That PR is the rust rewrite. That's some time in the past now. As of this comment, there is no tagged 1.4 release. This is the present. Anthropic is using apparently a version of Bun that is not publicly available. This is orthogonal to it being Rust-based, as all Bun releases now will be.
It's publicly available in the GitHub repository and if you run "bun upgrade --canary" - https://github.com/oven-sh/bun/releases/tag/canary
That commit (and main) still purports to be 1.3.14, the version numbers haven't changed. Does that not still suggest Anthropic is using something else?
I think Bun/Anthropic should document which commit hash their "1.4" as shipped in Claude Code uses.
Come on, "not publicly available"? You know how git works right? Each Claude release probably has the HEAD of main compiled as "1.4.0" until there is a real official release.
I do know how git works and in my experience, while the version number sometimes doesn't get bumped until just before a release is tagged, the version number comes from the codebase. If they're building something that says 1.4.0, then they have a codebase that disagrees with ours.
Where is the previous version referred to in the codebase? I'm guessing that would be the place to look for changes.
If you can't find an update at that place in the codebase saying 1.4.0 you can ask where it is. It seems after doing that and not receiving an answer would be the appropriate time to start making the claims that people are throwing around.
This seems like a candidate
https://github.com/oven-sh/bun/commit/b18bf6d1d0a92238f240bf...
The commit hash reported by "1.4" doesn't exist in the public repo