OpenAI GPT-5.4 Complete Guide: Benchmarks, Use Cases, Pricing, API, and GPT-5.4 Pro Comparison

OpenAI released GPT-5.4 on March 5, 2026, and this is the first GPT release in a while that feels less like a narrow benchmark bump and more like a model-line reset. The reason is simple: GPT-5.4 is the first mainline OpenAI reasoning model that comb...