Map
Explore the current project codebase and generate a structured context section in CLAUDE.md. This section includes a domain summary, mermaid entity diagram, key concepts glossary, architecture overview, and gotchas.
Uses <!-- map:start --> / <!-- map:end --> markers for idempotent updates.
Instructions
1. Explore the Codebase
Use a Task agent with subagent_type=Explore (thoroughness: "very thorough") to gather project context. The exploration prompt should cover:
Detect project type from manifest files:
package.json(Node/JS/TS) - check for Next.js, Express, Remix, Astro, etc.Cargo.toml(Rust)go.mod(Go)pyproject.toml/requirements.txt(Python)mix.exs(Elixir)Gemfile(Ruby)composer.json(PHP)
Read the data model (if present):
- Prisma schema (
prisma/schema.prisma) - SQL migrations (
migrations/,drizzle/,db/migrate/) - TypeORM/Sequelize entities
- GraphQL schema files
Map routes and endpoints:
- Next.js
app/orpages/directories - Express/Fastify route files
- tRPC routers
- API route patterns
Identify key directories: Where business logic, components, utilities, services, and config live.
Understand the domain: From schema + routes + README + key files, determine what the app does in business terms.
The Explore agent should return a structured summary with all findings. Keep the exploration focused on understanding, not cataloguing every file.
2. Generate Content
From the exploration results, write the content that goes between markers. Follow this template:
<!-- map:start -->
## Domain
[One paragraph: what this project does, who it's for, and its business domain.]
## Entity Diagram
erDiagram [Core entities and their relationships] [Limit to ~15-20 relationships max - key entities only]
If there's no data model (CLI tools, libraries, config projects), use a flowchart instead:
graph TD [Key components/modules and how they connect]
## Key Concepts
- **[Entity/Concept]**: [One-line description]
- [5-10 entries covering the domain vocabulary]
## Architecture
[Where things live. Key directories and their roles. Data flow summary. Reference actual paths like `src/services/` or `app/api/`.]
## Gotchas
- [Non-obvious patterns, edge cases, or decisions future sessions should know]
- [Unusual config, env requirements, or conventions specific to this project]
3. Write to CLAUDE.md
Determine the CLAUDE.md path: use the project root (current working directory).
Three cases:
No CLAUDE.md exists: Create CLAUDE.md with just the markers and generated content.
CLAUDE.md exists, no markers: Read the file. Append two blank lines, then the markers and content at the end.
Markers already exist: Read the file. Use the Edit tool to replace everything from <!-- map:start --> through <!-- map:end --> (inclusive) with the new markers and content. Content outside markers is never touched.
4. Verify
After writing, read back CLAUDE.md and confirm:
- Markers are present and properly paired
- Mermaid diagram syntax is valid (no unclosed blocks)
- Content is between markers
- Nothing outside markers was changed (if file pre-existed)
Output
Tell the user:
- What project type was detected
- How many entities/routes were found
- Whether CLAUDE.md was created, appended to, or updated
- Suggest re-running
/mapafter major schema or architecture changes