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maid

Model Context Protocol server for Mermaid diagram validation using Maid

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npx @probelabs/maid-mcp

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Maid

Fast, accurate Mermaid diagram validator with clear, actionable diagnostics. Built for the AI age where Mermaid has become essential—but validation shouldn't require a browser.

Why Maid?

Built for AI: Designed for AI agents and LLMs that generate Mermaid diagrams
Render Guarantee: When Maid says it's valid, your diagram will render
Lightning Fast: Validates in milliseconds without launching a browser
Human-Friendly: Clear error messages with line numbers, carets, and actionable hints
Lightweight: ~5MB vs. mermaid-cli's 1.7GB (Puppeteer + Chrome)
Auto-Fix: Automatically corrects common AI-generated mistakes

Quick Start

# One‑off (npx)
npx -y @probelabs/maid diagram.mmd

# Or install locally (dev dependency)
npm install -D @probelabs/maid
npx maid diagram.mmd   # uses local bin from @probelabs/maid

# From stdin
cat diagram.mmd | npx -y @probelabs/maid -

# Markdown with multiple diagrams
npx -y @probelabs/maid README.md

# Lint an entire docs directory (recursively)
npx -y @probelabs/maid docs/

SDK Quick Example

Use Maid programmatically (ESM). See docs/SDK.md for more.

import { validate, fixText } from '@probelabs/maid';

const src = 'flowchart TD\nA->B';
const { errors } = validate(src);
if (errors.length) {
  const { fixed } = fixText(src, { level: 'safe' });
  console.log(fixed);
}

Exit codes

0: no errors (including when no Mermaid diagrams are found)
1: at least one error (warnings do not fail)

MCP Server for AI Assistants

Maid includes a Model Context Protocol (MCP) server that allows AI assistants like Claude Code to validate and fix Mermaid diagrams directly in conversations.

Quick Setup for Claude Code

Add Maid MCP server using the CLI:

claude mcp add -- npx -y @probelabs/maid mcp

Or configure manually in ~/.claude.json:

{
  "mcpServers": {
    "maid": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@probelabs/maid", "mcp"]
    }
  }
}

After configuration, restart Claude Code. The assistant will now be able to validate and fix Mermaid diagrams when you ask.

MCP Tool: `validate_mermaid`

Inputs:

text (string, required): Mermaid diagram text or Markdown content with ```mermaid blocks
autofix (boolean, optional): Set to true to automatically fix syntax errors

Returns (JSON):

valid (boolean): Whether the diagram is valid
diagramType (string): Detected diagram type (flowchart, pie, sequence, unknown)
errorCount, warningCount (number): Count of errors and warnings
errors (array): Detailed error objects with line, column, message, code, hint
fixed (string): Corrected diagram text (only when autofix=true)

Example Usage in Conversations

Once configured, you can ask Claude Code:

"Check this Mermaid diagram for errors"
"Validate the Mermaid diagrams in my README.md"
"Fix the syntax errors in this flowchart"

The assistant will use the MCP server to validate or fix diagrams and show you the results.

Using as an SDK

Maid can be used programmatically (ESM, CommonJS, and TypeScript). The public API lives at the package root export. See docs/SDK.md for complete examples.

For detailed examples (ESM, CommonJS, TypeScript) and API surface, see docs/SDK.md.

Browser Usage with Mermaid.js-Compatible API

Maid provides a drop-in replacement for Mermaid.js that works in the browser with no external dependencies. Perfect for validating and rendering diagrams client-side without Puppeteer or Chrome.

Quick Start (via CDN):

<!DOCTYPE html>
<html>
<head>
    <title>Maid Browser Example</title>
</head>
<body>
    <div id="diagram"></div>

    <script type="module">
        // Import from ProLabs CDN
        import { createMermaidAPI } from 'https://probelabs.com/maid/maid.bundle.js';

        // Create a Mermaid.js-compatible API
        const maid = createMermaidAPI();

        const diagramText = `
            flowchart TD
                A[Start] --> B{Decision}
                B -->|Yes| C[Process]
                B -->|No| D[End]
        `;

        // Use exactly like Mermaid.js
        const { svg } = await maid.render('diagram-id', diagramText);
        document.getElementById('diagram').innerHTML = svg;
    </script>
</body>
</html>

Features:

