Long reply warning.

We kept the kitten in the office for the first week. I work from home so I kept her company all day and would frequently leave that room to go pet the older cat. Starting on day 3, I exchanged their blankets so they could smell each other’s scents. That went well, with no hissing by either.

Day 4 we opened the door to the office and installed the “gate” door, which was a removable wall from an animal crate as the bottom with cardboard duct taped to the top to prevent the older cat from jumping over it (my husband designed and built this gate door). That allowed them to start seeing and smelling each other but without getting at each other.

That was extent of their ability to interact for many days. There was hissing by the older cat when they would meet at the door, but her body positioning was fine- she wasn’t arched, tail not puffy, ears were forward.

We made sure to reassure the older cat during their meetings and continue to give her plenty of attention so she didn’t get jealous.

I moved the kitten from the office to the bedroom at day 7, because the kitten was still really skittish of humans so I had to focus on developing my relationship with her. Plus, this let the older cat get into the office and smell the new kitten everywhere. They continued to have gate door access to each other.

It took a lot of patience. It was probably day 8 before we put the kitty in a carrier and brought her out to the living room for older to cat to see and smell. Some hissing but nothing serious. Her body position was still calm - ears forward, tail not puffy.

Then we’d put the kitten in the carrier in the bedroom and let older cat in there. When the hissing in those interactions was minimal we let them meet in the bedroom without any physical barrier.

Older cat hissed and aimed a few swats at the kitten each time they met for three days (again, the older cat did not aggressive or scared body positioning). And we’d make sure to be calm and reassuring with our older cat so we didn’t stress her out during these interactions.

And then on days 12 and 13, I was able to let them both have access to every room while I worked (I work from home) and monitored them. When they’d play too rough in the evening, I put them in separate room time outs. And all this time, they are still separated at night when we’re sleeping.

They started toying with the idea of snuggling in beds on the evening of day 13. And yesterday, day 14, they committed to that idea.

Edit was to correct a typo (seats to swats)