Spec42 SysML v2 Editor Screenshot

Spec42 VS Code Extension

This extension brings a practical SysML v2 and KerML editing experience to VS Code, powered by the spec42 language server. It is designed for day-to-day modeling work: writing models with live feedback, navigating large workspaces, visualizing model structure, and catching issues early while you edit.

If you are new to spec42, this is the recommended starting point. Published extension builds include the language server binary, so most users can install the extension and begin modeling without separate CLI setup.

Highlights

rich language support for .sysml and .kerml
workspace-first diagnostics, navigation, and symbols (background workspace indexing by default)
configurable library indexing with spec42.libraryPaths
bundled SysML standard library support via the spec42 server
snippets, semantic tokens, Model Explorer, and Model Visualizer
graphical views for structure, interconnections, actions, and state transitions
bundled server binary in published builds for simpler onboarding

What You Can Do With It

Author models efficiently with completion, snippets, hover details, semantic highlighting, and editing assists.
Catch quality issues early with live diagnostics while you work; the status bar and Validate Model reflect the whole workspace when a folder is open.
Move confidently through large models with definitions, references, rename, symbols, call hierarchy, and type hierarchy.
Use multiple SysML v2 views: text editing for precision, Model Explorer for structure, and Model Visualizer for graphical understanding.
Scale to real projects by analyzing workspace files and configured libraries together.
Keep familiar editor ergonomics with formatting, code actions, linked editing, folding, and selection ranges where supported.

Supported SysML v2 Views (Current)

General View: a high-level structural view to quickly understand the main elements in a model and how they relate.
Interconnection View: a connection-focused view for inspecting parts, ports, and connectors across the system architecture.
Action Flow View: a behavior-oriented view for following control and data flow through actions in a process.
State Transition View: a lifecycle view that shows states and transitions so you can reason about system behavior over time.
Sequence View: a software-interaction view for Spec42 SequenceView models (lifelines and messages).
Browser, Grid, and Geometry Views: provisional standard-view renderers while upstream SysML graphical notation details settle.

Getting Started

Try It in 2 Minutes

Install the extension.
Open examples/timer/KitchenTimer.sysml.
Run SysML: Show SysML Model Explorer.
Run SysML: Open SysML Visualizer.
Optionally run spec42 check examples/timer/KitchenTimer.sysml for the same validation outside VS Code.

Standard Setup

Install the extension.
Open any .sysml or .kerml file.
Try examples/timer/KitchenTimer.sysml if you want a compact first model.
Optionally configure spec42.libraryPaths for custom library roots.
Use the command palette to open the Model Explorer or Visualizer when needed.

Useful commands:

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

Extension Settings

spec42.serverPath
- Path to the spec42 binary.
- Default: "spec42"
- Published builds prefer the bundled binary when this stays at the default.
spec42.libraryPaths
- Array of library-root paths.
- Files under these paths are indexed for hover, go-to-definition, references, and completion.
spec42.standardLibrary.enabled
- Legacy setting; reserved for future use. The standard library is bundled with the server.
spec42.standardLibrary.version
- Display-only hint for the bundled release; matches the embedded sysml.library in the server.
- Default: "2026-03"
spec42.workspace.maxFilesPerPattern
- Discovery cap per workspace folder and file type.
- Default: 500
spec42.startup.workspaceIndexing
- When to load the full workspace model for Model Explorer: background (default, short delay), eager (immediately), or lazy (active file only until you request workspace mode).
spec42.visualization.exportScale
- Scale factor used for PNG/SVG export.
- Default: 2

All SysML visualizer views use the shared diagram renderer (shared/diagram-renderer). Legacy SysML renderer fallback has been removed.

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

cd vscode && npm run build:webview

(media/webview/visualizer.js is gitignored.)

spec42.logging.verbose
- Enable verbose runtime logs.
- Default: false

Example settings.json:

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

Editor + CLI

The extension focuses on interactive editor workflows. For terminal workflows (automation, CI validation, and environment diagnostics), use the spec42 CLI. Both experiences share the same core analysis engine, so behavior stays consistent between local editing and automated checks.

Common CLI checks:

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

Troubleshooting

If the server cannot start, check spec42.serverPath and open SysML: Show SysML Output (Logs).
If libraries do not resolve, validate spec42.libraryPaths and compare with spec42 doctor.
If you want a CLI view of the same environment problems, run spec42 doctor.
For broader troubleshooting guidance, see docs/TROUBLESHOOTING.md.

AI assistants (Copilot, Cursor, …)

VS Code 1.99+ with Copilot Agent: four Spec42 Language Model Tools ship with this extension (#spec42Check, #spec42Doctor, #spec42ModelSummary, #spec42ExplainDiagnostic). No mcp.json required — tools call the bundled spec42 CLI.

Cursor and other hosts: use the spec42-mcp stdio server. See docs/AI-ASSISTANTS.md and docs/examples/mcp-vscode.json.

SysML v2 Editor

Elan8