diff --git a/program-tests/compressed-token-test/tests/light_token/create.rs b/program-tests/compressed-token-test/tests/light_token/create.rs
index a9f9aa5296..f5509ea2f7 100644
--- a/program-tests/compressed-token-test/tests/light_token/create.rs
+++ b/program-tests/compressed-token-test/tests/light_token/create.rs
@@ -507,7 +507,70 @@ async fn test_create_compressible_token_account_failing() {
         light_program_test::utils::assert::assert_rpc_error(result, 0, 8).unwrap();
     }
 
-    // Test 10: Non-compressible account for mint with restricted extensions
+    // Test 10: Non-compressible account with wrong data length (not 165 bytes)
+    // Non-compressible accounts must be exactly BASE_TOKEN_ACCOUNT_SIZE (165 bytes).
+    // Error: 3 (InvalidAccountData)
+    {
+        use forester_utils::instructions::create_account::create_account_instruction;
+        use solana_sdk::instruction::{AccountMeta, Instruction};
+
+        println!("Test 10: Non-compressible account with wrong data length");
+
+        // Pre-allocate 200-byte token account owned by ctoken program (wrong size)
+        let token_account_keypair = Keypair::new();
+        let token_account_pubkey = token_account_keypair.pubkey();
+        let account_size = 200usize;
+
+        let create_account_ix = create_account_instruction(
+            &payer_pubkey,
+            account_size,
+            context
+                .rpc
+                .get_minimum_balance_for_rent_exemption(account_size)
+                .await
+                .unwrap(),
+            &light_compressed_token::ID,
+            Some(&token_account_keypair),
+        );
+
+        context
+            .rpc
+            .create_and_send_transaction(
+                &[create_account_ix],
+                &payer_pubkey,
+                &[&context.payer, &token_account_keypair],
+            )
+            .await
+            .unwrap();
+
+        // Build manual instruction for non-compressible path
+        let owner_pubkey = context.owner_keypair.pubkey();
+        let mut instruction_data = vec![18u8]; // discriminator
+        instruction_data.extend_from_slice(&owner_pubkey.to_bytes());
+
+        let create_non_compressible_ix = Instruction {
+            program_id: light_compressed_token::ID,
+            accounts: vec![
+                AccountMeta::new(token_account_pubkey, false),
+                AccountMeta::new_readonly(context.mint_pubkey, false),
+            ],
+            data: instruction_data,
+        };
+
+        let result = context
+            .rpc
+            .create_and_send_transaction(
+                &[create_non_compressible_ix],
+                &payer_pubkey,
+                &[&context.payer],
+            )
+            .await;
+
+        // Should fail with InvalidAccountData (3) - wrong data length
+        light_program_test::utils::assert::assert_rpc_error(result, 0, 3).unwrap();
+    }
+
+    // Test 10b: Non-compressible account for mint with restricted extensions
     // Mints with restricted extensions (Pausable, PermanentDelegate, TransferFee, TransferHook)
     // require the compression_only marker which is part of the Compressible extension.
     // Error: 6115 (MissingCompressibleConfig)
@@ -529,10 +592,10 @@ async fn test_create_compressible_token_account_failing() {
         .await;
         let mint_with_restricted_ext = mint_keypair.pubkey();
 
-        // Pre-allocate 200-byte token account owned by ctoken program
+        // Pre-allocate 165-byte token account owned by ctoken program
         let token_account_keypair = Keypair::new();
         let token_account_pubkey = token_account_keypair.pubkey();
-        let account_size = 200usize;
+        let account_size = 165usize;
 
         let create_account_ix = create_account_instruction(
             &payer_pubkey,
diff --git a/program-tests/compressed-token-test/tests/light_token/create_ata.rs b/program-tests/compressed-token-test/tests/light_token/create_ata.rs
index 6051155b14..da73589b2a 100644
--- a/program-tests/compressed-token-test/tests/light_token/create_ata.rs
+++ b/program-tests/compressed-token-test/tests/light_token/create_ata.rs
@@ -262,6 +262,95 @@ async fn test_create_ata_idempotent() {
     }
 }
 
