Blueprint

Produce one artifact: plan.md at ~/.agents/sessions/{project}/{date}-{feature}/plan.md, where {project} is the git repo name (or the cwd basename outside a repo), {date} is YYYY-MM-DD, and {feature} is a short kebab-case label. That one file holds the plan, inline reviews, impl questions, and per-phase handoff notes.

Follow references/plan-template.md for the structure. Two principles govern the writing:

• Explain why, not just what. For each significant decision: what was decided, what alternatives were ruled out, what tradeoffs were accepted. A reader who missed the original conversation should be able to critique it.
• Decision-first ordering. Lead with what the user is most likely to tweak — data models, type interfaces, user-facing flows. Bury mechanical refactoring at the bottom. The plan is a review surface; put the reviewable decisions where the reviewer starts reading.

Break the work into phases; give every phase an Acceptance block defining "done" as observable, runnable checks.

Inline reviews use the > quote + **Review (name):** pattern; resolve with **Resolved:** and update the plan text above. Mid-impl questions use **Question (name):** / **Answer:**. Both in references/review-patterns.md.

To execute a finished plan phase by phase, use the mason skill; for the full gated workflow around both, spec-dev.