Not really. I'm building now another fast C compiler with DeepSeek 4 Flash, and rarely have to step outside to use Pro or Sonnet, gpt or kimi-2.6. Flash is very capable of almost everything.
That's not a harness. That's an agent cli. A harness is something completely different. Wish people could use proper terminology.
A test harness is a collection of software and test data configured to test a program unit by running it under varying conditions and monitoring its behavior and outputs. It automates the execution of test suites, providing the necessary stubs, drivers, and runtime environments so developers can isolate and verify specific code components.
I use opencode (lockedcode is still vaporware), claude, kimi and codex.
And most models. Just no Google models so far, I don't trust them.
No, an agent cli is no harness. You have to provide a harness for an agent by yourself, otherwise it will run free. Which is called vibe coding. Free as you wish, without any harness.
May I ask about your trust issue regarding Google models?
Is it about quality issues (lack of guardrails, agent runs dangerous commands)? I have seen first-hand Gemini-cli going out of the project directory and using my home directory as a work area.
You're free to fight the terminology if you want (I did at first too), but the zeitgeist has chosen a meaning that disagrees with you, so people will see you as being deliberately obtuse and unpleasant when you fight back.
Learning when to let go is an incredibly important skill that I have learned way too late in life.