Prep the green beans: Rinse and pat them very dry with a clean towel. Trim the ends. Excess moisture leads to steaming instead of crisping.

Preheat the air fryer: Set to 375°F (190°C) for 3–5 minutes. A hot basket helps the coating set quickly.

Season and coat: In a large bowl, toss green beans with oil until lightly coated. Sprinkle over cornstarch, garlic powder, onion powder, salt, and pepper. Toss again until everything looks evenly coated with no dry patches.

Arrange in the basket: Lightly spray the basket if needed. Spread beans in a mostly single layer. A little overlap is okay, but avoid packing them in tightly. Work in batches if needed.

Air fry: Cook for 8–12 minutes, shaking the basket halfway through. Start checking at the 8-minute mark. They’re done when edges are browned and crisp, and the beans feel light and snappy.

Finish and serve: While hot, taste and add a pinch more salt if needed. For extra flavor, sprinkle Parmesan, lemon zest, or a dusting of smoked paprika right after cooking.

Optional double-crisp step: For super crunchy chips, let the beans rest for 2 minutes, then air fry 1–2 minutes more. Keep a close eye to prevent burning.