✅ Same API as Mermaid.js - Drop-in replacement for mermaid.render()
✅ No dependencies - Works completely offline (~350KB bundle)
✅ Built-in validation - Auto-fixes common errors before rendering
✅ Experimental renderer - Supports flowchart and pie diagrams

Toggle Between Renderers:

<script type="module">
    import { createMermaidAPI } from 'https://probelabs.com/maid/maid.bundle.js';
    import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.esm.min.mjs';

    const maidRenderer = createMermaidAPI();
    mermaid.initialize({ startOnLoad: false });

    // Choose renderer based on user preference
    const useMaid = true; // or read from checkbox
    const renderer = useMaid ? maidRenderer : mermaid;

    // Both use the same API!
    const { svg } = await renderer.render('id', diagramText);
</script>

Interactive Demo: Try it live at https://probelabs.com/maid/demo.html

API Reference:

createMermaidAPI() - Creates Mermaid.js-compatible instance
maid.render(id, text, options?) - Async render (returns { svg })
maid.renderSync(id, text, options?) - Sync render (returns { svg })
maid.initialize(config?) - No-op for compatibility

Supported Diagram Types (Browser Rendering):

✅ Flowcharts (flowchart, graph)
✅ Pie charts (pie)
🚧 Other types fall back to validation only

Bundle Sizes:

Maid browser bundle: ~350KB minified
Mermaid.js: ~400KB (CDN) or 1.7GB (mermaid-cli + Puppeteer)

Rendering Diagrams (Experimental)

# Render to SVG (default)
npx -y @probelabs/maid render diagram.mmd

# Render to PNG
npx -y @probelabs/maid render diagram.mmd output.png

# Render from stdin
cat diagram.mmd | npx -y @probelabs/maid render - output.svg

# Force output format
npx -y @probelabs/maid render diagram.mmd -f png

Notes

The renderer is experimental and primarily for parser validation
Currently supports flowchart, pie, and sequence diagrams
PNG output requires rsvg-convert or ImageMagick installed
See "Development > Experimental Renderer" for technical details

Renderer Parity / Visual Comparison

To compare our renderer vs Mermaid CLI across fixtures, see AGENTS.md for the step‑by‑step parity workflow. Quick start:

npm run build
npm run compare:renderers:sequence   # or :flowchart / :pie

Outputs (Mermaid+Maid SVG/PNG and diffs) go to .tmp-compare-all/.

Development

Parsing Parity Quick Loop

Compare against Mermaid CLI for one type: node scripts/compare-linters.js flowchart
Run error-code tests for all: npm run test:errors:all
Regenerate previews (all types): npm run generate:previews
CI parity bundle locally: npm run ci:test and npm run ci:previews

Autofix in a nutshell

# Safe fixes only (mechanical)
npx -y @probelabs/maid --fix docs/

# Safe + heuristic fixes (more aggressive)
npx -y @probelabs/maid --fix=all docs/

# Preview the fixed content without writing (single file or stdin)
npx -y @probelabs/maid --fix --dry-run --print-fixed diagram.mmd

Notes

Safe fixes are idempotent and conservative (arrows, inner quotes to ", missing :, missing end, etc.).
--fix=all additionally enables conservative heuristics (e.g., wrap unquoted labels, close unclosed quotes/brackets).
In directory mode, Maid prints "All diagrams valid after fixes. Modified X file(s)." when it succeeds post-fix.
See "Autofix" below for details and examples.

Directory Scans: Include/Exclude and .gitignore

Include globs: --include or -I (repeatable or comma‑separated)
Exclude globs: --exclude or -E (repeatable or comma‑separated)
Respect .gitignore by default; disable with --no-gitignore

Examples

# Respect .gitignore (default)
npx -y @probelabs/maid docs/

# Only files under docs/content
npx -y @probelabs/maid docs/ -I "docs/content/**/*.md,docs/content/**/*.mmd"

# Exclude legacy and drafts
npx -y @probelabs/maid docs/ -E "docs/legacy/**" -E "**/*.draft.md"

# Do not respect .gitignore
npx -y @probelabs/maid docs/ --no-gitignore

# JSON report for CI
npx -y @probelabs/maid --format json -I "**/*.mdx" -E "**/node_modules/**" docs/

Why Maid Exists

Mermaid has become an essential part of modern engineering culture. It's in our documentation, our AI workflows, and our development processes. Every major LLM knows Mermaid syntax because they've been trained on millions of diagrams. But there's a challenge.

