VS Code shows “Unbound breakpoint” when setting breakpoints in Node.js core files under lib/internal

[Scoheart]

Node.js Version

v24.3.0

NPM Version

11.4.2

Operating System

Darwin Scohearts-MacBook-Pro.local 24.6.0 Darwin Kernel Version 24.6.0: Mon Jul 14 11:30:40 PDT 2025; root:xnu-11417.140.69~1/RELEASE_ARM64_T6041 arm64

Subsystem

Other

Description

When I try to debug Node.js core by setting breakpoints directly in files under lib/internal/* (opened from the Node.js source checkout) using VS Code, those breakpoints remain Unbound and never hit.

Minimal Reproduction

.vscode/launch.json

{
  "version": "0.2.0",
  "configurations": [
    {
      "type": "cppdbg",
      "request": "launch",
      "name": "lldb-node",
      "program": "${workspaceFolder}/out/Debug/node",
      "args": [
        "--inspect-brk=9229",
        "--import=${workspaceFolder}/mytest/register.mjs",
        "${workspaceFolder}/mytest/index.js"
      ],
      "cwd": "${workspaceRoot}",
      "environment": [
        {
          "name": "NODE_DEBUG",
          "value": "*"
        }
      ],
      "MIMode": "lldb"
    },
    {
      "name": "js-attach",
      "type": "node",
      "request": "attach",
      "port": 9229,
      "restart": true,
      "skipFiles": [],
      "smartStep": false
    }
  ],
  "compounds": [
    {
      "name": "C++ + JS",
      "configurations": [
        "lldb-node",
        "js-attach"
      ]
    }
  ]
}

Output

No response

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[avivkeller]

The node executable bundles all of its source files. Adding breakpoints to the lib folder, which, are the un-bundled files, won't do anything.

However, if you compile the node with https://github.com/nodejs/node/blob/main/BUILDING.md#loading-js-files-from-disk-instead-of-embedding, VSCode breakpoints will work.