
Postdoctoral Fellow @PrincetonPLI. Ph.D. @mldcmu @cmuneurosci. Prev. @yutori_ai @MSFTResearch.
Pittsburgh, PA
Joined January 2022
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Online evals are the gold standard for visual agents, but realistic VQA can serve as a fast, reliable proxy for testing the strengths and limitations. Excited to announce AgentVQA, composed of real-world, challenging agent inputs across five domains.
Gabriel Sarch retweeted
Human thought is thought to be systematic.
Do reasoning models have systematicity of thought?
With @LakeBrenden , we study this question in our new preprint now on arxiv.
Gabriel Sarch retweeted
Replying to @phillip_isola @Michael_J_Black
One way to think about this is that the existence of a powerful vision system (humans) did not make vision science an uninteresting field. Computer vision could become more like vision science. The creature now exists. Let's figure out how it works.
Gabriel Sarch retweeted
Replying to @Michael_J_Black
This resonates with me.
One option is to work less on solving tasks and more on understanding the solutions.
A paper that analyzes Astra + open models might have more lasting impact than one that tries to solve a new task that Astra+ will inevitably solve.
I’ll be presenting Vero this week at #ECCV2026. Come say hi!
Sept. 9 - Oral at the UniWorld workshop
Sept. 12 - Poster Session 6, 3pm, Poster #107
Efficient, small VLMs for the win!
Today, we release LFM2.5-VL-3B, a lightweight vision-language model that reads screens, documents, and the physical world. It handles digital screens across mobile, web, and desktop, grounds objects to coordinates, reads text and charts, and calls tools from either text or image input.
Built on LFM2.5-2.6B base, with a SigLIP2 400M NaFlex vision encoder
> Pre-trained on ~34T tokens
> Vocab size: 128K
Comparable or better scores compared to models up to 2.6x its size:
> ScreenSpot-v2 80.7, ahead of Gemma-4-E4B at 51.2
> RealWorldQA 73.1, ahead of InternVL-3.5-4B at 67.7
> TextVQA 84.3, ahead of Qwen3.5-4B at 81.2
> RefCOCO-avg 87.9, up from 57.1 on LFM2-VL-3B
> ToolSandbox 59.5, up from 26.4 on LFM2-VL-3B
🧵
Gabriel Sarch retweeted
My summer project is done! A 20 video, free course on post-training to accompany my book is all on YouTube with slides open for modification & re-use.
~12 hours of content covers the core foundations and some research areas I think will grow in importance. It was a fun time to review all the fundamentals again, as it is clear in the next 1-3 people the amount of people wanting to learn post training will likely 100X again from today, as we have already 100X'ed from two years ago.
As AI agents get increasingly capable at coding and discussing these fundamentals (see the code exercises accompanying the book that I am refining with the community) I think developing clear intuitions for how models work and why is one of the most important skills going forward in AI. Still, learning the post-training math is the best way to battle test them. I personally just in this course am starting to master how forward/reverse KL relates to post-training topics.
Thanks to all my viewers, and I'm happy to answer questions in the book discord or understand how to better teach the various reward models, on-policy distillation, new RL algorithms, etc.
Plus, the book is 50% off right now with the code PBLambert on Manning to celebrate the launch.
I'll share the relevant links below.
Who's going to make this course for pretraining?
Gabriel Sarch retweeted
.@danqi_chen, an expert in large language models, has been featured by the Communications of the ACM for her foundational work building small LLMs, which are vital to making modern models available on edge devices such as mobile phones.
bit.ly/4vhH5T0
Open weights are great, but open recipes are what make progress reproducible, accessible, and easy to build on. i1 releases a fully open path to strong text-to-image models, including 300+ experiments and lots of training insights. Happy to have played a small role in this.
Gabriel Sarch retweeted
Can a small academic team build a strong text-to-image model using only public datasets?
Introducing i1: a simple, fully open recipe for strong text-to-image models
100% agree with @natolambert here. The best recipe work does two things: as science, it explains why something works w/ careful analysis & ablations; for practitioners, makes the findings accessible and usable.
