Writing Specifications

Overview

A specification defines WHAT to build and WHY. It is NOT an implementation plan.

Core principle: Reference constitutions, link to docs, keep it lean. The /plan command handles task decomposition.

Spec = Requirements + Architecture Plan = Tasks + Dependencies

When to Use

Use this skill when:

• Invoked from /spectacular:spec slash command
• Creating a new feature specification from scratch
• Need the complete spec workflow (Run ID, worktree, brainstorm, spec, validation)

Do NOT use for:

• Implementation plans with task breakdown – Use /spectacular:plan instead
• API documentation – Goes in code comments or separate docs
• Runbooks or operational guides – Different document type

Announce: “I’m using the writing-specs skill to create a feature specification.”

Workspace Detection

Before starting the spec workflow, detect the workspace mode:

# Detect workspace mode
REPO_COUNT=$(find . -maxdepth 2 -name ".git" -type d 2>/dev/null | wc -l | tr -d ' ')
if [ "$REPO_COUNT" -gt 1 ]; then
  echo "Multi-repo workspace detected ($REPO_COUNT repos)"
  WORKSPACE_MODE="multi-repo"
  WORKSPACE_ROOT=$(pwd)
  # List detected repos
  find . -maxdepth 2 -name ".git" -type d | xargs -I{} dirname {} | sed 's|^\./||'
else
  echo "Single-repo mode"
  WORKSPACE_MODE="single-repo"
fi

Single-repo mode (current behavior):

• Specs stored in specs/{runId}-{feature}/spec.md at repo root
• Worktree created at .worktrees/{runId}-main/
• Constitution referenced from @docs/constitutions/current/

Multi-repo mode (new behavior):

• Specs stored in ./specs/{runId}-{feature}/spec.md at WORKSPACE root
• NO worktree created (specs live at workspace level, not inside any repo)
• Each repo’s constitution referenced separately

Constitution Adherence

All specifications MUST follow: @docs/constitutions/current/

• architecture.md – Layer boundaries, project structure
• patterns.md – Mandatory patterns (next-safe-action, ts-pattern, etc.)
• schema-rules.md – Database design philosophy
• tech-stack.md – Approved libraries and versions
• testing.md – Testing requirements

The Process

Step 0: Generate Run ID

First action: Generate a unique run identifier for this spec.

# Generate 6-char hash from feature name + timestamp
TIMESTAMP=$(date +%s)
RUN_ID=$(echo "{feature-description}-$TIMESTAMP" | shasum -a 256 | head -c 6)
echo "RUN_ID: $RUN_ID"

CRITICAL: Execute this entire block as a single multi-line Bash tool call. The comment on the first line is REQUIRED – without it, command substitution $(...) causes parse errors.

Store for use in:

• Spec directory name: specs/{run-id}-{feature-slug}/
• Spec frontmatter metadata
• Plan generation
• Branch naming during execution

Announce: “Generated RUN_ID: {run-id} for tracking this spec run”

Step 0.5: Create Isolated Worktree

Announce: “Creating isolated worktree for this spec run…”

Multi-repo mode: Skip worktree creation. Specs live at workspace root, not inside any repo.

if [ "$WORKSPACE_MODE" = "multi-repo" ]; then
  echo "Multi-repo mode: Specs stored at workspace root, no worktree needed"
  mkdir -p specs/${RUN_ID}-${FEATURE_SLUG}
  # Skip to Step 1 (brainstorming)
fi

Single-repo mode: Continue with worktree creation as normal.

Create worktree for isolated development:

1. Create branch using git-spice:

   • Use using-git-spice skill to create branch {runId}-main from current branch
   • Branch name format: {runId}-main (e.g., abc123-main)

2. Create worktree:

   # Create worktree at .worktrees/{runId}-main/
   git worktree add .worktrees/${RUN_ID}-main ${RUN_ID}-main
   

3. Error handling:

   • If worktree already exists: “Worktree {runId}-main already exists. Remove it first with git worktree remove .worktrees/{runId}-main or use a different feature name.”
   • If worktree creation fails: Report the git error details and exit

Working directory context:

• All subsequent file operations happen in .worktrees/{runId}-main/
• Brainstorming and spec generation occur in the worktree context
• Main repository working directory remains unchanged

Announce: “Worktree created at .worktrees/{runId}-main/ – all work will happen in isolation”

Step 0.6: Install Dependencies in Worktree

REQUIRED: Each worktree needs dependencies installed before work begins.

