Bun developer Jarred Sumner has written a blog entry detailing the reasons behind introducing the new bundler. These include improving performance and avoiding repetitive transpilation. The bundler uses target: “bun” to generate pre-transpiled files and optimize execution performance to prevent unnecessary re-transpilations.
In terms of performance, the release includes innovations such as faster performance and bug fixes. Fas.writeFile is expected to execute 20% faster under Linux with large files. Additionally, the bun transpiler now has parser support for TypeScript 5.0 and import attributes, resolving cyclic import errors from previous npm packages.
More information, including the changelog for the new release, is available on the official Bun blog.