Unable to start mcp-inspector using the command "npx @modelcontextprotocol/inspector"

[GildeshAbhay]

Iam getting this error below:-

Starting MCP inspector...
⚙️ Proxy server listening on localhost:6277
🔑 Session token: 27725d1d7c87319b32c58e0b073314aa31dbe7f48097a36435dbd7b98c43e8c2
   Use this token to authenticate requests or set DANGEROUSLY_OMIT_AUTH=true to disable auth

🚀 MCP Inspector is up and running at:
   http://localhost:6274/?MCP_PROXY_AUTH_TOKEN=27725d1d7c87319b32c58e0b073314aa31dbe7f48097a36435dbd7b98c43e8c2

🌐 Opening browser...
node:internal/child_process:420
    throw new ErrnoException(err, 'spawn');
          ^

Error: spawn UNKNOWN
    at ChildProcess.spawn (node:internal/child_process:420:11)
    at Object.spawn (node:child_process:754:9)
    at baseOpen (file:///C:/Users/abhay.saini/AppData/Roaming/npm/node_modules/@modelcontextprotocol/inspector/node_modules/open/index.js:244:34)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5) {
  errno: -4094,
  code: 'UNKNOWN',
  syscall: 'spawn'
}

Node.js v22.17.1
Error:
🚀 MCP Inspector is up and running at:
   http://localhost:6274/?MCP_PROXY_AUTH_TOKEN=27725d1d7c87319b32c58e0b073314aa31dbe7f48097a36435dbd7b98c43e8c2

🌐 Opening browser...
node:internal/child_process:420
    throw new ErrnoException(err, 'spawn');
          ^

Error: spawn UNKNOWN
    at ChildProcess.spawn (node:internal/child_process:420:11)
    at Object.spawn (node:child_process:754:9)
    at baseOpen (file:///C:/Users/abhay.saini/AppData/Roaming/npm/node_modules/@modelcontextprotocol/inspector/node_modules/open/index.js:244:34)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5) {
  errno: -4094,
  code: 'UNKNOWN',
  syscall: 'spawn'
}

Node.js v22.17.1

Failed with exit code: 1
    at Object.error (C:\Users\abhay.saini\AppData\Roaming\npm\node_modules\@modelcontextprotocol\inspector\node_modules\spawn-rx\lib\src\index.js:314:27)
    at ConsumerObserver.error (C:\Users\abhay.saini\AppData\Roaming\npm\node_modules\@modelcontextprotocol\inspector\node_modules\rxjs\dist\cjs\internal\Subscriber.js:124:33)
    at Subscriber._error (C:\Users\abhay.saini\AppData\Roaming\npm\node_modules\@modelcontextprotocol\inspector\node_modules\rxjs\dist\cjs\internal\Subscriber.js:84:30)
    at Subscriber.error (C:\Users\abhay.saini\AppData\Roaming\npm\node_modules\@modelcontextprotocol\inspector\node_modules\rxjs\dist\cjs\internal\Subscriber.js:60:18)
    at Subscriber._error (C:\Users\abhay.saini\AppData\Roaming\npm\node_modules\@modelcontextprotocol\inspector\node_modules\rxjs\dist\cjs\internal\Subscriber.js:84:30)
    at Subscriber.error (C:\Users\abhay.saini\AppData\Roaming\npm\node_modules\@modelcontextprotocol\inspector\node_modules\rxjs\dist\cjs\internal\Subscriber.js:60:18)
    at Object.next (C:\Users\abhay.saini\AppData\Roaming\npm\node_modules\@modelcontextprotocol\inspector\node_modules\spawn-rx\lib\src\index.js:286:26)
    at ConsumerObserver.next (C:\Users\abhay.saini\AppData\Roaming\npm\node_modules\@modelcontextprotocol\inspector\node_modules\rxjs\dist\cjs\internal\Subscriber.js:113:33)
    at Subscriber._next (C:\Users\abhay.saini\AppData\Roaming\npm\node_modules\@modelcontextprotocol\inspector\node_modules\rxjs\dist\cjs\internal\Subscriber.js:80:26)
    at Subscriber.next (C:\Users\abhay.saini\AppData\Roaming\npm\node_modules\@modelcontextprotocol\inspector\node_modules\rxjs\dist\cjs\internal\Subscriber.js:51:18) {
  exitCode: 1,
  code: 1
}

Failed with exit code: 1

[cliffhall]

Hi @GildeshAbhay!