The AI Challenge

When AI generates complex Mermaid diagrams, the success rate is surprisingly low. The syntax is too free-form, making it easy for AI to generate invalid diagrams that look correct but won't render. You can see this yourself in Mermaid's own live editor—even simple mistakes lead to cryptic errors.

The Validation Gap

You can't know if a Mermaid diagram will render without actually rendering it. This architectural constraint exists because:

Tightly Coupled Architecture: Mermaid's parser (based on Jison, a JavaScript port of the 1990s Bison parser) tightly couples parsing with rendering. Validation requires rendering.
mermaid-cli's Approach: The official CLI tool bundles Puppeteer and Chrome—a 1.7GB dependency—to validate by actually rendering your diagram.
Cryptic Error Messages: When validation fails, you get messages like:
```
Expecting 'SEMI', 'NEWLINE', 'EOF', 'AMP', 'START_LINK', 'LINK', 'LINK_ID', got 'MINUS'
```
These token-based errors are difficult for both humans and AI to understand.

The Maid Solution

Maid fills this gap with a modern, lightweight validator. We built a parser from scratch that:

Decouples validation from rendering - No browser needed
Provides semantic error messages - AI and humans can understand and fix issues
Guarantees rendering - When Maid says it's valid, it will render
Auto-fixes common mistakes - Especially those AI agents frequently make
Stays lightweight - 5MB, not 1.7GB

This isn't about competing with Mermaid—it's about making Mermaid more accessible and reliable for everyone, especially in the AI age.

Supported Diagrams (today)

Flowchart (flowchart, graph)
Sequence (sequenceDiagram)
Pie (pie)
Class (classDiagram)
State (stateDiagram, stateDiagram-v2)

Note: Other Mermaid diagram types (e.g., gantt, journey, erDiagram, etc.) are treated as valid (pass‑through). We’ll add native validation over time.

What It Catches

❌ Common Errors

Invalid arrow syntax (-> instead of -->)
Unclosed brackets and mismatched node shapes
Invalid directions (must be TD, TB, BT, RL, LR)
Missing diagram type declaration
Malformed class and subgraph syntax

⚠️ Best Practice Warnings

Link text without proper pipe delimiters
Empty diagrams
Problematic HTML entities

Testing & Validation

Commands

Run baseline tests: npm test
Error‑code assertions (all types): npm run test:errors:all
Autofix smoke tests: node scripts/test-fixes.js
- CI runs these automatically on every PR/commit.
Markdown extraction and offsets: npm run test:markdown
Directory scan behavior: npm run test:dir
Compare with mermaid‑cli (non‑blocking): node scripts/compare-linters.js flowchart|pie|sequence

Current coverage

Flowchart: 20 valid • 18 invalid
Pie: 4 valid • 8 invalid
Sequence: 13 valid • 20 invalid

Roadmap & Support

As of 2025‑09‑30. Mermaid statuses summarized from the docs.

Diagram	Mermaid status	Maid support	Notes
Flowchart	Stable	Yes	TD/TB/BT/RL/LR; subgraphs; strict mode optional
Sequence	Stable	Yes	Blocks (alt/opt/par/critical/etc.), autonumber, notes
Pie	Stable	Yes	Titles, showData, label/number rules
Class	Stable	Yes	Class/members/relations; stereotypes; alias
State	Stable	Yes	Transitions, start `[*]`, state blocks, notes
ER	Experimental	Pass-through
Gantt	Stable	Pass-through
User Journey	Stable	Pass-through
GitGraph	Stable	Planned
Mindmap	Stable (icons experimental)	Planned
Timeline	Stable (icons experimental)	Planned
Quadrant Chart	Stable	Planned
XY Chart	Stable	Planned
Requirement	Stable	Planned
C4	Experimental	Planned
Sankey	Experimental	Planned
Block Diagram	New/experimental	Planned
Treemap	Beta/New	Planned

Support

Channel	Use for
GitHub Issues	Bugs, feature requests, questions
Pull Requests	Improvements to validators, diagnostics, docs

Testing / CI

Baseline tests (flowchart): a fast harness that runs Maid over curated valid/invalid fixtures and expects 100% pass/fail parity with our intended behavior. In CI this step is labeled “Run linter tests (flowchart baseline)”.
- Command: npm test (runs scripts/test-chevrotain.js).
Error-code assertions (all types): verifies that each invalid fixture surfaces the expected stable error codes across flowchart, pie, and sequence.
- Command: npm run test:errors:all.
Compare with mermaid-cli: runs mermaid-cli on all fixtures and checks overall VALID/INVALID parity with Maid. This intentionally prints differences but does not fail the job.
- Commands: node scripts/compare-linters.js flowchart|pie|sequence.
Markdown extraction and offsets: validates multi-diagram Markdown parsing and line-number accuracy.
- Command: npm run test:markdown.
Directory scan: validates recursive scanning, include/exclude, .gitignore handling, and exit codes.
- Command: npm run test:dir.

