Output Notes

The output_note module creates and updates notes during a transaction.

extern crate alloc;

use alloc::vec::Vec;
use miden::{output_note::{self, OutputNoteAssetsInfo}, Asset, NoteIdx, Tag, NoteType, Recipient};

Create a note

let note_idx: NoteIdx = output_note::create(tag, note_type, recipient);

create returns a NoteIdx used by subsequent operations in the same transaction. It may only be called from an account component procedure. Transaction and note scripts must call an account procedure such as BasicWallet::create_note and use the returned index.

Add assets to a note

output_note::add_asset(asset, note_idx);

add_asset only adds the asset to the output note; it does not remove it from the native account's vault. When funding a note from that vault, remove the asset first or use BasicWallet::move_asset_to_note.

Call add_asset multiple times with the same note_idx to attach several assets to one note. A note can carry both fungible and non-fungible assets.

Query output note state

// Asset commitment and count
let info: OutputNoteAssetsInfo = output_note::get_assets_info(note_idx);

// All assets on the note
let assets: Vec<Asset> = output_note::get_assets(note_idx);

// The recipient hash
let recipient: Recipient = output_note::get_recipient(note_idx);

OutputNoteAssetsInfo contains commitment: Word and num_assets: u32.

Note metadata

get_metadata() returns the encoded metadata header:

let metadata: NoteMetadata = output_note::get_metadata(note_idx);

The SDK's NoteMetadata contains a single header: Word. Attachment content and its commitment are queried separately. On the protocol side, the full NoteMetadata combines PartialNoteMetadata (sender, note type, tag) with attachment headers and the attachments commitment. See Reading Notes — Note metadata for details.

Note attachments

Notes can carry auxiliary data as attachments. The attachment API uses a Felt-typed scheme identifier; the payload shape is selected by the function:

// Single-word attachment; the helper hashes and inserts the word.
output_note::add_word_attachment(note_idx, attachment_scheme, word_data);

Use add_attachment when you already have an attachment commitment and the raw data is present in the advice map. Use add_attachment_from_memory for multi-word data that should be hashed and inserted from memory. Attachments are committed into note metadata, and the consumer must have access to the corresponding advice map entries to read the full data.

Computing a Recipient

When creating notes programmatically, an account component needs a Recipient to pass to output_note::create. The Recipient is a commitment to the note's serial number, script, and storage, which together define the conditions under which the note can be consumed.

The protocol computation is:

recipient = hash(hash(hash(serial_num, [0;4]), script_root), storage_commitment)

script_root is the hash of the note script program, and storage_commitment is the commitment to the note's storage values. MASM authors can use note::compute_recipient for an existing storage commitment or note::compute_and_store_recipient when the raw storage values should also be inserted into the advice map.

Example: creating and funding a note

A complete flow for creating a note inside an account component:

use miden::{
    component, component_storage, felt, native_account, output_note, Asset, NoteIdx, NoteType,
    Recipient, Tag,
};

#[component_storage]
struct NoteSenderStorage;

#[component]
trait NoteSender {
    #[account_procedure]
    fn send_asset(&mut self, recipient: Recipient, asset: Asset, tag: Tag) -> NoteIdx;
}

#[component]
impl NoteSender for NoteSenderStorage {
    fn send_asset(&mut self, recipient: Recipient, asset: Asset, tag: Tag) -> NoteIdx {
        // 1. Create the note
        let note_idx = output_note::create(tag, NoteType::from(felt!(1)), recipient);

        // 2. Remove the asset from the native account's vault
        let _ = native_account::remove_asset(asset);

        // 3. Add the asset to the note
        output_note::add_asset(asset, note_idx);

        note_idx
    }
}

Full API docs on docs.rs: miden::output_note