The arrangement that works in a two-dog household runs in one direction: the older dog's life stays as it was, and the puppy's life is managed around it. A senior dog who wants peace should never have to growl, snap or hide to get it, and a puppy should never learn that pestering an old dog is how the game works. You are the referee, the gatekeeper and the puppy's teacher, so the older dog does not have to become any of those things.
The Older Dog's Retreat Is Protected Territory
Choose the rooms and resting places that are his and hold that line absolutely. His bed goes where it has always been, in a room the puppy enters only by your invitation or not at all, with a baby gate or a closed door doing the guarding so he can sleep deeply without listening for small feet. His meals are served in his own space, his walks keep their familiar routes and pace, and his time on the sofa beside you remains his, with the puppy settled on its own mat rather than climbing over him for a share. The puppy must never be allowed to invade his retreat to play, to steal his toys or to demand attention, because a retreat that can be invaded is not a retreat at all. When he chooses to leave a room, let him go without calling him back into the puppy's orbit; leaving is his right, not a problem to solve.
Manage the Puppy With Gates, a Lead and Settle Training
The puppy is the one who gets managed, because the puppy is the one still learning. Keep a light house lead on the puppy during shared time so you can quietly step in before chasing, mouthing at ears, body-slamming or toy-stealing begins, and guide the puppy away the moment its play stops being gentle. Place gates so the puppy's world expands room by room under supervision instead of arriving all at once. Teach a settle on a mat as a real skill, rewarding the puppy for lying quietly near the older dog without engaging him, in short sessions that end while the puppy can still succeed. Give the puppy its own programme of play, training, chewing and naps in a pen or crate away from the senior dog, so its considerable energy is spent on you and on its toys, not on the household member least able to enjoy it.
Shared Time Is Supervised, Short and Ended Early
Read his responses as the timetable for the whole arrangement. An older dog who begins choosing to stay in the room, who greets the puppy with a soft body and then settles, is telling you shared time can lengthen gradually. One who leaves sooner, sleeps more heavily after visits or starts guarding his bed is telling you the puppy's access grew too fast, and the kind response is to tighten the gates again without treating it as failure for either dog.
Time together should be frequent, brief and always watched, with you close enough to intervene in a second. Parallel pleasures work better than direct play at the start: both dogs chewing in the same room, a calm walk together with the puppy managed on its lead, or training turns where the older dog is rewarded for watching calmly. End each session while it is going well, separating them before tiredness or excitement tips the mood. Feed them in different places from the very beginning, and pick up food bowls afterwards, because food is where a tolerant old dog is apt to be pushed past politeness. Across the weeks, note who did which feed, walk and play session in KinsLe, where Care Teams assigns those puppy and senior duties to household members and marks each one done, keeping his routine steady.