draw.io Diagram Skill

Create, read, and edit diagrams in draw.io format (.drawio).

Supported Diagram Types (Examples)

• Architecture diagrams
• Domain model diagrams
• Object diagrams
• ER diagrams
• Flowcharts
• Wireframes
• Sequence diagrams
• Class diagrams

Any other diagram type that can be expressed in draw.io is also supported.

Workflow

1. Read (Reference during development)

Read domain model or architecture diagrams and use them as development context.

Trigger examples: "Check the domain model", "Read the design diagram", "Reference the architecture", "What's in this diagram?"

Steps:

1. Load reference files: Read the following
   • references/xml-reference.md — mxCell patterns, parsing examples
2. Use Glob to search for .drawio files
3. Use Read to load the XML
4. Extract information from mxCell attributes:
   • value attribute: labels (entity names, method names, etc.)
   • parent attribute: parent-child relationships (group membership)
   • source/target attributes: edge connections
   • fillColor in style attribute: element classification (color-based)
5. Output a structured summary

2. Create / Edit

Create new diagrams or update existing .drawio files.

Trigger examples: "Create a diagram", "Make a flowchart", "Draw an architecture diagram", "Create an ER diagram", "Update the diagram", "Add an entity", "Change a relationship"

Steps:

1. Clarify requirements: Confirm the diagram type and elements to include with the user
2. Load reference files: Always load the following before starting work
   • references/xml-reference.md — mxCell patterns, styles, color palette
   • references/layout-guide.md — layout principles, coordinate calculations
3. Check existing files: Use Glob to search for the target .drawio file
   • File exists → Use Read to get the XML and check existing IDs
   • No file → Proceed as a new creation
4. List elements: Enumerate boxes, relationships, and groups
5. Generate / Edit XML:
   • New creation: Combine the base structure template with mxCells, and save as .drawio using Write
   • Editing existing: Assign new IDs that don't conflict with existing ones, and update the XML using Edit
6. Show path: Display the file path to the user (do not open automatically)

3. Open in Desktop App

Trigger examples: "Open this file", "Open the .drawio file", "Open the diagram"

Steps:

1. Identify the file path (if not specified, use Glob to search for .drawio files)
2. Run open -a "draw.io" <file-path> using Bash

Prerequisite: draw.io must be installed via brew install --cask drawio

XML Base Structure

Important: Always specify darkMode="0". This disables Adaptive Colors, preventing color inversion when opened in a dark-mode editor, and maintains light-mode colors during SVG/PNG export.

<mxfile host="app.diagrams.net" agent="Claude" version="21.0.0">
  <diagram name="Diagram Name" id="unique-id">
    <mxGraphModel dx="1200" dy="800" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="1169" pageHeight="827" math="0" shadow="0" darkMode="0">
      <root>
        <mxCell id="0" />
        <mxCell id="1" parent="0" />
        <!-- Add elements here -->
      </root>
    </mxGraphModel>
  </diagram>
</mxfile>

For multiple pages, add multiple <diagram> elements. Specify darkMode="0" in each <mxGraphModel>.

Important Constraints

• Always specify darkMode="0" — omitting it causes color inversion in dark mode
• Keep IDs unique — manage with prefixes like box1, edge1
• Use 
 for line breaks — for text line breaks within XML
• Specify parent-child relationships with the parent attribute — coordinates of child elements within a group are relative to the parent
• vertex="1" for shapes, edge="1" for edges
• Do not open after editing — only display the file path; open only when the user explicitly asks
• Do not include -- in XML comments — <!-- Order ---> Customer --> causes an XML error; write as <!-- Order to Customer -->

Troubleshooting

XML Parse Error

Cause: -- is included in a comment Fix: Avoid -- as in <!-- Order to Customer -->. See the beginning of references/xml-reference.md for details

Colors Inverted in Dark Mode

Cause: Missing darkMode="0" specification Fix: Add darkMode="0" to <mxGraphModel>. For multiple pages, specify it on all pages

Shapes Overlapping / Edges Crossing

Cause: Layout calculation issues Fix: Check layout principles in references/layout-guide.md. Distribute edge connection points using exitX/exitY/entryX/entryY

Rendering Broken Due to Duplicate IDs

Cause: Multiple mxCells with the same ID exist Fix: Check existing IDs before editing and assign unique IDs

draw.io App Won't Open

Cause: draw.io desktop app is not installed Fix: Install with brew install --cask drawio

Reference Files

• XML Patterns & Styles → references/xml-reference.md Contents: mxCell patterns (rectangle, text, edge, group, DB, stack layout), style attributes, color palette, edge styles, custom properties, connection points, parsing examples for reading Load for reading, creating, and editing

• Layout Guide → references/layout-guide.md Contents: Layout principles, coordinate calculations, placement patterns, boundary coordinate calculations Load for creating and editing