Mermaid

Mermaid Diagrams

[mermaid] visualize→ASCII|SVG | via beautiful-mermaid

supported: flowchart, state, sequence, class, ER
output: terminal-friendly ASCII or SVG file
themes: 15 built-in (tokyo-night, github-dark, etc.)

Usage

When user asks for a diagram, architecture visualization, or flowchart:

1. Write the Mermaid code based on their description
2. Render as ASCII for immediate terminal display
3. Optionally save SVG if user wants a file

Mermaid Syntax Quick Reference

Flowchart

graph TD
    A[Start] --> B{Decision}
    B -->|Yes| C[Action]
    B -->|No| D[End]

Sequence Diagram

sequenceDiagram
    Alice->>Bob: Hello
    Bob-->>Alice: Hi back

State Diagram

stateDiagram-v2
    [*] --> Idle
    Idle --> Processing: start
    Processing --> Done: complete
    Done --> [*]

Class Diagram

classDiagram
    Animal <|-- Duck
    Animal <|-- Fish
    Animal : +int age
    Animal : +isMammal()

ER Diagram

erDiagram
    CUSTOMER ||--o{ ORDER : places
    ORDER ||--|{ LINE-ITEM : contains

Rendering

Use the mermaid-render script to render diagrams:

# ASCII output (terminal)
mermaid-render ascii "graph LR; A --> B --> C"

# SVG output (file)
mermaid-render svg "graph TD; A --> B" output.svg

# With theme
mermaid-render svg "graph TD; A --> B" output.svg --theme tokyo-night

Available Themes

• tokyo-night (default)
• github-dark
• github-light
• dracula
• monokai
• nord
• one-dark
• solarized-dark
• solarized-light
• gruvbox-dark
• gruvbox-light
• catppuccin-mocha
• catppuccin-latte
• rose-pine
• rose-pine-dawn

Process

1. Understand the request - What needs to be visualized?
2. Choose diagram type - flowchart, sequence, state, class, or ER
3. Write Mermaid code - Use proper syntax
4. Render - Show ASCII in response, offer SVG if complex

Example

User: "Show me the hook lifecycle"

graph TD
    A[SessionStart] --> B[UserPromptSubmit]
    B --> C{Tool Call?}
    C -->|Yes| D[PreToolUse]
    D --> E[Tool Executes]
    E --> F{Success?}
    F -->|Yes| G[PostToolUse]
    F -->|No| H[PostToolUseFailure]
    G --> I{More Tools?}
    H --> I
    I -->|Yes| C
    I -->|No| J[Stop]

Then render as ASCII for terminal display.