DeepSeek Harness: Building and Extending AI Coding Agents Training Course

Introduction to DeepSeek Harness

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

Installation and Initial Setup

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

Model Configuration

• Configuring the DeepSeek API key.
• Methods for selecting and switching between models.
• Integrating OpenAI-compatible endpoints.

Workspaces and Session Management

• Techniques for choosing and switching workspaces.
• Understanding the session composer and conversation dynamics.
• Processes for reading, editing, and generating files.

Executing Coding Tasks

• Summarizing repositories and navigating codebases.
• Running commands and delegating specific workloads.
• Maintaining and tracking a structured task plan.

Permissions and Sandbox Environment

• Implementing approval and permission policies.
• Restricting file and command access for security.
• Utilizing local and remote sandbox backends.

Native Tools and Integrations

• Using 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 for parallel tasks.
• Using product providers for other coding agents.
• Distributing work across an active 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 configurations via cordis.patch.yml.
• Inspecting the boot-up process and tree structure.

Core Subsystems

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

Events and Extension Points

• Handling session, agent, and capability events.
• Managing waterfall and interceptor events.
• Mapping specific behaviors to extension points.

Plugin Development

• Registering services using context keys.
• Incorporating new tools and model adapters.
• Publishing and discovering available plugins.

SDK, Headless Mode, and Automation

• Controlling the harness from external processes.
• Leveraging the TypeScript and Python SDKs.
• Implementing CLI and headless automation workflows.