"failed to authorize: DeadlineExceeded" pushing to Artifact Registry with BuildKit

TL;DR Link to heading Image pushes from GitHub Actions to Google Artifact Registry kept failing with failed to authorize: DeadlineExceeded after 60 seconds, because the buildx client’s token POST gets a 405 and sometimes doesn’t complete. Setting BUILDKIT_NO_CLIENT_TOKEN=1 on the runners stops the client sending that POST, and I haven’t seen the error in the first day since. Motivation Link to heading At work our image builds run on self-hosted GitHub Actions runners and push to Artifact Registry. A few times a day, a build would get through each Dockerfile step and then die at the push: