markdown-mermaid

name	markdown-mermaid
description	Clear documentation through visual excellence
lastReviewed	2026-04-30T00:00:00.000Z

Markdown & Mermaid

Clear documentation through visual excellence

A skill for markdown authoring, Mermaid diagramming, multi-tool visualization, VS Code integration, and cross-platform rendering consistency.

Staleness Watch: See EXTERNAL-API-REGISTRY.md for source URLs and recheck cadence

When to Use

• Creating technical documentation with diagrams
• Choosing the right diagramming tool for your audience
• Troubleshooting Mermaid rendering issues
• Styling markdown previews in VS Code
• Converting unicode escapes to proper emojis
• Enterprise documentation with visual standards
• Interactive diagrams in VS Code chat (1.109+)

---

⚠️ MANDATORY: Start Every Diagram With This Template

Do NOT write Mermaid code without this template. Copy-paste first, then customize:

%%{init: {'theme': 'base', 'themeVariables': {'lineColor': '#57606a', 'primaryColor': '#ddf4ff', 'primaryBorderColor': '#0969da', 'primaryTextColor': '#1f2328', 'edgeLabelBackground': '#ffffff'}}}%%
flowchart LR
    A[Input]:::blue --> B[Process]:::purple --> C[Output]:::green

    classDef blue fill:#ddf4ff,color:#0550ae,stroke:#80ccff
    classDef green fill:#d3f5db,color:#1a7f37,stroke:#6fdd8b
    classDef purple fill:#d8b9ff,color:#6639ba,stroke:#bf8aff
    classDef gold fill:#fff8c5,color:#9a6700,stroke:#d4a72c
    classDef red fill:#ffebe9,color:#cf222e,stroke:#f5a3a3
    classDef neutral fill:#eaeef2,color:#24292f,stroke:#d0d7de

    linkStyle default stroke:#57606a,stroke-width:1.5px

Three required components:

1. Init directive (line 1) — Sets theme, colors, white edge label background
2. classDef — Semantic colors for all node types
3. linkStyle default — Gray arrows at 1.5px width

Color Class	Use For	Example
:::blue	Input, source, start	A[Audio]:::blue
:::green	Output, result, data	C[Transcript]:::green
:::purple	Processing, model	B[WhisperX]:::purple
:::gold	Decision, condition	D{Valid?}:::gold
:::red	Error, warning	E[Failed]:::red
:::neutral	Context, optional	F[Cache]:::neutral

---

Mandatory Workflow: ATACCU

Every Mermaid diagram MUST follow this 6-step protocol. No exceptions — this prevents forgotten palettes, broken layouts, and inconsistent styling.

Step	Action	What to Do
A	Analyze	What data/process am I visualizing? Who is the audience? What diagram type fits?
T	Think	Which layout pattern? (Medallion/Lineage/Pipeline) How many nodes? Will it be too wide/tall?
A	Apply	COPY THE TEMPLATE ABOVE — init directive + classDef + linkStyle. No exceptions.
C	Create	Write the Mermaid code. Every node gets :::className. Every flowchart gets linkStyle default.
C	Check	Render the diagram. Verify: pastels (not saturated), layout (not lopsided), labels (readable), arrows (gray #57606a).
U	Update	Write the final diagram into the target .md file. Add **Figure N:** *description* label.

Pre-Flight Checklist (Steps A-T-A)

Before writing any Mermaid code, answer these:

□ Diagram type selected (flowchart/sequence/gantt/quadrant/etc.)
□ Layout direction chosen (LR preferred for flow, TD for hierarchy)
□ Subgraph strategy decided (Medallion vs Lineage vs Pipeline)
□ Color assignments mapped (what color = what meaning)
□ Multi-line node labels use <br/> NOT \n

Quality Gate (Steps C-C-U)

After creating the diagram, verify ALL of these:

□ Init directive is FIRST line inside mermaid block
□ edgeLabelBackground is '#ffffff' (white background for edge labels)
□ ALL nodes have style/classDef (no unstyled nodes)
□ Colors are GitHub Pastel v2 (NOT saturated: no #51cf66, #339af0, #fab005)
□ linkStyle default stroke:#57606a,stroke-width:1.5px (flowcharts)
□ Node labels use <br/> for line breaks, NOT \n
□ Diagram rendered and visually inspected
□ No dimension > 3x the other (use subgroups to balance)
□ Figure label added below diagram block
□ Written to target file (not just shown in chat)

Common Violations This Prevents

Violation	ATACCU Step That Catches It
Saturated colors instead of pastels	Apply Skills — load palette first
Missing init directive	Apply Skills — it's step 3
edgeLabelBackground: 'transparent' used	Apply Skills — use '#ffffff' (white background)
\n in node labels (renders as literal text)	Create — use <br/> for line breaks
Missing linkStyle	Create — every flowchart needs it
Lopsided layout (7-way fan-out)	Think — choose layout pattern
Diagram only in chat, not in file	Update — write to .md file
No figure label	Update — add label

---

VS Code 1.109+ Native Chat Rendering

VS Code 1.109 introduces native Mermaid rendering in chat via the renderMermaidDiagram tool.

When to Use Native Rendering

When creating diagrams in Copilot Chat (not markdown files), use the native tool for:

• Interactive exploration: Pan, zoom, and full-screen viewing
• Immediate feedback: See diagrams without switching to markdown preview
• Iterative refinement: Quick edits with instant re-render
• Copy source: Extract the Mermaid code for documentation

Usage Pattern

User: Create a sequence diagram showing OAuth flow

the AI assistant: [uses renderMermaidDiagram tool]
       → Interactive diagram appears in chat
       → User can pan/zoom/fullscreen
       → "Copy source" extracts code for docs

When NOT to Use

• Documentation authoring: Use markdown code blocks for .md files
• GitHub rendering: Embed Mermaid in markdown for native GitHub support
• Presentations: Export to image formats or use D2

Combined Workflow

1. Design in chat: Use renderMermaidDiagram for rapid iteration
2. Finalize: Copy the Mermaid source code
3. Document: Paste into markdown file with ```mermaid code fence

---

Assets

File	Purpose
polish-mermaid-setup.prompt.md	Interactive Mermaid configuration helper

Markdown Preview: Uses VS Code user-level defaults. Optional personal styling belongs in the user profile, not project configuration.

