Edit:

This repo is setup with a serverless function that just returns {"message":"Hello World!"}

When I hit http://localhost:3000/api/hello I would expect to see my console.logs and debugger breakpoints in my chrome debugger which I open by clicking this

However, I get the following output in my CLI

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🐚 NODE_OPTIONS='--inspect' vercel dev
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Debugger listening on ws://127.0.0.1:9229/35b6777e-d127-49fe-a43b-da3872639b3d
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For help, see: https://nodejs.org/en/docs/inspector
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Vercel CLI 39.2.5
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> Ready! Available at http://localhost:3000
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Starting inspector on 127.0.0.1:9229 failed: address already in use
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This is a log message from the serverless function
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Starting inspector on 127.0.0.1:9229 failed: address already in use

Does it work if you switch to a different port? There's an example of how to do that in this guide: Access local servers and Chrome instances with port forwarding

This did not fix the issue. I did modify my command to use NODE_OPTIONS="--inspect-brk" and the chrome debugger will halt execution here.

However, this looks like internal vercel code. I cannot get the debugger; statement I put in my hello.ts file to work as a breakpoint. It seems like node wants to do something but I continue to get this message in my console

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Starting inspector on 127.0.0.1:9229 failed: address already in use

Just soft-bumping this issues to get some community comments.

What is the debugging experience for other devs that use the vercel cli? Are other people using Chrome's built-in debugger or something in VS Code or another technique?