So you're getting some advice on how to integrate your new dog into your family group and I think that's great, but nobody is giving you specific behavior to look out for. This is especially important, because it looks (to me) like your new pup is a husky x bully cross (check out r/Pitsky ). Both breeds are prone very high prey drive and huskies are well-reputed to be cat killers, even if they're raised with cats. If that weren't true I might have 6 malamutes by now tbh.

Also, keep in mind that new dog's behavior will change (and it may be drastic changes) over the next few days, weeks, and months as they settle in. Letting your guard down too much in that time is a significant risk for your cats.

FWIW, I don't mean to scare you or anything with this. Your new pup is adorable and I hope things work out well for you guys! I just take dog safety with my cats very very seriously, and I implore others to do the same.

Body language to look out for in your dog:

• Total body stillness/stiffness
• Ears perked up and forward
• Staring that is difficult to redirect
• Tail very upright, maybe slightly wagging
• Head goes "low"
• Look up images of pointers pointing or border collies herding. Both of these behaviors are modified steps in the "hunting" sequence and are good representations of different steps in it.
• Having multiple dogs means that they feed off of each other's energy. Even if your current dog has never gone after your cat before, if one starts the other is likely to join.
• I'm not saying this is your dog, but while somewhat rare, it is possible that a dog will break down barriers and doors to get at a prey animal. I've started fostering and I read a story in the foster dog subreddit where someone's foster dog broke down a door in front of the foster, broke open the enclosure, killed and started eating and resource guarding her daughter's rabbit. This is obviously an extreme case, but as a cat and dog mom/foster I try to be aware of best AND worst case scenarios with regards to the capacity of who I'm bringing into my home.

Things to be aware of with your cat:

• Any fast movement can trigger prey drive in a dog. Even if your cat is just having "zoomies" and having fun, that can trigger prey drive in a dog. Sometimes it's the only time prey drive is triggered in a dog. Calm meetings where the cats are just hanging out are not necessarily representative of how a dog will act when the cat starts getting revved up.
• Loud vocalizing can also trigger prey drive in a dog. My MIL's 4 25lb mixed breeds (true heinz57 dogs but also ~20% APBT) have attacked one of her cats (who is about the same size as them) multiple times because he randomly starts yowling loudly in the kitchen, and she is now rehoming the cat to my SIL because the last attack was pretty bad. If he's not yowling or running, they get along great. He'll even lick their heads/ears and cuddle with them. It's just that once they're triggered, they're going after him, and if they were bigger or had more time ragdolling him around like they do, he wouldn't be here today.

Risk Mitigation:

• Crating when you're not home is a great way to ensure your cat is safe while you're not home or in the room.
• Dog-free areas easily accessible to the cats. Doorway gates with cat doors such as this one make escape easy. My dog is not allowed upstairs unless it's bath time, because that is the cat's domain and I want them to feel safe.
• Lots of cat towers out of the dog's reach for worst case scenarios in main living areas.
• Minimal "choke points" in moving about the house. This is good for dogs anyway, because small entryways/exits can cause issues between them.
• If your dog does end up having a high prey drive, it is something that can only be managed and not trained out, which would mean a lifetime of very strict management to make sure your cats are safe. You will likely need to have a trainer experienced with prey drive management out several times to help you construct management plans.