DeepSeek Harness: Building and Extending AI Coding Agents Training Course

Introduction to DeepSeek Harness

• The nature of DeepSeek Harness and its role in the ecosystem
• The design philosophy of "everything is a plugin"
• Web UI, CLI, and headless operational modes

Installation and Initial Setup

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

Model Configuration

• Setting the DeepSeek API key
• Selecting and toggling between different models
• Integrating OpenAI-compatible endpoints

Workspaces and Sessions

• Selecting and switching between 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 delegating tasks
• Maintaining a structured task plan

Permissions and Sandboxing

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

Built-in Tools and Integrations

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

Subagents and Task Delegation

• Spawning and forking subagents
• Using product providers for other coding agents
• Distributing work across a session

The Cordis Plugin Model

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

Profiles, Bundles, and Configuration

• Managing profiles and bundle layering
• Modifying configuration via cordis.patch.yml
• Inspecting the booted component tree

Core Subsystems

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

Events and Extension Points

• Session, agent, and capability events
• Waterfall and interceptor events
• Mapping behaviors to specific 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
• Using the TypeScript and Python SDKs
• Automating tasks via CLI and headless mode