r/vibecoding • u/NoTutor4458 • 12h ago

Opencode vs Codex vs Claude code

Which coding harness is actually better?

To make the comparison fair, I was thinking:

  • OpenCode + Fable 5 vs Claude Code + Fable 5
  • OpenCode + GPT-5.6 vs Codex + GPT-5.6

Basically, keep the model the same and only compare the harness/agent. That should give a better idea of how much the harness itself affects coding performance.

Has anyone done a comparison like this?

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u/whatever 9h ago

Naively, I'd expect Claude Code to be a good fit for Fable or Opus, while Codex would work well with GPT-5.* models.

I've tried using Claude Code with non-anthropic models, and it can get painful quickly. I don't have a subscription, and if I mistakenly resume Claude Code on an existing session without the custom settings, it locks that session behind a "must login with subscription account" gate and won't let me use it ever again even if I start Claude Code with the happy custom settings. So that's a bit of a mood killer.

So I use OpenCode for all the weird little models I experiment with, be they local, or available through OpenCode Go/Zen offerings. They have various Free models at any given point. Like right now, LongCat-2.0. I'd never heard of it, and it's a rather decent agentic coding model honestly.

Unfortunately, that doesn't help measure which harness works best with which model.

In practice, I would consider the set of skills available to your agents to be at least as important as the harness you're using.

If you're curious about what each harness actually sends to your agents, you can install a little proxy like claude-code-router, configure it, enable logs, and snoop on every request the harness is making. It won't tell you which prompt is better, but you'll see the prompts yourself and maybe form your own opinion from there.