After waking up a few times to discover that the cat had opened the back door and let himself out of the house. I took a video if you want to see him let the dog/cats out.
We decided something needed to be done, so this is the...

Mark IV Bad Cat Door Latch!

This probably wouldn't stop even a more determined human, but it has been improved over the v3 latch. A human did break the v3 latch, and, though it was glued, the cat was also then able to destroy the latch and leave the house :(

• Stronger latch so that it won't break as easily
• Stronger mount for the same reason!
• Bigger diameter hole for the screw (it was tight enough it cracked one of mine)
• It stays in the "unlocked" position more reliably! (Don't lock yourself out!)
• When open, if it falls down, it stays horizontal.
• and it has a slope so that it'll climb over the door handle without help
• Improved cat-proof-i-ness

Obviously, this is intended to fit my Pella sliding door handle, however other folks may have handles that can work with simple modification. Sketchup file is attached.

It needs 3 screws. 2 wood screws (or metal) to attach to the door frame, and one to act as a pin between the "hook" and "mount" parts.

As you can see in the photo, my cat's mechanically inclined, always trying to figure out how things work. This may not stop him for long, but so far it's been a huge help!

Video of the Bad Cat (door latch): https://youtu.be/goiY7Q03bSY
And the actual Bad Cat (himself): https://youtu.be/aBWv2REA68c