Which IOS jailbreaking technique patches the kernel during the device boot so that it becomes jailbroken after each successive reboot?

Tethered jailbreaking requires the device to be connected to a computer and use specialized software each time it reboots, because the kernel patch does not persist across reboots on its own.

Semi-untethered jailbreaking allows the device to boot normally after a reboot, but the jailbreak must be re-enabled manually by running an on-device app each time, rather than being applied automatically during boot.

Semi-tethered jailbreaking allows the device to reboot into a non-jailbroken state and still function normally, but requires a computer connection to re-apply the jailbreak patch if the jailbroken state is needed again.

Untethered jailbreaking works by patching the kernel at a low level during the boot process itself, so the exploit is baked into the device startup sequence. This means the device remains jailbroken after every reboot without requiring a computer or app to re-trigger the exploit, making it the most persistent and autonomous form of jailbreak.