Just hit this panic on 9.99.64:
[ 6717.5700161] panic: kernel diagnostic assertion "l == curlwp" failed: file
"/home/source/ab/HEAD/src/sys/kern/kern_lwp.c", line 2063
[ 6717.5800161] cpu18: Begin traceback...
[ 6717.5900170] trace fp ffffc0088f5d3c50
[ 6717.5900170] fp ffffc0088f5d3c70 vpanic() at ffffc000004b0334
netbsd:vpanic+0x15c
[ 6717.6000167] fp ffffc0088f5d3ce0 kern_assert() at ffffc000007ce26c
netbsd:kern_assert+0x5c
[ 6717.6100211] fp ffffc0088f5d3d70 lwp_thread_cleanup() at ffffc0000045f368
netbsd:lwp_thread_cleanup+0x80
[ 6717.6200270] fp ffffc0088f5d3d90 lwp_exit() at ffffc0000045f4ac
netbsd:lwp_exit+0xcc
[ 6717.6200270] fp ffffc0088f5d3dd0 sys__lwp_create() at ffffc000004c2f00
netbsd:sys__lwp_create+0xe8
[ 6717.6300215] fp ffffc0088f5d3e20 syscall() at ffffc0000008a63c
netbsd:syscall+0x18c
[ 6717.6400221] tf ffffc0088f5d3ed0 el0_trap() at ffffc00000088c74
netbsd:el0_trap
[ 6717.6500214] ---- trapframe 0xffffc0088f5d3ed0 (304 bytes) ----
[ 6717.6500214] pc=0000f8abc4638958, spsr=0000000020000000
[ 6717.6600309] esr=0000000056000135, far=0000f8abc465b030
[ 6717.6600309] x0=0000ffffffe68500, x1=0000f8abc4a1a260
[ 6717.6700228] x2=0000f8abc49fe200, x3=0000000000000000
[ 6717.6800338] x4=0000ffffffe684d0, x5=0000000000000030
[ 6717.6800338] x6=0000ffffffe68500, x7=0000f8abc4760208
[ 6717.6900234] x8=0000000000000001, x9=0000000000001003
[ 6717.6900234] x10=000000000000000c, x11=0000000000000001
[ 6717.7000252] x12=0000f8abc49e91d8, x13=0000000000000000
[ 6717.7000252] x14=0000000000000000, x15=0000f8abc4000980
[ 6717.7100242] x16=0000f8abc4a122e0, x17=0000f8abc4638954
[ 6717.7200306] x18=0000000000000001, x19=0000ffffffe68500
[ 6717.7200306] x20=0000fffff9a72e60, x21=0000000000000002
[ 6717.7300283] x22=0000f8abc4a1a260, x23=0000f8abc49fe200
[ 6717.7300283] x24=0000fffff9a72000, x25=0000ffffffe684d0
[ 6717.7400357] x26=0000fffff9a732a8, x27=0000fffff9a73070
[ 6717.7400357] x28=0000f8abc4a1b400, fp=x29=0000ffffffe68510
[ 6717.7500291] lr=x30=0000f8abc49fe224, sp=0000ffffffe68420
[ 6717.7600300] ------------------------------------------------
[ 6717.7600300] cpu18: End traceback...
Stopped in pid 152.152 (conftest) at netbsd:cpu_Debugger+0x4: ret
db{18}>