Reproduction link or steps

Minimal reproduction: https://github.com/KurtGokhan/rolldown-checkglobals-repro

git clone https://github.com/KurtGokhan/rolldown-checkglobals-repro
cd rolldown-checkglobals-repro
npm install
npm run build

grep -c 'checkGlobals()'        dist/assets/*.js   # => 1  (call kept)
grep -c 'function checkGlobals'  dist/assets/*.js   # => 0  (definition gone)

npm run preview   # blank page; console: "ReferenceError: checkGlobals is not defined"

The bug surfaces in the wild via msw: its core/index.mjs calls checkGlobals() at module top level, while its package.json declares "sideEffects": false.

// node_modules/msw/lib/core/index.mjs
import { checkGlobals } from './utils/internal/checkGlobals.mjs';
// ...
checkGlobals();           // top-level side effect
export { http, HttpResponse, /* ... */ };

Relevant config (vite.config.js):

export default defineConfig({
  build: {
    minify: false,
    rolldownOptions: { output: { strictExecutionOrder: true } },
  },
});

Trigger conditions (all required):

• output.strictExecutionOrder: true — without it, both the call and the definition are removed together (no dangling reference)
• the dependency declares "sideEffects": false
• that dependency calls an imported cross-module function at its module top level
• other exports of the dependency are used, so its module is retained

What is expected?

A referenced binding must be retained whenever the reference (the checkGlobals() call) is retained, regardless of "sideEffects": false. Either keep both the call and the definition, or remove both — never keep the call while dropping the definition.

This is what rolldown 1.0.3 (vite 8.0.16) does: the definition is present and the app works.

What is actually happening?

rolldown keeps the top-level checkGlobals() call but tree-shakes the checkGlobals function definition out of every chunk, leaving a free identifier → ReferenceError: checkGlobals is not defined at module-eval time → blank app.

This is a regression between rolldown 1.0.3 and 1.1.3:

System Info

  System:
    OS: macOS 26.5.1
    CPU: (12) arm64 Apple M3 Pro
    Memory: 845.58 MB / 36.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.18.0
    npm: 11.16.0
    pnpm: 10.28.1
    bun: 1.3.13
    Deno: 2.8.3+
  Browsers:
    Chrome: 149.0.7827.156
    Firefox Developer Edition: 151.0
    Safari: 26.5
  npmPackages:
    rolldown: 1.1.3 (transitive, via vite 8.1.0)
    vite: 8.1.0
    msw: 2.14.6

Any additional comments?

msw declaring "sideEffects": false while running checkGlobals() at import time is arguably inaccurate on msw's side, but a bundler must still not drop a referenced binding — so this looks like a rolldown correctness bug in scope-hoisting / side-effect handling. The concerning part is that the same mechanism could silently drop other referenced cross-module bindings that don't happen to throw loudly at load.

Originally hit while bumping vite 8.0.x → 8.1.0 in a real app, where it produced a fully blank page (ReferenceError: checkGlobals is not defined).