We're doing the same for VLMs at Princeton: vero-reasoning.github.io
TMax: An open RL recipe for terminal agents
I’m very excited to get to share a new RL paper today that I got to have a small part in – a type of paper I suspect we’ll see much more of in the future. The key is that RL research is very different today, in mid-2026, than what most observers have in their context. The average conception of an RL paper is grounded in the RLVR revolution of early 2025, where many people could use vanilla RLVR libraries to hillclimb on math benchmarks. Crucially, this style of math work could be done on base models or fairly stably on already trained models. With agents, the tasks of focus are very hard, requiring complex tool-use, harnesses where the model automatically manages its history, and much more training to make smaller eval improvements. We’re shifting from a renaissance of RL study to rapidly needing to improve its empirical rigor and common community engagements.
TMax is the best open data for hillclimbing on frontier terminal tasks. It’s been validated with rigorous experiments, and if the authors wanted to just form a “RL environments startup” they could probably sell it for millions of dollars. This data work is some of my favorite stuff to be around in my 2.5+ years at Ai2.
As a general summary, the recipe is open data and recipe lessons from hillclimbing the Qwen 3.5 smaller, dense models on terminal tasks. These models are super hard to hillclimb in this area, as they’re already trained heavily on the task. The training is very infrastructure-dependent, and most of the RL innovations are more designed to make training stable than to improve the rate of learning.
I strongly recommend this paper. I joke around that I was happy to be an author just so I had to read it twice! You can find Hamish’s thread sharing more here or read the paper here. You can click through to find the model weights, the data, and even some fun further artifacts to study like all the RL rollouts from a training run – where the model sometimes became aware that it was being tested.
The biggest takeaway I have from following this work, and more of the work in the community, is how important recipe work is. Let me define “recipe work.” It is a style of paper that explains all the steps you need to make crucial model improvements – data, algorithm, codebase, pitfalls, etc.
Getting started in meaningful RL experiments today is a substantial expense. There are a ton of companies, an entire industry emerging really, around the idea of taking open-weight language models and finetuning them with RL on your domain-specific tasks. What I see in many projects is that getting an initial baseline is very hard. This phase, which can cost weeks and anywhere from $10K to $1M+, feels like spinning your wheels (A fun fact is that an RL step on a model like Nvidia Nemotron 3 Ultra on Tinker costs $1K and a meaningful RL run would be hundreds of steps – credit Edward Hu). It takes a lot of time to get traction in learning signal on meaningful, hard RL tasks.
What we need as a community is a way for people to study small ablations to established RL recipes, as most labs won’t have the resources to do it from scratch in a meaningful way. This is what I hope TMAX can be for terminal agents, or the start of. Yes the training jobs are expensive, as the paper documents a standard training job being 8 nodes of H100s (2 train 6 inference) for 2-3 days, but that is approaching something academics can study. The establishment of this recipe took O(100) of these training jobs to get right.
This isn’t my first time trying to establish this direction. When we launched Olmo 3 we had the “RL Zero“ model families, which are clean RL runs from a base model on a certain domain. This type of recipe-dependent work is a clear indicator that meaningful post-training work today looks much more like pretraining work of years past. We need decision-making ladders, clear ways of seeing small improvements in the models, stability, and so on.
Part of this is down to academic gatekeepers, who won’t reward a paper doing very clean empirical work to push a recipe 1-2% up. They’ll favor a “new algorithm” that matches results, or something sort of bogus. My hope is that we can have multiple, stable, clear recipes across agent types, so innovations can be tested more clearly in multiple domains. (If you’re working on this, please reach out – I’m happy to support if I can, but I likely can’t reply to every email).
As a quick aside, the RL frameworks in vogue today seem to be SLIME and SkyRL. The libraries of choice have shifted throughout these seasons in RL, which further contributes to a form of fragility in the literature. A bit of continuity will go a long way.
So, go read this paper. It’s a really great example of how seemingly simple data and infrastructure work can be very hard and impactful. It’s also got me looking for more applications of Divergence Proximal Policy Optimization (DPPO) as another small evolution to the best RL algorithms of the day, by virtue of being a bit more stable by improving token-level clipping.
