In a large pot of salted water cook the pasta according to the package’s directions. Reserve 1/4 cup pasta cooking water. Drain pasta.
Meanwhile, in a large deep skillet, heat the oil over medium-high heat. Add the celery and carrots. Cook and stir for 2 minutes. Reduce the heat to medium and stir in the chicken, green onions, buffalo wing sauce, butter, soy sauce, 1/4 tsp. salt, cooked spaghetti, and reserved pasta water. Cook, tossing, until heated through, about 4 minutes. Top with sliced green onions and serve.