Excalidraw Diagram Generator

Generate architecture diagrams as .excalidraw files directly from codebase analysis, with optional export to PNG and SVG.

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Quick Start

User just asks:

"Generate an architecture diagram for this project"
"Create an excalidraw diagram of the system"
"Visualize this codebase as an excalidraw file"

Claude Code will:

1. Analyze the codebase (any language/framework)
2. Identify components, services, databases, APIs
3. Map relationships and data flows
4. Generate valid .excalidraw JSON with dynamic IDs and labels
5. Optionally export to PNG and/or SVG using Playwright

No prerequisites: Works without existing diagrams, Terraform, or specific file types.

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Critical Rules

1. NEVER Use Diamond Shapes

Diamond arrow connections are broken in raw Excalidraw JSON. Use styled rectangles instead:

Semantic Meaning	Rectangle Style
Orchestrator/Hub	Coral (#ffa8a8/#c92a2a) + strokeWidth: 3
Decision Point	Orange (#ffd8a8/#e8590c) + dashed stroke

2. Labels Require TWO Elements

The label property does NOT work in raw JSON. Every labeled shape needs:

// 1. Shape with boundElements reference
{
  "id": "my-box",
  "type": "rectangle",
  "boundElements": [{ "type": "text", "id": "my-box-text" }]
}

// 2. Separate text element with containerId
{
  "id": "my-box-text",
  "type": "text",
  "containerId": "my-box",
  "text": "My Label"
}

3. Elbow Arrows Need Three Properties

For 90-degree corners (not curved):

{
  "type": "arrow",
  "roughness": 0,        // Clean lines
  "roundness": null,     // Sharp corners
  "elbowed": true        // 90-degree mode
}

4. Arrow Edge Calculations

Arrows must start/end at shape edges, not centers:

Edge	Formula
Top	(x + width/2, y)
Bottom	(x + width/2, y + height)
Left	(x, y + height/2)
Right	(x + width, y + height/2)

Detailed arrow routing: See references/arrows.md

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Element Types

Type	Use For
rectangle	Services, databases, containers, orchestrators
ellipse	Users, external systems, start/end points
text	Labels inside shapes, titles, annotations
arrow	Data flow, connections, dependencies
line	Grouping boundaries, separators

Full JSON format: See references/json-format.md

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Workflow

Step 1: Analyze Codebase

Discover components by looking for:

Codebase Type	What to Look For
Monorepo	packages/*/package.json, workspace configs
Microservices	docker-compose.yml, k8s manifests
IaC	Terraform/Pulumi resource definitions
Backend API	Route definitions, controllers, DB models
Frontend	Component hierarchy, API calls

Use tools:

• Glob → **/package.json, **/Dockerfile, **/*.tf
• Grep → app.get, @Controller, CREATE TABLE
• Read → README, config files, entry points

Step 2: Plan Layout

Vertical flow (most common):

Row 1: Users/Entry points (y: 100)
Row 2: Frontend/Gateway (y: 230)
Row 3: Orchestration (y: 380)
Row 4: Services (y: 530)
Row 5: Data layer (y: 680)

Columns: x = 100, 300, 500, 700, 900
Element size: 160-200px x 80-90px

Other patterns: See references/examples.md

Step 3: Generate Elements

For each component:

1. Create shape with unique id
2. Add boundElements referencing text
3. Create text with containerId
4. Choose color based on type

Color palettes: See references/colors.md

Step 4: Add Connections

For each relationship:

1. Calculate source edge point
2. Plan elbow route (avoid overlaps)
3. Create arrow with points array
4. Match stroke color to destination type

Arrow patterns: See references/arrows.md

Step 5: Add Grouping (Optional)

For logical groupings:

• Large transparent rectangle with strokeStyle: "dashed"
• Standalone text label at top-left

Step 6: Validate and Write

Run validation before writing. Save to docs/ or user-specified path.

Validation checklist: See references/validation.md

Step 7: Export to PNG/SVG (Optional)

After writing the .excalidraw file, ask the user if they want PNG, SVG, or both exports.

Uses Playwright MCP tools and @excalidraw/utils to programmatically render the diagram — no manual upload to excalidraw.com needed.

Requires: Playwright MCP tools (browser_navigate, browser_run_code, browser_close).

Full export procedure: See references/export.md

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Quick Arrow Reference

Straight down:

{ "points": [[0, 0], [0, 110]], "x": 590, "y": 290 }

L-shape (left then down):

{ "points": [[0, 0], [-325, 0], [-325, 125]], "x": 525, "y": 420 }

U-turn (callback):

{ "points": [[0, 0], [50, 0], [50, -125], [20, -125]], "x": 710, "y": 440 }

Arrow width/height = bounding box of points:

points [[0,0], [-440,0], [-440,70]] → width=440, height=70

Multiple arrows from same edge - stagger positions:

5 arrows: 20%, 35%, 50%, 65%, 80% across edge width

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Default Color Palette

Component	Background	Stroke
Frontend	#a5d8ff	#1971c2
Backend/API	#d0bfff	#7048e8
Database	#b2f2bb	#2f9e44
Storage	#ffec99	#f08c00
AI/ML	#e599f7	#9c36b5
External APIs	#ffc9c9	#e03131
Orchestration	#ffa8a8	#c92a2a
Message Queue	#fff3bf	#fab005
Cache	#ffe8cc	#fd7e14
Users	#e7f5ff	#1971c2

Cloud-specific palettes: See references/colors.md

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Quick Validation Checklist

Before writing file:

• Every shape with label has boundElements + text element
• Text elements have containerId matching shape
• Multi-point arrows have elbowed: true, roundness: null
• Arrow x,y = source shape edge point
• Arrow final point offset reaches target edge
• No diamond shapes
• No duplicate IDs

Full validation algorithm: See references/validation.md

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Common Issues

Issue	Fix
Labels don't appear	Use TWO elements (shape + text), not label property
Arrows curved	Add elbowed: true, roundness: null, roughness: 0
Arrows floating	Calculate x,y from shape edge, not center
Arrows overlapping	Stagger start positions across edge

Detailed bug fixes: See references/validation.md

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Reference Files

File	Contents
references/json-format.md	Element types, required properties, text bindings
references/arrows.md	Routing algorithm, patterns, bindings, staggering
references/colors.md	Default, AWS, Azure, GCP, K8s palettes
references/examples.md	Complete JSON examples, layout patterns
references/validation.md	Checklists, validation algorithm, bug fixes
references/export.md	PNG/SVG export procedure via Playwright

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Output

• Location: docs/architecture/ or user-specified
• Filename: Descriptive, e.g., system-architecture.excalidraw
• Exports (optional): system-architecture.svg and/or system-architecture.png in same directory
• Testing: Open .excalidraw in https://excalidraw.com or VS Code extension; .svg and .png can be viewed directly or embedded in documentation