Mermaid Config: Run the "Polish Mermaid Setup" prompt to configure Mermaid rendering for your VS Code environment.

---

Markdown Best Practices

Document Structure Template

# Title

> Brief description or tagline

---

## Overview

Introductory paragraph explaining the purpose.

---

## Section 1

Content with proper formatting.

### Subsection 1.1

More detailed content.

---

## Tables

**Table N:** *Description of what the table shows*

| Column 1 | Column 2 |
| -------- | -------- |
| Data     | Data     |

---

## Diagrams

` ` `mermaid
flowchart LR
    A --> B
` ` `

**Figure N:** *Description of what the diagram shows*

---

*Footer or closing statement*

Figure and Table Conventions

Mandatory Labeling: Every diagram and table MUST have a label:

**Figure 1:** *Description in italics*
**Table 1:** *Description in italics*

• Numbering: Sequential within document, reset per document
• Placement: Label immediately follows the diagram/table block

---

🏷️ Shields.io Badges

Badges use Shields.io. URL structure: https://img.shields.io/badge/{LABEL}-{MESSAGE}-{COLOR}?{OPTIONS}

[![Alt Text](https://img.shields.io/badge/Label-Message-color?style=for-the-badge&logo=iconname&logoColor=white)](#)

Style	Parameter
Flat	style=flat
For-the-Badge	style=for-the-badge

Encode	As
Space	_ or %20
Dash	--
Underscore	__

Icons from Simple Icons via logo=iconname&logoColor=white. Colors: blue, green, gold, red, purple, or custom hex without #.

---

Emoji Usage

Best Practice: Use actual emoji characters, not HTML entities or unicode escapes.

Good ✅	Bad ❌
# 🧠 Brain	# 🧠 Brain
**💻 Local**	**\ud83d\udcbb Local**

---

🎯 Diagram Tool Selection Framework

Step 1: Identify Your Communication Goal

What You're Showing	Best Tools	Example Use Cases
Process/Workflow	Mermaid Flowcharts, User Journey	Onboarding, approvals, troubleshooting
System Architecture	Mermaid Flowcharts with subgraphs, D2	Microservices, API design
Relationships	Mermaid ER, Mindmaps, Graphviz	Database schemas, org charts
Time/Sequence	Mermaid Sequence, Gantt	API interactions, timelines
Data/Metrics	Mermaid XY Charts, Sankey, Quadrant	Performance, resource allocation

Step 2: Consider Your Audience

Audience	Primary Goal	Recommended Tools	Style
Executives	Strategic overview	D2, simple flowcharts	Clean, minimal
Architects	Technical accuracy	PlantUML, Mermaid C4	Detailed, precise
Developers	Implementation	Mermaid Sequence, Class	Code-focused
Product Managers	User flows	User Journey, Flowcharts	Business-outcome
Documentation	Learning	All Mermaid types	Progressive disclosure

Step 3: Consider Platform

Platform	Best Tools	Why
GitHub/GitLab	Mermaid	Native rendering, no setup
Confluence/Wiki	Mermaid, PlantUML	Plugin support
VS Code	All tools (extensions)	Live preview
Presentations	D2, simple Mermaid	Executive-friendly

Quick Decision Tree

Need diagram? → What are you showing?
├── Process/Workflow → Mermaid Flowchart
├── System Architecture → Mermaid with subgraphs (or D2 for exec)
├── Relationships → Mermaid ER/Mindmap (or Graphviz for complex)
├── Time/Sequence → Mermaid Sequence/Gantt
└── Data/Metrics → Mermaid XY/Sankey/Quadrant

---

🛠️ Multi-Tool Ecosystem

Tool Comparison Matrix

Tool	Native GitHub	Complexity	Best For
Mermaid	✅ Yes	Low-Medium	General purpose, quick diagrams
PlantUML	❌ No	Medium-High	Enterprise UML, AWS/Azure
Graphviz	❌ No	High	Complex networks, dependencies
D2	❌ No	Low	Clean architecture overviews
WaveDrom	❌ No	Medium	Digital timing diagrams

VS Code Extension Setup

{
  "recommendations": [
    "bierner.markdown-mermaid",
    "vstirbu.vscode-mermaid-preview",
    "mermaidchart.vscode-mermaid-chart",
    "jebbs.plantuml",
    "joaompinto.vscode-graphviz",
    "terrastruct.d2",
    "shd101wyy.markdown-preview-enhanced",
    "yzane.markdown-pdf",
    "bierner.markdown-preview-github-styles"
  ]
}

Syntax Examples

PlantUML (Enterprise UML):

@startuml
!theme aws-orange
participant User
participant System
participant Database

User -> System: Request
System -> Database: Query
Database --> System: Response
System --> User: Result
@enduml

Graphviz DOT (Complex Networks):

digraph G {
    rankdir=TB;
    node [shape=box, style=filled, fillcolor=lightblue];
    A -> B;
    A -> C;
    B -> D;
    C -> D;
}

D2 (Modern Architecture):

users -> web_server: HTTPS requests
web_server -> database: SQL queries

users.style.fill: "#e1f5fe"
web_server.style.fill: "#f3e5f5"

---

🎨 Mermaid Diagram Reference

⚡ Quick Start — Pastel v2 Template

Use the MANDATORY template at the top of this skill. Copy-paste from there — it is the single source of truth.

Four things every diagram needs:

1. %%{init}%% directive with edgeLabelBackground: '#ffffff'
2. classDef or style for node colors
3. linkStyle default stroke:#57606a for arrow color
4. Edge labels |text| with white background (from init)

💡 For color theory and design principles, see the graphic-design skill. The palette values here come from that skill's color system, optimized for GitHub rendering.

