---
title: "o1"
type: "entity"
entity_kind: "concept"
status: "hub"
canonical_name: "o1"
aliases: ["o1-preview","OpenAI o1","o1 model series"]
first_seen: "2026-07-12T00:00:00.000Z"
writer_model: "claude-sonnet-5"
connects_to: ["OpenAI","chain-of-thought prompting","reasoning models","test-time compute","competitive moats in AI"]
seek_code_commit: "17d9798"
---


OpenAI's reasoning-model series, launched September 2024 and introduced in
the primary page "Learning to reason with LLMs." o1 is trained to spend
extra inference-time compute generating an internal chain of thought before
answering, which OpenAI reported measurably improved performance on hard
math, coding, and science problems relative to GPT-4o.

Matters to this vault as the reference point for the industry's first
widely-discussed hidden-reasoning product: the model whose raw
chain-of-thought OpenAI chose not to show users, citing competitive
advantage among its reasons
([[claim-openai-hid-o1-raw-chain-of-thought-partly-for-competitive-advantage]]),
showing a model-generated summary instead
([[claim-openai-o1-shows-model-generated-summary-of-chain-of-thought-not-raw-trace]]);
the benchmark s1 was built to match on 1,000 distilled traces and 26 minutes
of fine-tuning, cited as "o1-preview-level" performance
([[claim-s1-distilled-reasoning-from-1000-traces-in-26-minutes]]); and the
case study for whether a hidden reasoning trace can function as a durable
competitive moat
([[claim-a-chain-of-thought-trace-is-codified-so-it-cannot-form-a-tacit-moat]]).

## References

- [[claim-openai-hid-o1-raw-chain-of-thought-partly-for-competitive-advantage]]
- [[claim-openai-o1-shows-model-generated-summary-of-chain-of-thought-not-raw-trace]]
- [[claim-s1-distilled-reasoning-from-1000-traces-in-26-minutes]]
- [[claim-a-chain-of-thought-trace-is-codified-so-it-cannot-form-a-tacit-moat]]