Astro 6.0.5+ dev error: context method emitFile() is not supported in serve mode. #16026
Description
Astro Info
Astro v6.0.8
Node v24.14.0
System Linux (x64)
Package Manager pnpm
Output static
Adapter none
Integrations @astrojs/react
@astrojs/mdx
@astrojs/sitemap
If this issue only occurs in one browser, which browser is a problem?
No response
Describe the Bug
Summary
When using astro dev for Astro 6.0.5+, the command may output a Vite warning with certain plugins:
[WARN] [vite] [plugin:astro:scripts] context method emitFile() is not supported in serve mode. This plugin is likely not vite-compatible.Steps to reproduce
- Clone
https://github.com/southwellmedia/velocity - In
package.json, set the Astro version to 6.0.5 or later - Run
pnpm update - Run
pnpm dev. The error appears
Details
I was using the Astro template https://github.com/southwellmedia/velocity. When I updated it from Astro 6.0.4 to 6.0.5, the Vite warning started appearing.
Requested an analysis from Claude, which responded as follows:
● Root Cause
The warning comes from Astro's own internal vite-plugin-scripts — nothing in your project config is wrong.
What changed in 6.0.5: PR #15904 fixed a bug where the before-hydration script chunk wasn't being emitted for the
client Vite environment. The fix added an this.emitFile() call in buildStart() for the client environment. However,
buildStart() also runs during dev, and emitFile() is a Rollup build-time API that Vite stubs out in serve mode —
hence the warning.
In 6.0.4, the client environment was accidentally excluded from that emitFile() call (the bug), so no warning
appeared. The 6.0.5 fix is correct for production builds but introduces this cosmetic dev warning.
Why your project triggers it: You use @astrojs/react with hydration directives (client:load, client:visible, etc.),
which relies on the before-hydration script path.
Impact: The warning is harmless — dev and production builds both work correctly. It needs an upstream fix in Astro
(guarding emitFile() to only run during build, not serve)What's the expected result?
No warning appears.
Link to Minimal Reproducible Example
https://github.com/southwellmedia/velocity
Participation
- I am willing to submit a pull request for this issue.