OpenAI describes Pando, a Git-compatible backend built for Codex-scale development

OpenAI's engineers say the load on the company's monorepo grew so fast with Codex (more branches, pushes, merges, fetches and clones from development environments, research jobs and CI) that, from around the end of 2025, fetches and pushes were slow and merges failed, with reliability at times below 90%. In response they built Pando, a new backend for Git repositories, which OpenAI says now powers all development in its monorepo.

OpenAI says Pando works with the standard Git protocol and client, so engineers and agents did not have to change their workflow. It coordinates each branch's updates independently, so pushes to different branches do not wait on each other, and it reuses packfiles across fetches instead of building one per client. The trade-off OpenAI describes is causal consistency: a client reading several branches cannot assume they reflect a single point in time, while updates to one ref stay strictly ordered.

OpenAI reports that in production Pando cut median push latency by nearly 5x and delivers nearly a petabyte of Git data per day. It compares the design with three-phase-commit and write-ahead-log approaches in a simulation of 1,000 writers, and says it plans to contribute client improvements from its fork of Git upstream. These are OpenAI's own figures.