DeepSeek has formally launched its first Agent product, DeepSeek Harness, and the software package has been published on npm. The product expands beyond a coding assistant by supporting project management, long-running tasks, multi-agent coordination, skills, internet-connected search and context management, while also allowing users to create different Agent presets for tasks such as coding, research and writing. Its defining feature is a plugin-first architecture built around the idea that "Everything is a plugin," meaning models, tools, prompts, storage, context and even the interface can be replaced or combined through plugins. Internal testing users have already built plugins for functions including long-term memory and interface modification. The source frames the distinction by saying Codex is more like a finished agent, while DeepSeek Harness is closer to a runtime for assembling agents, giving users control not only over model choice but also over the tools, rules and workflows an agent uses.