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 principle
• Web UI, CLI, and headless operational modes

Setup and Initial Execution

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

Model Setup

• Configuring the DeepSeek API key
• Model selection and switching mechanisms
• Integrating OpenAI-compatible endpoints

Workspaces and Sessions

• Managing workspace selection and transitions
• Using the session composer and dialogue flow
• File reading, editing, and generation capabilities

Executing Coding Tasks

• Repository summarization and code navigation
• Command execution and task delegation
• Maintaining structured task plans

Permissions and Sandbox Environment

• Approval workflows and permission policies
• Restricting file and command access
• Local and remote sandbox backend configurations

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
• Product providers for other coding agents
• Delegating tasks across different sessions

The Cordis Plugin Architecture

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

Profiles, Bundles, and Configuration

• Profile management and bundle layering
• Configuring settings via cordis.patch.yml
• Reviewing the boot process tree

Core Subsystems

• The append-only session logging mechanism
• Assembly of system prompts and tool schemas
• Agent loop structure and turn flow

Events and Extension Points

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

Plugin Development

• Registering services on specific context keys
• Incorporating new tools and model adapters
• Plugin publishing and discovery processes

SDK, Headless Mode, and Automation

• Controlling the harness from external processes
• Utilizing the TypeScript and Python SDKs
• CLI-based and headless automation strategies