---
id: "2024-09-12-openai-o1"
url: "https://postcutoff.com/e/2024-09-12-openai-o1/"
as_of: "2026-11-13T13:49:00+01:00"
date: "2024-09-12"
date_precision: day
category: model-release
importance: 5
confidence: high
status: [Confirmed]
sources: 2
editor: human editor
human_review: null
version: "2026-10-04"
---

As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/e/2024-09-12-openai-o1/

# OpenAI o1: reasoning models trained with reinforcement learning

OpenAI released o1-preview and o1-mini, models trained with large-scale RL to 'think' via a long private chain of thought before answering, yielding large gains in math, science and coding and introducing test-time compute scaling.

## Key facts
- Announced 12 September 2024 (o1-preview, o1-mini); full o1 released 5 December 2024
- AIME 2024: o1 averaged 74% (single sample) vs 12% for GPT-4o, per OpenAI
- Exceeded PhD-level accuracy on GPQA Diamond science questions, per OpenAI
- Performance improved with both more RL training compute and more thinking time
- Codenamed 'Strawberry' in press reports

## What happened

OpenAI introduced a new model series that spends variable inference-time compute reasoning before responding.

## Why it matters

Opened the 'reasoning model' era and a new scaling axis (test-time compute); every major lab followed within months.

## Your AI and this story

- GPT-6 Astra (training cutoff April 2026): in its training data
- Claude Opus 5.5 (training cutoff June 2026): in its training data
- Gemini 4 Hydrogen (training cutoff March 2026): in its training data
- Grok 4.7 (training cutoff May 2026): in its training data

## Sources

1. [Learning to reason with LLMs (OpenAI)](https://openai.com/index/learning-to-reason-with-llms/) (openai.com, official)
2. [Introducing OpenAI o1-preview (OpenAI)](https://openai.com/index/introducing-openai-o1-preview/) (openai.com, official)

## Changes

- 2026-09-29 (filed): Created

## Related

- 2025-01-20: [DeepSeek-R1: open-weights reasoning model rivals o1 and shakes markets](https://postcutoff.com/e/2025-01-20-deepseek-r1/index.md)
- 2024-12-20: [OpenAI announces o3, scoring 75.7–87.5% on ARC-AGI](https://postcutoff.com/e/2024-12-20-openai-o3/index.md)
- 2022-01-28: [Chain-of-thought prompting elicits reasoning in LLMs](https://postcutoff.com/e/2022-01-28-chain-of-thought/index.md)