Arc Diagrams

Arc is a visual diagram editor for creating architecture diagrams. This skill enables you to generate Arc-compatible diagram configs that can be rendered in React applications.

When to Use

Activate this skill when the user asks to:

• "Create an architecture diagram"
• "Draw a system diagram"
• "Visualize the architecture"
• "Make a diagram showing..."
• "Design a flow diagram"

Diagram Format

Arc diagrams are JSON objects with this structure:

interface ArcDiagramData {
  layout: { width: number; height: number }
  nodes: Record<string, NodePosition>
  nodeData: Record<string, NodeData>
  connectors: Connector[]
  connectorStyles: Record<string, ConnectorStyle>
}

Creating a Diagram

1. Define Layout

Set canvas dimensions (default 1600x900 for editor, smaller for exports):

"layout": { "width": 860, "height": 400 }

2. Position Nodes

Each node needs an x, y position and size:

"nodes": {
  "frontend": { "x": 50,  "y": 100, "size": "l" },
  "api":      { "x": 300, "y": 100, "size": "m" },
  "database": { "x": 550, "y": 100, "size": "m" }
}

Size options (canonical — use these):

Source: src/utils/constants.ts → NODE_SIZES. Do not use large/normal/small.

3. Define Node Data

Each node needs an icon, name, and color:

"nodeData": {
  "frontend": {
    "icon": "Monitor",
    "name": "Frontend",
    "subtitle": "React",
    "description": "User interface",
    "color": "violet"
  },
  "api": {
    "icon": "Server",
    "name": "API",
    "subtitle": "Node.js",
    "description": "REST endpoints",
    "color": "emerald"
  },
  "database": {
    "icon": "Database",
    "name": "PostgreSQL",
    "subtitle": "Storage",
    "description": "Persistent data",
    "color": "blue"
  }
}

Available icons (from Lucide):

• Devices: Monitor, Server, Smartphone, Watch, Cloud, Cpu, Database, HardDrive
• Network: Wifi, Globe
• Users: User, Users
• Security: Lock, Key, Shield
• Media: Mic, Camera, Speaker, Headphones
• Code: Code, Terminal, FileCode, Folder
• Data: Zap, Activity, BarChart, PieChart
• Flow: ArrowRight, ArrowDown, RefreshCw, Repeat
• Structure: Box, Package, Layers, Grid
• UI: Settings, Bell, Mail, MessageSquare, Search, Filter
• Actions: Download, Upload, Play, Pause, Square, Circle

Available colors: violet | emerald | blue | amber | sky | zinc | rose | orange

4. Connect Nodes

Define connections between nodes:

"connectors": [
  {
    "from": "frontend",
    "to": "api",
    "fromAnchor": "right",
    "toAnchor": "left",
    "style": "http"
  },
  {
    "from": "api",
    "to": "database",
    "fromAnchor": "right",
    "toAnchor": "left",
    "style": "sql"
  }
]

Anchor positions: top | bottom | left | right | bottomLeft | bottomRight | topLeft | topRight

Optional: Add "curve": "natural" or "curve": "step" for curved connectors.

5. Style Connectors

Define appearance for each connector style:

"connectorStyles": {
  "http": { "color": "amber", "strokeWidth": 2, "label": "HTTP" },
  "sql": { "color": "blue", "strokeWidth": 2, "label": "SQL" },
  "async": { "color": "zinc", "strokeWidth": 1.5, "dashed": true }
}

Complete Example

Here's a full diagram for a typical web application:

{
  "layout": { "width": 700, "height": 300 },
  "nodes": {
    "client":   { "x": 50,  "y": 100, "size": "l" },
    "api":      { "x": 300, "y": 100, "size": "m" },
    "cache":    { "x": 300, "y": 220, "size": "s" },
    "database": { "x": 520, "y": 100, "size": "m" }
  },
  "nodeData": {
    "client":   { "icon": "Monitor",  "name": "Client",   "subtitle": "React",    "color": "violet" },
    "api":      { "icon": "Server",   "name": "API",      "subtitle": "Express",  "color": "emerald" },
    "cache":    { "icon": "Zap",      "name": "Cache",    "subtitle": "Redis",    "color": "amber" },
    "database": { "icon": "Database", "name": "Database", "subtitle": "Postgres", "color": "blue" }
  },
  "connectors": [
    { "from": "client", "to": "api",      "fromAnchor": "right",  "toAnchor": "left", "style": "http" },
    { "from": "api",    "to": "database", "fromAnchor": "right",  "toAnchor": "left", "style": "sql" },
    { "from": "api",    "to": "cache",    "fromAnchor": "bottom", "toAnchor": "top",  "style": "cache" }
  ],
  "connectorStyles": {
    "http":  { "color": "amber",   "strokeWidth": 2, "label": "HTTP" },
    "sql":   { "color": "blue",    "strokeWidth": 2, "label": "SQL" },
    "cache": { "color": "emerald", "strokeWidth": 2, "label": "cache" }
  }
}

Layout Tips

1. Prefer auto-layout — use autoLayout() from @arach/arc when you don't need pixel-perfect placement
2. Grid alignment: Position nodes on a ~50px grid for clean manual layouts
3. Spacing: Leave ~150–200px between connected nodes horizontally
4. Flow direction: Left-to-right or top-to-bottom for data flow
5. Grouping: Use groups + layoutHints for framed sections (see docs/group-layout.md)
6. Large nodes: Use l size for primary/entry-point components
7. Connectors: Match connector colors to the source or destination node

Validation

Before handing off JSON, ensure every nodes key has a matching nodeData entry. In the repo, validateDiagramShape() in src/utils/diagramValidation.ts returns a human-readable error or null.

Output

When generating a diagram, output:

1. The complete JSON config
2. Brief explanation of the architecture shown
3. Suggest the user save it as a .arc.json file or paste into the Arc editor

TypeScript Export

For React projects, diagrams can be exported as TypeScript:

import type { ArcDiagramData } from '@arach/arc'

const diagram: ArcDiagramData = {
  // ... config here
}

export default diagram