A command may run 15,360 processes and threads

One command and everything it starts may hold up to 15,360 processes and threads together, of a sandbox's 16,384; it was 1,024. Test runs that start many processes, Java and parallel builds on a sandbox with several vCPUs no longer fail to start a thread. A sandbox gets it the next time it starts; a custom image, once it is built again. See limits.