Server islands do not work OOTB with Cloudflare Pages and a 404 page

[soopyc]

Astro Info

Astro                    v5.0.9
Node                     v23.2.0
System                   Linux (x64)
Package Manager          pnpm
Output                   static
Adapter                  @astrojs/cloudflare
Integrations             none

Describe the Bug

When using the Cloudflare adapter with a prerendered 404 page, the server islands route is not included in the _routes.json file, causing server islands to not function.

{
  "version": 1,
  "include": [
    "/",
    "/_image"
  ],
  "exclude": []
}

Local wrangler output on the minimal example:

[wrangler:inf] GET / 200 OK (5ms)
[wrangler:inf] GET /_server-islands/Defer 404 Not Found (9ms)

Tested with local wrangler and production Cloudflare pages.

Manually adding /server_islands/* to routes.extend.include[] works but that does not feel like an intended behavior.

What's the expected result?

/_server-islands/* is included in the generated _routes.json file if one or more server island exists, or in some other way that server islands work.

Link to Minimal Reproducible Example

https://github.com/soopyc/astro-cf-404-mre

Participation

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

[soopyc]

Just peeked at PRs and looks like #454 would resolve this. Should this be closed now or until the PR has been merged?

[alexanderniebuhr]

Please keep this open. In theory the /_server-islands/* definition should be added in the current approach too, not sure why it doesn't. Any ideas @florian-lefebvre?
Still hoping to land #454 soon :)

[florian-lefebvre]

I think this issue may be the same as withastro/astro#12744, I haven't check the repro but the description sounds similar.

EDIT: it may be a combination of the astro issue i linked with a bug introduced in a astro PR that the PR Alex linked will fix

[Trombach]

I'm having the same issue on Vercel. Server island route returns 404 since 5.0.6 or something