+/// Tests that idempotent ATA creation rejects when the existing account's
+/// owner field has been changed (e.g. via authority transfer).
+/// The PDA derivation passes (same address) but stored owner differs.
+#[tokio::test]
+async fn test_create_ata_idempotent_owner_mismatch() {
+    let mut context = setup_account_test().await.unwrap();
+    let payer_pubkey = context.payer.pubkey();
+
+    let compressible_data = CompressibleData {
+        compression_authority: context.compression_authority,
+        rent_sponsor: context.rent_sponsor,
+        num_prepaid_epochs: 2,
+        lamports_per_write: Some(100),
+        account_version: light_token_interface::state::TokenDataVersion::ShaFlat,
+        compress_to_pubkey: false,
+        payer: payer_pubkey,
+    };
+
+    // Create ATA (first creation)
+    let ata_pubkey = create_and_assert_ata(
+        &mut context,
+        Some(compressible_data.clone()),
+        true,
+        "idempotent_owner_mismatch_first",
+    )
+    .await;
+
+    // Modify the stored owner to a different pubkey
+    let mut account = context.rpc.get_account(ata_pubkey).await.unwrap().unwrap();
+    let different_owner = Pubkey::new_unique();
+    // Owner is at bytes 32-63 in SPL token account layout
+    account.data[32..64].copy_from_slice(&different_owner.to_bytes());
+    context.rpc.set_account(ata_pubkey, account);
+
+    // Second idempotent creation should fail because stored owner != instruction owner
+    create_and_assert_ata_fails(
+        &mut context,
+        Some(compressible_data),
+        true,
+        "idempotent_owner_mismatch_second",
+        3, // InvalidAccountData
+    )
+    .await;
+}
+
+/// Tests that idempotent ATA creation rejects when the existing account's
+/// mint field has been tampered with.
+#[tokio::test]
+async fn test_create_ata_idempotent_mint_mismatch() {
+    let mut context = setup_account_test().await.unwrap();
+    let payer_pubkey = context.payer.pubkey();
+
+    let compressible_data = CompressibleData {
+        compression_authority: context.compression_authority,
+        rent_sponsor: context.rent_sponsor,
+        num_prepaid_epochs: 2,
+        lamports_per_write: Some(100),
+        account_version: light_token_interface::state::TokenDataVersion::ShaFlat,
+        compress_to_pubkey: false,
+        payer: payer_pubkey,
+    };
+
+    // Create ATA (first creation)
+    let ata_pubkey = create_and_assert_ata(
+        &mut context,
+        Some(compressible_data.clone()),
+        true,
+        "idempotent_mint_mismatch_first",
+    )
+    .await;
+
+    // Modify the stored mint to a different pubkey
+    let mut account = context.rpc.get_account(ata_pubkey).await.unwrap().unwrap();
+    let different_mint = Pubkey::new_unique();
+    // Mint is at bytes 0-31 in SPL token account layout
+    account.data[0..32].copy_from_slice(&different_mint.to_bytes());
+    context.rpc.set_account(ata_pubkey, account);
+
+    // Second idempotent creation should fail because stored mint != instruction mint
+    create_and_assert_ata_fails(
+        &mut context,
+        Some(compressible_data),
+        true,
+        "idempotent_mint_mismatch_second",
+        3, // InvalidAccountData
+    )
+    .await;
+}
+
 /// Tests creation of an ATA with 0 prepaid epochs (immediately compressible).
 /// All Light Token accounts now have compression infrastructure, so we pass
 /// CompressibleData with num_prepaid_epochs: 0.
diff --git a/program-tests/compressed-token-test/tests/light_token/transfer.rs b/program-tests/compressed-token-test/tests/light_token/transfer.rs
index 5ac4b2d370..a5346b9d14 100644
--- a/program-tests/compressed-token-test/tests/light_token/transfer.rs
+++ b/program-tests/compressed-token-test/tests/light_token/transfer.rs
@@ -438,6 +438,139 @@ async fn test_ctoken_transfer_mint_mismatch() {
     .await;
 }
 
