SysML v2 for Visual Studio Code

A complete modeling environment for SysML v2 and KerML — language intelligence and live, editable diagrams, right inside your editor.

⚒️ Under Development ⚒️

Write SysML v2 and KerML the way you write code — with completion, hover, real diagnostics, refactorings, and go-to-definition — then see and edit your model as a diagram in the native SysML v2 graphical notation. The whole OMG standard library is built in, so import SI::* just works. No Java runtime, no PlantUML, no extra downloads. Everything runs locally and offline.

Why you'll like it

• 🎯 The full language, not a subset — every SysML v2 and KerML construct from the OMG specification, parsed by a real language server.
• 🖼️ Diagrams you can edit — all nine standard views in authentic SysML v2 notation, rendered on a React Flow canvas with SysML-specific vector nodes. Drag, resize, add, connect, rename — changes flow back to your source.
• 📚 The OMG standard library, bundled — Parts, ISQ, SI, Requirements, and the rest resolve out of the box, offline.
• 🧠 Editor intelligence everywhere — context-aware completion, rich hover, a documented diagnostic catalogue with one-click fixes, cross-file rename, and AST-based formatting.
• 🤖 AI-agent ready — server-backed language-model tools let VS Code AI agents reason about your model deterministically.
• 🔒 Private by default — zero telemetry. Nothing about you, your code, or your usage ever leaves your machine.
• ☕ No runtime to install — a pure TypeScript Langium language server. No JDK, no separate generator.

Quick start

1. Install the extension. The Get Started with SysML v2 walkthrough opens automatically (or run Welcome: Open Walkthrough…).
2. Open or create a .sysml file. The status bar reads "SysML: ready" once the bundled library is indexed.
3. Type sysml- and pick a scaffold — sysml-part-def, sysml-requirement, sysml-state-machine, and 40+ more.
4. Save — diagnostics appear in the Problems panel, and unambiguous cross-package imports are added for you.
5. Run SysML: Show Diagram (or the graph button in the editor title bar) to open the live, editable diagram. Ctrl+Alt+D toggles side / tab mode.

Language intelligence

• Syntax highlighting for .sysml and .kerml, including quantity literals (1500 [kg]), escaped names ('name with spaces'), and the full operator set (:>, :>>, ::>, **, ??, ===, hastype, as, ->, #( … ), .?, …).
• Smart completion — 45+ snippets, context-aware keyword / member / import / unit completion for every SysML and KerML construct, inline ghost-text suggestions, and signature help for calc / action / constraint calls.
• Hover — element kind, typing, plain-English multiplicity, relationship details, the modeled doc comment, library-function signatures, and a From standard library link straight into the bundled OMG sources.
• Diagnostics — a stable, documented catalogue (LEX / SYN / RES / SEM / SSM / KSM / UNIT / STYL / MIG families) with per-code severity overrides, dimensional analysis of quantity expressions, and a SysML v1 guardrail that maps block / «stereotype» idioms to their v2 constructs.
• Quick fixes & refactorings — add a missing import, &&→and, import…as…→alias, add a missing subject, convert def↔usage, extract to a new package, move to a new file, generate a verification case from a requirement, and more.
• Navigation — document outline (Ctrl+Shift+O), workspace symbols (Ctrl+T), cross-file go-to-definition (into the read-only library too), find references (including satisfy / verify targets), cross-file rename, document highlight, and go-to-declaration for aliases.
• Auto-import on save — unambiguous unqualified cross-package names get their import added automatically; ambiguous ones open a picker.
• Formatting — AST-based, element-per-line, with author-placed blank lines preserved (uses your editor.tabSize).
• Semantic tokens & inlay hints — definitions / usages / library symbols get distinct colors (a bundled SysML v2 Default theme is included; semantic highlighting is on by default), plus implicit-multiplicity and opt-in physical-dimension hints.
• CodeLens — N references on requirement defs, Run verification on verification-case defs (evaluates the case and reports pass/fail), and Show diagram on parts, states, actions, and cases.

