffold. Setup comes before features and tests before fixes. Keep commits small and single-purpose.

Slices. Instead of building all the database, then all the API, then all the UI — build one complete feature path at a time. Each vertical slice delivers working, testable functionality. Tackle the riskiest or most uncertain piece first. If Slice 1 fails, you discover it before investing in Slices 2 and 3.

Delivery. Stack commits and PRs in the order that proves the work. The canonical shape is the failing test first, then the fix on top. Other story orders are a subtraction before the reshape, a baseline capture before the treatment, the scaffold before the feature. Each commit lands on its own and the sequence reads as an argument. One dependency per change. Upgrade and merge them individually (or in small related groups). In a debugging session, keep the diff to the fix.

The sequencing complement to the prove-it-works principle skill, which keeps each check real, and the build-the-lever principle skill, which makes the per-unit check cheap.