Why the dev toolbar crashes under Rolldown
Vite 8 switched its dependency optimizer from esbuild to Rolldown, and ships an esbuild-plugin compatibility shim so existing optimizeDeps.esbuildOptions.plugins configs keep working without every plugin author rewriting for Rolldown’s own plugin API.
Astro’s own built-in astro:dev-toolbar integration registers exactly this kind of plugin: an esbuild plugin with an onEnd callback that reads result.metafile, a field esbuild’s real dependency-scan output includes. Rolldown doesn’t produce an esbuild-style metafile, and its compatibility shim doesn’t implement that field. Calling the callback throws instead of quietly returning nothing:
Not implemented
at PluginContextImpl.generateBundle (vite/dist/node/chunks/node.js:33847)The crash was reported directly: “vite rolldown compatibility issue,” opened 2026-05-07 against Astro 6.2.2 and Vite 8.0.11. It was closed as not planned; a workaround shipped for one specific project’s own config, not a fix to Astro’s dev-toolbar plugin itself.
Verified: current Astro 7.1.3 no longer triggers this specific path
Checked directly against this site’s own installed
node_modules/astro/dist/toolbar/vite-plugin-dev-toolbar.js (astro@7.1.3):
its config() hook only sets optimizeDeps.include today, not
optimizeDeps.esbuildOptions.plugins at all. The exact crash described above
doesn’t appear to trigger from Astro’s own dev-toolbar integration on current
7.x releases. It’s still real and worth knowing the fix for if you’re on an
older Astro 6.x project, or if a different plugin in your app sets an
esbuild onEnd callback that reads result.metafile, the fix below is
defensive against that exact pattern regardless of which plugin triggers it.
Fix it: strip the incompatible esbuild plugin
Before: default Astro config
export default defineConfig({
// dev toolbar enabled by default (the Astro 7 default) —
// its esbuild plugin crashes under Rolldown (BROKEN)
});After: add a plugin that clears the broken hook
export default defineConfig({
vite: {
plugins: [
{
name: "fix-rolldown-esbuild-compat",
configResolved(config) {
// FIXED: the dev toolbar's esbuild onEnd callback reads
// result.metafile, which Rolldown's compat shim doesn't
// implement — clearing the plugin list avoids the crash
if (config.optimizeDeps?.esbuildOptions?.plugins) {
config.optimizeDeps.esbuildOptions.plugins = [];
}
},
},
],
},
});This runs at config-resolution time, before the dev server starts optimizing dependencies, so it removes the broken callback before anything can invoke it. The dev toolbar itself keeps working; only the specific esbuild onEnd hook that Rolldown can’t satisfy gets cleared.
This edits a live config object
configResolved receives Vite’s final, merged config; mutating
optimizeDeps.esbuildOptions.plugins here only removes the array Astro’s
dev-toolbar integration already pushed onto, not anything you configured
yourself under a different plugin name. If you also rely on other
optimizeDeps.esbuildOptions.plugins entries, filter this list instead of
clearing it outright.
Confirmed version range
Reported against Astro 6.2.2 and Vite 8.0.11. Checked directly against this site’s own astro@7.1.3 install: its dev-toolbar plugin’s config() hook has already moved away from setting optimizeDeps.esbuildOptions.plugins, so the specific crash reported in the original issue doesn’t reproduce from Astro’s own integration on current 7.x. If you’re on Astro 6.x, or hitting the identical Not implemented error from a different plugin, the fix above still applies: the trigger is any esbuild plugin with an onEnd callback reading result.metafile, not something specific to the dev toolbar itself. Browse more posts like this in the Guides & Fixes archive.