Live, editable diagrams

A live view of your model in the SysML v2 graphical notation, rendered on a React Flow canvas with SysML-specific vector nodes and automatic layouts — not PlantUML, no image server. The extension offers only the canvas/table views that actually have content in the file you're looking at, and keeps the Browser View available as a panel.

• Editable. A view-specific toolbox at the canvas side adds elements and draws relationships with two clicks — connect, transition, succession, message, include, satisfy — each view offering its own tools. In the Interconnection View, ports behave as small boxes with top / right / bottom / left docking points, so connectors attach to a real port edge instead of one center point; hovering a port highlights just that port and reveals its connect dots, and selected connectors keep draggable endpoints for reconnection. Connectors draw below the parts and are smart-routed around them; container part frames are kept translucent so the wiring beneath stays visible, while leaf parts keep an opaque, readable body. Connector lines are movable: drag the hollow dot on any segment to bend it through a new waypoint, drag a waypoint to move it, or double-click to remove it — waypoints follow the active line style and stay glued to their ports/parts. Drag to rearrange, resize any node, and rename / add / delete elements; changes are applied through the language server with cross-file rename and a syntax-safety re-parse.
• Your layout, your repo. Positions, sizes, and connector waypoints persist under .vscode/sysml/diagrams/ — never in the .sysml text — so diagrams are git-friendly and the model stays text-only.
• Theme-aware. Every color adapts to your active VS Code theme (light, dark, high-contrast), with a redesigned toolbar of consistent theme-colored icons and a layout control tailored to each view's real options.
• Side panel or full tab — toolbar, Browser View panel on the left, toggleable properties inspector on the right, minimap, and SVG export. The BV and Properties toggles are arrow icons in the canvas's upper-left / upper-right corners in both modes. The side columns are resizable; the BV header shows a folder-tree icon plus Browser View in both modes, BV branches can be expanded/collapsed, and BV highlights the elements present on the current diagram. Toggle side/tab with Ctrl+Alt+D.
• Not sure which view you need? SysML: Which Diagram? recommends one from the question you want answered — and understands the SysML v1 names you already know (bdd, ibd, act, stm, sd, req, uc, pkg, par).

The OMG standard library, built in

The full official model library ships with the extension, so import Parts::*, import ISQ::*, and import SI::* resolve immediately — no separate download, no GitHub clone.

The library loads from a precomputed index at startup, so cold open is fast and nothing is parsed until you need it. Point at your own checkout with sysml.standardLibraryPath — it accepts an unzipped sysml.library/ tree, a .kpar archive, or a directory of .kpar archives. JSON abstract-syntax archives are projected to readable .sysml for indexing.

Works with your AI agents

The extension exposes a native VS Code language-model tool surface for agents that can use VS Code tools, including GitHub Copilot Chat / agent mode. These tools are contributed in the extension manifest, activate on demand, and are backed by the SysML language server instead of prompt-only guessing:

This is not a separate chatbot and it does not ship a model runtime, credentials, telemetry, an MCP server, or Claude/Codex-specific skill packages. Agents that consume VS Code language-model tools can discover these capabilities directly; agents that only consume MCP servers, standalone plugins, or their own skill format need a bridge before they can call the same deterministic SysML operations.

Archive & JSON interchange

Open and extract OMG .kpar package archives, and import / export SysML v2 abstract-syntax JSON through generated textual projections — all from the command palette or the Explorer context menu.

Private by default

This extension collects no telemetry and transmits nothing about you, your code, or your usage. There is no analytics SDK, no usage reporting, and no network calls beyond the local language server. That's a deliberate, privacy-first choice.

Reference

Attribution

The bundled sysml.library/ files are taken verbatim from the OMG SysML v2 Release under their LICENSE / LICENSE-GPL, reproduced inside resources/sysml.library/.

Built with Langium, vscode-languageclient, and React Flow.

Issues & feedback

The extension is being actively developed. If you have any feedback, feature suggestions or bug reports feel free to use the marketplace comment section.

Open an issue at https://github.com/voidaliot/sysml-v2-vscext-release/issues.