What
The worker journal, a record file kept by internal worker processes, gained writtenByNewerBuild. It reports true when reading the file fails with the reason unsupported_version.
Why
In practice, a journal file from a newer build can now be recognised as such, rather than looking like an ordinary unreadable file.
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
The finding does not say what Claude Code does once it detects such a file.