zsh and OS Kernel: Signal Propagation Order for Concurrent Background Jobs

Zsh manages background processes through a built-in job control system, utilizing signal traps to handle process termination and interrupts across concurrent tasks. While the shell facilitates the execution of multiple background jobs via the & operator, the actual scheduling and signal delivery are handled by the underlying Unix kernel.

A technical uncertainty exists regarding the deterministic nature of signal delivery when a single shell signal is used to terminate multiple active background children simultaneously. Because zsh is primarily a single-threaded process, the interaction between the shell's internal job list and the kernel's process scheduler may result in inconsistent termination sequences across different operating systems, such as macOS and various Linux distributions.

• Does zsh guarantee a specific order of signal propagation to background jobs based on their job ID?
• How does the shell's signal handling logic interact with the kernel scheduler to ensure all concurrent processes are terminated without leaving orphaned tasks?