Yi

Yi (meaning "one" in Chinese, stylised as Yi or 易) is a family of open-source large language models developed by 01.AI (零一万物, Língyī Wànwù), a Beijing-based AI startup founded in March 2023 by Kai-Fu Lee. Lee is a prominent figure in the global AI industry, having led AI divisions at Apple, SGI, Microsoft, and Google before founding the venture capital firm Sinovation Ventures. 01.AI was one of several well-capitalised Chinese AI startups founded rapidly in 2023 following the public launch of ChatGPT.

Founding and Positioning

01.AI was founded with the explicit goal of competing in the global frontier of large language model development, distinguishing itself from many Chinese AI startups by prioritising international-standard open-weight model releases alongside domestic applications. Kai-Fu Lee's international reputation and English-language communication provided the company visibility in Western AI communities that Chinese-language-only startups typically lacked.

The company reached a unicorn valuation (exceeding USD 1 billion) within months of its founding, backed by investors including Alibaba and leading Chinese and international venture capital firms.

Yi-34B and Early Releases

In November 2023, 01.AI released Yi-34B, a 34-billion-parameter model supporting Chinese and English that outperformed significantly larger models including Llama 2-70B and Falcon-180B on standard benchmarks at the time of release. Yi-34B demonstrated that aggressive pretraining on high-quality bilingual data could produce competitive models at a fraction of the parameter count of competing open-weight releases.

01.AI subsequently open-sourced Yi-9B, positioning it as particularly strong for code and mathematical tasks within the same model family. A Yi-6B variant provided a smaller, more hardware-accessible option. The release of Yi models on Hugging Face attracted widespread downloads and fine-tuning experiments from the global open-source AI community.

Yi-1.5 and Yi-Lightning

Yi-1.5 (May 2024) introduced an updated series with improved instruction following and conversational capabilities, incorporating lessons from RLHF alignment and expanding context window support. The series included 6B, 9B, and 34B parameter variants.

Yi-Lightning, released October 2024, was 01.AI's flagship model at the time of its release. In the LMSYS Chatbot Arena leaderboard — which ranks models based on human pairwise preferences — Yi-Lightning placed joint third among all AI companies globally, alongside xAI's Grok-2, behind only OpenAI and Google. This represented a significant achievement for a Chinese startup in a benchmark designed around human preference rather than automated metrics.

Strategic Pivot

In March 2025, 01.AI announced a strategic pivot away from pretraining its own frontier LLMs. The company cited the commoditisation of foundation model training — driven largely by DeepSeek's release of highly capable open-weight models — as making independent pretraining economically unjustifiable for a startup of its scale. Instead, 01.AI repositioned as a company selling tailored AI business solutions and applications built on top of DeepSeek's open-weight models, optimising for enterprise deployment and industry-specific fine-tuning rather than frontier model research.

See Also

References

References

1. Wikipedia. (2025). 01.AI. en.wikipedia.org.
2. TechCrunch. (2023). Valued at $1B, Kai-Fu Lee's LLM startup unveils open source model. techcrunch.com.
3. VentureBeat. (2023). Chinese AI unicorn's 34B LLM outperforms larger Llama 2 and Falcon models. venturebeat.com.
4. LabLab.ai. (2025). 01.AI's Yi series large language models. lablab.ai/tech/yi-llms.
5. Hugging Face. (2025). 01-ai model collection. huggingface.co/01-ai.