From 0.25, ESBuild can not read back the source map it generates for defines. [See this repro](https://esbuild.github.io/try/#YgAwLjI1LjMAewogIGRlZmluZTogewogICAgTlVNOiAneyJ0ZXN0IjogM30nLAogIH0sCiAgc291cmNlbWFwOiAnYm90aCcsCiAgb3V0ZmlsZTogJ291dC5qcycsCn0AZQBlbnRyeS50cwBjb25zdCBuID0gTlVNOwovLyMgc291cmNlTWFwcGluZ1VSTD10ZXN0LmpzLm1hcAAAdGVzdC5qcy5tYXAAewogICJ2ZXJzaW9uIjogMywKICAic291cmNlcyI6IFsiPGRlZmluZTpOVU0+IiwgImVudHJ5LnRzIl0sCiAgInNvdXJjZXNDb250ZW50IjogWyIiLCAiY29uc3QgbiA9IE5VTTsiXSwKICAibWFwcGluZ3MiOiAiQUFBQSwyQkFBQyxNQUFRLEVBQUM7QUNBVixNQUFNLElBQUk7IiwKICAibmFtZXMiOiBbXQp9) The generated source map has: ```json "sources": ["<define:NUM>", "", "entry.ts"], ``` But from 0.25, ESBuild expects `sources` to be URL, it will then generate the following error when parsing the source map: <img width="803" alt="Image" src="https://github.com/user-attachments/assets/19e8ea45-d87a-4885-b5c7-520bdc85f827" /> It sounds like ESBuild should probably encode the `<define:NUM>` as an URL when it generates it.