Some features use private cloud, but it's pretty decent in terms of security and privacy.

https://security.apple.com/blog/private-cloud-compute/

"Pretty decent" is irellevant for proprietary code that's not my property.

The only safe option is if it's guaranteed to not leave my machine, so for this app, to disable anything that has a chance of exfiltrating data.

I encourage you to try to understand how verifiable transparency works.

https://security.apple.com/blog/pcc-security-research/

I doubt my customer - on whose proprietary code I want to try running LLMs - cares :)

Or to rephrase: would you go to court with the contents of that link as evidence that you haven't inadvertently published someone else's proprietary data in some external database?

Apple Intelligence image generation is fully offline

isn't apple intelligence image generation fully offline?

I don't know, I'm asking.

Only want it for some code so it looks like it can be fully offline, but it's worth being paranoid about it.