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 is understood, not a lookalike subset.
• 🖼️ Diagrams you can edit — all nine standard views in authentic SysML v2 notation. Drag, resize, add, connect, rename — your changes flow straight back into the source text.
• 📚 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 set of diagnostics with one-click fixes, cross-file rename, and tidy auto-formatting.
• 🤖 AI-agent ready — VS Code AI agents can ask the extension real questions about your model and get grounded answers instead of guesses.
• 🔒 Private by default — zero telemetry. Nothing about you, your code, or your usage ever leaves your machine.
• 🌐 Runs in the browser too — the same language intelligence and the same editable diagrams on vscode.dev and github.dev, including a GitHub repository opened straight from the browser.
• ☕ Nothing to install — no Java, no PlantUML, no extra downloads. Everything ships inside the extension and runs locally.

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 — clean, element-per-line layout, 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, with automatic layouts — not PlantUML, no image server, no screenshots to regenerate. 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. Right-click a blank diagram surface to add an element with the view-specific icon-and-text menu; it lands in that diagram's exact model anchor. Right-click an element or port to choose only relationships valid from that source, then click a compatible target. Or hover an eligible graph endpoint and drag its visible connection dot: General packages set package ownership, definitions specialize definitions, usages redefine usages; Interconnection connects; Action Flow creates succession (or item flow from a pin); State Transition creates transitions; Sequence creates messages only between dashed lifeline-line points; Case creates includes. Incompatible drops are refused, and Geometry/Grid expose no relationship drag. Interconnection View ports keep their specialized drag-to-connect handles and top / right / bottom / left docking points, while selected connectors expose draggable endpoints for reconnection. Connectors draw below the parts and are smart-routed around them; container part frames stay translucent so the wiring beneath remains visible. Connector lines are movable: drag the hollow dot on a segment to add a waypoint, move a waypoint directly, or double-click one to remove it. Drag to rearrange, resize any node, and rename / add / delete elements; semantic changes go 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).

Your model in your CI pipeline

The same diagrams render outside VS Code, from a terminal or a build job — no editor, browser, or display server:

npx sysml-diagram export --file model.sysml --view iv --out docs/diagrams/iv.svg
npx sysml-diagram export --file model.sysml --all --out-dir docs/diagrams

And validate the model itself — the same diagnostics as the Problems panel, as text, JSON, SARIF for GitHub code scanning, or inline workflow annotations:

npx sysml-validate models/ --strict
npx sysml-validate models/ --format github

Both tools also ship inside this extension — no separate install needed. Run SysML: Copy Headless CLI Command from the command palette to put the ready-to-run command on your clipboard.

Standalone vector SVG with the full SysML notation (--view grv writes the Grid table as CSV), a --theme light palette for documentation, the OMG standard library bundled in, and a non-zero exit code when the model has errors so a pipeline can gate on it. It reads the diagram settings in .vscode/sysml/project.json and the committed per-view layout in .vscode/sysml/diagrams/, so a pipeline renders the diagram your team arranged — --auto-layout opts out.

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. (Desktop only — see below.)

In the browser

The extension works in VS Code for the Web — vscode.dev, github.dev, and any browser-hosted VS Code — with the full language server and the diagram preview, not a syntax-highlighting subset. Open a repository in the browser and you get completion, hover, diagnostics with quick fixes, cross-file navigation and rename, formatting, the outline, the AI-agent tools, and all nine editable diagram views. The bundled OMG standard library comes with the extension, so MassValue, Real, and everything else resolves with no setup.

Four things are desktop-only, because a browser gives an extension no filesystem or temp directory for them. Their commands are hidden in the browser rather than shown and failing:

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

Licenses & attribution

The extension itself is distributed under its own Freeware License — see the top-level LICENSE file.

The bundled sysml.library/ files are taken verbatim from the OMG SysML v2 Release (release tag 2026-04) and are licensed by their copyright holders under the Eclipse Public License v2.0, reproduced with the release notice in resources/sysml.library/ (LICENSE, NOTICE.md).

The extension bundles the following open-source components, each under its own license:

Full license texts ship inside each dependency in the packaged extension.

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.