As per https://wpt.fyi/results/fetch/api/basic/request-upload.any.html?label=master&label=experimental&aligned&view=interop&q=label%3Ainterop-2026-fetch, Safari is failing the test named Fetch with POST with text body on 421 response should be retried once on new connection.
421 is most useful for HTTP/2+ connections and it is unclear whether closing a HTTP/1 connection in case of 421 is actually useful.
For that reason, until we get to a consensus, we wonder whether this particular test should not be removed from Interop 2026, especially since it is not related to fetch stream uploads or range requests.
As per https://wpt.fyi/results/fetch/api/basic/request-upload.any.html?label=master&label=experimental&aligned&view=interop&q=label%3Ainterop-2026-fetch, Safari is failing the test named
Fetch with POST with text body on 421 response should be retried once on new connection.421 is most useful for HTTP/2+ connections and it is unclear whether closing a HTTP/1 connection in case of 421 is actually useful.
For that reason, until we get to a consensus, we wonder whether this particular test should not be removed from Interop 2026, especially since it is not related to fetch stream uploads or range requests.