Spec42 VS Code Extension

This extension brings a complete 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 faster, navigating large workspaces, 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-aware diagnostics, navigation, and symbols
• 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.
• 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.

Getting Started

1. Install the extension.
2. Open any .sysml or .kerml file.
3. Try examples/timer/KitchenTimer.sysml if you want a compact first model.
4. Optionally configure spec42.libraryPaths for custom library roots.
5. 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.visualization.exportScale

  • Scale factor used for PNG/SVG export.
  • Default: 2

• 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.

Links

• Source and releases: https://github.com/elan8/spec42
• Issues: https://github.com/elan8/spec42/issues
• SysML v2: https://www.omg.org/sysml/sysmlv2/
• SysML v2 reference libraries: https://github.com/Systems-Modeling/SysML-v2-Release