Write Phase Plan

Write Phase Plan

Goal

Produce a plan document that a phase-orchestrator run can execute without re-deriving structure. Each phase must be implementable by a worker that has no chat history: the phase section is the worker's entire brief, plus repo rules and the code itself.

The plan is the source of truth during the run. The orchestrator updates phase status and appends log entries as it goes, so the document must be written to absorb that.

Where The Plan Lives

Follow the repo's convention for design docs (for example plans/<author>/ in repos that define one). One markdown file per plan. Link out to the PRD/spec rather than duplicating it.

Document Structure

# <Feature name>

## Overview
One or two paragraphs: what is being built and why. Link the PRD/spec.

## Constraints
Repo-wide facts every phase needs: commit/PR policy, validation commands,
branch or worktree requirements, anything the orchestrator must not infer.

## Phases
A short table or list: phase ID, name, depends-on, parallelizable-with.

## Phase 1: <name>
- **Status:** Not started
- **Depends on:** none | Phase N
- **Objective:** one sentence, the outcome not the activity.
- **Scope:** the files/modules this phase owns (its write scope).
- **Out of scope:** adjacent work this phase must not touch.
- **Approach:** implementation notes — key decisions already made, pointers
  to the code the worker should read first, known landmines.
- **Acceptance criteria:** checkable statements (see below).
- **Validation:** exact commands to run, plus any manual checks.

## Phase 2: <name>
...

## Implementation log
(Empty at authoring time. The orchestrator appends one entry per phase:
date, phase, summary, validation results, review outcome, commit SHAs,
deviations, remaining risks.)

Sizing And Ordering Phases

• One phase = one implementer worker session. If a phase's Approach section needs subheadings to stay coherent, split it.
• Order by dependency, foundations first. A schema/migration phase is always its own phase (and in many repos its own PR — record that in Constraints).
• Phases that can run in parallel must have disjoint write scopes. Declare parallelizability explicitly in the phase list; the orchestrator will not guess.
• If a phase exists only to set up a later phase, say which one, so the orchestrator knows a deviation there propagates.

Writing For A Context-Free Worker

The implementer sees the plan, the repo, and nothing else. So:

• Use standalone spec language. No "as discussed", "still", "instead of the old approach", or references to conversations that produced the plan.
• Name concrete things: file paths, function names, commands — not "the relevant helper" or "the usual checks".
• State decisions as decisions. If something is genuinely unresolved, mark it as an explicit open question and say who resolves it (the worker may decide in-scope questions; the orchestrator escalates cross-cutting ones).
• Put shared context in Constraints once rather than repeating it per phase.

Acceptance Criteria

Each criterion must be checkable by the reviewer from the diff and the running code, without asking the author:

• Good: "POST /orgs/:id/invites returns 403 for a non-admin member; covered by a route test."
• Bad: "Invites are properly secured."

Include the negative space: what must not change (existing behavior, public contracts, performance characteristics) when regression there is a real risk.

Status And Log Conventions

• Phase status vocabulary: Not started, In progress, Done, Partial, Blocked.
• The orchestrator owns status transitions and log entries during the run; the author sets everything to Not started.
• Keep the Implementation log section present even when empty, so run updates have a stable place to land.

Anti-Patterns

• Phases split by activity (design/build/test) instead of by deliverable — every phase should end with validated, committable work.
• Two phases that edit the same files marked as parallel.
• Acceptance criteria that restate the objective instead of testing it.
• A plan that embeds the whole PRD — link it and keep the plan operational.
• Hidden sequencing: prose that implies an order the phase list doesn't state.