[Bug 294516] bhyve(8): serial console is resized to abysmal size after upgrade 14.4-STABLE

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=294516

            Bug ID: 294516
           Summary: bhyve(8): serial console is resized to abysmal size
                    after upgrade 14.4-STABLE
           Product: Base System
           Version: 14.4-STABLE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: bhyve
          Assignee: virtualization@FreeBSD.org
          Reporter: michaelo@FreeBSD.org

Upgraded host to:
FreeBSD deblndw013x.innomotics.net 14.4-STABLE FreeBSD 14.4-STABLE 818243722
GENERIC amd64

running bhyve via vm-bhyve:
# cat kinexon.conf
loader="uefi"
uefi_vars="yes"
graphics="yes"
graphics_res="1280x1024"
graphics_listen="127.0.0.1"
xhci_mouse="yes"
cpu="8"
memory="16G"
network0_type="virtio-net"
network0_switch="VL-G-DE-SP02-4181"
disk0_type="nvme"
disk0_name="disk0.img"
uuid="291fed2d-71d4-11f0-8490-b499bac04fbe"
network0_mac="58:9c:fc:09:5e:14"
bhyve_options="-K de -o system.serial_number=CZ3139VJ30KNXE"
fwcfg="qemu"

When I try to attach to the serial console via null modem "vm console kinexon"
the PuTTY terminal window is resized beyond good and evil. I can't find
anything related to a behavior change in
https://www.freebsd.org/releases/14.0R/relnotes/

See video of the behavior:
https://people.freebsd.org/~michaelo/bhyve/bhyve-putty-resize.mp4

bhyve input:
2026-04-14T13:40:27+02:00:  [bhyve options: -c 8 -m 16G -AHPw -l
bootrom,/usr/local/share/uefi-firmware/BHYVE_UEFI.fd,/usr/local/bhyve/kinexon/uefi-vars.fd
-K de -o system.serial_number=CZ3139VJ30KNXE -U
291fed2d-71d4-11f0-8490-b499bac04fbe -u]
2026-04-14T13:40:27+02:00:  [bhyve devices: -s 0,hostbridge -s
31,lpc,fwcfg=qemu -s 0:4:0,nvme,/usr/local/bhyve/kinexon/disk0.img -s
0:5:0,virtio-net,tap1,mac=58:9c:fc:09:5e:14 -s
0:6:0,fbuf,tcp=127.0.0.1:5901,w=1280,h=1024 -s 0:7:0,xhci,tablet]
2026-04-14T13:40:27+02:00:  [bhyve console: -l com1,/dev/nmdm-kinexon.1A]

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