DeepSeek Harness: Building and Extending AI Coding Agents Training Course

Introduction to DeepSeek Harness

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

Installation and Initial Setup

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

Model Configuration

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

Workspaces and Sessions

• Selecting and changing active workspaces
• Using the session composer and managing conversation flow
• Reading, modifying, and creating files

Executing Coding Tasks

• Summarizing repositories and exploring code structures
• Running commands and distributing tasks
• Tracking and maintaining a task plan

Permissions and Sandbox Environment

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

Integrated Tools and Features

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

Subagents and Task Delegation

• Creating and branching subagents
• Product providers for alternative coding agents
• Distributing work across a session

The Cordis Plugin Model

• Viewing plugins as services, events, and effects
• Understanding shared context and lifecycle management
• The rationale behind the absence of a privileged core

Profiles, Bundles, and Configuration

• Managing profiles and bundle layering
• Modifying configuration via cordis.patch.yml
• Reviewing the initialized configuration tree

Core Subsystems

• The append-only session log structure
• Assembly of system prompts and tool schemas
• The agent loop and turn processing flow

Events and Extension Points

• Handling session, agent, and capability events
• Processing waterfall and interceptor events
• Linking behaviors to specific extension points

Plugin Development

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

SDK, Headless Mode, and Automation

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