GPT-5.5

• 🆕 OpenAI's newest GPT-5-series frontier model, released April 2026.
• 📏 Ships with a 1M-token context window for long-context work.
• 🧠 Adaptive reasoning dynamically allocates compute, with effort levels up to xhigh.
• 🔧 Built for agentic coding, computer use, and tool orchestration.
• 👁️ Multimodal capabilities span text, vision, function calling, and web search.
• 🏢 Positioned as OpenAI's premium flagship for complex professional work.
• 💬 Integrates with OpenAI's Responses and Chat Completions APIs.

OpenAI

OpenAI is an American artificial intelligence research organization headquartered in San Francisco, structured as both a for-profit public benefit corporation and a nonprofit foundation. The lab developed the GPT family of large language models, the DALL-E…

GPT-5.5 is OpenAI's newest frontier model in the GPT-5 series, released April 23, 2026, and positioned for the most complex professional work, including agentic coding, computer use, knowledge work, and early scientific research. It is the first OpenAI model to ship with a 1M-token context window in the API, and it uses adaptive reasoning to dynamically allocate computation, supporting effort settings up to xhigh.

Compared with its same-family predecessor GPT-5.4, OpenAI positions GPT-5.5 as a capability step up for agentic and long-context tasks. Stepping back further to GPT-5.2, the series has continued emphasizing long-context understanding and agentic tool-calling.

OpenAI describes GPT-5.5 as delivering strong results on its Artificial Analysis Coding Index evaluation, while noting that pure knowledge-recall benchmarks such as Humanity's Last Exam remain a relative weak spot.

GPT-5.5 supports the same tool-calling patterns as recent siblings, including function tools, web search, and computer use, and integrates with OpenAI's Responses and Chat Completions APIs. A higher-end sibling, GPT-5.5 Pro, targets the most demanding reasoning tasks.