Bruce was not a stupid man.
This was often overlooked, of course. Even those people who recognised that he was a scientist before he was a green mass of muscle and rage, that he was actually a mass of muscle and rage because he was first a scientist ... they still tended to forget it. Not obviously. They put him with Stark, after all. They summoned him more for technical reasons than physical.
Or so they said, at least.
But they also ... looked at him mostly as the vessel for the Hulk. The prelude, not the main event. He wasn't Bruce Banner anymore. Not to most people. He was just the Hulk waiting to happen. Whether that meant he was viewed as a threat or an asset, or both, it still meant that most people looked at him, and saw ... the other guy.
But the thing was, he was still Bruce Banner. Inside himself. He still knew. And he wasn't a stupid man. He was a scientist.
And he recognised the scientific method when he saw it. Or, well. The bastardised, incredibly abbreviated version Tony used, anyway.
"Stress-testing," he said, more or less randomly, one day at the lab. Leaning back against the workstation, arms folded, watching Tony blink up at him. Watching, if he was honest, the man try to switch tracks on the fly, which was always amusing. It shouldn't be. Bruce was a horrible, horrible man. But he took his amusements where he could, these days.
It'd been a long decade.
"What?" Tony asked. His mind leapt and flew like quicksilver, so much of the time, switching tracks on a dime, linking concepts in unholy unions that probably no sane person would entertain. But if someone else tried to switch his tracks for him, introduced a roadblock or stray topic, things could get ... interesting.
And amusing. Bruce mentioned he was a horrible person, right? But he did have a purpose, this time.
"Stress-testing," he repeated, mildly. "You use it, right? For the armour?"
Tony blinked owlishly at him. He'd gotten oil on his face again. Or something liquid, anyway. Bruce hoped it wasn't caustic. Though Tony was actually pretty careful about things like that. He just didn't look like he was.
"Of course," Tony said, blankly. As if it was a really stupid question. Which, admittedly, it was. If you were standing it on its own, anyway. Bruce ... Bruce really wasn't stupid.
"What?" The owlish look was never getting old, you know that? Bruce was quietly convinced it was why Miss Potts liked to confound Tony as much as she did. It was ... kind of adorable.
"How do you test it," Bruce explained, patiently. Visibly patiently. He liked the effect it had, sometimes. Being patient. It made people ... irritable. For a man who spent so much of his life on the brink of rage, striving for control, it was sometimes ... soothing, to watch other people have to as well. To remember that his anger was only more visible. Not more present.
Tony blinked some more, but he was booting up now, switching gears. His eyes were narrowing, squinting suspiciously at Bruce. Who hid a smile, a little bit. Tony was ... fascinatingly paranoid, for a man who'd never been on the run.
"What, you want test logs?" He was standing up, now, wrench still absently swinging from one hand. Completely without threat, for all the snappishness in the tone. Tony ... didn't threaten people. He smiled at them, light and easy, right up until he destroyed them. It made Bruce want to ... poke at him, sometimes.
It also made Bruce think. About why, and maybe ... who else was doing it.
"Just an idea," he demurred, smiling faintly. "I've seen you work, on the little things. I just wondered what you were like with the bigger things. Like the suit. You do test it, right?"
"Of course I do." But not snapping, now. Tony frowned over at him, putting down the wrench, wandering over to lean his hip against the other end of Bruce's station, matching Bruce's posture. Tony was actually a pretty excellent mimic. And he could use it as a weapon, too. "What did you want to know?"
Bruce grinned at him. "Just wondering how many times you blew yourself up, maybe?"
Tony narrowed his eyes, then grinned, scoffing. "You've been listening to JARVIS again, haven't you? You shouldn't trust him, you know. He likes to tell scurrilous stories about me. It makes him sound long-suffering."
"He is long-suffering," Bruce pointed out, still smiling faintly. "A paragon of virtue and patience. But to be fair, it wasn't him. Most people seem to think you spend a lot of your time blowing yourself up. Possibly on purpose."
And there was a darker thread under that, they both knew that, Bruce could see the recognition in Tony's eyes. But he shook his head, wry and rueful. No. Not that.
"Nah." Then he paused. "Well. Not like that. Controlled explosions, yes. You said it yourself. Stress-testing. You have to know where the limits are, and the only way to do that is to push past them." A little grin. "Sometimes you gotta run before you can walk. Or fly before you can walk."
... Yes. That fit. Oh, it did. That was so very ... Tony.
Bruce ... paused. Asked the next question carefully. "And you ... You're in the suit? When you stress-test?"
Tony looked at him. Dark eyes and faint smile, and the knowing little curve of one lip. "Not for the base level ones," he said, quietly. "But beyond that? Yeah. I have to know how it'll perform with me in it. Have to know what I can handle inside it." The smile widening, a grin, fierce and more than a little challenging, a dare. "I have to know where the limits are, don't I?"
And that ... Bruce felt something clear, inside him. The little click inside you, when the jumble cleared and the hypothesis settled out from it. The clean, clear calm of knowledge.
"That's what you were doing with me, wasn't it?" he asked, gently. Tony blinked, suddenly looking a little wary. Bruce smiled. "In the beginning. With the taunts, and the shock, that time. Throwing it up into my face."
Tony ... winced, a little. Looked uneasy. "You didn't seem to mind," he said, uncomfortably. "Well, I mean, you minded, obviously. But you also seemed to find it ..."
"Amusing?" Bruce asked, gently enough. Tony twitched a bit, and Bruce took pity on him. "Actually, it was kind of a relief. Most people treat me like a potential bomb. You ..." He stopped, grinned. "Well. You also treat me like a bomb, a lot of the time. You just also seem to have never met a bomb you didn't like."
