Overview
GPT-5.1 Pro was OpenAI's highest-compute consumer reasoning model, released on November 19, 2025 as part of the GPT-5.1 family. It rolled out inside ChatGPT and replaced GPT-5 Pro in the model picker. Like the rest of the GPT Pro line, GPT-5.1 Pro is the 'thinking-first' option built for hard problems: it spends extended, parallel test-time compute to produce the most careful and reliable answers OpenAI offered at the time, trading speed for quality.
Unlike the broader GPT-5.1 release, GPT-5.1 Pro was a ChatGPT product feature rather than a published API model. It was available to ChatGPT Pro and Business subscribers through the model picker, with the Pro plan priced at $200 per month. At launch OpenAI did not ship a separate gpt-5.1-pro API endpoint; developers wanting Pro-grade compute used the existing GPT-5 Pro API line, while GPT-5.1 itself shipped to the API as the standard model. Third-party trackers noted the GPT-5.1 Pro API had not been officially released.
GPT-5.1 Pro had an unusually short life at the top. OpenAI released the full GPT-5.2 family on December 11, 2025 — under a month later — and GPT-5.2 Pro took over as the smartest, most trustworthy ChatGPT option for difficult questions. GPT-5.1 Pro is therefore best understood as a brief, transitional step between GPT-5 Pro and GPT-5.2 Pro during OpenAI's rapid late-2025 release cadence.
| Released | 2025-11-19 |
|---|---|
| License | Proprietary (OpenAI). Available through ChatGPT subscriptions under OpenAI's terms of use; not open-weight. |
| Weights | API only |
| Parameters | Not disclosed by OpenAI. |
| Context | GPT-5.1 Pro ran inside ChatGPT, where OpenAI did not publish a token context limit for the Pro tier. The GPT-5.1 API model it is based on uses a 400,000-token context window. |
| Max output | Not separately published for the ChatGPT Pro tier. The GPT-5.1 API model supports up to 128,000 output tokens. |
| Architecture | Proprietary transformer-based reasoning model. As part of OpenAI's GPT Pro line, GPT-5.1 Pro uses scaled, parallel test-time compute to think for longer than the standard Thinking model before answering. OpenAI has not published the architecture details. |
| Knowledge cutoff | Not separately published for GPT-5.1 Pro. The underlying GPT-5.1 API model lists a September 30, 2024 knowledge cutoff. |
| Modalities | Text input, Image input, Text output |
| Status | Superseded. Released November 19, 2025 in ChatGPT; replaced GPT-5 Pro and was itself replaced by GPT-5.2 Pro on December 11, 2025. |
Benchmarks
Scores on a 0–100 scale (25-point gridlines); higher is better. Each benchmark links to its published source.
Pricing
| Input | No published API price per 1M tokens |
|---|---|
| Output | No published API price per 1M tokens |
GPT-5.1 Pro was a ChatGPT product feature, not a published API model. Access was via the ChatGPT Pro subscription at $200/month (also available to Business users); OpenAI did not publish per-token API pricing for a gpt-5.1-pro endpoint. The underlying GPT-5.1 API model was priced at $1.25/M input and $10/M output tokens.
Strengths
- Highest-quality, most reliable answers in the GPT-5.1 family for hard, multi-step problems
- Extended parallel test-time compute for careful reasoning rather than fast responses
- Strong fit for science, math, and complex coding work that rewards a higher-quality answer over speed
- Inherits the GPT-5.1 family's adaptive reasoning, improved instruction-following, and warmer conversational tone
- Multimodal input (text and image) for analyzing documents, charts, and screenshots
Best for
- Tackling difficult technical or scientific questions where answer quality matters more than latency
- Complex, multi-step coding and debugging tasks
- Deep research and analysis on hard reasoning problems
- Reviewing and reasoning over long or intricate documents
- Professional knowledge work for ChatGPT Pro and Business power users
How to access
| Provider | Model ID |
|---|---|
| OpenAI (ChatGPT) ↗ | GPT-5.1 Pro (ChatGPT model picker) |
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 was GPT-5.1 Pro?
GPT-5.1 Pro was OpenAI's highest-compute reasoning model in the GPT-5.1 family, released on November 19, 2025. It was the 'thinking-first' ChatGPT option that used extended, parallel test-time compute to give the most careful and reliable answers for hard problems, replacing GPT-5 Pro in the model picker.
Could you use GPT-5.1 Pro through the API?
Not at launch. GPT-5.1 Pro was a ChatGPT product feature for Pro and Business subscribers, not a published API model. OpenAI shipped standard GPT-5.1 to the API, but third-party trackers noted that a dedicated GPT-5.1 Pro API endpoint had not been officially released.
How much did GPT-5.1 Pro cost?
Access was through the ChatGPT Pro subscription at $200 per month (it was also available to Business users). OpenAI did not publish separate per-token API pricing for GPT-5.1 Pro; the underlying GPT-5.1 API model was priced at $1.25 per million input tokens and $10 per million output tokens.
Is GPT-5.1 Pro still available?
No. GPT-5.1 Pro was superseded quickly: OpenAI released the GPT-5.2 family on December 11, 2025, under a month after launch, and GPT-5.2 Pro took over as the top ChatGPT reasoning model.