hash locked multisig, can one cosigner sign without the pre-image? Consider Alice and Bob created the following native segwit script:

hash SHA256 defined as H | Alice PubKey | Bob Pubkey

Only Bob has the pre-image (plain text that hashes [sha256] to H). Can Alice just sign a transaction without revealing H, and just hand over the partially signed transaction off chain to Bob so he can reveal H + add his signature, make the transaction final and spend it?

The catch here is that neither Alice and Bob to be in total and exclusive control of the funds, but for Bob to have to reveal an additional secret as spending condition.
Can Alice just sign a transaction without revealing H, and just hand over the partially signed transaction off chain to Bob so he can reveal H + add his signature, make the transaction final and spend it?


Certainly. Of course the software will need to know how to handle that data, but it is not that hard to do.

The pre-image is not used in signing in any way; it is just additional data required by the script in order for the script to validate correctly.