Automating fork maintenance with AI agents

Maintaining a long-lived fork of an actively developed project is challenging, as each upstream release introduces changes that can disrupt the fork's functionality. The described method leverages AI coding agents to automate the cycle of syncing, measuring, fixing, and shipping updates to such forks, significantly reducing the time required for these tasks from weeks to days. This approach, applied to Cohere's fork of the vLLM project, uses a control theory framework to treat upstream changes as disturbances and employs a feedback loop to restore the fork to a working state with minimal human intervention. The process involves detecting upstream releases, rebasing the fork, running tests, and applying fixes until the desired outcome is achieved. This method, which enhances efficiency and reduces manual effort, is open-sourced at cohere-ai/vllm-skills and can be adapted to other codebases by defining measurable criteria for maintaining a "healthy" fork.