tl;dr: DeepSeek has released a developer preview of DeepSeek Harness, a plugin-based framework for building AI agents where capabilities (models, tools, sandboxes, storage, UI, etc.) are modular plugins managed by a Cordis kernel. Developers can swap or extend any component via configuration without modifying source code, and can try it via `npx @deepseek-ai/dsh web` or clone the repo from GitHub.