OpenAI launches GPT-5.5
OpenAI launches GPT-5.5 for agentic coding, knowledge work and scientific research; the model first becomes available in ChatGPT and Codex, enters the API the following day and supports a context window of more than 1 million tokens.
What happened
Event details
OpenAI launches GPT-5.5 on April 23, 2026, positioning it for agentic coding, complex knowledge work and scientific research. The model first becomes available in ChatGPT and Codex, and the API opens on April 24 with a 1,050,000-token context window.
Assessment
Why it matters
GPT-5.5 brings a context window of more than 1 million tokens and capabilities for agentic coding, knowledge work and scientific research to ChatGPT, Codex and the API, affecting consumers, developers and professional researchers.
Availability
Access notes
Available to paid ChatGPT and Codex plans; enters the OpenAI API on April 24, 2026.