tsdown --watch bug reproduction repo

Versions used for reproduction:

• NodeJs v25.2.1
• NPM 11.6.4
• OS Manjaro Linux Linux 6.17.13-1-MANJARO

How to reproduce

1. Clone this repository
2. npm install
3. tsdown --watch

Expected:dist/ folder contains compiled library. Actual: dist/ is empty.

Variations

If the tsdown.config.ts is modified to only contain one format, so either cjs OR esm, then watch mode works as expected and will compile the library. If both are present, watch mode does nothing.

Another way to get tsdown to work is to run it without watch mode like this: tsdown.