How do you stop Cursor or Claude from inventing new styles on every screen?

Vibe coding with agents is super fast until every new page gets its own weird button style fonts and layout quirks.

Adding design guidelines to prompt files helps a bit but the model starts drifting after a few prompts anyway. Manually tweaking components at the end fixes it but it defeats the whole point of speeding up build times.

What's your setup for keeping visual components unified across multiple generated views?