arc-diagrams · diff
git:20260826.a296511 to git:20260920.4d0ec25
24 added, 4 removed. Audit A to A.
---
name: arc-diagrams
description: Create architecture diagrams using Arc's JSON format. Use when asked to "create an architecture diagram", "draw a system diagram", "visualize the architecture", or "make a diagram of".
---
# 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:
```typescript
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):
```json
"layout": { "width": 860, "height": 400 }
```
### 2. Position Nodes
Each node needs an `x`, `y` position and `size`:
```json
"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):
| Size | Key | Dimensions (px) |
|------|-----|-----------------|
| Extra Small | `xs` | 80 × 36 |
| Small | `s` | 110 × 48 |
| Medium | `m` | 160 × 75 |
| Large | `l` | 220 × 90 |
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:
```json
"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:
```json
"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.
+ **Stable identity:** Give a connector an `id` when it may be referenced by a focus story, reviewed in a diff, or when another connector shares the same `from`/`to` pair. Without an `id`, a connector is only addressable by endpoint pair or array index.
+
### 5. Style Connectors
Define appearance for each connector style:
```json
"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:
```json
{
"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
+ ## Validation and repair
- 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`.
+ Always validate before handing off JSON.
+
+ - In the repo, call `validateDiagram(value)` from `src/utils/diagramDiagnostics.ts`.
+ - Through MCP, call `validate_diagram`; it returns `{ ok, diagnostics }`.
+ - `validateDiagramShape()` remains the low-level shape gate; `validateDiagram` wraps it and adds repairable diagnostics.
+
+ Each diagnostic has a stable `code`, `severity`, `subject`, human `message`, optional `evidence`, and `supportedFixes`.
+
+ Repair loop:
+
+ 1. Read `diagnostics`; fix `severity: "error"` before warnings.
+ 2. Apply one `supportedFixes` entry when offered, or make the direct correction it names.
+ 3. Re-validate the edited document.
+ 4. Repeat until no error-severity diagnostics remain; leave warnings only when intentional.
+
+ Common codes:
+
+ - `shape/*` — malformed document or entries; fix these before anything else.
+ - `semantic/dangling-connector-endpoint` — retarget `from`/`to` or remove the connector.
+ - `semantic/unknown-*` and `semantic/duplicate-connector-id` — use the suggested valid value or unique connector `id`.
+ - `geometry/node-overlap`, `geometry/connector-through-node`, `geometry/node-outside-layout` — move nodes or run `autoLayout()`.
## 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:
```typescript
import type { ArcDiagramData } from '@arach/arc'
const diagram: ArcDiagramData = {
// ... config here
}
export default diagram
```