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 operation modes.

Installation and Initial Setup

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

Model Configuration

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

Workspaces and Sessions

• Managing and switching between workspaces.
• The session composer and conversational workflow.
• Operations for reading, editing, and generating files.

Executing Coding Tasks

• Summarizing repositories and navigating codebases.
• Running commands and delegating specific tasks.
• Maintaining and tracking task plans.

Permissions and Sandbox Environment

• Defining approval and permission policies.
• Restricting file and command access.
• 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 Delegation

• Creating and forking subagents.
• Product providers for integrating other coding agents.
• Distributing work across a session.

The Cordis Plugin Model

• Plugins defined as services, events, and effects.
• Shared context and lifecycle management.
• The rationale behind having no privileged core.

Profiles, Bundles, and Configuration

• Profile and bundle layering strategies.
• Modifying configuration via cordis.patch.yml.
• Examining the initialized configuration tree.

Core Subsystems

• The append-only session logging mechanism.
• Assembly of system prompts and tool schemas.
• The agent loop and turn processing flow.

Events and Extension Points

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

Plugin Development

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

SDK, Headless, and Automation

• Controlling the harness from external processes.
• Utilizing TypeScript and Python SDKs.
• Automation via CLI and headless modes.