DeepSeek Harness: Building and Extending AI Coding Agents Training Course

Introduction to DeepSeek Harness

• Overview of DeepSeek Harness and its role in the ecosystem
• The "everything is a plugin" design approach
• Web UI, CLI, and headless operating modes

Installation and Initial Setup

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

Model Configuration

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

Workspaces and Sessions

• Selecting and switching between workspaces
• Using the session composer and managing conversation flow
• Reading, modifying, and generating files

Executing Coding Tasks

• Summarizing repositories and navigating codebases
• Running commands and delegating specific tasks
• Maintaining and updating task plans

Permissions and Sandboxing

• Approval workflows and permission policies
• Restricting file and command access
• Configuring local and remote sandbox backends

Native Tools and Integrations

• Filesystem, terminal, and shell utilities
• Support for the Model Context Protocol
• Integration with the Language Server Protocol

Subagents and Task Delegation

• Creating and forking subagents
• Connecting to providers for other coding agents
• Distributing work across a session

The Cordis Plugin Model

• Plugins defined as services, events, and effects
• Shared context and lifecycle management
• The absence of a privileged core structure

Profiles, Bundles, and Configuration

• Layering profiles and bundles
• Modifying configuration via cordis.patch.yml
• Reviewing the initialized component tree

Core Subsystems

• The append-only session logging mechanism
• Assembling system prompts and tool schemas
• The agent loop and turn processing flow

Events and Extension Hooks

• Session, agent, and capability events
• Waterfall and interceptor event handling
• Aligning behavior with specific extension points

Plugin Development

• Registering services under context keys
• Incorporating custom tools and model adapters
• Releasing and discovering plugins

SDK, Headless Mode, and Automation

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