🔵 We’re releasing a major Vero update:
• Expanded dataset, models & baselines
• Vero-1.6M, expanding Vero-600K to 1.6M samples
• Vero-Qwen35-9B and Vero-Qwen35-9B-Base, improving 9B: 74.4 / 73.0 across 30 evals
Accepted to #ECCV2026!
Check it out: vero-reasoning.github.io
It’s clear VLMs still struggle across diverse visual inputs. Introducing WorldBench, our new VLM benchmark with visually diverse, realistic, and challenging VQA questions! All questions are annotated *by hand* and checked meticulously for quality. Try it out for yourself!
Today’s vision benchmarks suggest VLMs are nearing saturation, but real-world visual understanding is far from solved.
Introducing WorldBench: 2,000 hand-written, human-verified VQA questions focused on visual diversity and designed to be challenging for frontier models. Gemini-3.1-Pro leads with just 64.0% accuracy. (1/10)
Great to see this level of transparency from an industry lab. Detailed recipes and reporting like this are a real asset to the research community and the public!
MAI-Thinking-1 is out!
Excited to share what we are building and how climbing from scratch (no distillation) actually works: simple recipes, rigorous science, self-distillation, patience, and great infra.
Check out our tech report has the full story of our RL climbs.
microsoft.ai/wp-content/uplo…
I’ll be at CVPR June 3-6 and excited to talk with folks!
We’ll be presenting Vero at June 3 workshops (vero-reasoning.github.io):
- DataMFM Oral 2:40pm, Room 111
- MMFM Poster, 3pm, 3A
- ViScale Poster, 5pm, 506
And be sure to come by the CogVL Workshop cogvl.github.io!
Gabriel Sarch retweeted
CogVL Workshop at #CVPR2026 is less than a week away!
We have an exciting lineup of keynote speakers across Vision, NLP and Cog Sci, and orals/posters on reasoning methods for VLM models.
🕐 June 3, 1 PM
📍 Rooms 610/612
🔗 Schedule: cogvl.github.io
Happy to be recognized as an outstanding reviewer at CVPR!
We are grateful to all of the 17,491 reviewers who helped make #CVPR2026 possible. We are especially pleased to recognize the following Outstanding Reviewers, whose high-quality reviews (as judged by their Area Chairs) placed them among the top 5% of reviewers.
Really excited about this new work scaling VLMs to 100+ turns for playing Mario! Games are a great testbed for long-horizon agentic tasks, and this setting makes it clear the default short-horizon tricks for VLM training often fall short. Check out the thread and paper!
🔥 Excited to share our new paper:
🚀 Odysseus: Scaling VLMs to 100+ Turn Decision-Making in Games via Reinforcement Learning
🎮 We study how to make RL stable and effective for training VLM agents in long-horizon, visually grounded environments — using the video game Super Mario Land as a testbed.
📜 Paper: arxiv.org/abs/2605.00347
🔗 Project page (w/ video demos): odysseus-project.github.io/
Gabriel Sarch retweeted
AI agents can work pretty well on the web now for short tasks. I wanted to know: could they go longer, on harder tasks?
Can an agent plan 2 weddings in different cities and a honeymoon within the same month, or find the most suitable culinary arts school across the US for my post PhD plans?
We are releasing Odysseys: a benchmark of 200 long-horizon web agent tasks evaluated on the live internet. All our tasks are inspired from real human data and many take hours to complete.
The best frontier model we tested (Claude Opus 4.6) reaches only 44.5% perfect-task success, leaving substantial room for improvement.
I donated a couple of my own automation wishes to this benchmark. My favorite contribution was to “Rank the top 10 ACL + Meniscus surgeons in the area” - as this took me a decent amount of time to do myself when I got my own knee fixed. GPT 5.5 was able to do this for me with 4 dollars and 30 minutes!
Gabriel Sarch retweeted
Hi all. I just put up my course materials for my Multimodal LLM Agents course at @UUtah online so it can be used by the broader community. I really tried to tie together LLMs with RL and CV to give students the full picture of how MLLMs can be incorporated into embodied agents.






























