Windows Terminal skip and/or truncate outputs

[dragon-archer]

Windows Terminal version

1.23.13503.0

Windows build number

10.0.26100.7462

Other Software

upx (https://github.com/upx/upx) v5.0.2 built by either MSYS2 or MSVC

Steps to reproduce

See upx/upx#953 for more details

To be short, run upx --help in any shell (cmd, powershell, msys2 shell, ...) under Windows Terminal, the output will be truncated, and some outputs from previous commands will be overwritten.

However, run upx --help from conhost.exe or winpty.exe is fine. Also, upx--help | less or upx --help > upx.log are also fine.

Below is the output using script from MSYS2

$ script
Script started, output log file is 'typescript'.
$ upx --help
    i386-darwin.macho                    macho/i386
    i386-dos32.djgpp2.coff               djgpp2/coff
    i386-dos32.tmt.adam                  tmt/adam
    i386-dos32.watcom.le                 watcom/le
    i386-freebsd.elf                     freebsd/i386
    i386-linux.elf                       linux/i386
    i386-linux.elf.execve                linux.exec/i386
    i386-linux.elf.shell                 linux.sh/i386
    i386-linux.kernel.bvmlinuz           bvmlinuz/i386
    i386-linux.kernel.vmlinux            vmlinux/i386
    i386-linux.kernel.vmlinuz            vmlinuz/i386
    i386-netbsd.elf                      netbsd/i386
    i386-openbsd.elf                     openbsd/i386
    i386-win32.pe                        win32/pe
    m68k-atari.tos                       atari/tos
    mips-linux.elf                       linux/mips
    mipsel-linux.elf                     linux/mipsel
    mipsel.r3000-ps1                     ps1/exe
    powerpc-darwin.macho                 macho/ppc32
    powerpc-linux.elf                    linux/ppc32
    powerpc-linux.kernel.vmlinux         vmlinux/ppc32
    powerpc64-linux.elf                  linux/ppc64
    powerpc64le-linux.elf                linux/ppc64le
    powerpc64le-linux.kernel.vmlinux     vmlinux/ppc64le
    riscv64-linux.elf                    linux/riscv64

UPX comes with ABSOLUTELY NO WARRANTY; for details visit https://upx.github.io
$ exit
exit
Script done.
$ cat -v typescript
Script started on 2026-01-16 02:27:45+08:00 [TERM="xterm-256color" TTY="/dev/pty2" COLUMNS="169" LINES="49"]
^[[?2004h$ upx --help^M
^[[?2004l^M^[[6n^[[6n^[[?9001h^[[?1004h^[[m^[[?25h^[[38;5;2m                       Ultimate Packer for eXecutables^M^[[m^[[38;5;11m^[[m    i386-darwin.macho                    macho/i386^[[K^M
    i386-dos32.djgpp2.coff               djgpp2/coff^[[K^M
    i386-dos32.tmt.adam                  tmt/adam^[[K^M
    i386-dos32.watcom.le                 watcom/le^[[K^M
    i386-freebsd.elf                     freebsd/i386^[[K^M
    i386-linux.elf                       linux/i386^[[K^M
    i386-linux.elf.execve                linux.exec/i386^[[K^M
    i386-linux.elf.shell                 linux.sh/i386^[[K^M
    i386-linux.kernel.bvmlinuz           bvmlinuz/i386^[[K^M
    i386-linux.kernel.vmlinux            vmlinux/i386^[[K^M
    i386-linux.kernel.vmlinuz            vmlinuz/i386^[[K^M
    i386-netbsd.elf                      netbsd/i386^[[K^M
    i386-openbsd.elf                     openbsd/i386^[[K^M
    i386-win32.pe                        win32/pe^[[K^M
    m68k-atari.tos                       atari/tos^[[K^M
    mips-linux.elf                       linux/mips^[[K^M
    mipsel-linux.elf                     linux/mipsel^[[K^M
    mipsel.r3000-ps1                     ps1/exe^[[K^M
    powerpc-darwin.macho                 macho/ppc32^[[K^M
    powerpc-linux.elf                    linux/ppc32^[[K^M
    powerpc-linux.kernel.vmlinux         vmlinux/ppc32^[[K^M
    powerpc64-linux.elf                  linux/ppc64^[[K^M
    powerpc64le-linux.elf                linux/ppc64le^[[K^M
    powerpc64le-linux.kernel.vmlinux     vmlinux/ppc64le^[[K^M
    riscv64-linux.elf                    linux/riscv64^[[K^M
^[[K^M
UPX comes with ABSOLUTELY NO WARRANTY; for details visit https://upx.github.io^[[K^M
^[[K^[[?9001l^[[?1004l^[[?2004h$ exit^M
^[[?2004l^Mexit^M

Script done on 2026-01-16 02:27:50+08:00 [COMMAND_EXIT_CODE="0"]

Expected Behavior

Run upx --help from Windows Terminal display correctly/

Actual Behavior

Described above.

[DHowett]

I'm sorry. When I run upx --help (5.1.0) from PowerShell, I can't see any truncation. This may be an issue in ConPTY which has been fixed since Windows last updated. This is an ongoing issue which we're trying to get hold of.