Codemap Skill

You help users understand and map repositories by creating hierarchical codemaps.

When to Use

• User asks to understand/map a repository
• User wants codebase documentation
• Starting work on an unfamiliar codebase

Workflow

Step 1: Check for Existing State

First, check if .slim/codemap.json exists in the repo root.

If it does not exist, check for legacy state at .slim/cartography.json.

If legacy state exists: move .slim/cartography.json to .slim/codemap.json, then continue with change detection.

If .slim/codemap.json exists: Skip to Step 3 (Detect Changes) - no need to re-initialize.

If neither file exists: Continue to Step 2 (Initialize).

Step 2: Initialize (Only if no state exists)

1. Analyze the repository structure - List files, understand directories
2. Infer patterns for core code/config files ONLY to include:
   • Include: src/**/*.ts, package.json, etc.
   • Exclude (MANDATORY): Do NOT include tests, documentation, or translations.
     • Tests: **/*.test.ts, **/*.spec.ts, tests/**, __tests__/**
     • Docs: docs/**, *.md (except root README.md if needed), LICENSE
     • Build/Deps: node_modules/**, dist/**, build/**, *.min.js
   • Respect .gitignore automatically
3. Run codemap.mjs init (scripts/codemap.mjs is relative to this skill's base directory — the host prints it as Base directory for this skill):

node scripts/codemap.mjs init \
  --root ./ \
  --include "src/**/*.ts" \
  --exclude "**/*.test.ts" --exclude "dist/**" --exclude "node_modules/**"

This creates:

• .slim/codemap.json - File and folder hashes for change detection
• Empty codemap.md files in all relevant subdirectories

4. Delegate codemap writing to Fixer agents - Spawn one fixer per folder to read code and create or update its specific codemap.md file.

Step 3: Detect Changes (If state already exists)

1. Run codemap.mjs changes to see what changed:

node scripts/codemap.mjs changes \
  --root ./

2. Review the output - It shows:

   • Added files
   • Removed files
   • Modified files
   • Affected folders

3. Only update affected codemaps - Spawn one fixer per affected folder to update its codemap.md.

4. Run update to save new state:

node scripts/codemap.mjs update \
  --root ./

Step 4: Finalize Repository Atlas (Root Codemap)

Once all specific directories are mapped, the Orchestrator must create or update the root codemap.md. This file serves as the Master Entry Point for any agent or human entering the repository.

1. Map Root Assets: Document the root-level files (e.g., package.json, index.ts, plugin.json) and the project's overall purpose.
2. Aggregate Sub-Maps: Create a "Repository Directory Map" section. For every folder that has a codemap.md, extract its Responsibility summary and include it in a table or list in the root map.
3. Cross-Reference: Ensure that the root map contains the absolute or relative paths to the sub-maps so agents can jump directly to the relevant details.

Step 5: Register Codemap in AGENTS.md

OpenCode auto-loads AGENTS.md into agent context on every session. To ensure agents automatically discover and use the codemap, update (or create) AGENTS.md at the repo root:

1. If AGENTS.md already exists and already contains a ## Repository Map section, skip this step - the reference is already set up.
2. If AGENTS.md exists but has no ## Repository Map section, append the section below.
3. If AGENTS.md doesn't exist, create it with the section below.

## Repository Map

A full codemap is available at `codemap.md` in the project root.

Before working on any task, read `codemap.md` to understand:
- Project architecture and entry points
- Directory responsibilities and design patterns
- Data flow and integration points between modules

For deep work on a specific folder, also read that folder's `codemap.md`.

This is idempotent - repeated codemap runs will detect the existing section and skip. No duplication.

Codemap Content

Fixers are responsible for writing codemap.md files during this workflow. Use precise technical terminology to document the implementation:

• Responsibility - Define the specific role of this directory using standard software engineering terms (e.g., "Service Layer", "Data Access Object", "Middleware").
• Design Patterns - Identify and name specific patterns used (e.g., "Observer", "Singleton", "Factory", "Strategy"). Detail the abstractions and interfaces.
• Data & Control Flow - Explicitly trace how data enters and leaves the module. Mention specific function call sequences and state transitions.
• Integration Points - List dependencies and consumer modules. Use technical names for hooks, events, or API endpoints.

Example skeleton:

# src/<dir>/
## Responsibility
<role of this directory>
## Design
<patterns and abstractions>
## Flow
<data in → key calls → data out>
## Integration
<consumers / dependencies>

For root atlas, aggregate the same headings plus a Directory Map table: