Preheat your air fryer to 400°F (200°C).
Slice the russet potato into thin matchsticks, soak in cold water for 10 minutes, then pat completely dry with a clean towel.
Toss the dried potato sticks with olive oil, half of the sea salt, garlic powder, and paprika until evenly coated.
Place the potatoes in the air fryer basket in a single layer and cook for 15-18 minutes until golden and crisp, shaking the basket halfway through.
While the chips cook, whisk together the flour, light beer, remaining sea salt, and black pepper in a shallow bowl until a smooth batter forms.
Pat the cod fillets dry with paper towels to ensure the batter adheres properly to the surface of the fish.
Dip each cod fillet into the beer batter, allowing any excess to drip off before placing it on a clean plate.
Remove the chips from the air fryer and keep them warm; place the battered cod in the basket, using a parchment liner if needed to prevent sticking.
Air fry the cod at 400°F for 10-12 minutes, flipping carefully halfway through, until the exterior is crunchy and the fish flakes easily.
Serve the crispy cod alongside the hand-cut chips with a fresh lemon wedge for squeezing over the fish.