Releasing

We publish to npm when a Git tag is pushed that matches the package version.

Rules

Tags must be in the form vX.Y.Z.
The tag must match package.json's version. CI will fail if they differ.

Steps

Bump the version in package.json and commit.
- Or use npm to bump and create a tag in one step: npm version patch|minor|major.
Push the tag: git push --follow-tags.
GitHub Actions (Release workflow) will build, run quick tests, and publish to npm.

Notes

The package includes only the compiled out/ folder, README, and LICENSE.
Node.js >= 18 is required (see engines).
Requires a repository secret NPM_TOKEN with publish access to the npm package.

These layers give confidence in correctness (baseline), diagnostic quality (error codes), and compatibility with the reference renderer (mermaid-cli comparison).

Error Codes

Diagnostics include stable error codes and hints for quick fixes. See the full list in docs/errors.md.

Autofix Support

Use --fix for safe, mechanical fixes and --fix=all to include conservative heuristics.
A complete matrix of error codes and autofix behavior is in docs/errors.md (section “Autofix Support Matrix”).

Autofix

Maid can optionally fix many common issues for you. There are two levels:

Safe (--fix): mechanical, low‑risk changes, idempotent.
All (--fix=all): includes Safe and adds heuristic fixes that require mild inference.

What gets fixed (highlights)

Flowchart (Safe):
- -> → -->
- Inner quotes → " inside quoted labels
- direction keyword inside subgraphs (replace unknown kw)
- Mismatched closer for shapes (e.g., A(text] → A(text))
Flowchart (Safe):
- Wrap unquoted labels when a " appears inside (and normalize inner quotes)
- Insert a best‑guess missing closing bracket
- Add default direction TD after flowchart/graph header
- Insert --> when two nodes are placed on one line without an arrow
Sequence (Safe):
- Add : in messages and notes
- Replace else with option inside critical
- Insert a new end for unclosed blocks (keeps indentation)
- Move extraneous tokens after autonumber to the next line
- Fix inner quotes in participant/actor names by using " (e.g., participant "Logger \"debug\"" → participant "Logger "debug"")
Sequence (All):
- Normalize malformed autonumber to autonumber
- Close unclosed quotes at end of line
Pie (Safe):
- Insert missing : between label and number
- Wrap unquoted labels and normalize inner quotes to "
Pie (All):
- Close unclosed quotes (before colon if present, else end of line)
Flowchart (Safe):
- Remove empty shapes A[""] / A[" "] / A[] → A

Before/After examples

Flowchart (Safe — arrow and quotes)

%% before
flowchart TD
  A -> B
  C["He said \"Hi\""]

becomes

flowchart TD
  A --> B
  C["He said &quot;Hi&quot;"]

Flowchart (All — wrap unquoted label containing quotes)

%% before
flowchart TD
  A[Calls logger.debug("msg", data)]

becomes

flowchart TD
  A["Calls logger.debug(&quot;msg&quot;, data)"]

Sequence (Safe — message colon and missing end)

%% before
sequenceDiagram
  par Work
    A->B hi

becomes

sequenceDiagram
  par Work
    A->B : hi
  end

Pie (Safe — missing colon and unquoted label)

pie
  Dogs 10

becomes

pie
  "Dogs"  : 10

Tips

Run with a clean working tree so you can review diffs easily.
Use --dry-run --print-fixed to preview changes for a single file or stdin.
After --fix, run without --fix to confirm exit code 0.
Full code → fix mapping is in docs/errors.md (Autofix Support Matrix).

CLI Output Formats

Text (default): caret-underlined snippet style with codes, hints, and precise spans.
JSON: machine-readable report for editors/CI.

# Text (default)
npx -y @probelabs/maid diagram.mmd

# JSON
npx -y @probelabs/maid --format json diagram.mmd

Strict Mode

Enable strict mode to require quoted labels inside shapes (e.g., [ ... ], { ... }, ( ... )).

npx -y @probelabs/maid --strict diagram.mmd

In strict mode, unquoted labels are flagged with FL-STRICT-LABEL-QUOTES-REQUIRED. Use double quotes and " for inner quotes.

