Better Planning · Sync (milestone-boundary reconciliation)

Agents make architectural calls the human never sees, and the design of record rots unless someone reconciles the landed code against it. That someone should be the agent. The human's scarce resource at a boundary is judgment on genuine forks — not diff-reading, not ledger bookkeeping, and not proving they were paying attention. This skill's predecessor made the human walk every delta and sit a recall quiz at each boundary; in practice the walk got skipped or blanket-approved at the end of a long day, while the bookkeeping underneath was what actually fed the next milestone. Sync keeps the bookkeeping and inverts the ceremony: do everything reconcilable alone, ask only what only the human can answer.

It's a companion, not a step on the ladder — it runs during the build, at the boundaries.