Partitoned cookies have been discussed a lot in Privacy CG and some use cases seem to fit well with it. Safari shipped partitioned cookies 2017-2018, mostly saw compatibility issues, and replaced them with simple third-party cookie blocking instead. Since then, both Firefox and Edge have started blocking most/many third-party cookies and the need for partitioned cookies as a standardized behavior has emerged. Firefox has already implemented partitioned cookies and storage and WebKit+CFNetwork has a dormant implementation.

We should consider an optional parameter to document.requestStorageAccess() that allows for the embedee to signal all kinds of wishes, one of them that it is fine with partitioned cookies and storage. That could allow for prompt-free, undelayed cookie access. Perhaps even relax the user interaction requirement.

(Future uses of the optional parameter to document.requestStorageAccess() could be to allow the initiation of a login flow if unpartitioned storage access is granted but the user is not yet logged in to the embedee, something that several developers have asked for.)