OptionalkernelSee [CentralizedWorkerInitMessage#kernelAbiVersion].
Main process channel offset. The thread reads the process-wide dlopen archive head relative to this live shared-memory anchor before fork.
OptionalprogramOptionalptrPointer width: 4 for wasm32, 8 for wasm64. Defaults to 4.
Pre-allocated address in shared memory for Wasm TLS initialization.
Init message for thread Workers. Threads share the parent process's Memory and run a function pointer.