api.wordpress.org fails intermittently with HTTP3/quic

[samedwards]

Similar to #7965 (ticket), I'm experiencing intermittent connection errors when connecting to api.wordpress.org. This is mostly from a Composer plugin that's using the Plugin endpoints to check versions. This is using the curl library under the hood

Other users are experiencing the same issue:

• ​https://github.com/inpsyde/wp-translation-downloader/issues/43
• ​https://github.com/typisttech/wp-org-closed-plugin/pull/22

It's also reproducible from the command line:

$ curl -v --http3 https://api.wordpress.org/plugins/info/1.0/redirection.json
* Host api.wordpress.org:443 was resolved.
* IPv6: 2607:f978:5:8002::c68f:a4fb
* IPv4: 198.143.164.251
*   Trying [2607:f978:5:8002::c68f:a4fb]:443...
* SSL Trust Anchors:
*   Native: Apple SecTrust
*   OpenSSL default paths (fallback)
* SSL connection using TLSv1.3 / TLS_AES_256_GCM_SHA384 / X25519MLKEM768 / id-ecPublicKey
* Server certificate:
*   subject: CN=wordpress.org
*   start date: Jan 26 19:43:57 2026 GMT
*   expire date: Apr 26 19:43:56 2026 GMT
*   issuer: C=US; O=Let's Encrypt; CN=E8
*   Certificate level 0: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA384
*   Certificate level 1: Public key type EC/secp384r1 (384/192 Bits/secBits), signed using sha256WithRSAEncryption
*   Certificate level 2: Public key type RSA (4096/152 Bits/secBits), signed using sha256WithRSAEncryption
*   subjectAltName: "api.wordpress.org" matches cert's "*.wordpress.org"
* OpenSSL verify result: 0
* SSL certificate verified via OpenSSL.
* Established connection to api.wordpress.org (2607:f978:5:8002::c68f:a4fb port 443) from 2604:3d08:117d:4c05:45c0:86f4:67ba:72c3 port 58821
* using HTTP/3
* [HTTP/3] [0] OPENED stream for https://api.wordpress.org/plugins/info/1.0/redirection.json
* [HTTP/3] [0] [:method: GET]
* [HTTP/3] [0] [:scheme: https]
* [HTTP/3] [0] [:authority: api.wordpress.org]
* [HTTP/3] [0] [:path: /plugins/info/1.0/redirection.json]
* [HTTP/3] [0] [user-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:134.0) Gecko/20100101 Firefox/134]
* [HTTP/3] [0] [accept: */*]
> GET /plugins/info/1.0/redirection.json HTTP/3
> Host: api.wordpress.org
> User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:134.0) Gecko/20100101 Firefox/134
> Accept: */*
>
* Request completely sent off
* ngtcp2_conn_writev_stream returned error: ERR_DRAINING
* ngtcp2_conn_writev_stream returned error: ERR_DRAINING
* Connection #0 to host api.wordpress.org:443 left intact
curl: (56) ngtcp2_conn_writev_stream returned error: ERR_DRAINING