GPT-5.5 Pro
Parameters
Undisclosed
Context Length
1M
Modality
Multimodal
Architecture
Undisclosed
License
Proprietary
Release Date
23 Apr 2026
Knowledge Cutoff
-
API Pricing (per 1M)
Input: $30.00 · Output: $180.00
Evaluation Benchmarks
No evaluation benchmarks for GPT-5.5 Pro available.
Rankings
Overall Rank
-
Coding Rank
-
About GPT-5.5 Pro
GPT-5.5 Pro is OpenAI's maximum-performance variant of GPT-5.5, designed for the hardest questions and highest-accuracy work. Achieves top results on BrowseComp (90.1%), FrontierMath Tier 4 (39.6%), GeneBench (33.2%), and Humanity's Last Exam with tools (57.2%). Particularly strong for business, legal, education, and data science tasks. Available via API as gpt-5.5-pro at $30/M input and $180/M output tokens. Released April 23, 2026.
Technical Specifications
Architecture specifications are undisclosed for proprietary models.
Attention
Attention Structure
Multi-Head Attention
Attention Heads
Undisclosed
Key-Value Heads
Undisclosed
Attention Head Dimension
Undisclosed
Position Embedding
Absolute Position Embedding
RoPE Theta
Undisclosed
Sliding Window Attention
Undisclosed
Sliding Window Size
Undisclosed
Sliding Window Ratio
Undisclosed
Linear Attention
Undisclosed
Linear Attention Ratio
Undisclosed
Normalization
Undisclosed
Activation Function
Undisclosed
Dimensions
Hidden Dimension Size
Undisclosed
Number of Layers
Undisclosed
FFN Intermediate Size (Dense)
Undisclosed
Multi-Token Prediction Heads
Undisclosed
Tokenizer
Vocabulary Size
Undisclosed
Resources
About GPT-5.5
GPT-5.5 is OpenAI's smartest and most intuitive model yet, and the next step toward a new way of getting work done on a computer. It excels at agentic coding, computer use, knowledge work, and scientific research — areas where progress depends on reasoning across context and taking action over time. It matches GPT-5.4 per-token latency in real-world serving while performing at a significantly higher level of intelligence, and uses fewer tokens to complete the same tasks. State-of-the-art on Terminal-Bench 2.0 (82.7%), SWE-Bench Pro (58.6%), OSWorld-Verified (78.7%), and ARC-AGI-2 (85.0%). Features a 1M context window and costs $5/M input tokens and $30/M output tokens. Released April 23, 2026.