GPT-5.5 Pro

GPT-5.5 Pro is the highest-accuracy tier in the GPT-5.5 line, designed for slower, precision-heavy reasoning and coding. It is the successor to GPT-5.4 Pro in the gpt-pro line. It has a context window of 1,050,000 tokens and a max output of 128,000 tokens. Pricing is from $27.27 per million input tokens and $163.64 per million output tokens, with cached input at $3.00 per million. Weights are not open. It supports reasoning mode, tool calling, and accepts image, pdf, and text inputs, returning text. Knowledge cutoff is 2025-12-01.

Against GPT-5.4 Pro: input $24.00 to $27.27, output $144.00 to $163.64.

Range across the hosts that serve it: up to $30.00 per 1M input tokens.

• ·Highest-accuracy GPT-5.5 tier for precision tasks
• ·1.05M token context window
• ·128K max output tokens
• ·Supports reasoning mode and tool calling
• ·Accepts image, pdf, and text inputs

• Reach for it for precision-heavy reasoning and coding
• Reach for it for tasks needing large context up to 1.05M tokens
• Reach for it for multimodal input with image, pdf, and text

18 hosts serve this model at the price above · the maker's documentation

The registry keeps the six most recent versions of a line. Older ones stay in the file and can be surfaced without a rebuild.

What is the context window size?

The context window is 1,050,000 tokens.

Is GPT-5.5 Pro open weights?

No, the weights are not open.

What is the pricing per million tokens?

Input from $27.27, output from $163.64, cached input at $3.00.