What's new in Mermaid Studio 2026.2.4?

Last updated: May 1, 2026

2026.2.4 Release Notes

This release is largely a class diagram overhaul. Inline documentation, inlay hints, a full structure view with package grouping, gutter icons, live templates, smarter completions, two new intentions, and additional supported syntax forms all land for class diagrams. Outside class diagrams, Enter-key brace expansion is now available in every edition across every brace-using diagram type, and the default formatter indent has been flipped to one level below the diagram-type keyword to match upstream Mermaid layout.

Highlights

Inline documentation

Hover or press F1 Control + Q on any class, namespace, classDef style, statement keyword, relationship arrow, or stereotype annotation to see a structured popup. Class popups list members, inheritance, implementations, and applied styles; type names in member rows that resolve to a class declared in the same file render as clickable links that open the popup for that class.

Visibility and modifier inlay hints

Optional inlay hints spell out member visibility (+ / - / # / ~) and modifiers (*, $) as words at the start of each member line. The hints are off by default; enable them under Settings > Editor > Inlay Hints > Mermaid Class Diagram.

Class diagram with inlay hints rendering plus, minus, hash, and tilde sigils as public, private, protected, and package keywords

Structure view

The Structure tool window now renders class diagrams as a tree of classes, namespaces, notes, styles, and relationships, with member-visibility badges and dedicated icons for each row type. An optional Package toggle groups classes by their dotted-id prefix, so a diagram with com.billing.Invoice-style names reads like a Java package tree.

Gutter icons for inheritance and realization

Inheritance and realization relationships now appear as gutter icons on the parent and subclass/implementer declarations. Click an icon to jump straight between the related classes.

Live templates

A new set of live templates scaffolds class declarations, annotations, namespaces, notes, and relationships. Type a short abbreviation (clsi for an interface, cls for a plain class, relreal for realization, relinh for inheritance, nfc for a note for ..., etc.) and the template surfaces in completion. Relationship templates use class-name completion for both endpoints, so building a hierarchy never requires retyping a class id.

Smarter completions

Relationship operator completion now offers every combination of arrowheads and line styles, including bidirectional forms like <|--|>, <-->, and o--o, and asymmetric mixes like <|-->. Type a partial operator and the popup filters by prefix.

Relationship operator completion showing every bidirectional and asymmetric form

Cardinality slots offer presets like 1, 0..1, 1..*, *, n, many, and one or more; free-form text still works, since completion is a convenience rather than a constraint.

Cardinality completion presets inside a relationship's quoted cardinality slot

Click, link, and callback statements also get context-appropriate completions for href / call, link-target keywords, and the full upstream tooltip and call-arg grammar.

Quick fixes and intentions

Two new code intentions land for class diagrams:

Add class declaration — for any class that’s referenced but never declared (in a relationship, style/cssClass target, click/link/callback, or note), creates a declaration in the right place.
Merge class declarations — when a class is declared more than once across the file, consolidates every declaration into the one under the caret.

Add class declaration intention bulb on an unresolved class reference

A separate inspection now warns when a style or cssClass statement targets a class declared later in the file, with a quick fix to move the statement after its target.

New syntax forms recognized

Standalone class annotations — <<interface>> ClassName on its own line.
Inline class annotations — class ClassName <<interface>> and class Foo <<interface>> { ... } (Mermaid 11.14.0+).
Notes inside namespace bodies — note "..." and note for X "..." are now valid inside namespace { ... } (Mermaid 11.13.0+).
Bidirectional and asymmetric relationships — <|--|>, <-->, o--o, <|-->, etc.

Each form is version-gated: the grammar always accepts it (so editor features stay on while you experiment), but if the configured runtime predates the form, you get a clear error explaining the minimum required Mermaid version.

Flat-id reference resolution

Class reference resolution now matches upstream Mermaid’s flat-id semantics: dots in class names are literal characters, namespace association comes solely from enclosing namespace { ... } blocks, and references resolve by exact text. Dotted identifiers in style statements are now a parse error, matching upstream. Three previously-shipped namespace-qualified-reference inspections were removed (the underlying problems no longer exist), and the duplicate-class inspection was renamed to Class declaration namespace conflict with a tighter rule.

Cross-cutting changes

Enter brace expansion in every edition

Pressing Return Enter inside { } now expands to a multi-line block in every brace-using diagram type, in all editions (Free, Core, Studio). The closing brace lands at the parent line’s indent and respects your code-style indent options.

