MPS: Skill for Claude Code

Running MPS Root Nodes

Loading companion skills

Companion names in this skill are lazy dependencies: load only those relevant to the current task. If this skill came from an MCP server, use the host's skill loader to resolve the companion's unique discovered entry URI on the same host-assigned originating server. If the host has no server-backed skill loader, stop and report that limitation; do not silently fall back to a filesystem copy. If this skill came from a filesystem catalog, load the named sibling from that same catalog at <skills-root>/<skill-name>/SKILL.md, even if remote skill loaders are also available. Do not invent a tool name or server endpoint.

This skill covers the path from "an MPS root node exists in a model" to "a green IDE run / red stack trace in my hand," using only MCP tools. It targets user-level artifacts (DSL main-like roots, plain ClassConcept mains, test cases) — not launching MPS itself (the MPS / MPS (2nd inst.) configs are a different topic, see AGENTS.md or CLAUDE.md).

Critical Directives

• execute_run_configuration and get_run_configurations are provided both by MPS and IDEA. Use the ones provided by MPS for running MPS nodes/tests.
• mps_mcp_create_run_configuration accepts a root, an array of test roots, a model, or an array of models. A single root is one of four shapes: implements IMainClass, implements ITestCase, is another test root MPS test discovery recognizes (a GeneratorTest), or is a ClassConcept with a qualifying static main. One model alone stays a live JUnit config; any other set is a snapshot of the test roots present at creation. A model reference passed as nodeReference is rejected — pass it in modelReference. See references/create-and-execute.md.
• MAKE the module, not just the model, before running. Model MAKE regenerates source_gen but does not always compile into classes_gen; running launches bytecode, so a stale classes_gen silently runs old code. See references/compile-before-run.md.
• Keep configurationName stable across iterations. The tool replaces the existing config of the same <type>.<name> rather than creating duplicates — idempotent setup is the goal. Use distinct names only when you actually want parallel configs.
• Do not silently flip compileInMPS=false to true. Compile.None and JPS-compile settings are usually intentional (sandbox modules, externally-built modules, packaged libraries). Confirm with the user; otherwise take the IDEA MCP file-path fallback.
• Prefer the source-root path over generated-Java entry points. Source-root configs survive regeneration; file-path configs against source_gen only work while classes_gen is fresh.
• MPS MCP execute_run_configuration / get_run_configurations do not surface run points under source_gen. Use the IDEA MCP variants when you need a filePath+line launcher for generated Java.
• Reuse before you create. If the user already has a working run config, prefer get_run_configurations() + execute_run_configuration by its existing name — duplicates are pointless.