Baseline kernel (stock, all baseline runs incl. both panics):
  DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026  root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC x86_64
Fix-validation kernel (smbus compiled into X86_64_GENERIC => kernel rebuilt):
  DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #1: Tue Oct  6 22:05:46 UTC 2026  root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC x86_64
Modules (chain): iicbus.ko, iicsmb.ko, smb.ko (stock or locally rebuilt fixed variants), df5521_rig.ko (audit rig; NOT part of any production path)
smbus driver: compiled into the X86_64_GENERIC kernel ("device smbus" in the config)
/dev/smb0: crw------- root:wheel 0600
Guest reset (vm.sh reset with-src) after testing; /usr/src verified md5-identical to the repo tree before testing.
df5521_poc.c: 16fea8b1ba1d070dbd19dae52d1bcdaa1d4d6aeb3c9d4ad4d534a430677d5eb4
df5521_rig.c: 5196bf250af837a0449629059b7b85c2c0932c858e18dc5f1acd0c22afae6301