SysMLv2 LSP Server

A standalone LSP server for SysMLv2 and KerML files, wrapping the OMG SysML-v2-Pilot-Implementation parser. Usable with any LSP-compatible editor.

Latest release: v0.1.0

sysmlv2-lsp-server.jar — pre-built fat JAR, ~30 MB. Requires Java 21+ (Eclipse Temurin).

No build needed — just download and point your editor at the JAR (see Quick Start below).

The SysMLv2 Standard Library is live-indexed at startup: the bundled sysml.library is extracted and added as an Xtext workspace folder, so it is parsed and linked the normal way. Implicit imports (Base, ScalarValues, Integer, String, Boolean, etc.) and inherited / implicit-specialisation features (Action::start, Action::done, ...) resolve correctly. The Pilot's .index.json provides O(1) namespace lookups within that path. Cost: a one-time ~45–60 s indexing on server boot (run the server as a long-lived singleton so this is paid once, not per session).

Why not a pre-computed startup snapshot? An earlier optimisation serialised the Xtext index to a binary file and loaded it in ~2 s. It stored only resource descriptions (exported names) — enough for plain name lookup but not for inherited-feature resolution, which needs the library resources to be real, linkable workspace resources. Result: start/done (and other inherited members) silently failed to resolve. It was removed in favour of live indexing.

Option B (future spike) — correct fast startup. If the boot cost must come down, snapshot the parsed+linked resources, not just names, via Xtext's binary resource storage (StorageAwareResource / ResourceStorageFacade) and reload those. That preserves full model fidelity (so inheritance works) while skipping re-parse/re-link. Not yet implemented; needs a spike to confirm it actually restores inherited resolution.

Prerequisites: Java 21+ (Eclipse Temurin)

Download the latest release JAR, then:

claude --plugin-dir /path/to/sysmlv2-lsp

Claude Code will automatically start the LSP server when you open .sysml or .kerml files. The server takes ~15-30 seconds to start (Java + Standard Library indexing).

Add the following to your opencode.json (project-level) or ~/.config/opencode/opencode.json (global), and adjust the JAR path:

{
 "$schema": "https://opencode.ai/config.json",
 "lsp": {
 "sysmlv2": {
 "command": ["java", "-Xmx2g", "-jar", "/absolute/path/to/sysmlv2-lsp-server.jar"],
 "extensions": [".sysml", ".kerml"]
 }
 }
}

See the OpenCode LSP documentation for additional options (env, initialization, disabled).

java -Xmx2g -jar sysmlv2-lsp-server.jar

The server communicates via stdio (JSON-RPC/LSP). Add -trace for protocol message logging to stderr.

Only needed if you want to modify the server. End users can use the pre-built JAR.

Additional prerequisites: Maven 3.9+, Git with submodule support

# 1. Clone with submodules
git clone --recurse-submodules <repo-url>
cd sysmlv2-lsp
# 2. Build the Pilot Implementation (10-20 min on first run)
./scripts/build-pilot.sh
# 3. Extract JARs + Standard Library to server/lib/
./scripts/extract-jars.sh
# 4. Build the LSP server fat JAR
cd server && ./gradlew shadowJar
# Output: server/build/libs/sysmlv2-lsp-server.jar (~30 MB)

Claude Code <── stdio/JSON-RPC ──> sysmlv2-lsp-server.jar
 ├─ KerMLExpressions (.kermlexpr)
 ├─ KerML (.kerml)
 ├─ SysML (.sysml)
 ├─ Standard Library (.index.json)
 └─ Xtext 2.38.0 LSP framework

Three Xtext languages are registered via ServiceLoader (META-INF/services/org.eclipse.xtext.ISetup):

1. KerMLExpressionsIdeSetup
2. CustomKerMLIdeSetup (adds hover documentation provider)
3. CustomSysMLIdeSetup (adds hover documentation provider)

Key implementation details:

• Custom launcher captures System.out before redirecting to prevent JSON-RPC stream corruption from Xtext log messages
• EMF SysMLPackage is explicitly registered (required in standalone mode; Eclipse uses plugin.xml extension points)
• Guice ServerModule is overridden to inject SysMLWorkspaceConfigFactory for Standard Library workspace folder injection
• PrecalculatedLibraryIndexProvider requires library files under a sysml.library/ directory path segment to locate .index.json
• Shadow JAR merges META-INF/services files across all dependencies

MIT — see LICENSE.

The fat JAR bundles LGPL-3.0 (Pilot Implementation), EPL-2.0 (Xtext, LSP4J), and Apache-2.0 (Guice, Guava) dependencies. See NOTICE for details.