These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.50 s (backtrack: 0/20).

[ebuild     UD ] sys-kernel/linux-headers-6.15::gentoo [6.19::gentoo] USE="-headers-only" 147627 KiB

Total: 1 package (1 downgrade), Size of downloads: 147627 KiB