Tintin is content to rest in Ari's arms for quite some time. He feels - safe, safe enough to let down his guard and be vulnerable.
He does not consciously expect the very air to tear itself open into an eye-watering interdimensional portal as a result, but frankly he would be lying if he said it came as a particular surprise.
He's on his feet in seconds, his omni-tool forging a blade and his eyes glowing blue. He's ready for anything to come out of this portal.