Diagram Types

Type	Syntax	Best Use Case
Flowchart	flowchart TB/LR/BT/RL	Process flows, decision trees
Sequence	sequenceDiagram	API calls, interactions
State	stateDiagram-v2	State machines, lifecycles
Class	classDiagram	OOP design, relationships
ER	erDiagram	Database schema
Gantt	gantt	Project timelines
Pie	pie	Simple proportions
Mindmap	mindmap	Concept hierarchies
Quadrant	quadrantChart	2D positioning analysis
Git Graph	gitGraph	Branch workflows
XY Chart	xychart-beta	Data plotting
Sankey	sankey-beta	Flow analysis
Block	block-beta	Block diagrams

Node Shapes (Flowchart)

A[Rectangle]      B(Rounded)        C([Stadium])
D[[Subroutine]]   E[(Database)]     F((Circle))
G>Asymmetric]     H{Diamond}        I{{Hexagon}}
J[/Parallelogram/]

Edge Styles

A --> B           Standard arrow
A --- B           Line without arrow
A -.-> B          Dotted arrow
A ==> B           Thick arrow
A --"label"--> B  Labeled edge
A -->|"label"| B  Alternative label syntax

Color Palette (Legacy — GitHub-Compatible)

Note: Superseded by GitHub Pastel Palette v2 below. Kept for reference only.

Purpose	Background	Border/Stroke
GitHub Light	#f6f8fa	#d1d9e0
Text	-	#1f2328
Lines	-	#656d76
Success	#e8f5e9	#2e7d32
Info	#e3f2fd	#1565c0
Warning	#fff3e0	#ef6c00
Special	#f3e5f5	#7b1fa2
Danger	#ffebee	#c62828
Neutral	#f5f5f5	#424242

GitHub Pastel Palette v2 (Default)

Higher contrast, better accessibility. Always use this palette for new diagrams.

Node Style Pattern: style NODE fill:#FILL,color:#TEXT,stroke:#STROKE

Purpose	Fill	Text	Stroke	Usage
Bronze/Peach	#fff1e5	#953800	#ffb77c	Data ingestion, raw layer
Silver/Gray	#eaeef2	#24292f	#afb8c1	Processing, transformation
Gold/Yellow	#fff8c5	#9a6700	#d4a72c	Business logic, highlights
Blue/Sky	#ddf4ff	#0550ae	#80ccff	Actions, primary operations
Purple	#d8b9ff	#6639ba	#bf8aff	DevOps, tracking, special
Green/Mint	#d3f5db	#1a7f37	#6fdd8b	Success, validation, output
Red/Coral	#ffebe9	#cf222e	#f5a3a3	Errors, critical, warning
Neutral	#eaeef2	#24292f	#d0d7de	Background, containers

Arrow/Link Styling (CRITICAL for readability):

linkStyle default stroke:#57606a,stroke-width:1.5px

Complete Example: Use the MANDATORY template at the top, with only the classDefs you need.

Key Principles:

1. Light fills (#fff1e5, #ddf4ff) — Easy on the eyes
2. Medium text (#953800, #0550ae) — Readable but not harsh
3. Soft strokes matching fill family
4. Gray arrows (#57606a) — Neutral, doesn't compete with nodes
5. 1.5-2px stroke-width — Visible but not heavy
6. edgeLabelBackground: '#ffffff' — White background for readable edge labels

Fishbowl Pastel Palette (Alternative)

Softer palette with uniform dark text. Good for governance, compliance, and presentation diagrams.

Purpose	Fill	Stroke	Text
Primary	#cce5ff	#4a90d9	#333
Light Blue	#b3d9ff	#4a90d9	#333
Lavender	#e6d5f2	#8b6eb3	#333
Mint	#c2f0d8	#4db37d	#333
Cream	#fff3b3	#d4a849	#333
Soft Pink	#ffcccc	#cc6666	#333

Init directive (Fishbowl):

%%{init: {'theme': 'base', 'themeVariables': {
  'primaryColor': '#cce5ff',
  'primaryBorderColor': '#4a90d9',
  'primaryTextColor': '#333',
  'secondaryColor': '#e6d5f2',
  'tertiaryColor': '#c2f0d8',
  'lineColor': '#666',
  'edgeLabelBackground': '#ffffff'
}}}%%

When to choose Fishbowl over GitHub Pastel v2: Use Fishbowl when all nodes need equal visual weight (e.g., governance structures, compliance flows). Use GitHub Pastel v2 when nodes carry semantic meaning that should be color-coded by category.

Per-Diagram Theming (MANDATORY for consistency)

Add as FIRST line inside mermaid block:

Default init directive (GitHub Pastel v2):

%%{init: {'theme': 'base', 'themeVariables': {
  'primaryColor': '#ddf4ff',
  'primaryBorderColor': '#0969da',
  'primaryTextColor': '#1f2328',
  'lineColor': '#57606a',
  'edgeLabelBackground': '#ffffff'
}}}%%

Standard GitHub-compatible theme (legacy):

%%{init: {'theme': 'base', 'themeVariables': {
  'primaryColor': '#f6f8fa',
  'primaryBorderColor': '#d1d9e0',
  'primaryTextColor': '#1f2328',
  'lineColor': '#656d76',
  'edgeLabelBackground': '#ffffff'
}}}%%

Quadrant chart theme:

%%{init: {'theme': 'base', 'themeVariables': {
  'quadrant1Fill': '#d3f5db',
  'quadrant2Fill': '#fff8c5',
  'quadrant3Fill': '#ffebe9',
  'quadrant4Fill': '#ddf4ff',
  'quadrantPointFill': '#1f2328',
  'quadrantTitleFill': '#1f2328'
}}}%%

classDef Reusable Styles

Define style classes once and apply to multiple nodes. Cleaner than per-node style directives.

