MPS: Skill for Claude Code

Opening and closing an MPS project for MCP

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.

There is no MCP tool that can open a project. The IntelliJ MCP server rejects every tool call — including mps_mcp_list_open_projects — before dispatch unless some already-open IDE Project matches projectPath. On the welcome screen that set is empty, so MCP cannot help. The workaround is the platform CLI: pass the project directory to a second MPS process that shares the first instance's config/system directories. DirectoryLock activates the running IDE; the second process should exit in a few seconds.

Critical Directives

• Empty Currently open projects: {"projects":[]} means the welcome screen, not a bad path. Do not retry MCP with a guessed projectPath. Open the project via CLI first.
• Detect source-vs-standalone before choosing a command. open -a MPS.app will not talk to an MPS started as jetbrains.mps.Launcher from a checkout. Reconstructing a JVM command is the wrong move for a standalone .app / mps.sh / mps64.exe.
• Match idea.paths.selector (and any explicit config/system dirs). MPS (2nd inst.) uses a different selector and starts a real second IDE. See references/detect-source-vs-standalone.md.
• Do not split process command lines on spaces. Classpaths often contain IntelliJ IDEA.app or Program Files. Prefer jcmd PID VM.command_line (or /proc/PID/cmdline on Linux). When activating an already-running instance, strip -agentlib:jdwp and the IntelliJ idea_rt.jar javaagent.
• java_command from jcmd VM.command_line is "<main-class> [args]". Use only the first token as the main class. If MPS was itself started with a project path, the field is jetbrains.mps.Launcher /path/to/previous/project; passing it whole dies with ClassNotFoundException.
• Do not write helper scripts or jcmd dumps into the checkout. Use $TMPDIR / %TEMP% only.
• A non-force MODAL_BLOCKED close is still pending (details.closePending: true). The close is already queued on the EDT and completes as soon as the user answers or closes the blocking dialog. Ask the user to dismiss the dialog, then check mps_mcp_list_open_projects before retrying mps_mcp_close_project. Use force=true only if the project is still open after a timed-out or cancelled close. A timed-out force close is withdrawn (closePending: false); check mps_mcp_list_open_projects.