Can you try with the latest version using npx -y @modelcontextprotocol/inspector@latest and see if it makes a difference?

[GildeshAbhay]

same error @cliffhall

C:\Users\abhay.saini>docker run --rm --network host -p 6274:6274 -p 6277:6277 ghcr.io/modelcontextprotocol/inspector:latest
docker: error during connect: Head "http://%2F%2F.%2Fpipe%2FdockerDesktopLinuxEngine/_ping": open //./pipe/dockerDesktopLinuxEngine: The system cannot find the file specified.

Run 'docker run --help' for more information

C:\Users\abhay.saini>npx @modelcontextprotocol/inspector@latest
Need to install the following packages:
@modelcontextprotocol/inspector@0.16.6
Ok to proceed? (y) y

Starting MCP inspector...
⚙️ Proxy server listening on localhost:6277
🔑 Session token: fbcc04393331f5bb8285646dcc4aaece75fc50b181cc6a74bc6e49778f241502
   Use this token to authenticate requests or set DANGEROUSLY_OMIT_AUTH=true to disable auth

🚀 MCP Inspector is up and running at:
   http://localhost:6274/?MCP_PROXY_AUTH_TOKEN=fbcc04393331f5bb8285646dcc4aaece75fc50b181cc6a74bc6e49778f241502

🌐 Opening browser...
node:internal/child_process:420
    throw new ErrnoException(err, 'spawn');
          ^

Error: spawn UNKNOWN
    at ChildProcess.spawn (node:internal/child_process:420:11)
    at Object.spawn (node:child_process:754:9)
    at baseOpen (file:///C:/Users/abhay.saini/AppData/Local/npm-cache/_npx/9eac9498388ae25e/node_modules/open/index.js:244:34)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5) {
  errno: -4094,
  code: 'UNKNOWN',
  syscall: 'spawn'
}

Node.js v22.17.1
Error:
🚀 MCP Inspector is up and running at:
   http://localhost:6274/?MCP_PROXY_AUTH_TOKEN=fbcc04393331f5bb8285646dcc4aaece75fc50b181cc6a74bc6e49778f241502

🌐 Opening browser...
node:internal/child_process:420
    throw new ErrnoException(err, 'spawn');
          ^

Error: spawn UNKNOWN
    at ChildProcess.spawn (node:internal/child_process:420:11)
    at Object.spawn (node:child_process:754:9)
    at baseOpen (file:///C:/Users/abhay.saini/AppData/Local/npm-cache/_npx/9eac9498388ae25e/node_modules/open/index.js:244:34)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5) {
  errno: -4094,
  code: 'UNKNOWN',
  syscall: 'spawn'
}

Node.js v22.17.1

Failed with exit code: 1
    at Object.error (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\spawn-rx\lib\src\index.js:314:27)
    at ConsumerObserver.error (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:124:33)
    at Subscriber._error (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:84:30)
    at Subscriber.error (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:60:18)
    at Subscriber._error (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:84:30)
    at Subscriber.error (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:60:18)
    at Object.next (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\spawn-rx\lib\src\index.js:286:26)
    at ConsumerObserver.next (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:113:33)
    at Subscriber._next (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:80:26)
    at Subscriber.next (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:51:18) {
  exitCode: 1,
  code: 1
}

Failed with exit code: 1

C:\Users\abhay.saini>

[cliffhall]

@olaservo you use Windows a bit, right? Are you able to reproduce this locally on your machine?