Scanning Markdown and Directories

Maid validates:

Standalone Mermaid files (.mmd, .mermaid).
Markdown files with one or more Mermaid code fences (mermaid, mmd, or ~~~mermaid).
Entire directories (recursively), finding Markdown/Mermaid files and validating all embedded diagrams.

Behavior

Keeps precise line/column positions relative to the original Markdown file by offsetting diagnostics from each fenced block.
“No Mermaid diagrams found” is considered success (exit code 0). Text mode prints a short note; JSON includes diagramCount: 0.
Exit code is 1 only when errors are present. Warnings do not fail.

CLI Options

--format, -f text|json
- text: human-readable snippets with carets (default)
- json: machine-readable output for CI/editors
--strict, -s
- Require quoted labels inside shapes; emits FL-STRICT-LABEL-QUOTES-REQUIRED when violated.
Autofix flags:
- --fix Apply safe auto-fixes (e.g., replace -> with -->, normalize inner quotes to ", add missing : in sequence message and notes, replace else with option in critical, insert missing end for blocks, fix direction keyword in subgraphs).
- --fix=all Apply safe + heuristic fixes (e.g., wrap unquoted labels with quotes where it’s unambiguous, close unclosed quotes/brackets in limited contexts). Heuristics are conservative but may be opinionated.
- --dry-run, -n Don’t write files; useful with single files.
- --print-fixed When combined with --fix* on a single file or -, print the fixed content to stdout instead of a diagnostic report.
Directory scan flags:
- --include, -I Glob(s) to include (repeatable or comma‑separated)
- --exclude, -E Glob(s) to exclude (repeatable or comma‑separated)
- --no-gitignore Do not respect .gitignore (default is to respect it)

Examples

# Validate Markdown containing multiple diagrams
npx -y @probelabs/maid README.md

# Lint all docs, respecting .gitignore
npx -y @probelabs/maid docs/

# Only Markdown/Mermaid under docs/content
npx -y @probelabs/maid docs/ -I "docs/content/**/*.md,docs/content/**/*.mmd"

# Exclude legacy docs and any *.draft.md files
npx -y @probelabs/maid docs/ -E "docs/legacy/**" -E "**/*.draft.md"

# Disable .gitignore filtering
npx -y @probelabs/maid docs/ --no-gitignore

# JSON report for CI
npx -y @probelabs/maid --format json docs/

JSON Output

Single file (diagram or Markdown):

{
  "file": "README.md",
  "valid": false,
  "errorCount": 1,
  "warningCount": 0,
  "diagramCount": 1,
  "errors": [
    { "line": 12, "column": 3, "severity": "error", "code": "SE-AND-OUTSIDE-PAR", "message": "…" }
  ],
  "warnings": []
}

Directory scan:

{
  "valid": false,
  "errorCount": 2,
  "warningCount": 1,
  "diagramCount": 5,
  "files": [
    { "file": "docs/good.md", "valid": true,  "errorCount": 0, "warningCount": 0, "errors": [], "warnings": [] },
    { "file": "docs/bad.md",  "valid": false, "errorCount": 2, "warningCount": 1, "errors": [ … ], "warnings": [ … ] }
  ]
}

CI/CD Integration

SDK Details

Looking for programmatic usage? The full SDK guide (examples, exports, and tips) is in docs/SDK.md. The top of this README includes a short SDK Quick Example for convenience.

GitHub Actions

Validate entire docs directory on every push/PR (Node 22.x):

name: Lint Mermaid Diagrams
on:
  push:
    branches: [ main ]
  pull_request:
    branches: [ main ]

jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - uses: actions/setup-node@v4
        with:
          node-version: '22.x'
          cache: 'npm'
      - name: Lint docs/
        run: npx -y @probelabs/maid docs/

