Playground struggles loading packages from unpkg due to CORS sometimes

[gka]

Describe the bug

Some playground demos randomly fail because a request to unpkg fails. I think this happens more often for demos with a lot of dependencies, like this one.

After reloading the REPL a few times I get different packages failing, seemingly randomly:

Error fetching "d3-array" from unpkg. Does the package exist?

or

Error fetching "d3-dispatch" from unpkg. Does the package exist?

Reproduction

Just open this REPL and reload the browser a few times.

Logs

I looked up the request in the browser dev tools and it seems to be related to CORS problems:

GET /d3-dispatch@latest/package.json undefined
Host: unpkg.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:133.0) Gecko/20100101 Firefox/133.0
Accept: */*
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate, br, zstd
Referer: https://svelte.dev/
Origin: https://svelte.dev
DNT: 1
Connection: keep-alive
Sec-Fetch-Dest: empty
Sec-Fetch-Mode: cors
Sec-Fetch-Site: cross-site
Priority: u=4
TE: trailers

Response body is not available to scripts (Reason: CORS Failed)

System Info

Firefox 133.0.3 (aarch64)

Severity

annoyance

[Conduitry]

What I think is probably more likely than certain requests randomly failing CORS is that certain requests randomly fail with 5xx/etc. errors or are dropped and that those responses never have the appropriate CORS headers.