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

OpenAI GPT-5.4 is the new mainline reasoning model for professional work. This complete guide covers benchmarks, use cases, pricing, API details, long-context behavior, computer use, tool search, GPT-5.4 Pro, and how it compares with GPT-5.2 and GPT-5.3-Codex.