As of BuildKit v0.10.5, buildctl build --ssh default=$SSH_AUTH_SOCK seems incompatible with OpenSSH 8.9 (https://www.openssh.com/agent-restrict.html).

Any ssh-enabled command such as RUN --mount=type=ssh ssh git@github.com fails with ssh: parse error in message type 27 in the --debug log.

Tried to bump up x/crypto to v0.2.0, but no success; The ssh: parse error in message type 27 error disappears after bumping up x/crypto, but the ssh command still fails with git@github.com: Permission denied (publickey). (EDIT: just forgot to run ssh-add)

Initially reported by several people in golang/go#51689 (comment)

This issue does not affect the non-agent mode (--ssh default=$HOME/.ssh/id_rsa)