GoKawiilAnthropic defines 'agent,' 'harness,' and 'model' as distinct layers of AI systems
Anthropic published a terminology guide clarifying that an 'agent system' is not the same as a 'model.' It breaks the stack into three parts: the model (like Sonnet or Opus), the inference service that runs it (like AWS Bedrock or Anthropic's API), and the harness, the interface layer such as Claude Desktop or Claude CLI that manages tools and context.