Hiring for taste, not stack
Stack is teachable. Taste isn't. Here's how I screen for it without making it weird.
I've sat on more interview panels than I can count, and the strongest signal for a senior frontend hire is taste — the ability to look at a pull request and feel which parts are right. Stack experience is a proxy for it, but a noisy one.
How I screen: a code review exercise on a PR with three deliberate problems. One is a bug. One is an architectural mistake that compiles fine. One is a naming choice that's correct but reads badly. Senior candidates catch all three and rank them in roughly the right order.
What I don't do: ask people to whiteboard React. The job is to ship a product, not to perform algorithms.
What I look for in their portfolio: did they shape a system, or just build features inside one? Both are valuable, but they're different roles. A senior IC who's never owned a system boundary is going to struggle when you need them to design one.