Reference

Lookup pages: what each rule, flag, config key and type is, with no tutorial on the way. Each page links to the guide that shows it in use.

Page	What it lists
Rules	Every built-in rule, with its examples drawn before and after --fix
Command line	Every flag, the exit codes, the error codes and the output formats
Config file	The config keys, rule settings and rule options
Document model	The parsed file every rule reads: diagrams, style directives and stats
Plugin API	The plugin contract, findings, edits and the testing helpers
Library API	Every export of the package, for use from code
Changelog	What changed in each release, and what is not yet released

Rules at a glance

Rule	Category	Autofix	Reports
parse-diagram-unparseable	parse	no	A diagram mermaid's parser rejects
parse-fence-unterminated	parse	yes	A mermaid fence that is never closed
complexity-node-count-hard-limit	complexity	no	More nodes than the preset's hard limit
complexity-node-count-cognitive-limit	complexity	no	More nodes than a reader can follow, above the cognitive limit
complexity-node-count-acceptable-exceeded	complexity	no	More nodes than the preset's readable threshold
complexity-visual-score-critical	complexity	no	A visual complexity score above the preset's complex threshold
complexity-visual-score-acceptable-exceeded	complexity	no	A visual complexity score above the preset's readable threshold
complexity-subgraph-nesting-too-deep	complexity	no	Subgraphs nested three or more levels deep
contrast-text-below-aa	contrast	yes	Label text below 4.5:1 against its fill
contrast-border-below-ui-minimum	contrast	no	A border below 3:1 against its fill
contrast-directive-unauditable	contrast	no	A style directive whose contrast cannot be audited

Requirements and compatibility

Need	What is supported
Runtime	Bun, or Node >=20, the engines field of package.json
Mermaid	The mermaid package pinned at 11.17.2, because sequence diagram colours change between releases, and @mermaid-js/parser, both installed with this package
TypeScript local rules	Bun, through bunx --bun @jpeakai/mermaidjs-lint, or Node 22.18 or newer (23.6 or newer on Node 23)

npm ls mermaid in your project prints the mermaid version a run uses. A host such as GitHub draws diagrams with its own mermaid version. A diagram type newer than the host's mermaid may parse here and still fail to draw there.

Each diagram type is read by one of two parsers, and the parser_used field of its stats says which:

Parser	Diagram types
Langium, from @mermaid-js/parser	architecture, info, pie, gitGraph, packet, radar, treemap, treeView and wardley
Mermaid core, under a DOM shim	Every other type mermaid registers, such as flowchart, sequenceDiagram, classDiagram, stateDiagram and erDiagram

The types are named as mermaid's own detection names them. Mermaid detects some only by their -beta keyword, such as radar-beta, treeView-beta and wardley-beta. A Langium type that its grammar rejects is tried again under mermaid core before it is reported.

Versioning

The package follows semantic versioning. While it is at 0.x, a minor release may break the public surface, and a patch release does not.

The public surface is:

• The rule ids, and the category each rule belongs to.
• The --json output shape.
• The exit codes and error codes.
• The plugin contract, versioned by meta.apiVersion. A contract change that breaks a plugin raises it, and a plugin built for the old version fails to load with both numbers.
• The types and functions the package exports.

Finding message text is not part of it, so match on the rule id, not the message.

Changelog

CHANGELOG.md lists the user-visible changes in each release. These pages are published with each release, so they describe the latest release on npm. A change on main that is not yet released is listed under Unreleased in the changelog. mermaidjs-lint --version prints the version you run, and releases up to 0.1.1 lack the flag.