Planning in Vertical Slices

Plan by vertical slices wherever possible. Each slice delivers the smallest end-to-end behavior a real actor can observe, while leaving the codebase in a known-good state where all tests pass.

Horizontal work is allowed only when it explicitly unblocks the next vertical slice and is independently verifiable, or when it belongs to an explicitly selected reduction program whose terminal state retires one complete mechanism while conserving behavior.

Use the /plan command to create plans. Use /continue after a merged independent PR or to advance and sync an active stack.

Relationship To Story Splitting

story-splitting decides what small user-value stories exist. planning decides how to implement selected stories safely.

Use story-splitting before this skill when the request is still an epic, large story, feature idea, roadmap item, or backlog item with multiple possible customer outcomes. Once a child story or narrow capability has been selected, use this skill to turn it into a plans/<feature>.md file with implementation slices, acceptance criteria, evidence routes, and a delivery shape for each slice.

Keep three units distinct: