Cursor's composer models are finetuned kimi
They are unusable (unless you want to deliberately destroy your codebase). So if Cursor's models are Kimi based, then well. I'll skip them altogether.
Kimi works great in their CLI, but their CLI has a number of workarounds for quirks of their models, including detecting when the model gets into a loop, and reverting to a checkpoint but letting the model compose a "message" to its past self (search their CLI for "BackToTheFuture"...) It doesn't work so well in a harness that doesn't take those quirks into account.
I'm using Composer extensively, and it works great for me. Your experiences are not universal.
They are far from unusable. They aork great for 80-90% of a typical full stack dev. Alot less useful for more noche stuff
I wouldn't skip at least testing the original. Model distilling done by Cursor could be the culprit.
Composer 1.x was poor. The new one is a totally different beast and absolutely fine for day to day.
I only use composer 2.5 day to day and it works fine with human review.
They're not unusable, they're just bad when compared with all the real frontier models.