Tony grinned at him, a little bit. A flash of something smug. "Well, I was the world's premier weapons engineer, you know. I used to blow shit up for a living."
"Mmm," Bruce agreed. "With yourself in them, apparently." And Tony seemed to catch on, a little, then. "Most people don't poke at explosives while they're in a room with them, you know."
Tony ... looked at him. Not grinning, now. Serious, eyes dark and clear. "Most explosives don't also have the intelligence to know when not to blow up," he said, carefully. While Bruce did his level best not to quiver, not to betray the shake in his gut. Tony held his gaze, for a second. Tony held his eyes.
Then Tony, being Tony, started grinning again. "Well. Not without some Stark magic, anyway. But I do try not to give AIs to explosives. Or explosives to AIs." A strange little frown. "Too much like outfitting suicide bombers, you know? I wouldn't do that to them."
Bruce ... shook his head, feeling his face acquire that weird little expression somewhere between fondness and bemusement that so many people seemed to develope around Tony. The man could be ... strangely affecting, at the most random moments.
"I know," he agreed, smiling faintly. "And I'm sure JARVIS and Dummy are grateful for that."
Tony flashed him a look, suspicious, suspecting he was being laughed at. Bruce got the impression that people did that a lot. "Actually, technically, JARVIS does have explosives to hand," he said, almost testingly. "But he mostly knows what to do with them, and they won't hurt him. Though you should keep that part to yourself, hmm? People get strange when they find out I've been arming my AIs."
"I wonder why," Bruce shot back, drily. Tony just smirked.
And that was ... It was good, for a second, light and cleaner than ... so much of Bruce's life. But ...
"I have to ask, though," he said, carefully. Looking at Tony. Looking at the man standing casually alongside him, leaning against the station, looking utterly at ease. Not the false ease Bruce saw on people like Natasha or Clint, or even Cap. Not the loose readiness that only looked like it was relaxed, but was really in preparation to move, to fight, to fall. Tony was just ... easy. For now. "What would you have done, if I had ... hulked out? Back in the beginning. What would you have done?"
Tony tilted his head. Looked consideringly at Bruce. But he didn't tense. Didn't brace. Bruce tried -so often- not to be ridiculously grateful, for that.
"Well, that was what it was for, wasn't it?" Tony said, quietly. "Stress-testing. That's what it's for, right? To find out where the limits are. So you know when you're safe, and when things are about to go to hell." He smiled, odd and sort of distantly. "It's not just you, you know. It was never just you. People are ... explosive. You know that? Almost all of them. You've got to ... stress-test them. So you know when they're going to explode. When they're going to shear on you, and tear you open. When they're going to ... to snap, and turn on you. You've got to ... test them. Stress them. So you know. So you can ... see it coming."
And that ... Bruce stared at him, at that. Feeling the paradigm shift in his head, hypothesis sliding out, realigning. Looking at the man beside him, his friend, eyes dark and rueful and knowing, at his ease, with a hole in his chest stoppered only by desperation and his genius.
You have to test people, so you know when they'll shear. Because Tony was an engineer, wasn't he, the way Bruce was a scientist, and that was the way his mind worked. And people mightn't see it, might only see the swagger and the charm, insouciant and challenging, the way everyone looked at Bruce and saw the Hulk, but that wasn't what they were. That wasn't them.
"It's kinda funny, isn't it," Tony said, with that small, dark smile, leaning in beside Bruce and propping his shoulder gently against him. "Pretty ironic. But poking you was ... pretty much the safest I've ever been, around another person." A little curve of his lip. "Because you know when you'll shear beforehand. And you don't want to."
No. No, Bruce didn't want to. He never had. The entirety of SHIELD, all those people with guns and suspicious eyes, watching him warily, ready to bolt, or shoot, or bring him down. Them, he hadn't wanted to hurt, but he'd been prepared to. He'd long been prepared for that. But Tony ... Tony had poked, and grinned, and held out a hand, and waved the Hulk in his face, and worked with him anyway. More than that. Tried to reach him. Touch him. Be there. Bruce hadn't wanted to hurt him. Not at all.
He still didn't. And he knew, he did know, that Tony, in his way, didn't want to hurt him either. Would stand beside him, unfazed, whether he was Bruce or the Hulk. Muscle or scientist. Or both. Maybe Tony, of all of them, recognised both.
"I don't want to hurt you," he agreed, very quietly. Letting himself rest against the man at his side. Letting himself touch, and stand beside.
"Mmm," Tony said, still with that odd little smile. "And when you do, I'll know. You won't ..."
Betray him. Turn on him in the secret and the quiet, lay him open before he ever knew you were there. Bruce had seen the footage of Obadiah. Tony didn't know that, but he had. JARVIS had ... Well. Bruce strongly suspected JARVIS had been warning him. That he was being watched. That JARVIS knew what to watch for, now, and wasn't as helpless as he'd been then. And also ... wanting Bruce to understand, maybe. Wanting Bruce to know.
They were oddly protective of him, the people Tony built. Or maybe not so oddly. Tony treated them like they were real, like they were people too. Bristled and snapped at them, grinned with them, expected them to keep up. Treated them like they were real. It was hard ... not to want to keep someone, who treated you like that.
"I won't," he said, so softly. Letting his gaze wander, not at Tony, never at Tony, but feeling the warmth of him, light and easy, at his side. "Not that."
"Mmm," Tony said, with a smile in his voice. "And me. I won't either." A little laugh, and a fist nudged gently against Bruce's shoulder. "You're safe with me, buddy. Safe as houses."
Yeah. For the first time in a long, long time, more than six years ... Bruce really thought he was.
Though ... were they talking safe as Tony's house, here? Because between Tony's experiments, and external kidnap attempts ...
"Oh, shut up," Tony grumped, and punched him.
And Bruce, grinning, let him.