fix(ata): lock down ATA::Transfer recipient contract

Enforce at the ATA layer that the recipient token holding is already
initialized, owned by the same token program as the sender ATA, decodes
to a valid `TokenHolding`, and points at the same token definition as
the sender. Align the core instruction doc and guest wrapper doc with
that contract, and cover the boundary with unit tests (default,
foreign-owned, malformed, mismatched-definition recipients, plus the
missing-owner-auth and happy paths) and end-to-end integration tests
(default and mismatched-definition recipients).

Without this, the downstream `token::Transfer` default-recipient
`Claim::Authorized` path was reachable through ATA, so integrators had
to reverse-engineer recipient semantics from token/runtime internals.

ata/core/src/lib.rs

@@ -24,7 +24,10 @@ pub enum Instruction {
     /// Required accounts (3):
     /// - Owner account (authorized)
     /// - Sender ATA (owner's token holding)
-    /// - Recipient token holding (must be initialized)
+    /// - Recipient token holding. Must be:
+    ///   - already initialized (not a default account),
+    ///   - owned by the same token program as the sender ATA,
+    ///   - and point at the same token definition as the sender.
     ///
     /// `token_program_id` is derived from `sender_ata.account.program_owner`.
     Transfer { amount: u128 },

ata/methods/guest/src/bin/ata.rs

@@ -30,7 +30,8 @@ mod ata {
     }
 
     /// Transfer tokens FROM owner's ATA to a recipient token holding account.
-    /// The recipient holding account must already be initialized.
+    /// The recipient holding must already be initialized, be owned by the same token program
+    /// as the sender ATA, and point at the same token definition as the sender.
     #[instruction]
     pub fn transfer(
         ctx: ProgramContext,

ata/src/tests.rs

@@ -162,3 +162,131 @@ fn get_associated_token_account_id_differs_by_definition() {
         get_associated_token_account_id(&ATA_PROGRAM_ID, &compute_ata_seed(owner_id(), other_def));
     assert_ne!(id1, id2);
 }
+
+fn recipient_id() -> AccountId {
+    AccountId::new([0x03u8; 32])
+}
+
+fn initialized_recipient_account() -> AccountWithMetadata {
+    AccountWithMetadata {
+        account: Account {
+            program_owner: TOKEN_PROGRAM_ID,
+            balance: 0,
+            data: Data::from(&TokenHolding::Fungible {
+                definition_id: definition_id(),
+                balance: 0,
+            }),
+            nonce: nssa_core::account::Nonce(0),
+        },
+        is_authorized: false,
+        account_id: recipient_id(),
+    }
+}
+
+#[test]
+fn transfer_emits_chained_call_for_initialized_recipient() {
+    let (post_states, chained_calls) = crate::transfer::transfer_from_associated_token_account(
+        owner_account(),
+        initialized_ata_account(),
+        initialized_recipient_account(),
+        ATA_PROGRAM_ID,
+        25,
+    );
+
+    assert_eq!(post_states.len(), 3);
+    assert_eq!(chained_calls.len(), 1);
+
+    let mut sender_auth = initialized_ata_account();
+    sender_auth.is_authorized = true;
+    let expected_call = ChainedCall::new(
+        TOKEN_PROGRAM_ID,
+        vec![sender_auth, initialized_recipient_account()],
+        &token_core::Instruction::Transfer {
+            amount_to_transfer: 25,
+        },
+    )
+    .with_pda_seeds(vec![compute_ata_seed(owner_id(), definition_id())]);
+
+    assert_eq!(chained_calls, vec![expected_call]);
+}
+
+#[test]
+#[should_panic(expected = "Owner authorization is missing")]
+fn transfer_panics_when_owner_not_authorized() {
+    let mut unauthorized_owner = owner_account();
+    unauthorized_owner.is_authorized = false;
+
+    crate::transfer::transfer_from_associated_token_account(
+        unauthorized_owner,
+        initialized_ata_account(),
+        initialized_recipient_account(),
+        ATA_PROGRAM_ID,
+        1,
+    );
+}
+
+#[test]
+#[should_panic(expected = "Recipient token holding must be initialized")]
+fn transfer_panics_when_recipient_is_default() {
+    let default_recipient = AccountWithMetadata {
+        account: Account::default(),
+        is_authorized: false,
+        account_id: recipient_id(),
+    };
+
+    crate::transfer::transfer_from_associated_token_account(
+        owner_account(),
+        initialized_ata_account(),
+        default_recipient,
+        ATA_PROGRAM_ID,
+        1,
+    );
+}
+
+#[test]
+#[should_panic(expected = "Recipient must be owned by the same token program as the sender ATA")]
+fn transfer_panics_when_recipient_is_foreign_owned() {
+    let mut foreign_recipient = initialized_recipient_account();
+    foreign_recipient.account.program_owner = [9u32; 8];
+
+    crate::transfer::transfer_from_associated_token_account(
+        owner_account(),
+        initialized_ata_account(),
+        foreign_recipient,
+        ATA_PROGRAM_ID,
+        1,
+    );
+}
+
+#[test]
+#[should_panic(expected = "Recipient must hold a valid token")]
+fn transfer_panics_when_recipient_data_is_malformed() {
+    let mut malformed_recipient = initialized_recipient_account();
+    malformed_recipient.account.data = Data::try_from(vec![0xFFu8, 0xFE, 0xFD]).unwrap();
+
+    crate::transfer::transfer_from_associated_token_account(
+        owner_account(),
+        initialized_ata_account(),
+        malformed_recipient,
+        ATA_PROGRAM_ID,
+        1,
+    );
+}
+
+#[test]
+#[should_panic(expected = "Recipient and sender token definitions do not match")]
+fn transfer_panics_when_recipient_definition_mismatches_sender() {
+    let mut mismatched_recipient = initialized_recipient_account();
+    mismatched_recipient.account.data = Data::from(&TokenHolding::Fungible {
+        definition_id: AccountId::new([0xAAu8; 32]),
+        balance: 0,
+    });
+
+    crate::transfer::transfer_from_associated_token_account(
+        owner_account(),
+        initialized_ata_account(),
+        mismatched_recipient,
+        ATA_PROGRAM_ID,
+        1,
+    );
+}

