I use esbuild-sass-plugin to import SCSS and generate a CSS file. This plugin automatically resolve the SCSS @import instructions and return all additional files to watch in the watchFiles esbuild plugin output.

This works perfectly with an esbuild setup but not with tsup. For the later only a change to the main SCSS file triggers a rebuild. So it makes me think tsup somehow discards the watchFiles result, or just does not rely on esbuild watch mode ?

esbuild documentation for plugins https://esbuild.github.io/plugins/#on-resolve-results

demo repository (contains both esbuild and tsup config) https://github.com/mistic100/test-esbuild-sass