/product-tech-spec — Technical Specification

Write technical specs that bridge product requirements and implementation plans. Covers architecture, APIs, data models, and component hierarchy.

When to Use

• User says "tech spec", "technical spec", "architecture doc"
• After writing a PRD and before planning implementation
• When architecture decisions need to be documented

Process

Step 1: Gather Context

Check for existing artifacts:

1. docs/prds/ — Read the PRD this spec implements
2. docs/brainstorms/ — Additional context if available
3. User-provided description or $ARGUMENTS

Step 2: Research (Parallel Agents)

Spawn 2 agents IN PARALLEL using the Task tool:

Agent 1 — Codebase Analyst

Task(subagent_type: "general-purpose", description: "Analyze codebase for tech spec")
prompt: Analyze this project's architecture to inform a tech spec for [FEATURE].
  Focus on: tech stack and versions, existing data models, API patterns,
  component structure, auth patterns, state management approach.
  Return findings relevant to architectural decisions.

Agent 2 — Practices Researcher

Task(subagent_type: "general-purpose", description: "Research architecture patterns")
prompt: Research architecture best practices for [FEATURE TYPE] given [TECH STACK].
  Focus on: recommended patterns, data model design, API design,
  component architecture, security considerations.
  Return practical architectural guidance.

Step 3: Write Tech Spec

Write to docs/tech-specs/YYYY-MM-DD-<name>.md using the template in references/tech-spec-template.md.

Key sections:

1. Overview — What this spec covers and its relationship to the PRD
2. Architecture — System design, component hierarchy, data flow
3. Data Models — Database tables, types, relationships
4. API Design — Endpoints, server actions, or edge functions
5. Component Hierarchy — UI structure and state ownership
6. Security — Auth, RLS policies, input validation
7. Migration Plan — How to get from current state to target state

Writing rules:

• Reference specific existing patterns from the codebase analysis
• Make decisions, don't list options (that's what the brainstorm was for)
• Include concrete examples (schema SQL, TypeScript types, component trees)
• Call out risks and unknowns

Step 4: Review with User

Present key architectural decisions and use AskUserQuestion to confirm approach before finalizing.

Output

Save to: docs/tech-specs/YYYY-MM-DD-<name>.md

Next Steps

• Ready to plan tasks? → /engineer-plan
• Need to start building? → /engineer-work