AI can find bugs, and it can find targets for performance improvements. If you tell it to vibe code something that's fast, you're not going to get the results you want. Like the time Anthropic mostly but not quite created a compiler:
https://www.anthropic.com/engineering/building-c-compiler. And if you want it fix things that are complex, you're going to have a bad time:
https://1password.com/blog/why-ai-generated-patches-still-re...