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docs/user/guide/index.md

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+# Introduction
+
+English | [中文](index.zh.md)
+
+DeepSeek Harness is a **plugin-based agent development framework** built on the [Cordis](https://github.com/cordiverse/cordis) microkernel. Its central idea is simple: **everything is a plugin**.
+
+## What it is
+
+Harness implements every capability an AI agent needs—including LLM calls, tool execution, session management, and subtask delegation—as a composable plugin. A `cordis.yml` file declares which plugins to load and how to configure them, assembling a complete agent.
+
+```yaml
+# Select the LLM backend
+- name: '@deepseek-ai/dsh-llm-deepseek'
+  config:
+    apiKey: !!js process.env.DEEPSEEK_API_KEY
+
+# Select the application template
+- name: '@deepseek-ai/dsh-stdio-agent'
+  config:
+    model: deepseek-v4-flash
+```
+
+## Who it is for
+
+### Application users
+
+To run an existing agent application, such as a coding assistant or conversational agent:
+
+1. Copy an example template.
+2. Add an API key.
+3. Run it.
+
+No code is required. See the [quick start](./quickstart.md).
+
+### Plugin developers
+
+To add a custom tool, a new LLM adapter, or another execution backend, write a plugin. Harness provides explicit extension interfaces and a type-safe development experience. See [development](../develop/basic/).
+
+## Core features
+
+- **Configuration only** — `cordis.yml` selects the capability set; changing a model or adding a tool is a configuration edit.
+- **Hot replacement (HMR)** — edit plugin code during development without restarting the process.
+
+## Technology
+
+- **Runtime**: Node.js ^22.19 or >= 24
+- **Language**: TypeScript (ESM)
+- **Framework**: Cordis
+- **Package manager**: pnpm workspaces (the repository pins pnpm 11)