Pastel v2 classDef Quick Reference (copy-paste ready):

classDef blue fill:#ddf4ff,color:#0550ae,stroke:#80ccff
classDef green fill:#d3f5db,color:#1a7f37,stroke:#6fdd8b
classDef purple fill:#d8b9ff,color:#6639ba,stroke:#bf8aff
classDef gold fill:#fff8c5,color:#9a6700,stroke:#d4a72c
classDef red fill:#ffebe9,color:#cf222e,stroke:#f5a3a3
classDef bronze fill:#fff1e5,color:#953800,stroke:#ffb77c
classDef neutral fill:#eaeef2,color:#24292f,stroke:#d0d7de

Apply to multiple nodes: class A,B,C blue

Apply inline: A[Label]:::blue

Subgraph Styling

Style subgraph backgrounds with the style directive using the subgraph ID:

flowchart LR
    subgraph SG1["Phase 1"]
        direction TB
        A --> B
    end
    subgraph SG2["Phase 2"]
        direction TB
        C --> D
    end

    style SG1 fill:#ddf4ff,stroke:#80ccff,color:#0550ae
    style SG2 fill:#d3f5db,stroke:#6fdd8b,color:#1a7f37

Key: Use fill for background, keep it light. The color property sets the title text color.

Gantt Chart Theming

Gantt charts use different theme variables than flowcharts:

  'taskBkgColor': '#ddf4ff',
  'activeTaskBkgColor': '#d3f5db',
  'activeTaskBorderColor': '#6fdd8b',
  'doneTaskBkgColor': '#eaeef2',
  'doneTaskBorderColor': '#d0d7de',
  'critBkgColor': '#ffebe9',
  'critBorderColor': '#f5a3a3',
  'todayLineColor': '#cf222e',
  'gridColor': '#d0d7de',
  'sectionBkgColor': '#f6f8fa',
  'altSectionBkgColor': '#ffffff',
  'taskTextColor': '#24292f',
  'sectionBkgColor2': '#f6f8fa'
}}}%%

Section formatting: Gantt sections inherit alternating background colors. Use section keyword to group related tasks:

gantt
    title Project Timeline
    dateFormat YYYY-MM-DD
    section Phase 1
    Task A :done, a1, 2026-01-01, 14d
    Task B :active, a2, after a1, 7d
    section Phase 2
    Task C :crit, a3, after a2, 10d

Sequence Diagram Theming

  'actorBkg': '#ddf4ff',
  'actorBorder': '#80ccff',
  'actorTextColor': '#0550ae',
  'activationBkgColor': '#d3f5db',
  'activationBorderColor': '#6fdd8b',
  'signalColor': '#57606a',
  'labelBoxBkgColor': '#fff8c5',
  'labelTextColor': '#9a6700',
  'noteBkgColor': '#fff8c5',
  'noteTextColor': '#9a6700',
  'noteBorderColor': '#d4a72c'
}}}%%

---

🎨 Visual Design Principles

Color Psychology in Diagrams

Color	Association	Use For
💙 Blue	Trust, reliability	Human partnership, collaboration
💜 Purple	Consciousness, awareness	Identity, higher concepts
💚 Green	Growth, learning	Cognitive processing, success
🧡 Orange	Connection, energy	Memory networks, neural links
❤️ Red	Power, achievement	Advanced capabilities, warnings

Diagram Effectiveness Criteria

• Clarity: Audience understands in 30 seconds
• Accuracy: Correctly represents the system/process
• Completeness: All essential elements, no clutter
• Consistency: Follows visual conventions
• Maintainability: Easy to update

Accessibility Standards

• Provide alternative text descriptions
• Use color-blind friendly palettes
• Ensure sufficient contrast
• Don't rely on color alone for meaning

---

⚠️ Parser Pitfalls (Real Failures)

These are parse-level failures that prevent rendering entirely. Captured from real production diagrams that broke. Read this section before writing any non-trivial Mermaid block.

P1. Quote labels containing reserved characters

The Mermaid parser treats @, :, (, ), ,, #, & as tokens inside unquoted node labels. Wrap the label in double quotes whenever it contains any of those, or you will get errors like Parse error on line N: Expecting 'AMP', 'COLON', ... got 'LINK_ID'.

%% BAD — parser error
M1[fabric-capacity.bicep<br/>Microsoft.Fabric/capacities@2023-11-01]

%% GOOD
M1["fabric-capacity.bicep<br/>Microsoft.Fabric/capacities@2023-11-01"]

Trigger characters that require quoting:

Character	Where it appears
@	ARM API versions, npm scopes, email addresses
:	Outside of subgraph titles — namespaces, time stamps
()	Method signatures, URL parts, (optional) annotations
,	Multi-clause labels
#	Hash, anchor, hex codes
& literal	Standalone — see P3 for the operator

When in doubt, quote. Costs nothing, immunizes against parser updates.

P2. No HTML entities inside shape brackets

<, >, & inside stadium ([...]), cylinder [(...)], or hex {{...}} shapes break the parser. Drop the entity or quote the label.

%% BAD
Start([./deploy.ps1 -SubscriptionId <sub>])

%% GOOD
Start(["./deploy.ps1 -SubscriptionId <sub>"])

P3. Don't use the & edge-list operator

Mermaid's spec allows A & B & C --> D, but it renders inconsistently across versions (works in mermaid.live, fails in some VS Code preview builds). Always expand to individual edges.

%% BAD — flaky across renderers
M1 & M2 & M3 & M4 --> Outputs

%% GOOD — explicit
M1 --> Outputs
M2 --> Outputs
M3 --> Outputs
M4 --> Outputs

P4. Avoid cylinder shape with multi-line content

Cylinder [(...)] combined with <br/> line breaks has caused parse flakes. Use a regular rectangle and put the data-shape semantics in the label itself.

%% BAD
Outputs[(Bicep outputs:<br/>fabricCapacityId<br/>fabricCapacityName)]

%% GOOD
Outputs[Bicep outputs<br/>fabricCapacityId<br/>fabricCapacityName]

P5. stateDiagram-v2 ignores classDef

State diagrams do not accept classDef. Style states by overriding the init directive's primaryColor for the whole diagram, or accept theme defaults. Without theme: 'base', unstyled states render solid black in many renderers — always include the init directive.

