OpenAI Releases GPT-5.5 Pro with 1M+ Token Context Window

OpenAI has released GPT-5.5 Pro, a new model featuring a 1,050,000 token context window and pricing of $30 per million input tokens and $180 per million output tokens. The model was released on April 24, 2026.

Technical Specifications

GPT-5.5 Pro offers a split context window: 922,000 tokens for input and 128,000 tokens for output. According to OpenAI, the model is optimized for "deep reasoning and accuracy on complex, high-stakes workloads." It supports both text and image inputs, making it a multimodal model.

The pricing structure shows a 6:1 ratio between output and input tokens, with output tokens costing $180 per million compared to $30 per million for input tokens.

Intended Use Cases

OpenAI positions GPT-5.5 Pro for three primary applications:

• Long-horizon problem solving requiring extended context
• Agentic coding tasks
• Precise execution across multi-step workflows

The model includes reasoning capabilities with a step-by-step thinking process. Developers can enable this feature using the reasoning parameter in API requests and access the reasoning_details array in responses to view the model's internal reasoning chain.

Availability

GPT-5.5 Pro is available through OpenRouter, which routes requests across multiple providers with fallback support for uptime. The model is accessible via OpenRouter's API with standard OpenAI SDK compatibility.

What This Means

The 1M+ token context window represents a significant expansion in working memory compared to previous models, enabling applications that require processing entire codebases, long documents, or extended conversation histories. The $30/$180 pricing positions GPT-5.5 Pro in the premium tier, suggesting OpenAI expects it to be used for high-value tasks where the extended context and reasoning capabilities justify the cost. The 6:1 output-to-input pricing ratio incentivizes efficient prompt design and may make the model less suitable for long-form generation tasks compared to analytical or reasoning-heavy applications.