Module bundle 

rolldown bundle + tree-shake + TypeScript -> one ESM module -> compiled to QuickJS bytecode once.

rolldown (built on oxc) resolves the whole import graph including node_modules, transpiles .ts/.tsx, tree-shakes, and emits a single ESM chunk. That chunk is compiled to bytecode a single time; every realm that runs it links the bytecode (one Module::load, no parse, no resolver). A hidden source map is kept so a JS error in the bundled output is reported at the original .ts/.js location.

The native modules a realm serves stay EXTERNAL: the chunk keeps the bare import ... from 'node:fs' and the written bytecode re-links by name against whatever realm loads it. The Bundler reads which specifiers those are from the same ModuleRegistry the runtime was built with, so the two cannot disagree.

Structs

BundledSource

The result of one rolldown bundle.

Bundler

The bundle front-end for one runtime configuration: its options, the module table whose specifiers stay external, and the cache its compiles land in.

BundlerOptions

How a bundle resolves: shim aliases, inline virtual modules, the module resolution controls and the tsconfig selection.

Functions

is_typescript_path

True when a path’s extension marks it as TypeScript (.ts/.tsx/ .mts/.cts) and so must be transpiled through the bundler.

source_is_es_module

Heuristic: the source begins a line with a static import/export and so must run as an ES module (bundled). Dynamic import(...) is intentionally NOT matched — it is valid in a plain script, so such a script keeps top-level return. A false positive only costs an unnecessary bundle, never wrong output.