# Arc (LLM Guide)

Arc is a visual editor for building architecture diagrams that stay in code.
Dense reference: docs/llm.txt · Contributor guide: CLAUDE.md

## Quickstart

```bash
bun install && bun run dev    # → http://localhost:5188/editor
```

## Packages

| Need | Package |
|------|---------|
| Render 2D diagram | `@arach/arc` or `@arach/arc-viewer` |
| Mermaid sequences | `@arach/arc-viewer` |
| Isometric | `@arach/arc-iso` |
| Full studio | This repo |

## Diagram schema (canonical)

`src/types/diagram.ts` — sizes are `xs` | `s` | `m` | `l` (not large/normal/small)

```json
{
  "layout": { "width": 700, "height": 300 },
  "nodes": { "api": { "x": 100, "y": 100, "size": "m" } },
  "nodeData": { "api": { "icon": "Server", "name": "API", "color": "emerald" } },
  "connectors": [{ "from": "a", "to": "b", "fromAnchor": "right", "toAnchor": "left", "style": "http" }],
  "connectorStyles": { "http": { "color": "amber", "strokeWidth": 2, "label": "HTTP" } }
}
```

## Agent docs

- docs/llm.txt — full briefing
- docs/agent/*.agent.md — packages, actions, MCP, verification
- skills/arc-diagrams/SKILL.md — diagram generation
- CLAUDE.md — editor contributor guide

## MCP

Shipped: `@arach/arc-mcp` — `bun run build:mcp` then `packages/mcp/dist/index.js`.
Tools: validate, auto_layout, render_ascii, diagram_to_typescript, editor_handoff.
See docs/agent/mcp.agent.md.