I think Linux pipes can usually hold 128 KiB. This surely configurable.

Update:

$ perl -e'
   $|=1;
   $SIG{PIPE} = sub { die("SIGPIPE") };
   print "x" x 1..15_328;
' | sleep 0.25   # Child needs to be alive when the print occurs.

$ perl -e'
   $|=1;
   $SIG{PIPE} = sub { die("SIGPIPE") };
   print "x" x 1..15_329;
' | sleep 0.25
SIGPIPE at -e line 3.
[download]

It's 15,328 on my Ubuntu (over WSL2) system. What a weird number. That's 1,056 bytes less than 16 KiB (16,384).