Erratic debugging/breakpoint behavior with turbopack (and Cursor?)

[bernatfortet]

Link to the code that reproduces this issue

https://github.com/bernatfortet/reproduction-app

To Reproduce

In the reproduction app I've changed:

1. The script dev to use turbopack: "dev": "next dev --turbopack"
2. a .vscode/launch.json file and add what the Guides: Debugging page mentions to use for debugging with next.js
3. In src/app/page.tsx add a console log right below the Home function:

export default function Home() {
  console.log(`Add brakepoint in this line`)
  ...

4. Add a breakpoint to the console log

5. Refresh OR add a letter to the log and save.

Current vs. Expected behavior

Expected behavior: The breakpoint stops on the console log consistently on every refresh.

Behavior 1:

• Breakpoint works well, I click continue and it's fine.
• But if I change the text in the console it trigger behavior 2

Behavior 2:

• After reloading
• Breakpoint works well
• But when I "Continue" executing the code

- I'm sent to some cryptic part of the code

Behavior 3:

• After the breakpoint has been set, refreshing the page doesn't trigger anything.
• (is this because of caching?

Provide environment information

Node.js v23.3.0

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 23.5.0: Wed May  1 20:12:58 PDT 2024; root:xnu-10063.121.3~5/RELEASE_ARM64_T6000
  Available memory (MB): 32768
  Available CPU cores: 10
Binaries:
  Node: 23.3.0
  npm: 10.9.0
  Yarn: 1.22.22
  pnpm: N/A
Relevant Packages:
  next: 15.4.0-canary.43 // Latest available version is detected (15.4.0-canary.43).
  eslint-config-next: N/A
  react: 19.1.0
  react-dom: 19.1.0
  typescript: 5.8.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Turbopack

Which stage(s) are affected? (Select all that apply)

next dev (local)

Additional context

• Something tells me it's something related to this: https://github.com/microsoft/vscode-js-debug/pull/2223/files
• Or this: https://github.com/vercel/next.js/pull/76559/files#diff-bd5430ee7c51dc892a67b3f2829d1f5b6d223f0fd48b82322cfd45baf9f5e945
• other context here: [Windows] Server-side debugger doesn't stop in breakpoints after v15.0.3-canary.7 #73214 (comment)
• this happens on canary as well ^15.4.0-canary.43
• Cursor Version: 0.50.5
• VSCode Version: 1.96.2