principle-sequence-verifiable-unitslisted

# 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. The same discipline runs at two altitudes, how you execute and how you deliver. **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." **The unit is a vertical slice.** Cut work through the layers, not along them: one thin behavior end to end, not all the models, then all the services, then all the controllers. Only a vertical slice ends in a check against the real artifact; a horizontal slice verifies by proxy until every layer lands, which is what the **prove-it-works** principle skill bans. Horizontal cuts are reserved for scaffold every slice needs (the **foundational-thinking** principle skill); behavior always ships vertically. **Execution.** In a sweep, migration, or any run of similar edits, verify each change before starting the next. Never batch the edits and verify once at the end. 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. **Delivery.** Stack commits and PRs in