1. Check CLAUDE.md for setup commands:

   Look for this pattern in the project’s CLAUDE.md:

   ## Development Commands
   
   ### Setup
   
   - **install**: `bun install`
   - **postinstall**: `npx prisma generate`
   

2. If setup commands found, run installation:

   # Navigate to worktree
   cd .worktrees/${RUN_ID}-main
   
   # Check if dependencies already installed (handles resume)
   if [ ! -d node_modules ]; then
     echo "Installing dependencies..."
     {install-command}  # From CLAUDE.md (e.g., bun install)
   
     # Run postinstall if defined
     if [ -n "{postinstall-command}" ]; then
       echo "Running postinstall (codegen)..."
       {postinstall-command}  # From CLAUDE.md (e.g., npx prisma generate)
     fi
   else
     echo "Dependencies already installed"
   fi
   

3. If setup commands NOT found in CLAUDE.md:

   Error and instruct user:

   Setup Commands Required
   
   Worktrees need dependencies installed to run quality checks and codegen.
   
   Please add to your project's CLAUDE.md:
   
   ## Development Commands
   
   ### Setup
   
   - **install**: `bun install` (or npm install, pnpm install, etc.)
   - **postinstall**: `npx prisma generate` (optional - for codegen)
   
   Then re-run: /spectacular:spec {feature-description}
   

Announce: “Dependencies installed in worktree – ready for spec generation”

Step 1: Brainstorm Requirements

Context: All brainstorming happens in the context of the worktree (.worktrees/{runId}-main/)

Announce: “I’m brainstorming the design using Phases 1-3 (Understanding, Exploration, Design Presentation).”

Create TodoWrite checklist:

Brainstorming for Spec:
- [ ] Phase 1: Understanding (purpose, constraints, criteria)
- [ ] Phase 2: Exploration (2-3 approaches proposed)
- [ ] Phase 3: Design Presentation (design validated)
- [ ] Proceed to Step 2: Generate Specification

Phase 1: Understanding

Goal: Clarify scope, constraints, and success criteria.

1. Check current project state in working directory (note: we’re in the worktree)
2. Read @docs/constitutions/current/ to understand constraints:
   • architecture.md – Layer boundaries
   • patterns.md – Mandatory patterns
   • tech-stack.md – Approved libraries
   • schema-rules.md – Database rules
3. Ask ONE question at a time to refine the idea
4. Use AskUserQuestion tool for multiple choice options
5. Gather: Purpose, constraints, success criteria

Constitution compliance:

• All architectural decisions must follow @docs/constitutions/current/architecture.md
• All pattern choices must follow @docs/constitutions/current/patterns.md
• All library selections must follow @docs/constitutions/current/tech-stack.md

Phase 2: Exploration

Goal: Propose and evaluate 2-3 architectural approaches.

1. Propose 2-3 different approaches that follow constitutional constraints
2. For each approach explain:
   • Core architecture (layers, patterns)
   • Trade-offs (complexity vs features)
   • Constitution compliance (which patterns used)
3. Use AskUserQuestion tool to present approaches as structured choices
4. Ask partner which approach resonates

Phase 3: Design Presentation

Goal: Present detailed design incrementally and validate.

1. Present design in 200-300 word sections
2. Cover: Architecture, components, data flow, error handling, testing
3. After each section ask: “Does this look right so far?” (open-ended)
4. Use open-ended questions for freeform feedback
5. Adjust design based on feedback

After Phase 3: Mark TodoWrite complete and proceed immediately to Step 2.

Step 2: Generate Specification

Announce: “Generating the specification document…”

Task:

• Feature: {feature-description}
• Design context: {summary from brainstorming}
• RUN_ID: {run-id from Step 0}
• Output location: .worktrees/{run-id}-main/specs/{run-id}-{feature-slug}/spec.md
• Constitution: All design decisions must follow @docs/constitutions/current/
• Analyze codebase for task-specific context:
  • Existing files to modify
  • New files to create (with exact paths per @docs/constitutions/current/architecture.md)
  • Dependencies needed (must be in @docs/constitutions/current/tech-stack.md)
  • Schema changes required (following @docs/constitutions/current/schema-rules.md)
• Follow all Iron Laws (see below):
  • Reference constitutions, don’t duplicate
  • Link to SDK docs, don’t embed examples
  • No implementation plans (that’s /spectacular:plan‘s job)
  • Keep it lean (<300 lines)

Spec frontmatter must include:

---
runId: {run-id}
feature: {feature-slug}
created: {date}
status: draft
---

Use the Spec Structure template below to generate the document.