[GildeshAbhay]

yes. yes iam
you want a screenshot of my cmd?

[cliffhall]

Seem like maybe your node cache might be munged.

npm cache clean --force
npm cache verify

[GildeshAbhay]

thanks cliff, will try

[GildeshAbhay]

tried but still got error

please find my trace below

C:\Users\abhay.saini>npm cache clean --force
npm warn using --force Recommended protections disabled.
npm notice
npm notice New major version of npm available! 10.9.2 -> 11.6.0
npm notice Changelog: https://github.com/npm/cli/releases/tag/v11.6.0
npm notice To update run: npm install -g npm@11.6.0
npm notice

C:\Users\abhay.saini>npm cache verify
Cache verified and compressed (~\AppData\Local\npm-cache\_cacache)
Content verified: 0 (0 bytes)
Index entries: 0
Finished in 0.02s

C:\Users\abhay.saini>npm install -g npm@11.6.0

added 1 package in 10s

25 packages are looking for funding
  run `npm fund` for details

C:\Users\abhay.saini>npx -y @modelcontextprotocol/inspector@latest
npm warn deprecated node-domexception@1.0.0: Use your platform's native DOMException instead
Starting MCP inspector...
⚙️ Proxy server listening on localhost:6277
🔑 Session token: 73c5ecb166cbdda3c1fe7548c03d3bfd5b89c25a0e173c6f92169aa83038db1c
   Use this token to authenticate requests or set DANGEROUSLY_OMIT_AUTH=true to disable auth

🚀 MCP Inspector is up and running at:
   http://localhost:6274/?MCP_PROXY_AUTH_TOKEN=73c5ecb166cbdda3c1fe7548c03d3bfd5b89c25a0e173c6f92169aa83038db1c

🌐 Opening browser...
node:internal/child_process:420
    throw new ErrnoException(err, 'spawn');
          ^

Error: spawn UNKNOWN
    at ChildProcess.spawn (node:internal/child_process:420:11)
    at Object.spawn (node:child_process:754:9)
    at baseOpen (file:///C:/Users/abhay.saini/AppData/Local/npm-cache/_npx/9eac9498388ae25e/node_modules/open/index.js:244:34)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5) {
  errno: -4094,
  code: 'UNKNOWN',
  syscall: 'spawn'
}

Node.js v22.17.1
Error:
🚀 MCP Inspector is up and running at:
   http://localhost:6274/?MCP_PROXY_AUTH_TOKEN=73c5ecb166cbdda3c1fe7548c03d3bfd5b89c25a0e173c6f92169aa83038db1c

🌐 Opening browser...
node:internal/child_process:420
    throw new ErrnoException(err, 'spawn');
          ^

Error: spawn UNKNOWN
    at ChildProcess.spawn (node:internal/child_process:420:11)
    at Object.spawn (node:child_process:754:9)
    at baseOpen (file:///C:/Users/abhay.saini/AppData/Local/npm-cache/_npx/9eac9498388ae25e/node_modules/open/index.js:244:34)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5) {
  errno: -4094,
  code: 'UNKNOWN',
  syscall: 'spawn'
}

Node.js v22.17.1

Failed with exit code: 1
    at Object.error (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\spawn-rx\lib\src\index.js:314:27)
    at ConsumerObserver.error (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:124:33)
    at Subscriber._error (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:84:30)
    at Subscriber.error (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:60:18)
    at Subscriber._error (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:84:30)
    at Subscriber.error (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:60:18)
    at Object.next (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\spawn-rx\lib\src\index.js:286:26)
    at ConsumerObserver.next (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:113:33)
    at Subscriber._next (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:80:26)
    at Subscriber.next (C:\Users\abhay.saini\AppData\Local\npm-cache\_npx\9eac9498388ae25e\node_modules\rxjs\dist\cjs\internal\Subscriber.js:51:18) {
  exitCode: 1,
  code: 1
}

Failed with exit code: 1