how to debug constant 30% cpu usage in rsbuild dev

[scottbessler]

I'm converting my (rather large) project to rsbuild from webpack. I've got it working well. However, I notice that once the initial build has completed, and when no requests are being made the CPU is at a constant 30%. I've tried reproducing on a tiny repo to no avail which isnt surprising. However, I'm not quite sure how to proceed as I cannot share my private repo. I've attached some info below:

System Info

System:
OS: macOS 15.3.1
CPU: (14) arm64 Apple M4 Pro
Memory: 3.62 GB / 48.00 GB
Shell: 5.9 - /bin/zsh
Browsers:
Chrome: 134.0.6998.166
Safari: 18.3

@rsbuild/core@npm:1.2.19 (via npm:^1.2.19)

Details

When running rsbuild dev after the build is complete and before any files have been changed, the node-rsbuild process constantly uses about 30% cpu.

sample from activity monitor: https://gist.github.com/scottbessler/b154794d920f7b5ec7bc656aba3bc41e

Reproduce link

private repo

Reproduce Steps

1. run rsbuild dev
2. wait for build to finish
3. observe cpu usage