Not in a released/normal bcachefs build yet. The old behavior was the kernel rejecting swapfiles because of holes/unmapped extents. Support via SWP_FS_OPS is being developed in out-of-tree bcachefs-tools: PR #646 was closed in favor of PR #787, which is still open as of September 13, 2026.

The current work has the basic swap_activate/swap_deactivate/swap_rw plumbing, but it is still testing-branch territory. For production, use a swap partition or a file on ext4/xfs/etc. And this does not imply hibernation/resume support, which has stricter requirements.