I don't feel strongly about anything most folks are arguing back and forth about, but this one is obviously wrong.

Everybody and their brother has made an agent. There are toolkits. You can whip one up in an afternoon.

Not only that, I've found models often perform worse, or at least cost more and take longer, in a big complicated agent like Claude Code, including Anthropic models. They want proprietary doodads hanging off the side (multi agent orchestration, memory, things of that nature) to matter, because they can lock you into tools like that. But, top models can do everything with bash.

But harness is relatively easy to code yourself?

They're just system prompt composer, with some tool functions that the LLM can invoke. I've vibe coded my own in just one day.