Only lint files changed in a pull request:

name: Lint Changed Mermaid Files
on:
  pull_request:
    branches: [ main ]

jobs:
  lint-changed:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - uses: actions/setup-node@v4
        with:
          node-version: '22.x'
          cache: 'npm'
      - name: Get changed Mermaid/Markdown files
        id: changed
        run: |
          set -e
          base="${{ github.event.pull_request.base.sha }}"
          head="${{ github.sha }}"
          files=$(git diff --name-only --diff-filter=ACMR "$base"..."$head" -- \
            "**/*.md" "**/*.markdown" "**/*.mdx" "**/*.mmd" "**/*.mermaid")
          if [ -z "$files" ]; then
            echo "files=" >> "$GITHUB_OUTPUT"
          else
            # Space-separated list suitable for shell for-loop
            echo "files=$files" >> "$GITHUB_OUTPUT"
          fi
      - name: Lint changed files
        if: steps.changed.outputs.files != ''
        run: |
          # Install locally for faster repeated invocations
          npm i -D @probelabs/maid
          failed=0
          for f in ${{ steps.changed.outputs.files }}; do
            echo "Linting $f"
            npx maid "$f" || failed=1
          done
          if [ "$failed" -ne 0 ]; then
            echo "Linting failed for one or more files" >&2
            exit 1
          fi
      - name: No Mermaid files changed
        if: steps.changed.outputs.files == ''
        run: echo "No changed Mermaid/Markdown files. Skipping."

Pre-commit Hook

Lint only staged files, including Markdown files that contain Mermaid fences (```mermaid or ~~~mermaid):

#!/bin/sh
# .git/hooks/pre-commit
set -e

# Collect staged files (added/copied/modified/renamed)
STAGED=$(git diff --cached --name-only -z --diff-filter=ACMR)
[ -z "$STAGED" ] && exit 0

# Build lint list: .mmd/.mermaid, and Markdown files that contain Mermaid fences
LINT_LIST=""
while IFS= read -r -d '' f; do
  case "$f" in
    *.mmd|*.mermaid)
      LINT_LIST="$LINT_LIST\n$f" ;;
    *.md|*.markdown|*.mdx)
      if grep -Eq '^( {0,3})(```|~~~)[[:space:]]*(mermaid|mmd)([[:space:]]|$)' "$f"; then
        LINT_LIST="$LINT_LIST\n$f"
      fi
      ;;
  esac
done <<EOF
$STAGED
EOF

TMP=$(mktemp)
printf "%s\n" "$LINT_LIST" | sed '/^$/d' > "$TMP"
[ ! -s "$TMP" ] && { rm -f "$TMP"; exit 0; }

FAILED=0
while IFS= read -r FILE; do
  [ -z "$FILE" ] && continue
  echo "maid: $FILE"
  npx -y @probelabs/maid "$FILE" || FAILED=1
done < "$TMP"
rm -f "$TMP"

exit $FAILED

Architecture

Built from scratch with modern tooling for reliability and performance:

Chevrotain - Modern, fast parser framework (not 1990s Bison/Jison)
- Allows semantic validation without rendering
- Provides exact error locations and recovery
- Enables intelligent auto-fix suggestions
TypeScript - Type-safe implementation with great IDE support
Decoupled Design - Validation logic completely separate from rendering
Automated Testing - GitHub Actions CI on every commit
Render Guarantee - Our test suite validates against actual Mermaid rendering

Project Structure

├── src/
│   ├── core/
│   │   ├── router.ts         # Detects diagram type and routes
│   │   └── types.ts          # Shared types
│   ├── diagrams/
│   │   ├── flowchart/        # Flowchart lexer/parser/validation
│   │   ├── sequence/         # Sequence lexer/parser/validation
│   │   └── pie/              # Pie lexer/parser/validation
│   └── cli.ts                # CLI implementation
├── test-fixtures/
│   ├── flowchart/
│   │   ├── valid/
│   │   └── invalid/
│   └── pie/
│       └── valid/
└── scripts/
    ├── test-chevrotain.js    # Test runner
    ├── test-linter.js        # Alternate test runner
    └── compare-linters.js    # mermaid-cli comparison

Development

Build from Source

# Clone repository
git clone https://github.com/probelabs/maid.git
cd maid

# Install dependencies
npm install

# Build
npm run build

# Run tests
npm test

Experimental Renderer

Maid includes an experimental lightweight renderer for flowchart and pie diagrams. This renderer serves as a visual validation tool for our parser implementation.