%%{init: {'theme': 'base', 'themeVariables': {'primaryColor': '#fef3c7', 'primaryBorderColor': '#fcd34d', 'primaryTextColor': '#1f2937', 'edgeLabelBackground': '#ffffff'}}}%%
stateDiagram-v2
    [*] --> Healthy
    Healthy --> Overage : load spike

P6. Markdownlint table-pipe spacing (MD060)

Tables in markdownlint-strict repos require a space on either side of every pipe. Use | --- | not |---|. The compact form passes some renderers but fails strict lint.

| Resource | API version |
| --- | --- |
| Microsoft.Fabric/capacities | 2023-11-01 |

P7. Pipe inside inline code triggers MD056

Markdownlint's column-count check (MD056) counts a literal | inside an inline code span as a column separator and reports a column-count mismatch. Either drop the | from the example, escape it as \|, or move the example out of the table.

P8. No blank lines inside blockquotes (MD028)

Blank lines inside a blockquote break it into separate quotes for the linter. Either continue the quote with > on every line (including empty lines as >), or break out of the quote completely between paragraphs.

%% BAD — MD028
> First paragraph.
>
> Second paragraph.   ← (this works visually but `>` empty line is required)

%% GOOD
> First paragraph.
>
> Second paragraph.

(The empty > line above is required — a fully blank line ends the quote.)

