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 operational modes

Setup and Initial Execution

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

Model Setup

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

Workspaces and Sessions

• Selecting and changing workspaces
• Utilizing the session composer and managing conversation flow
• Reading, modifying, and generating files

Executing Coding Tasks

• Summarizing repositories and navigating codebases
• Running commands and assigning tasks
• Maintaining a structured task plan

Permissions and Sandbox Environment

• Managing approval and permission rules
• Restricting access to files and commands
• 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
• Using product providers for external coding agents
• Distributing work across a session

The Cordis Plugin Model

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

Profiles, Bundles, and Configuration

• Layering profiles and bundles
• Modifying configuration via cordis.patch.yml
• Examining the boot tree structure

Core Subsystems

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

Events and Extension Points

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

Plugin Development

• Registering services using context keys
• Integrating tools and model adapters
• Releasing and discovering plugins

SDK, Headless Mode, and Automation

• Controlling the harness from external processes
• Utilizing TypeScript and Python SDKs
• Implementing CLI and headless automation