When executing a remote command which contains commas in it's arguments the agent will respond with "ZBX_NOTSUPPORTED".
Here is a packet trace of the server/agent communication:
system.run[/etc/zabbix/scripts/ruby_proc_sender.rb -s 192.168.103.181 -h lisa -k trap.log -c "ps -eo pcpu\,pmem\,command|sort -k1|tail -10" -D >> /tmp/debug.out,nowait]
The internal commas are being interpreted as part of the [cmd,arg] structure. In the above example the agent is expecting the wait/nowait argument after the first comma.
There needs to be a way to escape or otherwise use commas in remote commands.