Any subscription-based 1Password can be accessed from the web. Couldn't they just demand those credentials?

Only if you know them. I don't know about you, but I don't have my long random account key memorized (only my master password). You can't log into the website without that account key.

Of course, you do need to be able to log in to turn travel mode back on, so if I were to use this I'd probably do something like set up a service to securely send me my account key after I'm expected to have finished crossing the border, or maybe just store it on a remote server that I have access to under the expectation that the TSA can't demand that I SSH into a remote server (especially one they don't even know about). Though if I'm traveling alone (instead of with my wife) I'd probably just call her and ask her to turn travel mode off for me.

That's a great solution if you're a US citizen and want to enjoy showing off to a border guard before being guaranteed entry, but for migrants (who are most affected by this), this kind of 'gotcha' logic would likely be considered insubordinate grandstanding, and get them denied entry.

> this kind of 'gotcha' logic would likely be considered insubordinate grandstanding

I'm not sure what you mean. I don't think it's unreasonable for anyone, migrants included, to tell CBP "I don't feel safe traveling with sensitive data, so I don't have any of that data on my computer". What's the 'gotcha' here? CBP isn't the only reason to want to have Travel Mode, there's also the increased risk of having your laptop stolen or misplaced.

In your original post, I took

> Only if you know them. ... You can't log into the website without that account key.

To mean that you'd openly have access to information in front of the guard, and then let them know that you can't access it at this time because of your elaborate scheme (e.g. tell them that it exists, but that they can't have it).

That's quite different to just not travelling with the data (or evidence of it existing) at all.

> CBP isn't the only reason to want to have Travel Mode

No, but it's the only 'reason' that's likely to use serious, life-altering coercion to make you to disable it, if they detect that it exists. It may be better to have no data that suggests capabilities, than openly posses partially disabled capabilities.

There's no way for a border agent to tell if you're refusing to disable travel mode because you won't or you can't (and little reason for them to care).

Of course it's not unreasonable, but 'reasonable' is not the relevant criterion here.

Yes, it does. And you provide them to the password for the local vault. Since you activated travel mode, they'll be able to see your "travel safe" passwords, but no indication that there are other passwords that were recently removed from the vault, and no indication that you entered travel mode.