Question: When Graphite starts merging a stack of PRs, is there a way to display some warning on the GitHub's PR pages like, "This PR is going to be merged soon by Graphite. So don't merge it by yourself!" Is it part of your browser extension? (I haven't tried it yet.)

We don’t currently have this, out of curiousity would it be more for you or for your coworkers?

I think this can be useful for whoever run into the PRs that are in the merge queue. We don't want anyone to mess up with it! Also, a relevant idea is, if a PR belongs to a stack, you could put a warning button on the merge button saying something like "you may want to merge this on Graphite instead of doing it here"