Distinguishing the parts

  • An interface is the part a human uses to interact with a system. Theo classifies Twitch and YouTube as straightforward examples. 14:40 15:06
  • A harness supplies the execution capabilities around the LLM. Theo uses the Claude Agent SDK as his example, describing tools, an agent loop, and context management. 15:06 15:32
  • An agent, in his definition, combines an LLM and a harness. The harness supplies tools, context, and a system prompt describing the model's role so it can complete tasks. 18:09 18:46

Why product names are confusing

  • Theo calls Claude Code an interface that bundles a harness. He distinguishes the desktop interface, the SDK used to embed the agent, and the underlying binary that performs the harness role. 15:58 16:29
  • The CLI is a terminal interface for interactive development and one-off tasks. The Agent SDK exposes the underlying agent functionality to a Python or TypeScript application. 15:58 16:29
  • A product can package multiple layers under one name. This is why asking whether "Claude Code" is a harness or an interface needs a more specific answer about which component is meant. 15:58 16:29
  • Theo explicitly classifies T3 Code as an interface, while acknowledging that it adds capabilities and changes some behavior around the harness. 16:55 17:17