DeepSeek Harness

DeepSeek Harness is an open source, local first coding agent and agent development environment from DeepSeek. It uses the Cordis plugin architecture to make models, tools, skills, sessions, sandboxes, storage, loops, scheduling, and the user interface composable parts of the runtime. The project is currently in developer preview and is intended for developers who want to build, customize, or study agent harnesses rather than simply use a hosted coding assistant. Developers can run the web interface locally, give agents file editing and shell access, search files and the web, use skills, create plans and goals, schedule work, and coordinate subagents. The runtime includes multiple modes for different workflows, including a full standard coding agent, a code mode for composing multi step tool calls, a minimal mode for benchmarking, and a creator mode for experimenting with runtime plugins and custom presets. Its main differentiator is the everything is a plugin architecture. Capabilities can be selected, replaced, or extended through configuration without rewriting the whole harness. DeepSeek also records agent runs in an append only session log that supports inspection, resume, fork, search, and replay. The project is still changing quickly, so compatibility breaking changes are possible and developers should review security guidance before giving an agent broad local permissions. For FutureStack, DeepSeek Harness belongs in AI Agents because its primary purpose is providing an extensible runtime for coding agents and agent developers. It is best for developers who want local control, composable agent infrastructure, traceable runs, and an open source foundation for experimentation.