Song Mei

Assistant Professor at UC Berkeley, Department of Statistics and EECS. Researcher at OpenAI working on LLM training.

[Song Mei @Song__Mei]

Excited to contribute to GPT-5.2! Thanks, and congrats to all teammates!

[OpenAI @OpenAI]

GPT-5.2 Thinking evals

[Song Mei @Song__Mei]

🧄🧄🧄🚀🚀🚀

[Yu Bai @yubai01]

🧄GPT-5.2 is here – one small step on version number, one giant leap in capabilities. 🚀

With *incredible* @Song__Mei @yaodong_yu @Yuf_Zh @ofirnachum and rest of the @OpenAI team, we applied new techniques to bring our frontier reasoning model to the next level. GPT-5.2-Thinking is much stronger on intelligence, agentic coding, professional use, long-context understanding, and extended thinking.

It’s also better on science/theory research – try pairing with it!

Congrats also to @yanndubs @ericmitchellai @.ishaan @christinahkim, and heartfelt thanks to the leadership @_aidan_clark_ @max_a_schwarzer @markchen90 @merettm @sama for making this come together!

[Song Mei @Song__Mei]

@yubai01 This cannot happen without amazing colleagues: @SebastienBubeck
@yanndubs
@ElaineYaLe6
@christinahkim
@ericmitchellai
@michpokrass
@max_a_schwarzer
@SebastienBubeck
@minyoung_huh
@_chris_lu_
@SuvanshSanjeev
@hadisalmanX

[Song Mei @Song__Mei]

Today’s the day — GPT-5 is here! One of the reasons I joined OpenAI was to train the next generation of GPT. It became my first big project, and to my surprise, I became one of the core contributors — together with @yubai01 and many amazing colleagues — developing unexpected but cool techniques that made it into the final training stack. Hard to believe that just two months here could lead to such a big impact.

[OpenAI @OpenAI]

GPT-5 is here.

Rolling out to everyone starting today.

https://t.co/rOcZ8J2btI

[Yu Bai @yubai01]

Today is the day -- we are excited to bring gpt5 to you.

Fortunate to have led several workstreams in GPT5 Thinking and Mini model training. Among many other improvements, with @Song__Mei @minyoung_huh @SebastienBubeck and co, we applied some unexpected but cool techniques to make the model smart, chatty, and a good model all-around.

Also honored to have worked together with the crew @yanndubs @ElaineYaLe6 @christinahkim @ericmitchellai @michpokrass @max_a_schwarzer and everyone else, it was fun coming together and doing things!

Let us know how you like or dislike it -- this will not be the last model we're gonna train.

[Song Mei @Song__Mei]

@SebastienBubeck Thanks @SebastienBubeck! It is a great pleasure to work together : )

[Song Mei @Song__Mei]

Yes, this is super exciting!

[Yu Bai @yubai01]

Surreal & beyond excited to have joined forces with @Song__Mei again -- more to come soon!

[Song Mei @Song__Mei]

Thanks, everyone! Just a quick note—I only contributed a little bit on oss, but I’m glad I had the chance to be involved.

[Song Mei @Song__Mei]

I’m excited to start at OpenAI this May and help ship the oss model. More to come soon!

[OpenAI @OpenAI]

We released two open-weight reasoning models—gpt-oss-120b and gpt-oss-20b—under an Apache 2.0 license.

Developed with open-source community feedback, these models deliver meaningful advancements in both reasoning capabilities & safety.

https://t.co/PdKHqDqCPf

[Song Mei @Song__Mei]

@COPSSNews Congrats, @hongtuzhu1 !

[Song Mei @Song__Mei]

Congrats @LesterMackey ! I learned my first PhD stats course from your Stats 300 and have enjoyed the beauty of stats theory ever since.

[COPSS @COPSSNews]

🙌🎉Our 2025 recipient of the COPSS Presidents' Award, is Lester Mackey! This award is given annually to a young member of the statistical community in recognition of outstanding contributions to the profession of statistics.

[Song Mei @Song__Mei]

This is a reminder that the FSML workshop (https://t.co/KWmHxDeeVE, co-located with JSM) paper submission deadline, Mar 3 AoE, is in less than 2 days. This is a non-archival workshop so feel free to submit any interesting statsML paper already submitted elsewhere. It is a great opportunity to get travel funding to JSM and communicate your recent research with the community. Submission portal here: https://t.co/JIIEnWoxCV

[Yuhang Cai @YuhangWillCai]

We show the implicit bias of GD for generic non-homogeneous deep nets (results of such were previously limited to homogenous ones). In particular, our results cover those with residual connections and non-homogeneous activation functions. It's a joint work with Kangjie Zhou, @uuujingfeng Jingfeng Wu, @Song__Mei Song Mei, Michael Lindsey, and Peter L. Bartlett!
Arxiv: https://t.co/X5TFvWKtah.

[Song Mei @Song__Mei]

Excited to share our review paper on LLM for statisticians!

[Jason Weston @jaseweston]

🚨 New Paper 🚨
An Overview of Large Language Models for Statisticians
📝: https://t.co/oklTYEAMvH

- Dual perspectives on Statistics ➕ LLMs: Stat for LLM & LLM for Stat
- Stat for LLM: How statistical methods can improve LLM uncertainty quantification, interpretability, trustworthiness & more.
- LLM for Stat: How LLMs can enhance statistical workflows: from data collection, synthesis, annotation to statistical modeling, with applications to medical research

Presents key LLM advances: Architecture, Training, Reasoning, and Self-Alignment:
(1) 🧠Evolution of LLM architectures with Transformers and Self-Attention
(2) LLM training pipeline from pre-training, SFT, to RLHF and Preference Optimization.
(3) 💭 System 2 Prompting and Chain-of-Thought for test-time scaling .
(4) 🚀 LLM Self-Alignment for achieving super-human intelligence

Statisticians play a key role in the development of large-scale AI models:
(1) 💡 Statistical insights improve LLM uncertainty quantification & interpretability
(2) 🤖 Watermarking for AI-generated content detection
(3) ⚖️ Privacy & algorithmic fairness to ensure responsible AI adoption

LLMs can also empower statistical science by:
(1) 📈 Scaling up data collection, synthesis, and annotation.
(2) 🖥️ Automating statistical coding & exploratory analysis
(3) 🔬 Facilitating medical research

By bridging statistics & AI, we can:
✅ Improve better LLMs with statistical methodologies.
✅ Leverage LLMs for statistical applications in high-stakes domains

[Song Mei @Song__Mei]

@JiequnH Congrats!!!

[Song Mei @Song__Mei]

@_sdbuchanan Thank you, Sam!

[Song Mei @Song__Mei]

Honored to receive the Sloan Fellowship! Grateful for the support I’ve received along the way. With this opportunity, I look forward to advancing research in the intersection of math, statistics, and AI. #SloanFellow

[Sloan Foundation @SloanFoundation]

🎉Congrats to the 126 early-career scientists who have been awarded a Sloan Research Fellowship this year! These exceptional scholars are drawn from 51 institutions across the US and Canada, and represent the next generation of groundbreaking researchers. https://t.co/MO8q8eABH4

[Song Mei @Song__Mei]

@hanzhao_ml Thanks, Han!

[Song Mei @Song__Mei]

@SharonYixuanLi Thanks Sharon! Also congrats to you!

[Song Mei @Song__Mei]

@wu_xiao1993 Thanks, Xiao!

[Song Mei @Song__Mei]

@risteski_a Thanks, Andrej!