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 philosophy
• Exploring Web UI, CLI, and headless modes

Installation and Initial Setup

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

Model Configuration

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

Workspaces and Sessions

• Selecting and managing workspaces
• Using the session composer and managing conversation flow
• Reading, editing, and generating files

Executing Coding Tasks

• Summarizing repositories and navigating codebases
• Running commands and delegating tasks
• Maintaining an organized task plan

Permissions and Sandboxing

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

Built-in Tools and Integrations

• Utilizing filesystem, terminal, and shell tools
• Support for the Model Context Protocol
• Integration with the Language Server Protocol

Subagents and Delegation

• Creating and forking subagents
• Product providers for other coding agents
• Delegating tasks across a session

The Cordis Plugin Model

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

Profiles, Bundles, and Configuration

• Layering profiles and bundles
• Modifying configuration via cordis.patch.yml
• Inspecting the booted component tree

Core Subsystems

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

Events and Extension Points

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

Plugin Development

• Registering services on context keys
• Adding tools and model adapters
• Publishing and discovering plugins

SDK, Headless Mode, and Automation

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