Comment by DanRosenwasser

> How does this affect downstream tools like tsdown and esbuild, which need to build the TypeScript codebase?

esbuild doesn't rely on TypeScript at all, so there's no issue there.

With tsdown on the other hand, it depends on if you use --isolatedDeclarations. If not, you can install TypeScript 6 side-by-side (instructions for this are on the blog)