Default formatter indent flipped to 1

Default base indent is now 1 across Sequence, Class Diagram, Gantt, Timeline, Requirement, XY Chart, Architecture, Flowchart, Block, C4, Git Graph, Mindmap, Ishikawa, and ER. Content sits one level below the diagram-type keyword by default, matching upstream Mermaid layout. If you preferred the old flush-left output, the indent is configurable per diagram type under Settings > Editor > Code Style > Mermaid.

After upgrading, reformatting will indent existing diagrams by one level. Use Reformat Code ( Option + Command + L Control + Alt + L ) to apply the new layout, or set the diagram type’s base indent back to 0 to keep the previous behavior.

Preview zoom shortcuts

Command + 0 Control + 0 fits the diagram to the preview viewport and Command + Shift + 0 Control + Shift + 0 resets the zoom to 100%. Both shortcuts work whether your focus is on the source editor or the preview pane, so you can re-fit without clicking away from where you’re typing. The on-screen zoom toolbar tooltips now display each shortcut hint, and the bindings stay accurate if you remap them under Settings > Keymap.

The preview’s pan/zoom keyboard handler now requires the platform-native modifier (Cmd on macOS, Ctrl elsewhere) for + / - zoom in/out. Plain +, -, 0, and 1 no longer trigger zoom, so they don’t compete with typing during inline edits. Cmd/Ctrl+wheel zoom is also OS-aware now (was previously either modifier on any platform). Arrow-key pan is unchanged.

Preview fixes

Smooth trackpad pan on Linux and Windows — diagonal two-finger pan no longer lags behind the gesture
No more edit-time render flicker — the visible diagram is no longer torn down at the start of every render
Auto live preview background fixed — inconsistent Auto behavior when setting the live preview background has been resolved
Selection follows undo/redo — undoing back through edits keeps no longer results in a stale selection in the live editor

Added

Class diagram navigation, find-usages, and rename now reach class identifiers in generic positions (List~Foo~, Map~K, V~, multi-word My Pair), with rename preserving any trailing ~T~ suffix
Class diagram inline documentation: hover and quick-doc popups for classes, namespaces, classDef styles, statement keywords, UML relationship arrows, and stereotype annotations, with clickable type and class-name links
Class diagram visibility and member-modifier inlay hints (opt-in, default off) that spell sigils like +, -, *, $ out as words
Class diagram structure view with a tree-style class / namespace / note / style / relationship hierarchy, member visibility badges, and an optional Package toggle that groups classes by their dotted-id prefix
Class diagram persistent element selection in edit mode (lays the foundation for upcoming class diagram style pane and live editor actions)
Class diagram inspection that flags a bare class identifier on its own line as unused
Class diagram intention to merge every declaration of a class into the one under the caret
Class diagram support for an inline annotation + body on a class declaration (class Foo <<interface>> { ... }, Mermaid 11.14.0+)
Class diagram future-syntax warning for namespace Foo ["Display Name"] { ... }
Additional class diagram contextual completions
Class diagram type highlighting now distinguishes built-in types from primitives, gives declared classes precedence over the type vocabulary, and resolves generic parameters against the owning class
Class diagram highlighting now spans free-form member lines that don’t match the structured grammar
Class diagram lollipop interface labels are now first-class class references for navigation, gutter icons, and intention placement
“Add class declaration” intention for implicitly-referenced classes in class diagrams, and matching quick fix behavior for unresolved classes in style/cssClass statements
Class-diagram inspection that warns when a style or cssClass statement targets a class declared later in the file, with a quick fix to move the statement to the end
Class-diagram completions for class references (in relationships, style/cssClass targets, click/link/callback/note statements, and at statement start for new relationships or inline member declarations), CSS property names in classDef and style property lists, and CSS class names in the cssClass statement name position
Class-diagram support for standalone class annotation statements (<<interface>> ClassName) and, on Mermaid 11.14.0+, inline class annotations (class ClassName <<interface>>), with an inspection that flags unresolved or forward-referenced classes in annotation statements and a version-gated error for the inline form on older runtimes
note support inside class-diagram namespace bodies, with a version-gated error when the runtime is older than Mermaid 11.13.0
Class-diagram rename validator that accepts dotted and backtick-quoted identifiers where Mermaid permits them
Class-diagram gutter icons for inheritance and realization relationships, with click-through navigation between parent and subclass/implementer declarations
Class-diagram contextual live templates for class declarations, annotations, namespaces, notes, and relationships
Preview Fit (Cmd/Ctrl+0) and Actual Size (Cmd/Ctrl+Shift+0) keyboard shortcuts that work from either the source editor or preview pane, with shortcut hints shown in the preview toolbar tooltips
Localized live-preview and markdown-preview UI strings (zoom toolbar tooltips, empty-diagram placeholder, copy/show-source/popout actions) into German, Japanese, Korean, and Chinese