+// ============================================================================
+// Self-Transfer Tests
+// ============================================================================
+
+#[tokio::test]
+async fn test_ctoken_self_transfer_frozen() {
+    let (mut context, source, _destination, _mint_amount, _source_keypair, _dest_keypair) =
+        setup_transfer_test(None, 1000).await.unwrap();
+
+    // Freeze the source account
+    let mut source_account = context.rpc.get_account(source).await.unwrap().unwrap();
+    source_account.data[108] = 2; // AccountState::Frozen
+    context.rpc.set_account(source, source_account);
+
+    let owner_keypair = context.owner_keypair.insecure_clone();
+
+    // Self-transfer on frozen account should fail
+    // from_account_info_checked rejects frozen accounts (state != initialized)
+    transfer_and_assert_fails(
+        &mut context,
+        source,
+        source, // self-transfer: source == destination
+        500,
+        &owner_keypair,
+        "self_transfer_frozen",
+        3, // InvalidAccountData (from_account_info_checked rejects frozen)
+    )
+    .await;
+}
+
+#[tokio::test]
+async fn test_ctoken_self_transfer_insufficient_funds() {
+    let (mut context, source, _destination, _mint_amount, _source_keypair, _dest_keypair) =
+        setup_transfer_test(None, 1000).await.unwrap();
+
+    let owner_keypair = context.owner_keypair.insecure_clone();
+
+    // Self-transfer with amount > balance should fail with InsufficientFunds
+    transfer_and_assert_fails(
+        &mut context,
+        source,
+        source, // self-transfer: source == destination
+        1500,   // more than the 1000 balance
+        &owner_keypair,
+        "self_transfer_insufficient_funds",
+        6154, // InsufficientFunds
+    )
+    .await;
+}
+
+#[tokio::test]
+async fn test_ctoken_self_transfer_success() {
+    let (mut context, source, _destination, _mint_amount, _source_keypair, _dest_keypair) =
+        setup_transfer_test(None, 1000).await.unwrap();
+
+    let owner_keypair = context.owner_keypair.insecure_clone();
+    let payer_pubkey = context.payer.pubkey();
+
+    // Self-transfer with valid amount should succeed
+    let transfer_ix = build_transfer_instruction(source, source, 500, owner_keypair.pubkey());
+    context
+        .rpc
+        .create_and_send_transaction(
+            &[transfer_ix],
+            &payer_pubkey,
+            &[&context.payer, &owner_keypair],
+        )
+        .await
+        .unwrap();
+
+    // Verify balance unchanged (self-transfer is a no-op)
+    let source_account = context.rpc.get_account(source).await.unwrap().unwrap();
+    let token_account =
+        spl_token_2022::state::Account::unpack_unchecked(&source_account.data[..165]).unwrap();
+    assert_eq!(token_account.amount, 1000);
+}
+
+#[tokio::test]
+async fn test_ctoken_transfer_checked_self_transfer_frozen() {
+    let (mut context, source, _destination, _mint_amount, _source_keypair, _dest_keypair) =
+        setup_transfer_checked_test_with_spl_mint(None, 1000, 9)
+            .await
+            .unwrap();
+
+    // Freeze the source account
+    let mut source_account = context.rpc.get_account(source).await.unwrap().unwrap();
+    source_account.data[108] = 2; // AccountState::Frozen
+    context.rpc.set_account(source, source_account);
+
+    let mint = context.mint_pubkey;
+    let owner_keypair = context.owner_keypair.insecure_clone();
+
+    // Self-transfer on frozen account should fail
+    // from_account_info_checked rejects frozen accounts (state != initialized)
+    transfer_checked_and_assert_fails(
+        &mut context,
+        source,
+        mint,
+        source, // self-transfer: source == destination
+        500,
+        9,
+        &owner_keypair,
+        "self_transfer_checked_frozen",
+        3, // InvalidAccountData (from_account_info_checked rejects frozen)
+    )
+    .await;
+}
+
+#[tokio::test]
+async fn test_ctoken_transfer_checked_self_transfer_insufficient_funds() {
+    let (mut context, source, _destination, _mint_amount, _source_keypair, _dest_keypair) =
+        setup_transfer_checked_test_with_spl_mint(None, 1000, 9)
+            .await
+            .unwrap();
+
+    let mint = context.mint_pubkey;
+    let owner_keypair = context.owner_keypair.insecure_clone();
+
+    // Self-transfer with amount > balance should fail with InsufficientFunds
+    transfer_checked_and_assert_fails(
+        &mut context,
+        source,
+        mint,
+        source, // self-transfer: source == destination
+        1500,   // more than the 1000 balance
+        9,
+        &owner_keypair,
+        "self_transfer_checked_insufficient_funds",
+        6154, // InsufficientFunds
+    )
+    .await;
+}
+
 // ============================================================================
 // Edge Case Tests
 // ============================================================================
diff --git a/programs/compressed-token/program/src/ctoken/create.rs b/programs/compressed-token/program/src/ctoken/create.rs
index 4da22191ce..04b895f211 100644
--- a/programs/compressed-token/program/src/ctoken/create.rs
+++ b/programs/compressed-token/program/src/ctoken/create.rs
@@ -92,6 +92,24 @@ pub fn process_create_token_account(
         // Non-compressible account: token_account must already exist and be owned by CToken program.
         // Unlike SPL initialize_account3 (which expects System-owned), this expects a pre-existing
         // CToken-owned account. Ownership is implicitly validated when writing to the account.
+        // Non-compressible accounts must be exactly BASE_TOKEN_ACCOUNT_SIZE (165 bytes).
+        if token_account.data_len() != light_token_interface::BASE_TOKEN_ACCOUNT_SIZE as usize {
+            msg!("Token account data length mismatch");
+            return Err(ProgramError::InvalidAccountData);
+        }
+        // Verify the account is rent-exempt to prevent garbage collection.
+        #[cfg(target_os = "solana")]
+        {
+            use pinocchio::sysvars::Sysvar;
+            let rent = pinocchio::sysvars::rent::Rent::get()
+                .map_err(|_| ProgramError::UnsupportedSysvar)?;
+            let min_lamports =
+                rent.minimum_balance(light_token_interface::BASE_TOKEN_ACCOUNT_SIZE as usize);
+            if token_account.lamports() < min_lamports {
+                msg!("Token account is not rent-exempt");
+                return Err(ProgramError::AccountNotRentExempt);
+            }
+        }
         None
     };
 
