# GPT-5.1 Pro

> OpenAI's research-grade ChatGPT reasoning tier, succeeded within a month

- Maker: OpenAI
- Line: GPT Pro
- Canonical page: https://ai-tldr.dev/models/gpt-5-1-pro/
- Updated: 2026-06-18

## In short

GPT-5.1 Pro is OpenAI's research-grade ChatGPT reasoning tier, succeeded within a month. OpenAI released it on 19 November 2025 as an API-only model. You can use it through OpenAI (ChatGPT).

## Facts

| Fact | Value | Source |
| --- | --- | --- |
| Context window | 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.) | [1] |
| Input price | No published API price | [2] |
| Output price | No published API price | [2] |
| Licence | Proprietary (OpenAI). Available through ChatGPT subscriptions under OpenAI's terms of use; not open-weight. · API only | [1] |
| Released | 19 November 2025 | [3] |
| Parameters | Not disclosed by OpenAI. | [1] |
| Knowledge cutoff | Not separately published for GPT-5.1 Pro. The underlying GPT-5.1 API model lists a September 30, 2024 knowledge cutoff. | [1] |

## Sources

1. [GPT-5.1 model page (OpenAI API docs)](https://developers.openai.com/api/docs/models/gpt-5.1)
2. [What is GPT-5.1 Pro? (CometAPI explainer)](https://www.cometapi.com/what-is-gpt-5-1-pro/)
3. [GPT-5.1: A smarter, more conversational ChatGPT (OpenAI)](https://openai.com/index/gpt-5-1/)

## 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.

## Benchmarks

- SWE-bench Verified (GPT-5.1 family): 76.3% ([source](https://openai.com/index/gpt-5-1-for-developers/))

## 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.

Source: https://www.cometapi.com/what-is-gpt-5-1-pro/

## 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

- [OpenAI (ChatGPT)](https://openai.com/index/gpt-5-1/) — model id `GPT-5.1 Pro (ChatGPT model picker)`

## GPT Pro versions

- [GPT-5.5 Pro](https://ai-tldr.dev/models/gpt-5-5-pro/) (23 April 2026)
- [GPT-5.4 Pro](https://ai-tldr.dev/models/gpt-5-4-pro/) (5 March 2026)
- [GPT-5.2 Pro](https://ai-tldr.dev/models/gpt-5-2-pro/) (11 December 2025)
- GPT-5.1 Pro (19 November 2025) — this page
- [GPT-5 Pro](https://ai-tldr.dev/models/gpt-5-pro/) (7 August 2025)

## 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.

## Links

- [GPT-5.1: A smarter, more conversational ChatGPT (OpenAI)](https://openai.com/index/gpt-5-1/)
- [Introducing GPT-5.1 for developers (OpenAI)](https://openai.com/index/gpt-5-1-for-developers/)
- [GPT-5.1 model page (OpenAI API docs)](https://developers.openai.com/api/docs/models/gpt-5.1)
- [GPT-5.1 (Wikipedia)](https://en.wikipedia.org/wiki/GPT-5.1)
- [What is GPT-5.1 Pro? (CometAPI explainer)](https://www.cometapi.com/what-is-gpt-5-1-pro/)
- [Introducing GPT-5.2 (OpenAI) — the successor](https://openai.com/index/introducing-gpt-5-2/)

Source: AI/TLDR LLM registry, https://ai-tldr.dev/models/gpt-5-1-pro/