Astro 5.1 Vercel Server Islands (404 error)

[mrchantey]

Astro Info

Astro                    v5.1.0
Node                     v20.18.1
System                   Linux (x64)
Package Manager          npm
Output                   server
Adapter                  @astrojs/vercel
Integrations             none

If this issue only occurs in one browser, which browser is a problem?

No response

Describe the Bug

Upgrading to 5.1 broke server islands for my deployed vercel app (404 not found).
I'm guessing this is related to @astrojs/vercel because astro dev works and so does astro preview with the node adapter.

Downgrading back to Astro 5.0.3 fixes the issue.

Error message

GET https://bevyhub-nwfn5wvd4-petes-projects-607490fb.vercel.app/_server-islands/SceneList?e=SceneList&p=6206378E2AA7D4943B1A9B8ERr6EJavY%2FQcTfhxEVgYPhHg%2FGv6%2BIL581IbjZrUf6kpi00FN1XNfQ4snx9kCq0jH&s=%7B%7D 404 (Not Found)

Details

package.json

"@astrojs/vercel": "^8.0.1",
"astro": "^5.1.0",

astro.config.mts

export default defineConfig<never>({
  site: "https://bevyhub.dev",
  adapter: vercelAdapter(),
  output: 'server',
  scopedStyleStrategy: 'attribute',
})

src/pages/discover.astro

---
export const prerender = true
import { ContentLayout } from '@comp-astro/layout'
import { SceneList } from '@comp-astro/content'
import { CircularProgress } from '@design'

---
<ContentLayout>
  <h1>Discover</h1>
  <SceneList server:defer>
    <CircularProgress slot="fallback"/>
  </SceneList>
</ContentLayout>

What's the expected result?

For vercel server islands to work the same as in 5.0

Link to Minimal Reproducible Example

sorry im on the free plan so cant share vercel links

Participation

• I am willing to submit a pull request for this issue.

[Trombach]

Duplicate of #12803