=== PATCHED KERNEL (fix.diff applied; DragonFly 6.5-DEVELOPMENT #1: Wed Oct 7 03:43:23 UTC 2026) ===

$ sysctl debug.mddiag=maptest
DFRIG: maptest: va1=0xffffffffd0000000 (slot 8191) -> pa 0x109c26000, pre-panic bit=0
DFRIG: maptest: va2=0xffffffffa0000000 (slot 8190) -> pa 0x10a029000, pre-panic bit=0
panic: DF-5535 maptest: slot-8191 mapping vs slot-8190 control
Physical memory: 4060 MB
Dumping 644 MB: 629 613 ... 5
Dump complete

(after reboot, savecore -> /var/crash/vmcore.0)
$ /root/mddiag/dumpchk /var/crash/vmcore.0 0x109c26000 0x10a029000
minidump: version=2 msgbufsize=1048544 bitmapsize=163840 ptesize=2097152
bitmap at file offset 1052672 (163840 bytes)
pa 0x109c26000 (page 1088550): SET (in dump)     <- slot 8191: NOW PRESENT
pa 0x10a029000 (page 1089577): SET (in dump)     <- slot 8190 control: still present

RESULT: fix validated. Baseline: slot-8191 page CLEAR / slot-8190 SET.
        Patched:  both SET, dump completes normally.