P9. Always specify language on fenced code blocks (MD040)

```bicep not ```. Renderers and lints both depend on it. Use text for plain output if no language fits.

Quick reference card

Pitfall	Symptom	Fix
P1 reserved chars unquoted	Parse error: Expecting AMP, COLON…	Quote the label
P2 HTML entities in shapes	Parser fails on <	Drop the entity, quote
P3 & edge operator	Diagram renders in one viewer, not another	Expand to N edges
P4 cylinder + <br/>	Intermittent parser flake	Use rectangle
P5 classDef in state diagram	Styles ignored, black nodes	Init directive only
P6 MD060	Lint error on tables	Space around every pipe
P7 MD056	Column-count mismatch	Remove | from inline code
P8 MD028	Blockquote breaks	Use > on empty lines
P9 MD040	Lint error on fences	Always specify language

---

⚠️ Common Pitfalls & Solutions

Unicode Escape Sequences (Broken Emojis)

Problem: Emojis stored as \ud83d\udcbb display as raw codes instead of 💻

Detection (PowerShell):

Get-ChildItem -Recurse -Filter "*.md" | Select-String -Pattern '\\u[0-9a-fA-F]{4}' | Group-Object Path

Prevention (VS Code settings):

{
    "files.encoding": "utf8",
    "files.autoGuessEncoding": false
}

Emoji Mapping Table

Escape	Emoji	Name
\ud83e\udde0	🧠	Brain
\ud83d\udcbb	💻	Laptop
\ud83d\ude80	🚀	Rocket
\ud83c\udfaf	🎯	Target
\ud83d\udca1	💡	Lightbulb
\ud83d\udd0d	🔍	Search
\ud83d\udd04	🔄	Cycle
\u2699\ufe0f	⚙️	Gear
\ud83d\udd27	🔧	Wrench
\u26a1	⚡	Lightning
\ud83c\udf1f	🌟	Star
\ud83c\udf19	🌙	Moon
\u2601\ufe0f	☁️	Cloud
\ud83c\udf10	🌐	Globe
\ud83d\udcac	💬	Speech
\ud83d\udcdd	📝	Memo
\ud83d\udccb	📋	Clipboard
\ud83d\udcc8	📈	Chart Up
\ud83d\udcbe	💾	Floppy
\ud83d\udce6	📦	Package
\u2705	✅	Check
\u274c	❌	Cross
\u26a0\ufe0f	⚠️	Warning
\ud83d\udea8	🚨	Siren

Edge Label Dark Background

Problem: Arrow labels (|text|) appear with dark boxes in VS Code dark mode or break rendering

Root cause: Missing or incorrect edgeLabelBackground settings.

Fix: Always include edgeLabelBackground: '#ffffff' in your init directive:

%%{init: {'theme': 'base', 'themeVariables': {
  'primaryColor': '#ddf4ff',
  'lineColor': '#57606a',
  'edgeLabelBackground': '#ffffff'
}}}%%

flowchart LR
    A -->|label text| B

This provides a clean white background for edge labels, ensuring readability on any rendering surface.

⚠️ Never use theme: 'dark' — use theme: 'base' with the pastel palette instead.

Multi-Line Node Labels (\n vs <br/>)

Problem: \n in node labels renders as a literal backslash-n in VS Code and some Mermaid versions:

❌ A["First line\nSecond line"]   ← may render as "First line\nSecond line"
✅ A["First line<br/>Second line"] ← always works

Rule: Always use <br/> for multi-line node labels in flowcharts.

Dark Mermaid Backgrounds

Problem: Diagrams have dark backgrounds in VS Code preview

Solution 2: Keep colors explicit in the Mermaid init directive (for example, theme: 'base' with themeVariables).

Disproportionate Diagram Layouts (Too Wide/Too Tall)

Problem: Diagrams become too wide (horizontal) or too tall (vertical), causing poor readability

Detection: Look for diagrams where one dimension is 3x+ the other

Pattern: Use opposing directions for outer flowchart vs. inner subgraphs:

%% Pattern 1: TD outer with LR inner (vertical stack of horizontal lanes)
flowchart TD
    subgraph Phase1["Phase 1"]
        direction LR
        A --> B --> C
    end
    subgraph Phase2["Phase 2"]
        direction LR
        D --> E --> F
    end

%% Pattern 2: LR outer with TB inner (horizontal flow of vertical stacks)
flowchart LR
    subgraph Group1["Group 1"]
        direction TB
        A --> B --> C
    end
    subgraph Group2["Group 2"]
        direction TB
        D --> E --> F
    end

Key Rules:

Outer Direction	Inner Direction	Result
TD/TB	LR	Subgraphs stack vertically, content flows horizontally
LR	TB	Subgraphs flow horizontally, content stacks vertically

Anti-Pattern 1: Single subgraph with opposing direction has no effect (nothing to stack)

%% WRONG - single subgraph, direction LR does nothing useful
flowchart TD
    subgraph Only["Only Subgraph"]
        direction LR
        A --> B --> C --> D --> E  %% Still very wide!
    end

%% RIGHT - break into multiple subgraphs
flowchart TD
    subgraph Phase1["Setup"]
        direction LR
        A --> B
    end
    subgraph Phase2["Execute"]
        direction LR
        C --> D
    end

Anti-Pattern 2: Cross-subgraph edges defined inside subgraphs (causes layout confusion)

%% WRONG - edge to next subgraph defined inside source subgraph
flowchart TD
    subgraph Phase1["Setup"]
        direction LR
        A --> B
        B --> C  %% C is in Phase2!
    end
    subgraph Phase2["Execute"]
        direction LR
        C --> D
    end

%% RIGHT - cross-subgraph edges defined outside all subgraphs
flowchart TD
    subgraph Phase1["Setup"]
        direction LR
        A --> B
    end
    subgraph Phase2["Execute"]
        direction LR
        C --> D
    end
    B --> C  %% Cross-subgraph edge outside
    subgraph Phase3["Complete"]
        direction LR
        E
    end

Anti-Pattern 3: Independent subgraphs without connections default to vertical stacking

%% WRONG - no connections between subgraphs, ignores LR direction
flowchart LR
    subgraph A["Group A"]
        direction TB
        A1 --> A2
    end
    subgraph B["Group B"]
        direction TB
        B1 --> B2
    end
    %% Result: Groups stack vertically despite LR!

%% RIGHT - invisible links force horizontal layout
flowchart LR
    subgraph A["Group A"]
        direction TB
        A1 --> A2
    end
    subgraph B["Group B"]
        direction TB
        B1 --> B2
    end
    A ~~~ B  %% Invisible link forces LR arrangement

Named Layout Patterns

Use these named patterns for consistent, well-proportioned diagrams. Each combines an outer flowchart direction with inner subgraph directions.

Medallion Pattern (TD + LR)

Use when: Phases/layers stack vertically, each containing a horizontal flow.

flowchart TD
    subgraph Phase1["Phase 1: Ingestion"]
        direction LR
        A[Source] --> B[Validate] --> C[Store]
    end
    subgraph Phase2["Phase 2: Processing"]
        direction LR
        D[Load] --> E[Transform] --> F[Enrich]
    end
    Phase1 --> Phase2

Result: Compact rectangle. Good for pipelines, ETL stages, layered architectures.

Lineage Pattern (LR + TB)

Use when: Groups flow left-to-right, each containing a vertical stack.

flowchart LR
    subgraph Cluster1["Input"]
        direction TB
        A1[Raw] --> A2[Clean]
    end
    subgraph Cluster2["Process"]
        direction TB
        B1[Compute] --> B2[Validate]
    end
    subgraph Cluster3["Output"]
        direction TB
        C1[Format] --> C2[Deliver]
    end
    Cluster1 --> Cluster2 --> Cluster3

Result: Wide timeline-like layout. Good for data lineage, system boundaries, progression.

Pipeline Pattern (LR + LR)

