They nailed down the UX I would say and the models themselves are a lot better even outside of CC

Skills don't make any difference above having markdown files to point an agent to with instructions as needed. Context7 isn't any better than telling your agent to use trafilatura to scrape web docs for your libs, and having a linting/static analysis suite isn't a harness thing.

3.7 was kinda dumb, it was good at vibe UIs but really bad at a lot of things and it would lie and hack rewards a LOT. The difference with Opus 4.5 is that when you go off the Claude happy path, it holds together pretty well. With Sonnet (particularly <=4) if you went off the happy path things got bad in a hurry.

> I suspect it’s closer than you think!

It's not.

I've done this (although not with all these tools).

For a reasonable sized project it's easy to tell the difference in quality between say Grok-4.1-Fast (30 on AA Coding Index) and Sonnet 4.5 (37 on AA).

Sonnet 3.7 scores 27. No way I'm touching that.

Opus 4.5 scores 46 and it's easy to see that difference. Give the models something with high cyclomtric complexity or complex dependency chains and Grok-4.1-Fast falls to bits, Opus 4.5 solves things.