If you are using a device that previously accessed your vault, it will be cached and accessible. It just won't sync until you regain network connectivity.

Is there an actual guarantee that all passwords will be cached (and not just e.g. the N most recently accessed ones), and that the cache will not expire at some point?

I'm not sure, but I'm also not sure there's a guarantee that my self-hosted password vault won't die in the middle of a busy day.

That failure can be mitigated by having a local backup, though. In general, with local stuff, it's not so much that the guarantees are better, it's that you can dial them in yourself to the level you feel comfortable at.

How many passwords are required if you aren’t connecting to the internet? What would you be signing in to?

Do you only keep online passwords in your manager? I've got all sorts of things in mine, plenty that I might need without connectivity, such as the door code to that AirBnB or bank account numbers and PINs. Then again, I never would have done that without offline availability...

That's some low quality snark. I have plenty of local things with passwords. One example is encrypted external drives. That's all your snark gets from me on the off chance it's not actually snark. (must me the most I've used the word snark in one go)

> That's some low quality snark.

I'm on your side in all the comments I've read so far (especially the "freeloader" one), but this one is a clear "assume the worst" which isn't fair to GP. Their comment could very well have been a legitimate and innocent question. Of course it could have been a majorly failed attempt at a troll (since the question has great answers) but assuming the worst just drags everything down. IMHO better to give benefit of the doubt, even if only for the other people reading it later.

After the initial login all your passwords are cached locally anyway.