Use when: Everything flows left-to-right (flat pipeline, no vertical stacking needed).

flowchart LR
    A[Input] --> B[Stage 1] --> C[Stage 2] --> D[Output]

Result: Simple horizontal chain. Good for CI/CD, request flows, simple sequences.

Pattern Decision Matrix

Your Content	Pattern	Outer	Inner	Typical Shape
Phases with steps inside	Medallion	TD	LR	Tall rectangle
Groups flowing in sequence	Lineage	LR	TB	Wide rectangle
Simple linear flow	Pipeline	LR	—	Narrow strip
Hierarchy, org chart	Tree	TD	—	Triangle
Complex interconnected	Medallion	TD	LR	Structured layers

Independent Subgraphs (Invisible Links)

When subgraphs have no logical connections between them, Mermaid ignores the outer direction and stacks them vertically by default. Fix with invisible links (~~~):

flowchart LR
    subgraph A["Group A"]
        direction TB
        A1 --> A2
    end
    subgraph B["Group B"]
        direction TB
        B1 --> B2
    end
    A ~~~ B  %% Forces horizontal arrangement per outer LR

Rule: Always add ~~~ between independent subgraphs to enforce the outer direction.

Multiple independent groups: Chain invisible links: A ~~~ B ~~~ C ~~~ D

Subgraph Title Truncation (VS Code Only)

Problem: Subgraph titles get truncated in VS Code preview

Note: This is a VS Code Mermaid renderer bug. GitHub renders correctly.

Root Cause: VS Code calculates subgraph width from content nodes, NOT title text.

Workaround: Make content nodes wider so the subgraph expands:

%% BAD in VS Code - narrow nodes clip title
subgraph CONSCIOUS["🌟 Conscious Mind"]
    A["Chat"]
    B["Commands"]
end

%% GOOD - descriptive labels force wider box
subgraph CONSCIOUS["🌟 Conscious Mind"]
    A["💬 Chat Participant"]
    B["⚡ VS Code Commands"]
end

Mermaid Parse Errors

Problem: Nested quotes, parentheses, or reserved words cause cryptic parse errors

Rule 1: Don't nest quotes inside quoted node labels

%% ❌ FAILS - nested quotes
["Return with<br/>"🌐 Results<br/>(Info)"]

%% ✅ WORKS - no nested quotes
["🌐 Return Results<br/>Info"]

Rule 2: Avoid HTML tags inside node labels (some renderers choke on them)

%% ❌ RISKY - <i> tag may break parsing
CFG["config.json<br/><i>inert — rarely traversed</i>"]

%% ✅ SAFE - plain text with em dash
CFG["config.json — inert, rarely traversed"]

Rule 3: Avoid em dashes (—) in subgraph titles (some parsers treat them as operators)

%% ❌ RISKY - em dash in subgraph title
subgraph P1["Phase 1 — Compiled Graph"]

%% ✅ SAFE - colon or hyphen instead
subgraph P1["Phase 1: Compiled Graph"]
subgraph P1["Phase 1 - Compiled Graph"]

Rule 4: Place style directives for subgraphs outside the subgraph block

%% ❌ FAILS in some renderers - style inside subgraph
subgraph SG["My Group"]
    style SG fill:#ddf4ff,stroke:#80ccff
    direction TB
    A --> B
end

%% ✅ WORKS everywhere - style after all subgraphs
subgraph SG["My Group"]
    direction TB
    A --> B
end
style SG fill:#ddf4ff,stroke:#80ccff

classDiagram-Specific Pitfalls

Critical: classDiagram has a different parser than flowchart. Syntax that works in flowcharts often breaks in class diagrams. Never assume cross-compatibility.

Reserved Keyword Collisions

classDiagram reserves more keywords than flowcharts. Using them as classDef names or class annotations collides with the parser.

Reserved Word	Why It Breaks	Safe Alternative
abstract	Parsed as <<abstract>> annotation	abstractStyle, base, iface
interface	Parsed as <<interface>> annotation	ifaceStyle, contract
enumeration	Parsed as <<enumeration>> annotation	enumStyle, enumDef
service	Parsed as <<service>> annotation	svcStyle, serviceType

%% ❌ FAILS - "abstract" is a classDiagram keyword
classDef abstract fill:#ddf4ff,stroke:#80ccff

%% ❌ ALSO FAILS - "abstract" parsed as <<abstract>> annotation
class MemorySystem abstract

%% ✅ WORKS - renamed classDef avoids collision
classDef base fill:#ddf4ff,stroke:#80ccff
class MemorySystem base

Comma-Separated Class Lists

class A,B,C styleName syntax works in flowchart but NOT in classDiagram. Each class needs its own class X styleName line.

%% ❌ FAILS in classDiagram - comma syntax not supported
class UserStore,SessionStore,CacheStore storage

%% ✅ WORKS - one line per class
class UserStore storage
class SessionStore storage
class CacheStore storage

Note: In flowchart, class A,B,C styleName is valid (skillCatalog.ts uses this correctly).

classDef Property Limitations

classDef in classDiagram only supports SVG presentation attributes. CSS text properties are silently ignored.

Works	Silently Ignored
fill, stroke, stroke-width, color	font-weight, font-style, font-size
rx (border radius)	text-decoration, letter-spacing
opacity	padding, margin

%% ❌ SILENTLY IGNORED - font-weight does nothing
classDef important fill:#fff3e0,stroke:#ef6c00,font-weight:bold

%% ✅ WORKS - use only SVG attributes
classDef important fill:#fff3e0,stroke:#ef6c00,stroke-width:2px

stroke-dasharray Space Parsing

The space in stroke-dasharray:6 3 breaks Mermaid's comma-delimited property parser in classDiagram. In flowchart it may work.

%% ❌ FAILS in classDiagram - space in value breaks parser
classDef dashed stroke-dasharray:6 3

%% ⚠️ MAY WORK - single value, no space
classDef dashed stroke-dasharray:5

%% ✅ SAFE in flowchart - space tolerated
classDef dashed stroke-dasharray:5 5

Rule: In classDiagram, avoid stroke-dasharray entirely or use a single integer value. In flowchart, stroke-dasharray:5 5 works.

Decimal stroke-width

Decimal values like stroke-width:2.5px can cause inconsistent rendering across Mermaid renderers.

%% ⚠️ INCONSISTENT - decimal may not render
classDef thick stroke-width:2.5px

%% ✅ SAFE - integer values
classDef thick stroke-width:2px
classDef thicker stroke-width:3px

---

architecture-beta Pitfalls

Critical: architecture-beta is an experimental diagram type with a much stricter tokenizer than mature types. Assume nothing works unless proven.

Spaces in Bracket Labels

Labels in [...] do not support spaces. Multi-word labels cause the parser to treat each word as a separate token.

%% ❌ FAILS - space in bracket label
service api(server)[API Gateway]

%% ✅ WORKS - no spaces (use underscores or camelCase)
service api(server)[APIGateway]
service api(server)[Api_Gateway]

Hyphens in Labels

Hyphens like 4-3-3 are parsed as edge connectors (-- or -), not literal characters. There is no escape mechanism.

%% ❌ FAILS - hyphens parsed as edge syntax
service formation(server)[4-3-3]

%% ✅ WORKS - no hyphens
service formation(server)[Formation433]

Reserved IDs

Common programming keywords may conflict with the parser:

Avoid	Safe Alternative
var	varStore, envVar
in	input, inbound
out	output, outbound

Comments May Not Work

%% comments that work in all other diagram types may cause parse errors in architecture-beta.

%% ❌ MAY FAIL - standard comments
%% This is my architecture
architecture-beta

