Guest: QEMU/KVM (dfbsd-qemu/vm.sh), 6 vCPU, 4GB RAM, virtio disk/net.
Base kernel (all source analysis; /usr/src == audited tree):
  DragonFly dfbsd 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026
      root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC  x86_64
  kern.ident: X86_64_GENERIC (INVARIANTS, DDB in kernel)
  /usr/src/sys/vfs/hammer2/hammer2_strategy.c md5
      4c0018e3b60e8a23d41863f85f5644d4 == audited tree (stock baseline)
K2 = stock + harness.diff (panic reproduction kernel):
  DragonFly 6.5-DEVELOPMENT #2: Tue Oct 20 03:34:11 UTC 2026
      root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC
  sysctl vfs.hammer2.df2643_harness (0 default; 1 forces the post-race
      parent==NULL state in hammer2_xop_strategy_write)
K3 = stock + harness.diff + fix.diff (fix validation kernel):
  DragonFly 6.5-DEVELOPMENT #1: Tue Oct 20 03:49:24 UTC 2026
      root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC
Build: cd /usr/src && make -j6 nativekernel KERNCONF=X86_64_GENERIC
  (k3build.log BUILD_RC=0; ~15 min with modules) + make installkernel + reboot
Toolchain: cc 8.3 [DragonFly] Release/2019-02-22
vfs.usermount: 0; hw.ncpu: 6
Test media: 512MB newfs_hammer2 image (PFS LOCAL), rw mount, dd writes +
sync to fire the async strategy write xops.
Guest reset to clean-source snapshot (vm.sh reset with-src) after
verification; sys/ in the audit tree never modified.