Spec42 SysML v2 Editor Screenshot

Spec42 VS Code Extension

Spec42 brings practical SysML v2 and KerML language tooling to VS Code. It is built around the same spec42 analysis engine used by the CLI, GitHub Action, HTTP API, and assistant integrations, so editor feedback and automated validation stay aligned.

Published Marketplace builds include the matching language server binary. Most users can install the extension, open a .sysml or .kerml file, and start modeling without a separate CLI setup.

Highlights

Live diagnostics, semantic highlighting, completion, hover, snippets, and formatting.
Definitions, references, rename, document symbols, call hierarchy, and type hierarchy.
Workspace-first indexing for multi-file models and configured libraries.
Model Explorer for structural navigation.
Model Visualizer for supported SysML v2 graphical views.
Bundled SysML standard-library support through the spec42 server.
Built-in Copilot Language Model Tools for validation and model inspection.

Getting Started

Install SysML v2 Editor from the Visual Studio Marketplace.
Open a .sysml or .kerml file.
Try examples/timer/KitchenTimer.sysml if you want a compact first model.
Run SysML: Show SysML Model Explorer to browse the model.
Run SysML: Open SysML Visualizer to inspect graphical views.

Useful commands:

SysML: Show SysML Model Explorer
SysML: Open SysML Visualizer
SysML: Refresh SysML Model Explorer
SysML: Refresh Visualization
SysML: Validate Model
SysML: Show SysML Output (Logs)

The Spec42 sidebar also includes example and library views for opening recommended sample workspaces and inspecting configured library state.

Supported Views

View	Purpose
General View	High-level structure and relationships across a model.
Interconnection View	Parts, ports, connectors, and architecture wiring.
Action Flow View	Control and data flow through actions in a behavior.
State Transition View	States and transitions for lifecycle-oriented behavior.
Sequence View	Lifelines and messages for Spec42 `SequenceView` models.
Browser, Grid, and Geometry Views	Provisional standard-view renderers while upstream SysML graphical notation settles.

All visualizer views use the shared diagram renderer from shared/diagram-renderer. The legacy SysML renderer fallback has been removed.

Extension Settings

Core settings:

Setting	Default	Purpose
`spec42.serverPath`	`spec42`	Path to the `spec42` server binary. Published builds prefer the bundled binary when this stays at the default.
`spec42.libraryPaths`	`[]`	Additional library roots indexed for hover, references, completion, and validation.
`spec42.workspace.maxFilesPerPattern`	`500`	Discovery cap per workspace folder and file type.
`spec42.startup.workspaceIndexing`	`background`	Controls when the full workspace model is loaded: `lazy`, `background`, or `eager`.
`spec42.visualization.exportScale`	`2`	Scale factor used for visualizer export.
`spec42.statusBar.enabled`	`true`	Shows Spec42 workspace status in the status bar.
`spec42.codeLens.enabled`	`true`	Enables Spec42 CodeLens actions where available.
`spec42.logging.verbose`	`false`	Enables verbose runtime logs.
`spec42.performanceLogging.enabled`	`false`	Emits performance-oriented logs for indexing and visualization diagnostics.
`spec42.debug`	`false`	Enables extension debug behavior for development and troubleshooting.

Standard-library settings are retained for compatibility and display:

Setting	Purpose
`spec42.standardLibrary.enabled`	Legacy setting; the standard library is bundled with the server.
`spec42.standardLibrary.version`	Display-only hint for the bundled SysML release.
`spec42.standardLibrary.repo`	Legacy metadata for the upstream release repository.
`spec42.standardLibrary.contentPath`	Legacy metadata for the release content folder.

Example settings.json:

{
  "spec42.libraryPaths": ["../SysML-v2-Release", "./my-company-sysml-library"],
  "spec42.startup.workspaceIndexing": "background"
}

Editor And CLI

The extension focuses on interactive modeling. For terminal workflows, CI, and environment diagnostics, use the spec42 CLI from a release archive.

spec42 doctor
spec42 check path/to/model-or-workspace
spec42 check path/to/model-or-workspace --format sarif

Both paths use the same analysis engine, so diagnostics should stay consistent between VS Code and automation.

AI Assistants

With VS Code 1.99+ and Copilot Agent, the extension ships four built-in Language Model Tools:

#spec42Check
#spec42Doctor
#spec42ModelSummary
#spec42ExplainDiagnostic

These tools call the bundled spec42 CLI; no mcp.json is required for the VS Code Copilot path.

For Cursor and other MCP hosts, use the spec42-mcp stdio server from the release archive. See AI assistant setup and the MCP configuration example.

Troubleshooting

If the server cannot start, check spec42.serverPath and open SysML: Show SysML Output (Logs).
If imports or library symbols do not resolve, check spec42.libraryPaths and run spec42 doctor.
If the Model Explorer looks incomplete, increase spec42.workspace.maxFilesPerPattern or run SysML: Refresh SysML Model Explorer.
If the visualizer appears stale, run SysML: Refresh Visualization and inspect the SysML output channel.

For broader guidance, see Troubleshooting.

Development

After changing shared/diagram-renderer or webview TypeScript, rebuild the visualizer bundle:

cd vscode
npm run build:webview

media/webview/visualizer.js is generated and gitignored.

SysML v2 Editor

Elan8