%% ✅ SAFE - no comments at all
architecture-beta

Icons Only on service, Not group

(icon) syntax only works on service declarations. Using it on group causes a parse error.

%% ❌ FAILS - group does not accept (icon)
group cloud(cloud)[Infrastructure]

%% ✅ WORKS - group has only id and [label]
group cloud[Infrastructure]

%% ✅ WORKS - service accepts (icon)
service api(server)[API]

Rule: service id(icon)[Label] — icon required. group id[Label] — no icon, no parentheses.

---

Cross-Diagram Syntax Compatibility Matrix

This table summarizes which syntax features work in which diagram types:

Feature	flowchart	classDiagram	architecture-beta
class A,B,C style	✅	❌	N/A
classDef with font-weight	❌ (ignored)	❌ (ignored)	N/A
stroke-dasharray:5 5	✅	❌	N/A
Spaces in [labels]	✅	N/A	❌
Hyphens in labels	✅ (quoted)	✅ (quoted)	❌
%% comments	✅	✅	⚠️
(icon) on groups	N/A	N/A	❌

---

Reserved Words in Labels and Titles

Problem: Certain words are reserved syntax in specific diagram types. Using them as the first word in a task description or node label causes parse errors like got 'callbackname', got 'keyword', etc.

Gantt Chart Reserved Words (cause callbackname or keyword errors):

Reserved	Why	Safe Alternative
call	Click callback syntax	Invoke, Execute, Generate, Run
click	Click handler syntax	Select, Choose, Trigger
after	Dependency keyword (only at start)	Rephrase to not start with after
done	Task state modifier	Use as tag :done, not in description
active	Task state modifier	Use as tag :active, not in description
crit	Task state modifier	Use as tag :crit, not in description

%% ❌ FAILS - "Call" is reserved
Call Azure OpenAI embeddings API    :p1c, after p1b, 2d

%% ✅ WORKS - rephrase to avoid reserved word
Generate Azure OpenAI embeddings    :p1c, after p1b, 2d

Flowchart Reserved Words (cause unexpected parse behavior):

Reserved	Why	Safe Alternative
end	Subgraph terminator	Wrap in quotes: ["End"]
subgraph	Block keyword	Wrap in quotes: ["Subgraph"]
class	classDef application	Wrap in quotes: ["Class"]
style	Style directive	Wrap in quotes: ["Style"]
click	Click handler	Wrap in quotes: ["Click"]
default	Default linkStyle target	Wrap in quotes: ["Default"]

%% ❌ FAILS - "end" is reserved
A --> end

%% ✅ WORKS - quoted label
A --> E["End"]

classDiagram Reserved Words (cause parse errors when used as classDef names or class annotations):

Reserved	Why	Safe Alternative
abstract	Parsed as <<abstract>> stereotype	base, abstractStyle, iface
interface	Parsed as <<interface>> stereotype	ifaceStyle, contract
enumeration	Parsed as <<enumeration>> stereotype	enumStyle, enumDef
service	Parsed as <<service>> stereotype	svcStyle, serviceType

%% ❌ FAILS - "abstract" treated as keyword
classDef abstract fill:#ddf4ff,stroke:#80ccff
class MemorySystem abstract

%% ✅ WORKS - safe name
classDef base fill:#ddf4ff,stroke:#80ccff
class MemorySystem base

General Safety Rule: If a parse error occurs on a label or title, wrap it in double quotes ("text") or rephrase to avoid the reserved word. When in doubt, quote it.

XY Chart Bar Coloring (xychart-beta)

Problem: Individual bars all render the same color despite plotColorPalette

Root Cause: xychart-beta only applies different colors to different data series (multiple bar or line commands), not individual bars in a single series.

%% ❌ FAILS - single series, all bars same color
xychart-beta
    x-axis [A, B, C]
    bar [1, 2, 3]  %% All same color!

%% ✅ WORKS - multiple series, each gets color from palette
xychart-beta
    x-axis [A, B, C]
    bar [1, 2, 3]    %% Color 1
    bar [4, 5, 6]    %% Color 2

Alternative Solutions:

1. Pie chart — Use pie with theming when showing proportions:

   pie showData
       title "Task Distribution"
       "Task A" : 8
       "Task B" : 4
   

2. Visual ASCII table — Use markdown table with visual bars:

   | Task | Value | Visual |
   | ---- | ----- | ------ |
   | A | **8** | ████████░░░░ |
   | B | **4** | ████░░░░░░░░ |
   

3. Stacked bar (grouped) — Split data into multiple series

---

C4 Diagram Limitations

Problem: C4Component syntax not fully supported in standard Mermaid

Solution: Use flowcharts with subgraphs instead:

flowchart TB
    subgraph SYSTEM["🏦 System Name"]
        A["📝 Component A"]
        B["📊 Component B"]
    end
    USER(("👤 User"))
    USER --> A
    USER --> B

Blockquote Tall Boxes

Problem: Blockquotes render with excessive vertical padding

Solution: Use normal Markdown blockquotes. Optional personal preview styling belongs in the VS Code user profile, not project configuration.

---

🔍 Diagram Audit Methodology

When performing comprehensive diagram audits across a project or documentation set, follow this 4-step process:

Step 1: Enumerate

Identify all Mermaid diagrams in the target scope:

# Find all markdown files with mermaid blocks
Get-ChildItem -Recurse -Filter "*.md" |
  Select-String -Pattern '```mermaid' |
  Group-Object Path |
  Select-Object Name, Count

Step 2: Categorize

Create an inventory table to track diagram state:

#	File	Diagram Type	Status	Issues
1	README.md	flowchart	⚠️	Missing init
2	arch.md	sequence	✅	None
3	flow.md	flowchart	❌	Parse error

Status codes: ✅ OK, ⚠️ Needs fix, ❌ Broken

Step 3: Batch Fix

Apply fixes in batches by issue type:

1. Reserved word errors — Rephrase or quote labels
2. Parse errors — Apply 4 safety rules
3. Style inconsistencies — Apply GitHub Pastel v2 palette

Step 4: Validate

Re-render all diagrams and confirm fixes:

• All diagrams render in VS Code preview
• All diagrams render on GitHub
• Color palette is consistent
• No parse errors in console

Typical results: A 30-40 diagram audit catches 10-15 issues in the first pass.

---

✅ Quality Checklist

Before Committing

• All diagrams have figure labels
• All tables have table labels
• No unicode escape sequences
• Diagrams render correctly in preview AND GitHub
• Consistent heading hierarchy
• Links are valid

Diagram Review

• Node labels are clear and concise (but not over-simplified)
• Colors follow consistent palette
• Subgraphs logically group related items
• Subgraph content is wide enough for title (VS Code)

Don't Over-Simplify

KISS ≠ Remove all detail

KISS means removing unnecessary complexity while preserving meaningful information. If removing detail reduces understanding, keep it.

---

📚 References

Skill References (in references/)

• references/diagram-types.md — Per-type quick-reference syntax for all 23 Mermaid diagram types with examples and pitfalls

Official Documentation

• Mermaid Documentation
• Mermaid Live Editor
• PlantUML Documentation
• Graphviz Documentation
• D2 Documentation
• Shields.io

VS Code Resources

• VS Code Markdown Guide
• GitHub Flavored Markdown

Visual Design Theory

• Tufte, E.R. - The Visual Display of Quantitative Information
• Cairo, A. - The Functional Art
• Knaflic, C.N. - Storytelling with Data