Function serialized_actions_digest 

pub fn serialized_actions_digest(actions: &[SerializedAction]) -> [u8; 32]

A digest of serialized Orchard actions in wire order: every field of every action, hashed once. A group action stores it so every signer commits to exactly the same notes, and a pool mint or burn folds it into its group action id.

FROZEN once a protocol version ships it. This is a hash preimage, not a serialization format, so there is nothing to decode and no version byte to carry — but a group action stores the digest and a later block re-derives it to compare, and the comparison has no way to learn which version the action was proposed at. Changing the layout here would leave every pending group action permanently unconfirmable, and versioning the function on the current protocol version would not help, because that is not the version the stored digest came from. A new layout needs a new function and a new transition generation, the way calculate_action_id_with_fields is handled.

The concatenation carries no length prefixes, so it is only unambiguous because every field is fixed-width in practice: encrypted_note is a Vec<u8> that bundle reconstruction refuses unless it is exactly the Orchard ciphertext length, on every path where this digest matters.