MLR/
H Company / Berlin, Germany

Mats Leon
Richter.

Research Scientist
Pretraining, Posttraining & Agentic AI

Würstchen co-first author · ICLR 2024 oral

I develop foundation models and agentic systems through large-scale training, posttraining and synthetic data, including contributions to H Company’s Holo and Holotron models.

Across research
& industry
H Company
Mila
ServiceNow Research
Osnabrück University
01 / Selected research

More capable models.
More efficient training.

I want to make foundation models more capable for the compute spent training them. This connects my work on efficient generative models, continual pretraining, synthetic data and distributed systems.

I’m particularly interested in compact models with strong agentic capabilities, and the training methods and data that make them possible.

Complete publication record on Google Scholar ↗
TMLR 2024Coauthor

Continual pretraining

Simple and Scalable Strategies to Continually Pre-train Large Language Models

Matched a retraining-from-scratch baseline at 10B parameters with less compute, using learning-rate rewarming, redecay and data replay.

My contribution

Engineered the distributed training setup for ablations across model scales. Adapted PyTorch, DeepSpeed and Megatron forks to Summit’s POWER9 CPUs and six-GPU nodes, enabling runs on up to 13,824 GPUs.

Language modelsTraining efficiency
TMLR 2026 · FEATURED CERTIFICATIONCoauthor

MixtureVitae

Open web-scale pretraining data

A 422B-token pretraining corpus built from permissive-first text sources, including instruction and reasoning data.

My contribution

Designed and implemented distributed data-processing pipelines for the corpus.

Pretraining dataOpen research
ICLR 2025Coauthor

BigDocs

An Open Dataset for Training Multimodal Models on Document and Code Tasks

An open multimodal dataset for document understanding and code tasks.

My contribution

Designed and implemented distributed data-processing pipelines for the dataset.

Multimodal learningDocuments & code
02 / Agentic AI & computer use

Posttraining for
capable agents.

For Holo1–3, I built synthetic-data generation and desktop/web-agent evaluation pipelines, and ran supervised fine-tuning (SFT). My broader work spans Holo and Holotron model training and releases.

Holo3-35B-A3B · April 2026 evaluation80.36% OSWorld-Verified

Ranked #1 at the time of evaluation. 35B total / 3B active parameters.

Official OSWorld leaderboard ↗

NVIDIA collaborationCollaborated on official Nemotron releases at H.

Updates on LinkedIn
Selected release contributions
Holo

Holo1 · Holo2 · Holo3
Holo3.1 · Holo4

Holotron

Computer-use models

Surfer

Surfer-H · Surfer 2

03 / Experience

Training systems.
Research leadership.

From leading industry teams to academic research and foundation-model releases.

2024 — Present

H Company

Research Scientist · Core Team

Built synthetic-data and agent-evaluation pipelines and ran SFT for Holo1–3. Trained models for Holo releases on 1,024 H100 GPUs and collaborated with NVIDIA on official Nemotron releases.

Jan — Sep 2024

ServiceNow Research

Senior Research Scientist

Foundation-model safety evaluation and automated red teaming in the Trust and Governance Lab.

2022 — 2024

Mila / Université de Montréal

Postdoctoral Researcher · DAAD IFI Fellow

Designed experiments and ablation studies for Würstchen. Engineered distributed training for continual-pretraining studies on Summit and Frontier.

2021 — 2022

Osnabrück University

Research Associate

Neural architecture design and computer vision, including medical imaging.

2017 — 2021

Agile. IT. Management.

Data Scientist → Head of Data Science

Led a team of 10 data scientists and software engineers on applied machine-learning projects.

Leadership & research community

Teams, infrastructure and research mentorship.

Elected representation

Lab Representative
at Mila

Elected representative for Université de Montréal postdoctoral researchers; served on Mila’s Leadership Committee.

Research infrastructure

Supporting the systems
behind the science

Contributed benchmarks and code for future deep-learning clusters through Mila’s IDT Committee.

Teaching & mentorship

Developing the next
generation of researchers

Created Advanced Topics in Deep Learning at Osnabrück and mentored Mila master’s interns. Primary supervisor for four theses; second supervisor for one.

04 / Get in touch

Research worth
talking about.

I welcome conversations about training efficiency, synthetic data and capable agentic models.

Based in Berlin, Germany