Cursor with its tab completion. Iterate with the agent part to research, design, and plan. Let it generate boilerplate and scaffolding, perhaps with placeholders for you to fill in. Then fill in as you normally would, but with an auto-complete that uses all of your code and design docs and everything else to inform that completion rather than the limited set of info that shows up in an LSP.

I believe JetBrains IDEs have something similar too, but I don't have as much experience using theirs since my employer hasn't blessed their AI tools yet.