INACCESSIBLE_BOOT_DEVICE BSOD, severe performance degradation

December’s Patch Tuesday for Windows 11 24H2 was a nightmare before Christmas. INACCESSIBLE_BOOT_DEVICE BSODs bricked systems, with boot configuration data errors requiring Secure Boot to be temporarily disabled just to access your own computer. Installation failures cascaded with errors 0x800f081f, 0x800f0991, and 0x800f0922. Those who survived installation got significant CPU performance degradation — higher temperatures, gaming regression, and slowdowns that worsened over time. File Explorer behaved erratically when maximized. Fullscreen video streaming on Netflix and Prime Video became laggy. Microsoft’s holiday gift to its users: a slower, crashier, less functional computer.