redirect gdbserver stderr/debug vim via gdbserver

Hi,

I am trying to debug a console application  (neovim) with gdbserver.
 I've tried turning off all debug info from gdbserver (via monitor set
debug/remote-debug ...), yet I still see "Detaching from process"
mixed up with the debugged CLI application. In order to make these
messages disappear, I tried redirecting gdbserver stderr (zsh) to
'temp':
$ gdbserver localhost:7777 ./build/bin/nvim toto 2>temp
on the other side (same computer) I connect with:
$ gdb ./build/bin/nvim
(gdb) target remote :7777
(gdb) c

but then nothing appears on the gdbserver terminal, i.e., I can't see
neovim interface. Why is that ?

Best regards
Matt