diff --git a/programs/compressed-token/program/src/ctoken/create_ata.rs b/programs/compressed-token/program/src/ctoken/create_ata.rs
index 406981ea0f..d936c5b8cd 100644
--- a/programs/compressed-token/program/src/ctoken/create_ata.rs
+++ b/programs/compressed-token/program/src/ctoken/create_ata.rs
@@ -3,7 +3,7 @@ use borsh::BorshDeserialize;
 use light_account_checks::AccountIterator;
 use light_program_profiler::profile;
 use light_token_interface::instructions::create_associated_token_account::CreateAssociatedTokenAccountInstructionData;
-use pinocchio::{account_info::AccountInfo, instruction::Seed};
+use pinocchio::{account_info::AccountInfo, instruction::Seed, pubkey::pubkey_eq};
 use spl_pod::solana_msg::msg;
 
 use crate::{
@@ -67,6 +67,17 @@ fn process_create_associated_token_account_with_mode<const IDEMPOTENT: bool>(
 
     // If idempotent mode, check if account already exists
     if IDEMPOTENT && associated_token_account.is_owned_by(&crate::LIGHT_CPI_SIGNER.program_id) {
+        let token = light_token_interface::state::Token::from_account_info_checked(
+            associated_token_account,
+        )?;
+        if !pubkey_eq(token.base.mint.array_ref(), mint_bytes) {
+            msg!("Token account mint mismatch");
+            return Err(ProgramError::InvalidAccountData);
+        }
+        if !pubkey_eq(token.base.owner.array_ref(), owner_bytes) {
+            msg!("Token account owner mismatch");
+            return Err(ProgramError::InvalidAccountData);
+        }
         return Ok(());
     }
 
diff --git a/programs/compressed-token/program/src/ctoken/transfer/checked.rs b/programs/compressed-token/program/src/ctoken/transfer/checked.rs
index e7815a5cd3..0387fa46df 100644
--- a/programs/compressed-token/program/src/ctoken/transfer/checked.rs
+++ b/programs/compressed-token/program/src/ctoken/transfer/checked.rs
@@ -52,7 +52,12 @@ pub fn process_ctoken_transfer_checked(
 
