Harness Engineering: What Six Open Agent Codebases Teach About Production LLM Agents
Most writing about agents starts with models. The code tells a different story. I spent time reading six agent codebases: Codex, Goose, OpenCode, OpenClaw, NanoClaw, and Hermes. They differ in language, product surface, and philosophy. Codex is Rust-heavy and app-server shaped. Goose is a Rust MCP agent with desktop and text UI surfaces. OpenCode is a TypeScript/Bun/Effect runtime. OpenClaw is a wide TypeScript platform with gateway, plugins, policies, and native clients. NanoClaw is a host/container system where SQLite message files are the boundary. Hermes is a Python agent runtime with gateway, terminal, browser, desktop, and plugin surfaces. ...