DeepSeek Open-Sources 'DeepSeek Harness' (dsh) Under MIT — a Plugin-Tree Agent Runtime That Is a Direct Claude Code Rival

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DeepSeek released DeepSeek Harness, an MIT-licensed agent harness where every capability — models, tools, skills, sessions, sandboxes, storage, loops, scheduling, and the UI — is a swappable plugin, wired together by the Cordis service/event framework. Everything the model sees is written to an append-only session log (system prompts, reasoning, tool calls and results, subagent scheduling, every context injection), inspectable by source in a Trajectory view; it installs with `npx @deepseek-ai/dsh web` and serves a local UI on port 3080. The repo is already at 86.6k stars and is explicitly labeled developer preview with breaking changes expected; the r/LocalLLaMA thread drew 302 upvotes and 107 comments.