The rule that does most of the work
Separate when unsupervised is the single rule that prevents most harm. Gates, closed doors or a kitten room are not a failure of bonding; they are how bonding survives long enough to become genuine. A kitten can be injured in seconds by a boisterous adolescent dog's paw, by being shaken in what began as a game, or by an older cat whose patience ends suddenly. Even animals who adore each other should earn unsupervised time gradually, over weeks of calm supervised contact, and many households sensibly keep the rule in place until the kitten is near adult size. Make the kitten's separate space genuinely comfortable, with food, water, a tray and company visits, so separation never feels like exile.
Read play like a referee, not a spectator
Healthy cross-species play has a rhythm: pauses, role swaps, loose bodies, and either animal free to leave. Step in when that rhythm breaks. Warning signs include one animal always chasing and never chased, the kitten pinned on her back while struggling, play that keeps escalating in speed and noise, the bigger pet gripping the kitten's neck or scruff in its mouth, and the kitten going silent and still, which is fear rather than consent. Interrupt early and cheerfully, separate for a breather, and let them resume only if both return willingly. Consistent early interruptions also teach the older pet where the line is far better than a scolding after an injury has already happened.
Build the room around escape
Arrange shared spaces so the kitten is never cornered. She needs at least two exit routes from any area, a high perch or cat tree the dog cannot reach, and a gap, cat flap or raised barrier she can slip through that excludes the larger animal. Feed and let her rest in places where she cannot be ambushed mid-meal or mid-sleep, because those are the moments a kitten is least able to react. With an older, rougher cat, the same logic applies at cat scale: vertical escape, duplicate resources so the kitten is never forced to contest a tray or bowl, and a room of her own to retreat to when the older cat's mood changes.
Teach the older pet the behaviours you need
The bigger animal's training is half the safety plan. Practise calm behaviour around the kitten's room and during meetings: settling on a mat, responding to a recall away from the kitten, and leaving on cue, all richly rewarded. Short, controlled sessions where the older pet is rewarded for ignoring the kitten build the habit you actually need, which is indifference rather than fascinated attention. If the older pet has any history of harming small animals, cannot calm down around the kitten after weeks of gradual work, or fixates in a way that worries you, keep them permanently separated and seek professional advice rather than continuing to hope familiarity will fix it.
Safety rules written where everyone sees them
Visitors, children and pet sitters are the weak points in any supervision plan, because they do not know which door must stay shut or which pair may never be left together. Write the rules plainly: who may be together, under whose supervision, and where the kitten goes when nobody is watching. KinsLe Family Sharing keeps those safety rules with your kitten's profile and care information, visible to the family who help with her, so the standard does not depend on whoever happened to hear the original conversation.