Claude Code will:

Analyze the codebase (any language/framework)
Identify components, services, databases, APIs
Map relationships and data flows
Generate valid .excalidraw JSON with dynamic IDs and labels

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

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

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

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:

Create shape with unique id
Add boundElements referencing text
Create text with containerId
Choose color based on type

Color palettes: See references/colors.md

Step 4: Add Connections

For each relationship:

Calculate source edge point
Plan elbow route (avoid overlaps)
Create arrow with points array
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

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

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

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

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

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

Output

Location: docs/architecture/ or user-specified
Filename: Descriptive, e.g., system-architecture.excalidraw
Testing: Open in https://excalidraw.com or VS Code extension

excalidraw

Excalidraw Diagram Generator

Quick Start