San: A Lightweight, Open-Source AI Agent Framework

Overview

San is an open-source AI agent framework designed for flexibility, performance, and portability. Built as a single Go binary, it eliminates the need for external runtimes like Node.js or Python, offering a streamlined experience for developers and users alike. The project is licensed under Apache 2.0 and is actively maintained by a community engaged via Slack and a WeChat group for Chinese speakers.

Benefits

San is built with modularity at its core, ensuring that users are never locked into specific providers or configurations. Every layer of the system is swappable at runtime, allowing for dynamic adaptation to different needs without code changes.

Key advantages include:-Multi-LLM Providers: Users can integrate any Large Language Model (LLM), ranging from Anthropic to Z.ai. Switching models is as simple as using the/modelcommand.-Pluggable Search: The framework supports various search engines, including Exa, Tavily, Brave, and Serper. Users can switch search providers via the/searchcommand.-Skills & Extensions: San is compatible with Claude Code's ecosystem, supporting skills, plugins, MCP servers, and subagents. These can be run unmodified, ensuring a seamless transition for existing workflows.-Personas: Users can define custom personas using Markdown, bundling system prompts, skills, and configurations. These personas can be switched per user or project using the/personacommand.-Native Performance: As a single Go binary, San boasts exceptional performance metrics compared to Node.js-based alternatives.-Session Persistence: Sessions are automatically saved, allowing users to resume work later. The system also supports forking sessions and includes automatic context compaction to manage memory efficiently.-Self-Evolving Memory (Level 1): A background reviewer periodically distills recent work into durable memory and reusable skills. This feature allows the agent to "level up" as it works, improving its capabilities without manual tuning. Currently, Level 1 is live, with deeper levels planned for the future.

Use Cases

San is engineered to be small and fast, designed to run on a wide variety of hardware environments without runtime dependencies. The single ~12 MB binary runs unchanged across diverse environments, including:- macOS and Linux laptops- Cloud nodes and VMs- ARM edge devices-scratchcontainers- CI steps and lifecycle hooks- Air-gapped and locked-down hosts

When running the same model (claude-sonnet-4-6) and tasks on Apple Silicon, San significantly outperforms Claude Code (a Node.js-based reference) in terms of size, speed, and memory usage.

The performance gap is attributed to San's native Go binary architecture versus the Node.js runtime used by competitors.

Community and Contribution

San is open source, inviting community participation. Users can join the conversation through:-Slack: For the global community.-WeChat: For the Chinese community (Public Account: "极客外传"; reply "san" or "三" to join).

Developers are encouraged to star the repository if the tool is useful to them.

Getting Started

Users can begin using San in approximately 30 seconds by downloading the binary and following the standard setup procedures. The framework's simplicity and lack of complex dependencies make it accessible for immediate deployment.