DeepSeek Harness is an open-source agent harness built around the idea that every major capability should be replaceable as a plugin. It uses Cordis to compose model adapters, tools, session handling, agent loops, persistence, sandboxing, approvals, and interface layers into configurable profiles. Users can run a browser-based interface, select a workspace, configure DeepSeek or other compatible model endpoints, and launch agent sessions against local projects.