Thibault Sottiaux

Sottiaux holds degrees in computer science, computational mathematics, and applied mathematics from the Université catholique de Louvain (UCLouvain). Earlier in Sottiaux's career, Sottiaux worked as a software engineer at Google and in applied research roles.1

At DeepMind, Sottiaux built AI/ML workflow infrastructure for DeepMind research. In February 2021 Sottiaux was one of seven co-authors, with colleagues from DeepMind and Google Research, of the paper introducing Reverb, an efficient, extensible, and easy-to-use system designed for experience replay in reinforcement learning that works in distributed configurations. Reverb is published on GitHub by Google DeepMind as a data storage and transport system for machine learning research.198

Sottiaux also led human data work for Gemini at Google DeepMind.1

At OpenAI, Sottiaux is a Member of Technical Staff who leads Codex, OpenAI's software engineering agent, and the OpenAI Forum lists Sottiaux as Head of Codex. OpenAI describes Sottiaux's work as building AI systems that help developers understand codebases and complete engineering tasks.12

Sottiaux also writes code for Codex in the open. In the public openai/codex repository, home of the Codex coding agent that runs in a developer's terminal, Sottiaux's pull requests began merging on April 16, 2025, with early changes that added retries and exponential back-off for rate-limit errors and more native keyboard navigation in the multiline editor. On December 2, 2025, Sottiaux added experimental support for skills to Codex.5674

On December 1, 2025, Sottiaux and Codex team colleagues published "A Practical Approach to Verifying Code at Scale" on OpenAI's alignment research blog. It describes a dedicated agentic code reviewer trained for OpenAI's Codex models, given repo-wide tools and execution access, and explains why reviewer precision matters for adoption and why verification is often cheaper than generation. The reviewer is deployed on internal and external GitHub traffic.3

On May 13, 2026, Sottiaux joined an OpenAI Forum conversation, "Codex is for Everyone: Why Codex Matters Beyond Code," on how Codex is evolving from a coding tool for developers, what the team is learning from the people who use it, and why agentic tools matter beyond software engineering, for audiences from leaders and researchers to educators and small business owners.12