uname -a (baseline stock kernel):
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
(stock INVARIANTS kernel, QEMU/KVM guest, clean-source snapshot)

compiler: cc 8.3 [DragonFly] Release/2019-02-22
sysctl vfs.usermount: 0        (mount/umount are root-only by default)
NFS client: in-kernel module, loaded at first mount_nfs
fakesrv2: loopback-only listeners rpcbind/UDP 111, mountd/TCP 779, nfs/TCP 2049
no system rpcbind/mountd/nfsd running during the runs
mount invocation: mount_nfs -o tcp,port=2049 127.0.0.1:/P /mnt/nfsx
device node: server-supplied LOOKUP("dev") -> fattr3 type=NF3CHR,
             mode 020666, rdev specdata 14:2 (= /dev/null on this guest)
holder: /tmp/holder2 run as user `nobody` (su -m nobody -c)

baseline kernel: above (#0 Thu Jul 2 06:02:54 UTC 2026) -> panic (reproduced)
fix kernel:      built in-guest (make nativekernel KERNCONF=X86_64_GENERIC,
                 fix.diff applied to /usr/src) -> EBUSY, no panic (see VERDICT.md)