PRD to Plan

Break a PRD into a phased implementation plan using vertical slices (tracer bullets). Output is a Markdown file in ./plans/.

Process

1. Confirm the PRD is in context

The PRD should already be in the conversation. If it isn't, ask the user to paste it or point you to the file.

2. Explore the codebase

If you have not already explored the codebase, do so to understand the current architecture, existing patterns, and integration layers.

3. Identify durable architectural decisions

Before slicing, identify high-level decisions that are unlikely to change throughout implementation:

• Route structures / URL patterns
• Database schema shape
• Key data models
• Authentication / authorization approach
• Third-party service boundaries

These go in the plan header so every phase can reference them.

4. Draft vertical slices

Break the PRD into tracer bullet phases. Each phase is a thin vertical slice that cuts through ALL integration layers end-to-end, NOT a horizontal slice of one layer.

<vertical-slice-rules> - Each slice delivers a narrow but COMPLETE path through every layer (schema, API, UI, tests) - A completed slice is demoable or verifiable on its own - Prefer many thin slices over few thick ones - Do NOT include specific file names, function names, or implementation details that are likely to change as later phases are built - DO include durable decisions: route paths, schema shapes, data model names </vertical-slice-rules>

5. Quiz the user

Present the proposed breakdown as a numbered list. For each phase show:

• Title: short descriptive name
• User stories covered: which user stories from the PRD this addresses

Ask the user:

• Does the granularity feel right? (too coarse / too fine)
• Should any phases be merged or split further?

Iterate until the user approves the breakdown.

6. Write the plan file

Create ./plans/ if it doesn't exist. Write the plan as a Markdown file named after the feature (e.g. ./plans/user-onboarding.md). Use the template below.

<plan-template> # Plan: <Feature Name>

Source PRD: <brief identifier or link>

Architectural decisions

Durable decisions that apply across all phases:

• Routes: ...
• Schema: ...
• Key models: ...
• (add/remove sections as appropriate)

---

Phase 1: <Title>

User stories: <list from PRD>

What to build

A concise description of this vertical slice. Describe the end-to-end behavior, not layer-by-layer implementation.

Acceptance criteria

• Criterion 1
• Criterion 2
• Criterion 3

---

Phase 2: <Title>

User stories: <list from PRD>

What to build

...

Acceptance criteria

• ...

<!-- Repeat for each phase --> </plan-template>