DeepSeek Harness: Building and Extending AI Coding Agents Training Course

Introduction to DeepSeek Harness

• Overview of DeepSeek Harness and its place in the ecosystem
• The design philosophy of “everything is a plugin”
• Overview of Web UI, CLI, and headless modes

Setup and Initial Launch

• Node.js prerequisites and package setup
• Starting the Web UI using npx
• Compiling and running from source code

Configuring Models

• Configuring the DeepSeek API key
• Choosing and switching between models
• Integrating OpenAI-compatible endpoints

Managing Workspaces and Sessions

• Selecting and switching between workspaces
• Using the session composer for conversation management
• Reading, modifying, and generating code files

Executing Coding Tasks

• Summarizing repositories and navigating codebases
• Executing commands and distributing tasks
• Maintaining and updating task plans

Permissions and Sandbox Management

• Defining approval and permission policies
• Restricting file and command access
• Configuring local and remote sandbox backends

Native Tools and Integrations

• Utilizing filesystem, terminal, and shell utilities
• Supporting the Model Context Protocol
• Integrating with the Language Server Protocol

Subagents and Task Delegation

• Creating and forking subagents
• Product providers for alternative coding agents
• Distributing work across active sessions

The Cordis Plugin Architecture

• Plugins functioning as services, events, and effects
• Shared context and lifecycle management
• Understanding the absence of a privileged core

Profiles, Bundles, and Configuration

• Layering profiles and bundles
• Modifying configuration via cordis.patch.yml
• Inspecting the boot process tree

Essential Subsystems

• The append-only session log mechanism
• Assembling system prompts and tool schemas
• Understanding the agent loop and turn flow

Event Handling and Extension Points

• Handling session, agent, and capability events
• Waterfall and interceptor event patterns
• Aligning behaviors with specific extension points

Plugin Development

• Registering services using context keys
• Incorporating tools and model adapters
• Distributing and locating plugins

SDK, Headless Mode, and Automation

• Controlling the harness from external processes
• Using TypeScript and Python SDKs
• Automating workflows via CLI and headless mode