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Phase 1: Draft the Plan

Goal

Produce a single, detailed markdown plan that is agent-operable -- not just human-readable.

Your plan should have:

  • Unambiguous steps
  • Precise deliverables
  • Explicit constraints
  • Acceptance criteria per section

How to Draft

Use a web app with strong reasoning enabled (e.g., ChatGPT Pro with extended thinking, or Claude with extended thinking). The web interface is ideal for this because extended reasoning is cheap relative to code generation tokens.

Prompt: Plan Drafting

Copy and customize this prompt
You are a senior architect and staff engineer. We are starting a greenfield project:

Project: <PROJECT_NAME>
Users: <TARGET_USERS>
Problem: <PROBLEM_STATEMENT>
Constraints: <CONSTRAINTS>
Environment: <LANGUAGE/STACK/PLATFORM>

Write a single, extremely detailed markdown plan we can implement with coding agents.

Requirements:

- Start with Goals / Non-goals.
- Include a clear architecture section: components, boundaries, invariants, data flow.
- Include data model / schemas (as needed).
- Include security & privacy model (threats, mitigations, secrets handling).
- Include performance targets (with concrete numbers) and an instrumentation plan.
- Include error handling, retries, and "no silent fallback" philosophy.
- Include a test plan: unit + integration + e2e (with detailed logging expectations).
- Include rollout plan: feature flags, migrations, backwards compatibility (if relevant).
- Include a task breakdown section that could be converted into a dependency graph.

Be explicit and operational. Avoid vague advice.
Assume this plan will be executed by multiple parallel agents.

Output

Save the result as your canonical plan file (e.g., PLAN.md in repo root).

Agent-operable vs human-readable

A human-readable plan says "implement authentication." An agent-operable plan says "implement JWT-based authentication using RS256, with refresh token rotation, 15-minute access token TTL, stored in httpOnly cookies, with a /auth/refresh endpoint that validates the refresh token and issues a new pair."

Stop condition

You have a comprehensive first draft. It does not need to be perfect -- that's what Phase 2 is for.