DeepSeek launches Harness open-source framework for building AI agents

DeepSeek announced the v0.1 developer preview of Harness, an open-source framework under MIT license designed for building AI agents, released alongside DeepSeek-V4-Pro-0813 which is also open-source. Harness operates according to an everything is a plugin philosophy, allowing models, tools, skills, sessions, sandboxes and other components to be freely substituted and recombined. The tool offers a predefined web interface with multiple operational modes including programmatic tool calling, minimal mode, and creative mode. The framework supports both web and headless execution and allows extension through plugin mechanisms. Harness positions itself as a direct competitor to tools like OpenAI Codex and Anthropic Claude Cowork, focusing on programming and enterprise productivity scenarios.