Step 2.5: Commit Spec to Worktree

After spec generation completes, commit the spec to the worktree branch:

cd .worktrees/${RUN_ID}-main
git add specs/
git commit -m "spec: add ${feature-slug} specification [${RUN_ID}]"

Announce: “Spec committed to {runId}-main branch in worktree”

Step 3: Architecture Quality Validation

CRITICAL: Before reporting completion, validate the spec against architecture quality standards.

Announce: “Validating spec against architecture quality standards…”

Read the generated spec and check against these dimensions:

3.1 Constitution Compliance

• Architecture: All components follow layer boundaries (@docs/constitutions/current/architecture.md)
  • Models – Services – Actions – UI (no layer violations)
  • Server/Client component boundaries respected
• Patterns: All mandatory patterns referenced (@docs/constitutions/current/patterns.md)
  • next-safe-action for server actions
  • ts-pattern for discriminated unions
  • Zod schemas for validation
  • routes.ts for navigation
• Schema: Database design follows rules (@docs/constitutions/current/schema-rules.md)
  • Proper indexing strategy
  • Naming conventions
  • Relationship patterns
• Tech Stack: All dependencies approved (@docs/constitutions/current/tech-stack.md)
  • No unapproved libraries
  • Correct versions specified
• Testing: Testing strategy defined (@docs/constitutions/current/testing.md)

3.2 Specification Quality (Iron Laws)

• No Duplication: Constitution rules referenced, not recreated
• No Code Examples: External docs linked, not embedded
• No Implementation Plans: Focus on WHAT/WHY, not HOW/WHEN
• Lean: Spec < 300 lines (if longer, likely duplicating constitutions)

3.3 Requirements Quality

• Completeness: All FRs and NFRs defined, no missing scenarios
• Clarity: All requirements unambiguous and specific (no “fast”, “good”, “better”)
• Measurability: All requirements have testable acceptance criteria
• Consistency: No conflicts between sections
• Edge Cases: Boundary conditions and error handling addressed
• Dependencies: External dependencies and assumptions documented

3.4 Architecture Traceability

• File Paths: All new/modified files have exact paths per architecture.md
• Integration Points: How feature integrates with existing system clear
• Migration Impact: Schema changes and data migrations identified
• Security: Auth/authz requirements explicit

3.5 Surface Issues

If ANY checks fail, create .worktrees/{run-id}-main/specs/{run-id}-{feature-slug}/clarifications.md with:

# Clarifications Needed

## [Category: Constitution/Quality/Requirements/Architecture]

**Issue**: {What's wrong}
**Location**: {Spec section reference}
**Severity**: [BLOCKER/CRITICAL/MINOR]
**Question**: {What needs to be resolved}

Options:
- A: {Option with trade-offs}
- B: {Option with trade-offs}
- Custom: {User provides alternative}

Iteration limit: Maximum 3 validation cycles. If issues remain after 3 iterations, escalate to user with clarifications.md.

Step 4: Report Completion

IMPORTANT: After reporting completion, STOP HERE. Do not proceed to plan generation automatically. The user must review the spec and explicitly run /spectacular:plan when ready.

After validation passes OR clarifications documented, report to user:

If validation passed (single-repo mode):

Feature Specification Complete & Validated

RUN_ID: {run-id}
Worktree: .worktrees/{run-id}-main/
Branch: {run-id}-main
Location: .worktrees/{run-id}-main/specs/{run-id}-{feature-slug}/spec.md

Constitution Compliance: PASS
Architecture Quality: PASS
Requirements Quality: PASS

Note: Spec is in isolated worktree, main repo unchanged.

