Start the first meeting away from your front door
Do not let the foster dog walk straight into your resident dog's hallway. Your resident dog has history in that space, favourite resting spots, and a strong sense that the house is already settled, while the foster is arriving stressed from travel and change. Meet on neutral ground instead, with one calm adult handling each dog on a loose lead. Walk in the same direction on opposite sides of a quiet street or across a wide path, far enough apart that neither dog is staring, pulling, or vocalising. Let the distance shrink only as both dogs soften, sniff the ground, and look away easily. A parallel walk tells you far more than a forced greeting, and it gives the foster a chance to be a dog on a walk rather than an intruder at the door.
Read the pair you actually have, not the pair you hoped for
Loose, curved approaches, brief sniffs followed by moving away, and play bows that both dogs answer are encouraging signs for this particular pairing. Stiff stillness, hard staring, raised hackles that do not settle, growling when the other dog approaches a person, or one dog repeatedly trying to escape are reasons to increase distance and end the session while it is still manageable. Age, size, health, and past experience matter here: a frail senior resident should not be asked to cope with a boisterous young foster at close quarters on day one, and a foster who has just left a kennel may need sleep and decompression before any social test is fair. If either dog has a known bite history or you cannot safely separate them, pause the plan and ask the rescue or a qualified trainer who knows both animals for hands-on help.
Set the house up for separation before the foster comes in
Bring the foster home only after you have removed the items dogs most commonly argue over: food bowls, long-lasting chews, prized toys, and beds that belong to your resident dog. Give the foster a separate resting area behind a baby gate or closed door, with its own bedding, water, and feeding spot well away from your resident dog's bowl. Feed every meal separately and pick bowls up afterwards, because a foster who has known scarcity may guard food even if it is friendly on walks. For the first days, keep indoor time together short, supervised, and boring: both dogs settling in the same room with a barrier between them is more valuable than excited free play in the garden. Let your resident dog keep its usual routine, walks, and access to you, so the new arrival does not feel like a replacement.
Build shared time in small, repeatable steps
Progress in this order: parallel walks, then time in the same outdoor space with leads trailing only if both dogs are relaxed, then brief supervised time indoors with the gate open, then longer settled periods. End each step while things are going well rather than waiting for tiredness or frustration. Keep greetings when you come home low-key, because excitement at the door is where many foster and resident scuffles start. If a scuffle happens, separate the dogs calmly, give both a full break, and drop back to the previous successful step for a day or two; progress that goes backwards once is still progress. Note what you learn as you go: who needs more space at feeding time, which walk route keeps both dogs calm, and what time of day the foster settles best. Keeping those foster notes together in KinsLe through Family Sharing means the next person who walks, feeds, or supervises the two dogs follows the same separation and greeting plan you worked out.