Breaking change?

[jcavalieri]

All of a sudden, neither Claude Code nor Github Copilot can list the tools from the JetBrains MCP server.

These are my configurations:

~/.config/github-copilot/intellij/mcp.json

{
    "servers": {
        "jetbrains": {
            "command": "npx",
            "args": ["-y", "@jetbrains/mcp-proxy"]
        }
    }
}

~/.claude.json

      "mcpServers": {
        "jetbrains": {
          "type": "stdio",
          "command": "npx",
          "args": [
            "-y",
            "@jetbrains/mcp-proxy"
          ],
          "env": {}
        }
      },

[alok1111]

Same thing with the Amazon Q
~/.amazonq/mcp.json

{
  "mcpServers": {
    "jetbrains": {
      "command": "npx",
      "args": [
        "-y",
        "@jetbrains/mcp-proxy"
      ],
      "env": {},
      "timeout": 120000,
      "disabled": false
    }
  }
}

Looks like it stopped working after updating to:
IntelliJ IDEA 2025.2 (Ultimate Edition)
Build #IU-252.23892.409, built on August 1, 2025

[Cui-xf]

2025.2 bundles this plug-in, but the effect seems to be quite different from this repository. I am not sure whether the author will continue to update this repository code.

[jcavalieri]

Considering the Git history with the plugin, I wonder if this is a JetBrains IDE issue rather than a problem with the plugin itself.

Maxim Kolmakov (@MaXal) do you know?

[jcavalieri]

I think I have something working:

~/.config/github-copilot/intellij/mcp.json

{
  "servers": {
    "jetbrains": {
      "type": "stdio",
      "env": {
        "IJ_MCP_SERVER_PORT": "64342"
      },
      "command": "/Applications/RubyMine.app/Contents/jbr/Contents/Home/bin/java",
      "args": [
        "-classpath",
        "/Applications/RubyMine.app/Contents/plugins/mcpserver/lib/mcpserver-frontend.jar:/Applications/RubyMine.app/Contents/lib/util-8.jar",
        "com.intellij.mcpserver.stdio.McpStdioRunnerKt"
      ]
    }
  }
}

And I removed the previous one from Claude Code using claude mcp remove "jetbrains" -s user. You may need to use -s local if it is project-specific.

And then I did the following command:

claude mcp add -s user -t stdio -e IJ_MCP_SERVER_PORT=64342 jetbrains \
  /Applications/RubyMine.app/Contents/jbr/Contents/Home/bin/java \
  -- \
  -classpath \
  /Applications/RubyMine.app/Contents/plugins/mcpserver/lib/mcpserver-frontend.jar:/Applications/RubyMine.app/Contents/lib/util-8.jar \
  com.intellij.mcpserver.stdio.McpStdioRunnerKt

I couldn't get the pure SSE versions to work.

[jcavalieri]

Unfortunately, Claude is still not working with the MCP plugin. I tried both user and local configurations.

jetbrains:
  Scope: User config (available in all your projects)
  Status: ✗ Failed to connect
  Type: stdio
  Command: /Applications/RubyMine.app/Contents/jbr/Contents/Home/bin/java
  Args: -classpath /Applications/RubyMine.app/Contents/plugins/mcpserver/lib/mcpserver-frontend.jar:/Applications/RubyMine.app/Contents/lib/util-8.jar com.intellij.mcpserver.stdio.McpStdioRunnerKt -e IJ_MCP_SERVER_PORT=64342
  Environment:

[jcavalieri]

So, I think there is some quirk with the claude mcp add functionality.

I got it to work by directly adding this to my claude configuration

~/.claude.json

  "mcpServers": {
    "jetbrains": {
      "type": "stdio",
      "env": {
        "IJ_MCP_SERVER_PORT": "64342"
      },
      "command": "/Applications/RubyMine.app/Contents/jbr/Contents/Home/bin/java",
      "args": [
        "-classpath",
        "/Applications/RubyMine.app/Contents/plugins/mcpserver/lib/mcpserver-frontend.jar:/Applications/RubyMine.app/Contents/lib/util-8.jar",
        "com.intellij.mcpserver.stdio.McpStdioRunnerKt"
      ]
    }

[jcavalieri]

Ugh. 👎

Both Claude Code and CoPilot can see the 22 tools. But when they call them, it just hangs. 😢

[jcavalieri]

Maxim Kolmakov (@MaXal), we'll need your help.

[jcavalieri]

This might help:

 $ LOG_ENABLED=true IDE_PORT=64342 npx -y @jetbrains/mcp-proxy
Attempting to find a working IDE endpoint...
IDE_PORT is set to 64342. Testing this port.
Sending test request to http://127.0.0.1:64342/api/mcp/list_tools
Test request to http://127.0.0.1:64342/api/mcp/list_tools failed with status 404
Specified IDE_PORT=64342 but it is not responding correctly.
Failed to update IDE endpoint: Error: Specified IDE_PORT=64342 but it is not responding correctly.
    at findWorkingIDEEndpoint (file:///Users/jcavalieri/.npm/_npx/216f9f7f9928524d/node_modules/@jetbrains/mcp-proxy/dist/src/index.js:82:19)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)
    at async updateIDEEndpoint (file:///Users/jcavalieri/.npm/_npx/216f9f7f9928524d/node_modules/@jetbrains/mcp-proxy/dist/src/index.js:114:26)
    at async file:///Users/john_cavalieri/.npm/_npx/216f9f7f9928524d/node_modules/@jetbrains/mcp-proxy/dist/src/index.js:210:1

[jcavalieri]

👍 🥳

I thought I had tried this and it didn't work, but it is working now. Maybe I needed to restart sessions. I do know I did restart RubyMine after this configuration change. This works!

~/.claude.json

  "mcpServers": {
    "jetbrains": {
      "type": "sse",
      "url": "http://localhost:64342/sse"
    }
  }

~/.config/github-copilot/intellij/mcp.json

{
  "servers": {
    "jetbrains": {
      "type": "sse",
      "url": "http://localhost:64342/sse"
    }
  }
}

[jcavalieri]

And .... it stopped working. 👎

I think the issue might be that the MCP server stops responding.

[jcavalieri]

I have reverted to RubyMine Build #RM-251.27812.51, built on July 24, 2025, and restored my configurations. It appears to be related to the RubyMine update, which also changed the MCP Server plugin in some way.

[PtrZjc]

Just updated IntelliJ to Build #IU-252.23892.409, built on August 1, 2025 and all of sudden does not work. My current config:

"jetbrains": {
  "command": "npx",
  "args": [
    "-y",
    "@jetbrains/mcp-proxy"
  ]
}

The error I get is:

[2025-08-06 16:56:52.405][error]   [jetbrains]Failed to get tools list for MCP server jetbrains. message: MCP error -32603: No working IDE endpoint available. stack: McpError: MCP error -32603: No working IDE endpoint available.
    at Eoe._onresponse (/snapshot/copilot-client/node_modules/@modelcontextprotocol/sdk/src/shared/protocol.ts:464:21)

[hjed]

They moved to a different repo - apparently didn't think it was good idea to tell anyone that there was a breaking change. #16 (comment)

[jcavalieri-livefront]

Maybe it moved here? https://github.com/JetBrains/intellij-community/tree/master/plugins/mcp-server.

Maxim Kolmakov (@MaXal), Arthas (@bugstan), erdnax123, Sergey Ignatov (@ignatov),
Could any of you explain what is going on?