Please describe the problem.

As mentioned in various places on this wiki, git annex fails with S3 backends requiring v4 signatures, e.g. London, Frankfurt.

Support v4 has apparently been merged in upstream.

Would it be possible to migrate to v4 signing? I'd do the PR myself but my Haskell is currently non existent, sadly.

What steps will reproduce the problem?

Interact with a git annex remote using v4.

What version of git-annex are you using? On what operating system?

git-annex version
git-annex version: 10.20250630
build flags: Assistant Webapp Pairing Inotify DBus DesktopNotify TorrentParser MagicMime Servant Feeds Testsuite S3 WebDAV
dependency versions: aws-0.24.4 bloomfilter-2.0.1.2 crypton-1.0.4 DAV-1.3.4 feed-1.3.2.1 ghc-9.8.4 http-client-0.7.19 persistent-sqlite-2.13.3.0 torrent-10000.1.3 uuid-1.3.16 yesod-1.6.2.1
key/value backends: SHA256E SHA256 SHA512E SHA512 SHA224E SHA224 SHA384E SHA384 SHA3_256E SHA3_256 SHA3_512E SHA3_512 SHA3_224E SHA3_224 SHA3_384E SHA3_384 SKEIN256E SKEIN256 SKEIN512E SKEIN512 BLAKE2B256E BLAKE2B256 BLAKE2B512E BLAKE2B512 BLAKE2B160E BLAKE2B160 BLAKE2B224E BLAKE2B224 BLAKE2B384E BLAKE2B384 BLAKE2BP512E BLAKE2BP512 BLAKE2S256E BLAKE2S256 BLAKE2S160E BLAKE2S160 BLAKE2S224E BLAKE2S224 BLAKE2SP256E BLAKE2SP256 BLAKE2SP224E BLAKE2SP224 SHA1E SHA1 MD5E MD5 WORM URL GITBUNDLE GITMANIFEST VURL X*
remote types: git gcrypt p2p S3 bup directory rsync web bittorrent webdav adb tahoe glacier ddar git-lfs httpalso borg rclone hook external compute mask
operating system: linux x86_64
supported repository versions: 8 9 10
upgrade supported from repository versions: 0 1 2 3 4 5 6 7 8 9 10
local repository version: 10

On NixOs, although I think the same will happen anywhere.

Please provide any additional information below.

 git annex initremote s3 type=S3 bucket=thema-assembly-line region=EU datacenter=eu-west-2 encryption=none
initremote s3 (checking bucket...) (creating bucket in eu-west-2...)
git-annex: S3Error {s3StatusCode = Status {statusCode = 400, statusMessage = "Bad Request"}, s3ErrorCode = "InvalidRequest", s3ErrorMessage = "The authorization mechanism you have provided is not supported. Please use AWS4-HMAC-SHA256.", s3ErrorResource = Nothing, s3ErrorHostId = Just "Hi0geDlta/PbTTIhfzHvtGxcoWq14VWxp/y5RugFCDEext1aOw0wFBhRP8+jVkHHDqTvoWqCgcY=", s3ErrorAccessKeyId = Nothing, s3ErrorStringToSign = Nothing, s3ErrorBucket = Nothing, s3ErrorEndpointRaw = Nothing, s3ErrorEndpoint = Nothing}
failed
initremote: 1 failed

Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)

Yep. It's a great little tool; up till now always local network + rsync.