Butter

What is Butter?

Butter is an LLM proxy designed to improve consistency in agent-based automations. By caching and replaying language model responses, Butter enables automation systems to behave deterministically across multiple runs, reducing unpredictable behavior common in AI agents. The product provides a chat completions-compatible endpoint that integrates seamlessly into existing agent frameworks through a custom base_url, requiring minimal code changes. This approach allows developers to leverage their current infrastructure while adding reliability features. Butter also includes bVisor, a lightweight embedded sandbox runtime for AI agents that executes bash commands locally without requiring virtual machines or remote infrastructure. bVisor isolates command execution by intercepting Linux syscalls at the userspace level, inspired by gVisor but designed to run directly within applications. The tool is built for developers and teams implementing AI agent systems where consistent behavior and safe command execution are priorities. By eliminating the overhead of traditional sandboxing approaches, Butter enables faster local execution while maintaining security boundaries. Available as open source, Butter allows teams to self-host the solution and integrate deterministic caching into their agent workflows. The project targets the AI infrastructure and MLOps category, addressing a specific pain point in making autonomous systems more predictable and safer to deploy.