That doesn't answer my question at all.
Is the decision (regardless of who fucking decides) based on metadata attached to the key the client controls or from a breadcrumb included in the message itself?
Is the decision (regardless of who fucking decides) based on metadata attached to the key the client controls or from a breadcrumb included in the message itself?
In all cases the client application chooses the algorithm used when the user writes a DM. What do you mean by breadcrumb in the message. Message in what context? Message sent to the signer?
Edit: Maybe I should say the client developer? Is that the answer you're looking for? The developer _could_ give the user the option of choosing which to use, but clients generally are hard-coded to use one or the other.
https://github.com/nostr-protocol/nips/blob/master/17.md
Notice that nip44 IS the standard. again, nip04 is deprecated, and should be treated by clients as such.
When a user decides to send a DM to another user, the client must choose the standard for encryption, and message wrapping. Then hope the other user is using a client that implements the same standard, in order to decrypt the message.
Again, remember, DMs don't have a session. Every message derives a new symmetric key. The only metadata that makes a "chat" session is the timestamp, and the public keys of the users.