GPT-5.5

Last updated: April 2026 · Author: Ignacy Kwiecień · Reading time: ~12 min · Release-day coverage Introducing GPT-5.5: the first fully retrained base model since GPT-4.5 GPT-5.5 is OpenAI’s April 23, 2026 release — the first fully retrained base model since GPT-4.5. Headline numbers: 82.7% on Terminal-Bench 2.0 (SOTA agentic coding), 84.9% parity with experts … Read more