Failed running extprograms execute via socket - fatal recv(MSG_PEEK) failed disconnected

[E.B.]

I switched from running my extprograms execute script directly
to running with dovecot socket. Log shows only this

dovecot: lmtp(test at example.com): Debug: wdi0Tb5VPlGfPnEAM/SpMA: sieve: action execute: running program: test
dovecot: lmtp(test at example.com): Debug: Namespace : Using permissions from /vmail/example.com/test: mode=0770 gid=default
dovecot: script: Fatal: recv(MSG_PEEK) failed: disconnected

For testing I opened up the script and socket with
permissions 777 but the error seems to indicate
less about permissions more about some kind of
protocol problem i guessing.

Sieve script calls using this:

execute "test";

Plugin config:

plugin {
  sieve_plugins = sieve_extprograms
  sieve_global_extensions = +vnd.dovecot.execute
  sieve_execute_socket_dir = sieve-execute
  sieve_before = /usr/local/etc/dovecot/sieve
}
service test {
   executable = script /usr/local/etc/dovecot/sieve_globals/test.sh
   unix_listener sieve-execute/test {
      mode = 0660
      group = vmail
   }
}

FYI I have quota-warning sockets configured
identical to this and they work good.

Dovecot 2.2.16
Pigeonhole 0.4.7

Help appreciate a lot.