"I won't," Tony responded without hesitation, sharp and low, but the confidence was only in his voice. He could insist until he was out of breath, but Tony knew it wasn't a promise he could make; he would be gone the second he thought he was needed elsewhere, but not unless he was sure this time that he would really be doing better there than here and not out of any lack of consideration for Steve's wishes. Tony trusted him completely to do what he needed to, and to get the job done to the best of his ability. And that was better than anyone Tony knew.
In the place of an honest promise, Tony was back around the pool quickly, his helmet dropping heavily into the dry grass before Tony followed, on his knees at Steve's side. "Hey," he coaxed or warned before laying a bare hand along Steve's neck to bring him close, cheek to cheek. Fuck, he was sorry, he shouldn't have gone, but he needed Steve to return his trust or he really didn't have anything left.