What problem does it solve? Large features and epics often get implemented as monolithic changes or layer-by-layer plans that delay feedback, hide broken integration, and produce oversized pull requests. This Skill turns selected stories into implementation plans built from small, known-good vertical slices, each independently deployable and reviewable. ## Core Features & Use Cases - Vertical Slice Planning: Defines slices by actor, trigger, observable outcome, and production path, with explicit size heuristics and anti-patterns to avoid layer-cake plans. - TDD and Quality Gates: Enforces RED-GREEN-REFACTOR increments per behavior-changing slice, a pre-PR mutation-testing or alternate-evidence gate, and commit approval checkpoints. - Delivery Topology: Defaults each slice to one trunk-based PR, with explicit support for cross-slice or intra-slice stacked PRs and mechanism-reduction programs. - Use Case: Given a selected user story for a gift-tracking feature, produce a plans/gift-tracking.md plan with ordered slices, acceptance criteria, and per-slice PR boundaries, then implement each slice with tests first. ## Quick Start Ask the assistant to plan the selected story as vertical slices with acceptance criteria and one small pull request per slice.