Purpose:

Validate parser correctness by visually rendering diagrams
Identify parsing issues that are difficult to detect through other testing methods
Provide a lightweight alternative for basic diagram rendering (294KB vs Mermaid.js's 2.6MB)

Status:

⚠️ Experimental - Not intended for production use
Currently supports flowchart and pie diagrams
Primary goal is parser validation, not feature parity with Mermaid.js

Building the Browser Bundle:

npm run build:browser
# Generates site/maid/maid.bundle.js (294KB, 87KB gzipped)

Architecture:

Chevrotain parser for CST generation
Dagre.js for automatic graph layout
Custom SVG generation for shapes and edges
Pluggable design - Swap layout engines and output renderers

Pluggability:

The renderer uses a clean interface-based architecture that allows you to:

Use alternative layout engines (e.g., Graphviz DOT, D3 force-directed)
Generate different output formats (e.g., SVG, Canvas, DOT)

Example - Using a custom DOT renderer:

import { renderMermaid, DotRenderer } from '@probelabs/maid';

const result = renderMermaid(diagramText, {
  renderer: new DotRenderer()
});
// result.svg now contains Graphviz DOT format

Example - Custom layout engine:

import { renderMermaid, ILayoutEngine } from '@probelabs/maid';

class MyLayoutEngine implements ILayoutEngine {
  layout(graph: Graph): Layout {
    // Your custom layout algorithm
    return { nodes, edges, width, height };
  }
}

const result = renderMermaid(diagramText, {
  layoutEngine: new MyLayoutEngine()
});

Core Interfaces:

ILayoutEngine - Calculates node/edge positions from graph model
IRenderer - Generates output (SVG, DOT, etc.) from positioned layout

Implementations:

DagreLayoutEngine - Hierarchical layout using Dagre (default)
SVGRenderer - SVG output with Mermaid-like styling (default)
DotRenderer - Graphviz DOT format (example implementation)

See src/renderer/interfaces.ts for interface definitions.

Extending the Linter

Add a new module: src/diagrams/<type>/{lexer.ts,parser.ts,validate.ts}
Register in src/core/router.ts via header detection
Add fixtures under test-fixtures/<type>/{valid,invalid}
Build and verify: npm run build && node scripts/compare-linters.js <type>
Regenerate previews: node scripts/generate-preview.js <type>

Releasing

We publish to npm when a Git tag is pushed that matches the package version.

Rules

Tags must be in the form vX.Y.Z and match package.json’s version.

Steps

Bump version and tag: npm version patch|minor|major
Push with tags: git push --follow-tags
Release workflow builds, runs quick tests, and publishes to npm

Notes

Package includes only compiled out/, README, and LICENSE
Requires repository secret NPM_TOKEN (publish access)

Edge Cases Covered

Flowchart:
- Escaped quotes in labels (rejected)
- Double quotes inside single-quoted labels (rejected, mermaid-compat)
- Mismatched quotes inside labels (accepted, mermaid-compat)
- Link text outside pipes triggers warnings
Pie:
- Labels must be quoted (single or double quotes)
- Colon and numeric value are required for each slice
- title without colon is accepted (e.g., title "Pets"); title: is rejected by current mermaid-cli
- Current mermaid-cli may emit an error SVG instead of failing the process; our preview scripts detect this and surface the error text

Contributing

We welcome contributions! Please ensure:

All tests pass: npm test
100% mermaid-cli compatibility: npm run test:compare
Update test fixtures if needed
Regenerate previews: npm run generate:previews

License

ISC

Built with ❤️ for developers who care about documentation quality.

maid

Installation

Reviews

Documentation

Maid

Why Maid?

Quick Start

SDK Quick Example

MCP Server for AI Assistants

Quick Setup for Claude Code

MCP Tool: validate_mermaid

Example Usage in Conversations

Using as an SDK

Browser Usage with Mermaid.js-Compatible API

Rendering Diagrams (Experimental)

Renderer Parity / Visual Comparison

Development

Parsing Parity Quick Loop

Autofix in a nutshell

Directory Scans: Include/Exclude and .gitignore

Why Maid Exists

The AI Challenge

The Validation Gap

The Maid Solution

Supported Diagrams (today)

What It Catches

❌ Common Errors

⚠️ Best Practice Warnings

Testing & Validation

Roadmap & Support

Testing / CI

Releasing

Error Codes

Autofix Support

Autofix

CLI Output Formats

Strict Mode

Scanning Markdown and Directories

CLI Options

JSON Output

CI/CD Integration

SDK Details

GitHub Actions

Pre-commit Hook

Architecture

Project Structure

Development

Build from Source

Experimental Renderer

Extending the Linter

Releasing

Edge Cases Covered

Contributing

License

Tags

Security Checklist

MCP Tool: `validate_mermaid`