The model matters less than the harness now - agree or disagree?

July gave us GPT‑5.6, Claude Opus 5, Sonnet 5, and the return of Fable 5.

Every new release reshuffles the benchmarks - but I’m beginning to think the model is only half of the experience.

The harness around it increasingly decides how productive you actually are:

• How well it understands your codebase
• How it manages context across longer tasks
• Whether you can run and review multiple agents
• How clearly it presents diffs and changes
• How easily you can switch models or continue work elsewhere
• Whether it fits into your existing subscriptions and workflow

So I’m curious:

What coding harness are you actually using every day - Claude Code, Codex, Cursor, OpenCode, Grok, or something else?

And more importantly, what makes you stay with it?

I’m asking because tomorrow, August 3, I’m hunting T3 Code on Product Hunt.

I’m not the maker - just genuinely interested in what the T3 team is building: an open-source control plane where you can orchestrate Claude Code, Codex, OpenCode, Cursor, and Grok from one interface while continuing to use the subscriptions you already pay for.
Before the launch, I’d love to hear what the Product Hunt community currently uses - and whether you think the next major advantage will come from better models or better harnesses.