OpenAI's flagship as of April 2026 and its first fully retrained base model since GPT-4.5, built agentic-first. GPT-5.5 is OpenAI's strongest agentic coding model and the engine behind Codex, excelling at coding, computer use, knowledge work, and multi-step task completion. Features a 1M-token context window and multimodal (text + vision) input.
Context: 1,050,000 tokens
