Kent Overstreet announced in today's Bcachefs pull request for Linux 6.15 that the on-disk format is deemed "soft frozen" with no more required/automatic updates expected prior to dropping the experimental flag on the file-system.
Among the on-disk format changes for Bcachefs that were squeezed into this code for Linux 6.15 includes cached backpointers as a scalability improvement, stripe backpointers, stripe LRU also for better scalability, optional case-insensitivity directory support, and extent flags.
The case-folding / case-insensitivity support on a per directory basis was worked on in part by Joshua Ashton of Valve's Linux team. The per-directory case insensitive file/folder support can be useful for Windows games on Steam Play that are used to case-insensitive NTFS storage and the like on Windows.
Other Bcachefs changes submitted for this new merge window include scrub support, blocksize greater than page size support that builds off the other BS greater than PS work for Linux 6.15, improved journal pipelining, device option handling improvements, continued work on self-healing, and the ability for Bcachefs file-systems to scale into the petabyte range.
See this pull request for the full list of Bcachefs changes that will be part of Linux 6.15 -- assuming no objections from Linus Torvalds or other last-minute issues.