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name: brownfield-constitution description: This skill should be used when the user asks to "create constitution for existing codebase", "codify existing patterns", or mentions "brownfield", "existing codebase", "essential floor", "emergent ceiling", or "evolution roadmap". Extends authoring-constitution with Essential Floor + Emergent Ceiling approach.

Brownfield Constitution Authoring

Prerequisites

This skill extends the authoring-constitution skill. Before using brownfield mode:

1. Understand core principles: Read authoring-constitution for the Three-Part Principle Rule (Enforcement, Testability, Rationale)
2. Know RFC 2119 keywords: See authoring-constitution/RFC-2119-KEYWORDS.md
3. Understand SYNC IMPACT format: See authoring-constitution/SYNC-IMPACT-FORMAT.md

Brownfield constitutions follow all rules from authoring-constitution, plus additional guidance for existing codebases.

Purpose

Write project constitutions for existing codebases using the Essential Floor + Emergent Ceiling approach.

• Essential Floor: Four NON-NEGOTIABLE categories every constitution MUST address
• Emergent Ceiling: Good patterns from the codebase worth codifying

Essential Floor (NON-NEGOTIABLE)

Every constitution MUST include principles for these four categories, regardless of codebase state:

See ESSENTIAL-FLOOR.md for detailed requirements and example principles for each category.

Writing Essential Floor Principles:

• If codebase has the capability → Principle codifies existing pattern with enforcement
• If codebase lacks the capability → Principle states "MUST implement" with roadmap gap

Emergent Ceiling (FROM CODEBASE)

Beyond the essential floor, identify existing good patterns worth codifying:

1. Read codebase analysis - Look for "Strengths to Preserve" section
2. Identify patterns - Naming conventions, architecture patterns, error formats
3. Codify as principles - With enforcement mechanisms

See EMERGENT-CEILING-PATTERNS.md for the pattern library with examples.

Common Pattern Categories:

Brownfield Constitution Structure

Copy# [Project] Constitution

<!-- SYNC IMPACT REPORT -->

## Core Principles

### Essential Floor Principles
I. Security by Default
II. Testing Discipline
III. Error Handling Standards
IV. Observability Requirements

### Emergent Ceiling Principles
V. [Pattern from codebase]
VI. [Pattern from codebase]
...

## Technology Stack
[From codebase analysis]

## Quality Gates
[From codebase analysis + essential floor requirements]

## Governance
[Standard governance section]

## Evolution Notes

This constitution was created from brownfield analysis.

**Essential Floor Status** (from codebase-analysis.md):
| Category | Status | Gap |
|----------|--------|-----|
| Security | partial | GAP-001 |
| Testing | partial | GAP-002 |
| Error Handling | present | - |
| Observability | absent | GAP-003 |

See `.humaninloop/memory/evolution-roadmap.md` for improvement plan.

Brownfield Quality Checklist

Additional checks for brownfield constitutions (beyond standard checklist):

• All four essential floor categories have principles
• Existing good patterns identified and codified
• Gap references included where codebase lacks capability
• Technology stack matches codebase analysis
• Quality gates reflect current + target state
• Evolution Notes section documents brownfield context

After completing brownfield constitution, run validation using validation-constitution skill.

Related Skills

• authoring-constitution - Core authoring (prerequisite)
• validation-constitution - Quality validation (use after authoring)
• analysis-codebase - Analyze existing codebase before writing