LLMs Broke REST: Why the Backend Runtime Needs Complete Rethinking

Traditional REST APIs were built around deterministic, stateless operations—but LLM workloads shatter these core assumptions with non-deterministic reasoning and complex multi-step execution. The protocol stays the same, yet the runtime beneath it must now handle unpredictable costs, dynamic tool invocation, and stateful workflows—fundamentally changing how we architect backend systems. This paradigm shift is critical for engineers building AI-driven applications in 2026.