Next Steps (User Actions - DO NOT AUTO-EXECUTE):
1. Review the spec: .worktrees/{run-id}-main/specs/{run-id}-{feature-slug}/spec.md
2. When ready, create implementation plan: /spectacular:plan @.worktrees/{run-id}-main/specs/{run-id}-{feature-slug}/spec.md

If validation passed (multi-repo mode):

Feature Specification Complete & Validated

RUN_ID: {run-id}
Workspace: {workspace-root}
Location: specs/{run-id}-{feature-slug}/spec.md

Repos affected:
- backend: @backend/docs/constitutions/current/
- frontend: @frontend/docs/constitutions/current/

Constitution Compliance: PASS
Architecture Quality: PASS
Requirements Quality: PASS

Note: Spec is at workspace root, affecting multiple repos.

Next Steps (User Actions - DO NOT AUTO-EXECUTE):
1. Review the spec: specs/{run-id}-{feature-slug}/spec.md
2. When ready, create plan: /spectacular:plan @specs/{run-id}-{feature-slug}/spec.md

If clarifications needed (single-repo mode):

Feature Specification Complete - Clarifications Needed

RUN_ID: {run-id}
Worktree: .worktrees/{run-id}-main/
Branch: {run-id}-main
Location: .worktrees/{run-id}-main/specs/{run-id}-{feature-slug}/spec.md
Clarifications: .worktrees/{run-id}-main/specs/{run-id}-{feature-slug}/clarifications.md

Note: Spec is in isolated worktree, main repo unchanged.

Next Steps:
1. Review spec: .worktrees/{run-id}-main/specs/{run-id}-{feature-slug}/spec.md
2. Answer clarifications: .worktrees/{run-id}-main/specs/{run-id}-{feature-slug}/clarifications.md
3. Once resolved, re-run: /spectacular:spec {feature-description}

If clarifications needed (multi-repo mode):

Feature Specification Complete - Clarifications Needed

RUN_ID: {run-id}
Workspace: {workspace-root}
Location: specs/{run-id}-{feature-slug}/spec.md
Clarifications: specs/{run-id}-{feature-slug}/clarifications.md

Repos affected:
- backend: @backend/docs/constitutions/current/
- frontend: @frontend/docs/constitutions/current/

Note: Spec is at workspace root, affecting multiple repos.

Next Steps:
1. Review spec: specs/{run-id}-{feature-slug}/spec.md
2. Answer clarifications: specs/{run-id}-{feature-slug}/clarifications.md
3. Once resolved, re-run: /spectacular:spec {feature-description}

Spec Structure

# Feature: {Feature Name}

**Status**: Draft
**Created**: {date}

## Problem Statement

**Current State:**
{What exists today and what's missing/broken}

**Desired State:**
{What we want to achieve}

**Gap:**
{Specific problem this feature solves}

## Requirements

> **Note**: All features must follow @docs/constitutions/current/

### Functional Requirements
- FR1: {specific requirement}
- FR2: {specific requirement}

### Non-Functional Requirements
- NFR1: {performance/security/DX requirement}
- NFR2: {performance/security/DX requirement}

## Architecture

> **Layer boundaries**: @docs/constitutions/current/architecture.md
> **Required patterns**: @docs/constitutions/current/patterns.md

### Components

**New Files:**
- `src/lib/models/{name}.ts` - {purpose}
- `src/lib/services/{name}-service.ts` - {purpose}
- `src/lib/actions/{name}-actions.ts` - {purpose}

**Modified Files:**
- `{path}` - {what changes}

### Dependencies

**New packages:**
- `{package}` - {purpose}
- See: {link to official docs}

**Schema changes:**
- {migration name} - {purpose}
- Rules: @docs/constitutions/current/schema-rules.md

### Integration Points

- Auth: Uses existing Auth.js setup
- Database: Prisma client per @docs/constitutions/current/tech-stack.md
- Validation: Zod schemas per @docs/constitutions/current/patterns.md

## Acceptance Criteria

**Constitution compliance:**
- [ ] All patterns followed (@docs/constitutions/current/patterns.md)
- [ ] Architecture boundaries respected (@docs/constitutions/current/architecture.md)
- [ ] Testing requirements met (@docs/constitutions/current/testing.md)

**Feature-specific:**
- [ ] {criterion for this feature}
- [ ] {criterion for this feature}
- [ ] {criterion for this feature}

**Verification:**
- [ ] All tests pass
- [ ] Linting passes
- [ ] Feature works end-to-end

## Open Questions

{List any unresolved questions or decisions needed}

## References

- Architecture: @docs/constitutions/current/architecture.md
- Patterns: @docs/constitutions/current/patterns.md
- Schema Rules: @docs/constitutions/current/schema-rules.md
- Tech Stack: @docs/constitutions/current/tech-stack.md
- Testing: @docs/constitutions/current/testing.md
- {External SDK}: {link to official docs}

