OpenAI hires the Git AI founders to work inside Codex, and the standalone company will likely wind down

Aidan Cunniffe and Sasha Varlamov, the founders of the open-source Git AI project, are joining OpenAI to work on the Codex team. Cunniffe announced the move in a LinkedIn post late Friday and in a blog post on the Git AI site the same day. Thibault Sottiaux, a member of technical staff working on ChatGPT and Codex at OpenAI, confirmed the hire on X.

What Git AI actually does

Git AI is a Git extension that links every line of code committed to a repository back to the AI coding agent, the model, and the prompts that produced it. That mapping survives commits, merges, and rebases, so a team can see the split between code a human wrote and code an agent wrote, and can look at how often an agent's code gets reworked or thrown out later. Cunniffe writes that the tool now runs on "hundreds of thousands of developer machines at scale-ups and across the F500."

The tool supports OpenAI Codex, Anthropic's Claude Code, Cursor, and Google's Gemini CLI, plus the background agents from those vendors: Codex Cloud, Claude Web, Cursor Agent, and Devin. Its selling point has been that cross-agent view: pick any two agents, run the same team on both, and get a real number for how much of each agent's output survived to production.

What OpenAI is buying

Sottiaux wrote that OpenAI's plan is to use Git AI's technology "to make it easier for businesses to see where Codex is making a difference." Cunniffe framed the shared belief as giving users "the data to compare model performance and understand the ROI of every token they spend." He also said OpenAI will keep investing in the open-source project.

Neither side has said what the deal was worth, whether it was an acquihire or an acquisition, or what happens to the commercial contracts already running on Git AI. Paul Sawers at The New Stack reports that "with both founders joining OpenAI, the standalone business will likely be wound down while the open-source project continues."

The cross-model question

Git AI worked as a measurement tool because it had no side in the fight. It could tell a team that Claude Code was producing more shippable code than Codex on their repo, or the other way, and neither vendor could push back on the numbers because the tool did not belong to either of them.

That posture is now hard to hold. A tool owned by OpenAI, staffed by former Git AI people who report to the Codex team, can still publish honest cross-agent numbers, but the reader has to trust it in a way they did not before. If the same measurement later shows Codex ahead of a competitor on the same repo, an engineering leader is now weighing whether to change tools based on data collected and analysed by the vendor that ships the winning tool. Teams that already use Git AI to decide between agents should watch what happens to the OSS project's governance, its release cadence, and whether anyone outside OpenAI keeps commit access.

Cunniffe founded developer-tools startup Optic in 2018, which Atlassian acquired in 2024. He started Git AI with Varlamov as a side project in summer 2025, left Atlassian in January 2026 to work on it full time, and is now on his way to OpenAI less than a year later.

Source

Primary source: Git AI is joining OpenAI on the Git AI blog. Reporting: Paul Sawers at The New Stack. Sottiaux's confirmation on X: @thsottiaux.