⚙️NET 11 Drops Support for Older CPUs With Stricter Instruction Set Baselines

Your old build server might stop running .NET 11

Microsoft just raised the floor for .NET 11. The x86-64 baseline moves from x86-64-v1 to x86-64-v2 on Windows, Linux, and Apple, and Windows Arm64 now requires the LSE instruction set. If your CPU is missing one of these, .NET 11 won't start and will print "The current CPU is missing one or more of the baseline instruction sets." If you run CI agents, old build boxes, or containers on aging VMs, this is the part to check first. Raspberry Pi-class Arm devices still work, since .NET keeps AdvSimd support, but the Windows Arm64 bar is higher. The bigger change for app code is Runtime Async V2, which moves async state machines out of the compiler and into the runtime. The ReadyToRun targets also moved: Windows and Linux now target x86-64-v3 (AVX, AVX2, FMA, BMI1, BMI2), while Apple M1-class chips stay on their existing target. Opt into Runtime Async with runtime-async=on in your project file. The catch: the LSE target may add some JIT overhead at launch.