# Plan Mode

When working in plan mode (`permission_mode: plan`):

**Before calling `ExitPlanMode`**, always write the complete plan to a file in the project root:

- **Filename:** `[MILESTONE]-[PURPOSE]-PLAN.md` — e.g. `M2-auth-PLAN.md`, `M3-monitoring-PLAN.md`
  - MILESTONE: the milestone identifier (e.g. `M2`) or a short label if not milestone-scoped (e.g. `initial`)
  - PURPOSE: a short kebab-case description of what the plan covers
- **Contents:** the full plan as developed in the planning conversation — steps, decisions, rationale, open questions
- **Location:** project root (same directory as CLAUDE.md)

This file becomes the implementation reference for the session that follows plan mode.

## Keep the plan updated during implementation

After each phase or significant step, update PLAN.md:
- Mark the phase/step status as **Complete**
- Add key commits, references, or artifacts produced
- Document deviations from the original plan (what changed and why)
- Note verification results

This keeps the plan accurate as a living document — useful for resuming across sessions, reflecting on the milestone, and understanding what actually happened vs. what was planned.