ata/src/transfer.rs

@@ -1,5 +1,5 @@
 use nssa_core::{
-    account::AccountWithMetadata,
+    account::{Account, AccountWithMetadata},
     program::{AccountPostState, ChainedCall, ProgramId},
 };
 use token_core::TokenHolding;
@@ -13,11 +13,38 @@ pub fn transfer_from_associated_token_account(
 ) -> (Vec<AccountPostState>, Vec<ChainedCall>) {
     let token_program_id = sender_ata.account.program_owner;
     assert!(owner.is_authorized, "Owner authorization is missing");
-    let definition_id = TokenHolding::try_from(&sender_ata.account.data)
+    let sender_definition_id = TokenHolding::try_from(&sender_ata.account.data)
         .expect("Sender ATA must hold a valid token")
         .definition_id();
-    let sender_seed =
-        ata_core::verify_ata_and_get_seed(&sender_ata, &owner, definition_id, ata_program_id);
+    let sender_seed = ata_core::verify_ata_and_get_seed(
+        &sender_ata,
+        &owner,
+        sender_definition_id,
+        ata_program_id,
+    );
+
+    // The recipient contract: ATA::Transfer requires a recipient token holding that is already
+    // initialized, owned by the same token program as the sender ATA, and that points at the same
+    // token definition as the sender. Anything else fails here rather than being silently
+    // materialized by the downstream token transfer (e.g. via `Claim::Authorized` on a default
+    // recipient), so integrators get an ATA-level failure rather than having to reverse-engineer
+    // token/runtime semantics.
+    assert_ne!(
+        recipient.account,
+        Account::default(),
+        "Recipient token holding must be initialized"
+    );
+    assert_eq!(
+        recipient.account.program_owner, token_program_id,
+        "Recipient must be owned by the same token program as the sender ATA"
+    );
+    let recipient_definition_id = TokenHolding::try_from(&recipient.account.data)
+        .expect("Recipient must hold a valid token")
+        .definition_id();
+    assert_eq!(
+        recipient_definition_id, sender_definition_id,
+        "Recipient and sender token definitions do not match"
+    );
 
     let post_states = vec![
         AccountPostState::new(owner.account.clone()),

integration_tests/tests/ata.rs

@@ -255,6 +255,85 @@ fn ata_transfer() {
     );
 }
 
+#[test]
+fn ata_transfer_rejects_default_recipient() {
+    let mut state = state_for_ata_tests();
+
+    let instruction = ata_core::Instruction::Transfer {
+        ata_program_id: Ids::ata_program(),
+        amount: 1_u128,
+    };
+
+    let message = public_transaction::Message::try_new(
+        Ids::ata_program(),
+        vec![Ids::owner(), Ids::owner_ata(), Ids::recipient_ata()],
+        vec![Nonce(0)],
+        instruction,
+    )
+    .unwrap();
+
+    let witness_set = public_transaction::WitnessSet::for_message(&message, &[&Keys::owner_key()]);
+
+    let tx = PublicTransaction::new(message, witness_set);
+    assert!(state.transition_from_public_transaction(&tx, 0, 0).is_err());
+
+    assert_eq!(
+        state.get_account_by_id(Ids::owner_ata()),
+        Accounts::owner_ata_init()
+    );
+    assert_eq!(
+        state.get_account_by_id(Ids::recipient_ata()),
+        Account::default()
+    );
+}
+
+#[test]
+fn ata_transfer_rejects_mismatched_definition_recipient() {
+    let mut state = state_for_ata_tests_with_precreated_recipient_ata();
+
+    // Replace the recipient ATA with a token holding pointing at a different definition.
+    let foreign_definition_id = AccountId::from(&PublicKey::new_from_private_key(
+        &PrivateKey::try_new([42; 32]).expect("valid private key"),
+    ));
+    let mismatched_recipient = Account {
+        program_owner: Ids::token_program(),
+        balance: 0_u128,
+        data: Data::from(&TokenHolding::Fungible {
+            definition_id: foreign_definition_id,
+            balance: 0_u128,
+        }),
+        nonce: Nonce(0),
+    };
+    state.force_insert_account(Ids::recipient_ata(), mismatched_recipient.clone());
+
+    let instruction = ata_core::Instruction::Transfer {
+        ata_program_id: Ids::ata_program(),
+        amount: 1_u128,
+    };
+
+    let message = public_transaction::Message::try_new(
+        Ids::ata_program(),
+        vec![Ids::owner(), Ids::owner_ata(), Ids::recipient_ata()],
+        vec![Nonce(0)],
+        instruction,
+    )
+    .unwrap();
+
+    let witness_set = public_transaction::WitnessSet::for_message(&message, &[&Keys::owner_key()]);
+
+    let tx = PublicTransaction::new(message, witness_set);
+    assert!(state.transition_from_public_transaction(&tx, 0, 0).is_err());
+
+    assert_eq!(
+        state.get_account_by_id(Ids::owner_ata()),
+        Accounts::owner_ata_init()
+    );
+    assert_eq!(
+        state.get_account_by_id(Ids::recipient_ata()),
+        mismatched_recipient
+    );
+}
+
 #[test]
 fn ata_burn() {
     let mut state = state_for_ata_tests();