Steven Feng

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@stevenyfeng

Research Fellow @AnthropicAI. Stanford CS PhD student @stanfordnlp @StanfordAILab. Master's @CarnegieMellon @LTIatCMU, undergrad @UWaterloo @UWCheritonCS.

Stanford, CA styfeng.github.io Joined August 2019

511 Following 3.3K Followers 498 Posts

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Steven Feng @stevenyfeng Jul 1

We keep saying LLMs "hallucinate." But what does that actually mean?

In our new position paper, we argue hallucination isn't just "wrong facts." It's inaccurate internal world modeling.

We formalize this precisely in a unified definition to appear at #ICML2026 (@icmlconf)👇

Steven Feng @stevenyfeng Sep 28

Excited to share our #NeurIPS2026 paper on benchmarking hallucinations in LLMs! We take a fresh world model-centric approach to measuring hallucinations in several environments including terminal, grid worlds, and chess. Thanks to the @DegenAI_Labs team for their hard work!

Also grateful to collaborators at @Stanford, @StanfordAILab, @stanfordnlp, @CarnegieMellon, @LTIatCMU, @OhioState, and @OhioStateCSE.

Emmy Liu @_emliu Sep 28

Hallucinations are hard to measure because reality is messy. So we built our own world.

Introducing HalluWorld 🌎, a controlled benchmark for LLM hallucinations.

Now accepted to #NeurIPS2026 Evaluations & Datasets! 🧵

halluworld.ai

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Steven Feng @stevenyfeng Aug 6

Man doesn't realize he's talking to an AI

Steven Feng @stevenyfeng Jul 6

Come check out our #ICML2026 poster on Wed @icmlconf!

Emmy Liu @_emliu Jul 5

🗺️ We Need a Unified Definition of Hallucination (it's the world model, stupid!)

Poster: Wed, Jul 8, 2026 • 10:30 AM – 12:15 PM KST, Hall A #3311

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Steven Feng @stevenyfeng Jun 30

Excited to spend the summer at @AnthropicAI as a Research Fellow!

I'll be working on alignment and reasoning in LLMs. Looking forward to working with an incredible group of researchers.

If you'll be around the Bay or are interested in these topics, I'd love to connect!