The scaffolding and system prompting around Claude 4 is really, really good. More importantly it’s advanced a lot in the last two months. I would definitely not make assumptions that things are equal without testing.

It's both Claude 4 Opus and the secret sauce that Claude Code has for UX (as well as Claude.md files for project/system rules and context) that is the killer I think. The describe, build, test cycle is very tight and produces consistently high quality results.

Aider feels a little clunky in comparison, which is understandable for a free product.

Yes. The tooling harness of Claude Code is really good, and Claude 4 is well-optimized for it. The combination is very powerful.

I think it’s also very nice that CC uses fancy search and replace for it’s edit actions. No waiting hours for the editor to scan over a completely regenerated file.

That's pretty much impossible comparison to make. Workflow between two is very different, aider has way more toggles. I can tell you that Aider using sonnet-4 started Node.js library in otherwise rust project given the same prompt as claud code that did finish the task.