Mermaid

Mermaid — Diagram and Documentation Skill

Mermaid diagram and documentation system with specialized guides and code-to-diagram capabilities.

Entry Points

Entry point	When to use
/mermaid-{type} commands	You know the diagram type — fastest path
/mermaid-diagram	Unsure of type — describe what you want, gets routed automatically
/mermaid-validate	Batch-check existing .md files for broken diagrams
/mermaid-render	Render an existing .mmd file to SVG
/mermaid-config	Configure defaults and check dependencies
/mermaid-architect	Analyze a codebase path and generate a diagram suite
diagram-architect agent	Claude detects diagram need during active development work
This skill (SKILL.md)	Extended sessions: design docs, code-to-diagram, multi-diagram projects

Diagram Type Routing

Load only the guide for the requested type. Do not pre-load all guides.

Suite requests ("generate diagrams from this codebase", "diagram this project"): use /mermaid-architect — it selects multiple diagram types automatically from actual code.

Ambiguous type (description matches multiple types): use /mermaid-diagram — it asks one clarifying question and routes automatically.

User wants	Load
Workflow, process, approval flow, user journey	references/guides/diagrams/activity-diagrams.md
Infrastructure, cloud, K8s, deployment	references/guides/diagrams/deployment-diagrams.md
System architecture, components, microservices	references/guides/diagrams/architecture-diagrams.md
API flow, service interactions, request/response	references/guides/diagrams/sequence-diagrams.md
Class hierarchy, OOP design, data models	references/guides/diagrams/class-diagrams.md
Database schema, ER model	references/guides/diagrams/er-diagrams.md
State machines, lifecycle, FSM	references/guides/diagrams/state-diagrams.md

Reference Guides

Need	Load
Syntax errors, rendering failures	references/guides/troubleshooting.md (18 documented patterns)
Learning Mermaid, preventing errors	references/guides/common-mistakes.md
Color schemes, accessibility, themes	references/guides/styling-guide.md
Production workflow, validation loop	references/guides/resilient-workflow.md
Quick routing from symptom to action	references/guides/quick-decision-matrix.md

styling-guide.md is a special-case reference. Do not load it by default. Load it only when the user explicitly asks for custom palette/theme behavior, brand colors, accessibility tuning, or style overrides.

Code-to-Diagram

Routing rule: if the user names a framework → use the row below. If no framework is named → use /mermaid-architect.

Framework	Load	Which diagram guide
Spring Boot	examples/spring-boot/README.md	Routes/controllers → sequence · Models/entities → class · Overview → architecture
FastAPI / Python API	examples/fastapi/README.md	Endpoints/deps → sequence · Pydantic models → class · Overview → architecture
React / frontend	examples/react/README.md	architecture (always)
Python ETL / batch	examples/python-etl/README.md	activity (always)
Node/Express	examples/node-webapp/README.md	Middleware/routes → sequence · Overview → architecture
Java Web App	examples/java-webapp/README.md	Routes → sequence · Models → class · Overview → architecture
Any codebase	references/guides/code-to-diagram/README.md	Master guide determines type

Design Document Templates (assets/)

Template	When to load
architecture-design-template.md	"Create architecture doc", "Document system design"
api-design-template.md	"API design doc", "Document REST API"
feature-design-template.md	"Feature design", "Plan new feature"
database-design-template.md	"Database design", "Document schema"
system-design-template.md	"System design doc", "Full system documentation"
local-config-template.md	"Create mermaid local config", "Generate .claude/mermaid.json template"

Scripts (scripts/)

Script	Use for
extract_mermaid.js	Extract diagrams from Markdown, validate syntax
resilient_diagram.js	Full workflow: save .mmd, generate SVG, validate, recover errors

Resilient Workflow

CRITICAL: Use resilient_diagram.js for all diagram generation — ensures validation and error recovery.

Key principle: Never add a diagram to Markdown until it passes validation via extract_mermaid.js --validate.

If no target file is specified for embedding: ask the user for the file path before proceeding with the embed step.

If resilient_diagram.js fails (Node.js not found, node_modules missing): stop and tell the user to run /mermaid-config → option 7 (health check) to diagnose missing dependencies.

Error recovery order: troubleshooting.md → common-mistakes.md → WebSearch

Full guide: references/guides/resilient-workflow.md

Unicode Symbols

Load references/guides/unicode-symbols/guide.md when user mentions "symbols", "icons", "emoji in diagrams".

Quick reference: ☁️ cloud · 🌐 load balancer · ⚙️ compute · 💾 data · 📬 messaging · 🔐 security · 🚨 alerts

Theme-First Styling

Default behavior: preserve the user's configured theme/themeVariables.

• Do not add classDef with hardcoded fill/stroke/color unless the user explicitly asks for custom node colors.
• Prefer semantic structure (subgraphs, labels, edges) over custom palette overrides.
• If custom styling is explicitly requested, keep overrides minimal and ensure readable contrast.

User Configuration

Read .claude/mermaid.json as a first step before routing. Supported keys: theme, auto_validate, output_directory. Sub-skills (mermaid-diagram, mermaid-architect, mermaid-render) handle their own config reads in their Step 2.

Common Mistakes

Mistake	Fix
Diagram won't render after adding to Markdown	Validate with extract_mermaid.js --validate first — see references/guides/resilient-workflow.md
Syntax error with no obvious cause	Check references/guides/troubleshooting.md (18 documented patterns)
Repeated syntax mistakes	Read references/guides/common-mistakes.md before generating
Generated diagram ignores configured theme	Remove hardcoded classDef fill/stroke/color; use theme-first defaults
Loading all guides upfront	Load only the guide for the requested diagram type