Epic slicing planning

Goal

Reduce planning risk for large features by separating:

1. Epic-level design decisions.
2. Slice-level detailed planning and task decomposition.

Deliverables

1. 03-epic-design.md:

   • boundaries
   • shared decisions
   • cross-cutting constraints
   • ADR links
   • Epic-level Q-NNN

2. 03a-epic-roadmap.md:

   • vertical slice backlog
   • dependency order
   • milestone intent
   • rollout notes

Slicing rules

• Prefer vertical, user-visible slices over horizontal layer slices.
• Keep each slice independently testable and releasable.
• Put shared infrastructure decisions in Epic design, not repeated per slice.
• Avoid planning every implementation task for the entire Epic up front.

Anti-patterns

• A roadmap that is only backend layers then frontend layers.
• Slices that are not user-visible and cannot be validated end-to-end.
• Unresolved Epic decisions pushed down into many slice tasks.
• Giant slices that require multiple teams and have undefined boundaries.

Handoff criteria

• Epic artifacts are approved.
• Epic-level Q-NNN are resolved or deferred with rationale.
• At least one first slice is ready for /plan detailed decomposition.