Changed

Default formatter base indent flipped to 1 across Sequence, Class Diagram, Gantt, Timeline, Requirement, XY Chart, Architecture, Flowchart, Block, C4, Git Graph, Mindmap, Ishikawa, and ER, so content sits one level below the diagram-type keyword by default. Configurable per diagram type under Code Style.
Class diagram highlighting palette refresh: relationship labels render as strings, annotation delimiters and inner text share one color, ::: styles as an operator, and visibility/abstract/static modifiers share the keyword color
Class diagram empty-namespace check moved from a hard error to a user-disable-able inspection; note-only namespaces are no longer flagged
Class diagram CSS dash-name error now fires only when the offending property is the first in the list, matching upstream’s actual parse-failure behavior
Replaced the generic property icon with a dedicated metadata icon (gray lowercase m) for title, accTitle, accDescr, and direction entries in structure view and navbar
Class-diagram class-name completions now use annotation-derived icons (interface, abstract, enum, service) matching the structure view, instead of a generic node icon
Trimmed redundant keyword prefixes and kind hints from structure-view rows across flowchart, requirement, venn, block, and architecture
Class-diagram class reference resolution now matches upstream Mermaid’s flat-id semantics: dots in class names are literal characters, namespace association comes solely from enclosing namespace { ... } blocks, and references resolve by exact text. Dotted identifiers in style statements are now a parse error. The three namespace-qualified-reference inspections were removed and the duplicate-class inspection was renamed to Class declaration namespace conflict with a new rule (see Added).
Class-diagram keyword recognition is now case-sensitive, matching upstream Mermaid: capitalized variants like Class, Note, Style lex as identifiers, so multi-word names like class Class Name {} parse normally. The contrast in syntax-highlight color (lowercase keyword vs. identifier) tells the typo-vs-intentional story at a glance.
Class-diagram direction is recognized at parse time rather than via a lexer keyword, so a class can be named direction (also as the leading word of a multi-word name like class direction Foo) without backtick quoting. direction <value> still parses as a direction statement when the value is TB/BT/LR/RL; otherwise it falls through to a dangling-class-ref or a multi-word identifier, matching upstream’s “the entire line is a direction statement only when the pattern is present” semantics.
Class-diagram stray ; outside a class body is now flagged as a parse error, matching upstream’s lexical error.
Improved class-diagram syntax guide
Class-diagram attribute/method name-conflict inspection demoted to a weak warning, off by default
Improved “enter inside braces” support for diagram types that already implement brace matching
Preview zoom in/out keys now require the platform-native modifier (Cmd on macOS, Ctrl elsewhere) to avoid interfering with typing during inline edits

Removed

Cardinality validation inspection in class diagrams (replaced by the new cardinality completion presets)
“Add CSS class name” intention in class diagrams

Fixed

Preview: smooth trackpad and mouse momentum pan on Linux and Windows
Preview: eliminated edit-time render flicker; the visible diagram is no longer torn down at the start of every render
Preview: fixed AUTO theme background inconsistency
Preview: selection now follows undo/redo
Preview: edit-mode tooltip now points to the correct documentation URL
Class diagram: relationship label terminates at ;, matching upstream
Class diagram: a stray token at file-level no longer abandons the rest of the file
Class diagram: parse errors inside a class or namespace body no longer propagate to sibling statements
Class diagram: unrecognized member declarations now keep their highlighting instead of falling through as parse errors
Class diagram: stray ; outside a class body is now flagged as a parse error, matching upstream
Class diagram: trailing content on the same line as a class or namespace body’s closing } is now flagged as a parse error
Requirement diagram: empty requirement and element bodies no longer grow a blank line on every reformat
ER diagram: accDescr { ... } blocks now reformat idempotently; accessibility nodes also preserve their source order in the structure view
Hover highlight clears when inline edit opens in the preview, instead of lingering behind the textarea

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