     // Self-transfer: validate authority but skip token movement to avoid
     // double mutable borrow panic in pinocchio process_transfer.
-    if validate_self_transfer(source, destination, &accounts[ACCOUNT_AUTHORITY])? {
+    if validate_self_transfer(
+        source,
+        destination,
+        &accounts[ACCOUNT_AUTHORITY],
+        instruction_data,
+    )? {
         return Ok(());
     }
 
diff --git a/programs/compressed-token/program/src/ctoken/transfer/default.rs b/programs/compressed-token/program/src/ctoken/transfer/default.rs
index 6920561407..e585746e20 100644
--- a/programs/compressed-token/program/src/ctoken/transfer/default.rs
+++ b/programs/compressed-token/program/src/ctoken/transfer/default.rs
@@ -46,7 +46,12 @@ pub fn process_ctoken_transfer(
 
     // Self-transfer: validate authority but skip token movement to avoid
     // double mutable borrow panic in pinocchio process_transfer.
-    if validate_self_transfer(source, destination, &accounts[ACCOUNT_AUTHORITY])? {
+    if validate_self_transfer(
+        source,
+        destination,
+        &accounts[ACCOUNT_AUTHORITY],
+        instruction_data,
+    )? {
         return Ok(());
     }
 
diff --git a/programs/compressed-token/program/src/ctoken/transfer/shared.rs b/programs/compressed-token/program/src/ctoken/transfer/shared.rs
index 8fc8d70ba8..43d9dcf462 100644
--- a/programs/compressed-token/program/src/ctoken/transfer/shared.rs
+++ b/programs/compressed-token/program/src/ctoken/transfer/shared.rs
@@ -17,6 +17,7 @@ use crate::{
 
 /// Validates self-transfer: if source == destination, checks authority is signer
 /// and is owner or delegate of the token account.
+/// Also checks that the account is not frozen and has sufficient funds.
 /// Returns Ok(true) if self-transfer was validated (caller should return Ok(())),
 /// Returns Ok(false) if not a self-transfer (caller should continue).
 #[inline(always)]
@@ -24,11 +25,12 @@ pub fn validate_self_transfer(
     source: &AccountInfo,
     destination: &AccountInfo,
     authority: &AccountInfo,
+    instruction_data: &[u8],
 ) -> Result<bool, ProgramError> {
     if !pubkey_eq(source.key(), destination.key()) {
         return Ok(false);
     }
-    validate_self_transfer_authority(source, authority)?;
+    validate_self_transfer_authority(source, authority, instruction_data)?;
     Ok(true)
 }
 
@@ -36,12 +38,22 @@ pub fn validate_self_transfer(
 fn validate_self_transfer_authority(
     source: &AccountInfo,
     authority: &AccountInfo,
+    instruction_data: &[u8],
 ) -> Result<(), ProgramError> {
     if !authority.is_signer() {
         return Err(ProgramError::MissingRequiredSignature);
     }
+    // from_account_info_checked rejects frozen accounts (state != 1)
     let token =
         Token::from_account_info_checked(source).map_err(|_| ProgramError::InvalidAccountData)?;
+    let amount = u64::from_le_bytes(
+        instruction_data[..8]
+            .try_into()
+            .map_err(|_| ProgramError::InvalidInstructionData)?,
+    );
+    if token.base.amount < amount {
+        return Err(ErrorCode::InsufficientFunds.into());
+    }
     let is_owner = pubkey_eq(authority.key(), token.base.owner.array_ref());
     let is_delegate = token
         .base