Overview
GPT-5.5 Pro is OpenAI's highest-capability reasoning model, launched alongside GPT-5.5 on April 23, 2026 and available in the API as gpt-5.5-pro. It is a dedicated reasoning model that, per OpenAI's docs, 'uses more compute to think harder and provide consistently better answers,' with individual requests potentially taking several minutes to complete.
It shares GPT-5.5's core specifications: a 1,050,000-token context window, up to 128,000 output tokens, a December 1, 2025 knowledge cutoff, and text-and-image input with text output. Unlike the standard model, it supports reasoning tokens and is optimized for difficulty over speed. It supports function calling and structured outputs but does not support streaming or fine-tuning.
GPT-5.5 Pro is aimed at research-grade and high-stakes problems where accuracy matters more than latency. In ChatGPT it is offered to Pro, Business, and Enterprise users, and it complements the faster standard GPT-5.5 for the hardest scientific, mathematical, and engineering tasks.
| Released | 2026-04 |
|---|---|
| License | Proprietary |
| Weights | API only |
| Parameters | Undisclosed |
| Context | 1.05M |
| Max output | 128K |
| Knowledge cutoff | 2025-12-01 |
| Modalities | Text, Vision |
| Status | Available |
Pricing
| Input | $30.00 / 1M tokens |
|---|---|
| Output | $180.00 / 1M tokens |
Strengths
- Highest-capability OpenAI reasoning model for the hardest problems
- Uses extended test-time compute for more reliable, consistent answers
- Same 1,050,000-token context window as flagship GPT-5.5
- Native reasoning-token support and structured outputs
- Strong on research-grade scientific, mathematical, and engineering tasks
Best for
- Research-grade math, science, and engineering problem solving
- High-stakes analysis where accuracy outweighs latency
- Complex agentic tasks needing deep multi-step reasoning
- Verification and review of difficult technical work
How to access
| Provider | Model ID |
|---|---|
| OpenAI API ↗ | gpt-5.5-pro |
GPT Pro — every version
The full lineage of the GPT Pro line, newest first. Every version has its own page — click any to compare specs, benchmarks and pricing.
| Version | Released | Context | License |
|---|---|---|---|
| GPT-5.5 Procurrent | 2026-04-23 | 1.05M | Proprietary |
| GPT-5.4 Pro | 2026-03-05 | — | Proprietary |
| GPT-5.2 Pro | 2025-12-11 | — | Proprietary |
| GPT-5.1 Pro | 2025-11-19 | — | Proprietary |
| GPT-5 Pro | 2025-08-07 | — | Proprietary |
FAQ
What is GPT-5.5 Pro?
GPT-5.5 Pro is OpenAI's highest-capability reasoning model, released April 23, 2026 alongside GPT-5.5. Available in the API as gpt-5.5-pro, it uses more test-time compute to think harder and return consistently better answers on the hardest problems, trading speed for accuracy.
How is GPT-5.5 Pro different from GPT-5.5?
GPT-5.5 Pro is a dedicated reasoning model that spends extra compute per request, so responses can take several minutes, whereas standard GPT-5.5 is fast. Pro adds reasoning-token support and is tuned for the hardest problems; it does not support streaming, and it costs significantly more per token.
How much does GPT-5.5 Pro cost?
According to OpenAI's official model docs, GPT-5.5 Pro is priced at $30.00 per 1M input tokens and $180.00 per 1M output tokens. Cached input pricing is not offered for the Pro model, reflecting its compute-intensive, deep-reasoning design.
What context window does GPT-5.5 Pro support?
GPT-5.5 Pro shares the flagship's specifications: a 1,050,000-token context window and up to 128,000 output tokens, with a December 1, 2025 knowledge cutoff. It accepts text and image inputs and returns text, making it suitable for deep reasoning over very large inputs.