create

Start another sub-client under an id.

zero client create p1
zero client create p2 --branch feat-x

Over MCP: tool_exec { script: "return await tools.use('client', 'create', 'p1')" }.

A multiplayer test starts one sub-client per player, then runs each player's calls on its own:

zero client create p1
zero client create p2

then execute { client: "p1", code: ... } and execute { client: "p2", code: ... }, and when the test is done:

zero client delete p1
zero client delete p2

A start is refused past four sub-clients and while the machine has less than 2560 MB of memory free, and a sub-client whose working set passes 4096 MB is stopped, its row saying why.

A sub-client runs under the editor profile only (the engine also boots as runtime, but only an editor hosts a sub-client), so profile takes editor and refuses any other value. A sub-client that ends before it is ready for a reason another start will not change (the program could not start, or it refused its arguments, or three starts in a row ended the same way) is not started again: its row reads failed with the reason, including the last lines it wrote on stderr, until zero client restart.