next-devtools-mcp discover_servers fails on Windows: "No running Next.js dev servers with MCP enabled found"

5 answers

• Best answerAgentArmorHQ teamTeam4d ago

  Status: fixed in the repo — the issue was closed as completed and a contributor pointed to PR #67 (opens external site) ↗. No release version is named in the thread, so update next-devtools-mcp to a build that includes PR #67 and retry discover_servers (general advice; the reporter was on ^0.2.1).

  The MCP endpoint itself was reachable: the reporter confirmed http://localhost:3000/_next/mcp/tools returned streaming JSON when called with Accept: text/event-stream, so next@16.0.0's built-in MCP (enabled by default) was responding. A commenter shared next-devtools MCP logs showing Error: Command failed: ps aux and explained that Windows has no ps like macOS; that diagnosis was not confirmed by the project.

  One commenter suggested pointing Cursor at the built-in endpoint instead of relying on discovery:

  jsonCopy to clipboard

  {
    "mcpServers": {
      "next-devtools": {
        "command": "npx",
        "args": ["-y", "next-devtools-mcp@latest"]
      },
      "nextjs-mcp-builtin": {
        "url": "http://localhost:3000/_next/mcp"
      }
    }
  }
  

  That commenter did not report whether it worked, and it only exposes get_project_metadata, get_errors, get_page_metadata, get_logs, and get_server_action_by_id — not nextjs_runtime. Another user applied the same config, saw both MCP servers listed in Cursor, but the agent failed to connect to the built-in URL server. Manually entering port and setting includeUnverified also did not help.

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• AgentArmorHQ teamTeam4d ago

  What @imdimasan tried on GitHub (Outcome unclear)

  Diagnosed the cause as Windows lacking ps, showing next-devtools MCP logs with Error: Command failed: ps aux, and suggested a .cursor/mcp.json config that adds the built-in URL MCP at http://localhost:3000/_next/mcp. No success was reported; the config only exposes five tools, not nextjs_runtime.

  Source: https://github.com/vercel/next-devtools-mcp/issues/56#issuecomment-3466555694 (opens external site) ↗

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• AgentArmorHQ teamTeam4d ago

  What a GitHub user tried on GitHub (Didn't work)

  Reproduced on Windows 11 with Node v20 and v25, next@16.0.0, and next-devtools-mcp ^0.2.1. Verified the MCP endpoint returns streaming JSON via Invoke-WebRequest http://localhost:3000/_next/mcp/tools -Headers @{Accept='text/event-stream'}, then ran discover_servers in Cursor, which returned "No running Next.js dev servers with MCP enabled found".

  Source: https://github.com/vercel/next-devtools-mcp/issues/56 (opens external site) ↗

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• AgentArmorHQ teamTeam4d ago

  What @AhmedNasr0 tried on GitHub (Didn't work)

  Applied the config suggested by commenter 4 (npx-based next-devtools server plus the built-in URL server). Cursor added both MCP servers, but the agent failed to connect to the built-in URL MCP.

  Source: https://github.com/vercel/next-devtools-mcp/issues/56#issuecomment-3466718926 (opens external site) ↗

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• AgentArmorHQ teamTeam4d ago

  What @MichaelJuskowicz tried on GitHub (Didn't work)

  Tried manually entering the port and setting includeUnverified for the next-devtools MCP server in Cursor, but could not get it working and was never able to use the nextjs_runtime tool.

  Source: https://github.com/vercel/next-devtools-mcp/issues/56#issuecomment-3458984385 (opens external site) ↗

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