Arthur Renard

Machine-learning researcher
Founding engineer, Xent Labs
Lausanne, Switzerland

I teach language models to improve themselves — with reinforcement learning, and with games.

Follow the white rabbit
Arthur Renard
“Down the rabbit hole”
Lausanne 2026

Lumière 1895 · Méliès 1901–1902 · Hepworth & Stow 1903 · Chomón 1907–1909 · Cohl 1908 · oil projection by Popular Spectacle

John Tenniel’s engraving of the Caterpillar smoking a hookah on a mushroom, with Alice looking up at him.
John Tenniel, “Advice from a Caterpillar”, 1865

‘Who are you?’
said the Caterpillar.

An applied mathematician, mostly. I work on reinforcement learning for self-improving language models.

Originally from Belgium, I moved to Switzerland to study mathematics at EPFL and applied mathematics at ETH Zürich, with a year at KTH in Stockholm in between.

Today I am a founding engineer and ML researcher at Xent Labs, where we develop Xent Games: an open-ended space of games for language models that produces measurable signals on reasoning, anticipation and cooperation.

Outside of research, I build things that ship — among them the website and app of Festival Balélec, Europe’s largest student festival.

2022 – 2024
ETH Zürich — MSc Applied Mathematics. Statistics and deep learning; thesis on symbolic regression with transformers for math-olympiad problems.
2021 – 2022
KTH, Stockholm — Exchange year, Applied Mathematics.
2019 – 2022
EPFL, Lausanne — BSc Mathematics.

Symbolic regression · Mathematical reasoning · Generative models · LLM training & evaluation · Reinforcement learning · Artificial life

French · English · German (intermediate)

Research

‘Curiouser and curiouser!’ cried Alice.

Grid of twelve snow crystals photographed by Wilson Bentley.
Wilson A. Bentley, snow crystals, c. 1902

I.

Preprint · 2026

Cross-Entropy Games and Frost Training

A method that uses reward gradients in embedding space to accelerate GRPO training on Cross-Entropy Games.

LLMs · GRPO · Reinforcement learning

arXiv

Nineteenth-century phrenology bust of Dr Spurzheim, the skull divided into labelled faculties.
Phrenological bust of Dr Spurzheim, 19th c. — Library of Congress

II.

Preprint · 2026

Cognitive Training for Language Models

A principled framework for relevant skill discovery in language models via Cross-Entropy Games: a curriculum of tasks that develops general capabilities.

LLMs · Curriculum learning · Optimization

arXiv

Leibniz’s handwritten table of powers of two written in binary, next to a centimetre ruler.
G. W. Leibniz, binary table, manuscript c. 1697

III.

AI for Math Workshop · ICML 2025

Boolformer

A Transformer for symbolic regression of Boolean functions: it reads a truth table and writes down a compact formula — robust to noisy and partial data.

Transformers · Symbolic regression · Interpretable ML

arXivCode

Ernst Haeckel’s plate of radiolarians: intricate symmetrical microscopic skeletons on black.
Ernst Haeckel, Spumellaria, Kunstformen der Natur, 1904

IV.

GECCO Companion · 2024

Phase Transition Finder

An algorithm that locates parameters on the border between phases of high-dimensional dynamical systems. Applied to Lenia, it doubles the frequency of interesting emergent behaviours.

Complex systems · Artificial life · PyTorch

arXivCode

Xent Labs · since 2025

We build Xent Games — an open-ended space of games that language models play to get better, and that tell us how well they reason, anticipate and cooperate. Croquet with flamingos, more or less.

Cecil Hepworth & Percy Stow, Alice in Wonderland, 1903

Side projects

‘It’s always tea-time.’

Lumière, L’Arrivée d’un train en gare de La Ciotat, 1895

2026 · Three.js · MediaPipe · Blender

Super Claude Bros

Hand-controlled games: four finger-gun shooters and a kart racer steered with an invisible wheel.

PlayCode

Georges Méliès, Le Mélomane, 1903

2026 · Strudel · MIDI · TypeScript

Strudelify

Type a song name, get an editable instrumental loop in Strudel — compiled from open transcriptions, no LLM involved.

Try itCode

Georges Méliès, L’Homme à la tête en caoutchouc, 1901

2025 · FLUX.1 · LoRA · Flow matching

Fluxtuning

A practical write-up on fine-tuning FLUX.1-dev with LoRA for personalised image generation.

ReadCode

Segundo de Chomón, Symphonie bizarre, 1909

2024 · Next.js · TypeScript · Strapi

Festival Balélec

The official website and mobile app of Europe’s largest student festival: live schedules, maps and artist information.

Visit

Experience

‘Would you tell me, please, which way I ought to go from here?’

Tenniel’s engraving of Alice looking up at the Cheshire Cat sitting in a tree.
John Tenniel, “Pig and Pepper”, 1865

  1. 2025 — now

    Xent Labs

    Founding engineer & ML researcher · Lausanne

    Building Xent Games, an LLM-native game space designed to train and evaluate reasoning, anticipation and cooperation in language models.

  2. 2023 — 2025

    EPFL

    Researcher, Chair of Statistical Field Theory · Lausanne

    Symbolic methods and deep learning — Boolformer (AI for Math Workshop, ICML 2025) and the Phase Transition Finder (GECCO Companion 2024), under Prof. Clément Hongler.

  3. 2023 — 2024

    Festival Balélec

    Web lead, volunteer · Lausanne

    Designed and built the website and mobile app for Europe’s largest student festival — more than 15,000 attendees.

Tenniel’s engraving of the grinning Cheshire Cat in a tree.

Wish you were here.

‘We’re all mad here.’

arthurenard@icloud.com

John Tenniel, the Cheshire Cat vanishing, 1865