DeepSeek open-sources Harness agent runtime with everything-is-a-plugin design

DeepSeek released DeepSeek Harness, an MIT-licensed agent environment where models, tools, sessions and UI are swappable plugins built on the Cordis system. It is available as the dsh CLI and the @deepseek-ai/dsh npm package, in developer preview (v0.1.5-rc series) with breaking changes possible.

• MIT license, code on GitHub in deepseek-ai/DeepSeek-Harness repo
• All components are plugins: models, tools, sessions, sandboxes, storage, UI
• Four modes: Standard, Code, Minimal and Creator
• Append-only session log with resume, fork and replay support