Multi-Repo Spec Template Addition

For multi-repo features, add this section to the spec:

## Constitutions

This feature must comply with constitutions from each affected repo:

**backend**: @backend/docs/constitutions/current/
- architecture.md - Backend layer boundaries
- patterns.md - Backend patterns (next-safe-action, etc.)
- schema-rules.md - Database design rules

**frontend**: @frontend/docs/constitutions/current/
- architecture.md - Frontend component structure
- patterns.md - Frontend patterns (React Query, etc.)

**shared-lib**: @shared-lib/docs/constitutions/current/
- (if applicable)

When brainstorming in multi-repo mode:

• Read constitutions from ALL relevant repos
• Note which repo each architectural decision applies to
• Ensure cross-repo consistency (e.g., API contracts)

Iron Laws

1. Reference, Don’t Duplicate

NEVER recreate constitution rules in the spec

The architecture has three layers:

• Models: Data access with Prisma
• Services: Business logic
• Actions: Input validation with Zod

</Bad>

<Good>
```markdown
## Architecture

> **Layer boundaries**: @docs/constitutions/current/architecture.md

Components follow the established 3-layer pattern.

2. Link to Docs, Don’t Embed Examples

NEVER include code examples from external libraries

import { z } from 'zod';

export const schema = z.object({
  name: z.string().min(3),
  email: z.string().email()
});

</Bad>

<Good>
```markdown
### Validation

Use Zod schemas per @docs/constitutions/current/patterns.md

See: https://zod.dev for object schema syntax

3. No Implementation Plans

NEVER include task breakdown or migration phases

Phase 1: Database Schema

1. Create Prisma migration
2. Run migration
3. Verify indexes

Phase 2: Backend Implementation

…

</Bad>

<Good>
```markdown
## Dependencies

**Schema changes:**
- Migration: `init_rooms` - Add Room, RoomParticipant, WaitingListEntry models

Implementation order determined by `/plan` command.

4. No Success Metrics

NEVER include adoption metrics, performance targets, or measurement strategies

1. Adoption: 80% of users use feature within first month
2. Performance: Page loads in <500ms
3. Engagement: <5% churn rate

</Bad>

<Good>
```markdown
## Non-Functional Requirements

- NFR1: Page load performance <500ms (measured per @docs/constitutions/current/testing.md)
- NFR2: Support 1000 concurrent users

Common Mistakes

Rationalization Table

Red Flags – STOP and Fix

Seeing any of these? Delete and reference instead:

• Full code examples from libraries (Zod, Prisma, Socket.io, etc.)
• Migration phases or implementation steps
• Success metrics or adoption targets
• Recreated architecture explanations
• Test implementation code
• Files in specs/{run-id}-{feature-slug}/notes/ directory
• Spec > 300 lines (probably duplicating constitutions)

All of these mean: Too much implementation detail. Focus on WHAT not HOW.

Quality Checklist

Before finalizing spec:

• Problem statement shows current – desired state gap
• All FRs and NFRs are testable/verifiable
• Architecture section lists files (not code examples)
• All constitution rules referenced (not recreated)
• All external libraries linked to docs (not copied)
• No implementation plan (saved for /spectacular:plan)
• No success metrics or timelines
• Single file at specs/{run-id}-{feature-slug}/spec.md
• Spec < 300 lines (if longer, check for duplication)

Error Handling

Worktree Creation Fails

• Check .worktrees/ is in .gitignore
• Run git worktree prune to clean stale entries
• Verify working directory is clean

Git-Spice Errors

• Run gs repo init to initialize repository
• Check gs ls to view current stack
• See using-git-spice skill for troubleshooting

Setup Commands Missing

• Project MUST define setup commands in CLAUDE.md
• See error message for required format
• Re-run spec command after adding commands

Validation Failures

• Maximum 3 iteration cycles
• If issues persist, escalate via clarifications.md
• Do not skip validation – it catches real problems

The Bottom Line

Specs define WHAT and WHY. Plans define HOW and WHEN.

Reference heavily. Link to docs. Keep it lean.

If you’re copy-pasting code or recreating rules, you’re writing the wrong document.