The contracts will usually say “You agree to the restrictions in our TOS” with a link to that page which allows for them to update the TOS without new signatures.

All the US megacorps tend send me emails saying "We want to change TOS, here's the new TOS that's be valid from date X, and be informed that you have the right to refuse it" (in which case they'll probably terminate the service, but I'm quite sure that if it's a paid service with some subscription, they would have to refund the remaining portion) - so they can change the TOS, but not without at least some form of agreement, even if it's an implicit one 'by continuing to use the service'.

Usually, contracts will note that you will be notified of changes ahead of time, if it's a good faith contract and company that is.

Here in Sweden contracts are a specific thing, otherwise it's not a contract, so agreeing to conditions that can be changed by the other party simply isn't a contract and therefore is just a bullshit paper of very dubious legal validity.

I know that some things like this are accepted in America, and I can't judge how it would be dealt with. I assume that contracts between companies and other sophisticated entities are actual contracts with unchangeable terms.

In theory yes, but you also have this stuff where people agree to get medical treatment and the price isn't specified.

This would be a non-contract in Swedish law, for example.

One thing about the US, is how we handle settings where one could conceptualize a contract as being needed, but where it would be way too inefficient and impractical to negotiate, write out, understand, and sign, a written contract. In those cases, which includes things like retail sales, restaurants, and may other cases, the UCC or Uniform Commercial Code[1][2] applies. Not sure offhand if that relates to the medical example or not, but I expect that at least some similar notion applies. So there are binding laws that cover these transactions, it's just not done the same way as a "full fledged contract".

[1]: https://en.wikipedia.org/wiki/Uniform_Commercial_Code

[2]: The UCC also covers other things, but these cases are a lot of what it's best known for.

Knowing medical prices up front would be entirely possible and practical. In most situations, you should be able to sign contract up front.

It is also illegal in USA, although that only changed recently.

Yeah, I’ve signed dozens of contracts for services and some are explicit in the way you expect but a lot of software or SAAS type contracts have flexible terms that refer to TOS and privacy policies that are updated regularly. It’s uncommon that any of those things are changed in a way that either party is upset with so companies are generally okay signing up and assuming good faith.

The contact's restriction is on the usage of the model, not the behavior of the model.