tl;dr: .NET 11 delivers another year of accumulated performance improvements across the JIT and runtime, with notable advances in deabstraction—including expanded escape analysis that eliminates more heap allocations for nullable boxing, enumerators, and generic virtual methods. The biggest architectural change is "runtime async," which shifts async/await state machine generation from the C# compiler to the JIT, enabling fused async call chains that skip intermediate Task allocations (3x faster in some cases) and dramatically cheaper exception propagation. Opt-in via a feature flag in .NET 11, with the goal of becoming default in .NET 12.