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skills/solana-development/references/tokens-2022.md

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+# SPL Token-2022 (Token Extensions Program)
+
+Token Extensions Program (Token-2022) guide covering extension types, setup for both Anchor and Native Rust, and practical examples including transfer hooks. Includes extension configuration, space calculation, and initialization patterns.
+
+**For related topics, see:**
+- **[tokens-overview.md](tokens-overview.md)** - Token fundamentals and account structures
+- **[tokens-operations.md](tokens-operations.md)** - Create, mint, transfer, burn, close operations
+- **[tokens-validation.md](tokens-validation.md)** - Account validation patterns
+- **[tokens-patterns.md](tokens-patterns.md)** - Common patterns and security
+
+## Table of Contents
+
+1. [What are Token Extensions?](#what-are-token-extensions)
+2. [Available Extensions](#available-extensions)
+3. [Using Token-2022 in Anchor](#using-token-2022-in-anchor)
+4. [Using Token-2022 in Native Rust](#using-token-2022-in-native-rust)
+5. [Transfer Hook Extension Example](#transfer-hook-extension-example-anchor)
+
+---
+
+## What are Token Extensions?
+
+The Token Extensions Program (Token-2022) provides additional features through extensions. Extensions are optional functionality that can be added to a token mint or token account.
+
+**Key Points:**
+- Extensions must be enabled during account creation
+- Cannot add extensions after creation
+- Some extensions are incompatible with each other
+- Extensions add state to the `tlv_data` field
+
+---
+
+## Available Extensions
+
+```rust
+pub enum ExtensionType {
+    TransferFeeConfig,           // Transfer fees
+    TransferFeeAmount,           // Withheld fees
+    MintCloseAuthority,          // Close mint accounts
+    ConfidentialTransferMint,    // Confidential transfers
+    DefaultAccountState,         // Default state for new accounts
+    ImmutableOwner,              // Cannot change owner
+    MemoTransfer,                // Require memos
+    NonTransferable,             // Cannot transfer tokens
+    InterestBearingConfig,       // Tokens accrue interest
+    PermanentDelegate,           // Permanent delegate authority
+    TransferHook,                // Custom transfer logic
+    MetadataPointer,             // Point to metadata
+    TokenMetadata,               // On-chain metadata
+    GroupPointer,                // Token groups
+    TokenGroup,                  // Group config
+    GroupMemberPointer,          // Group membership
+    TokenGroupMember,            // Member config
+    // ... and more
+}
+```
+
+---
+
+## Using Token-2022 in Anchor
+
+```rust
+use anchor_spl::token_2022::{self, Token2022};
+use anchor_spl::token_interface::{Mint, TokenAccount, TokenInterface};
+
+#[derive(Accounts)]
+pub struct CreateToken2022Mint<'info> {
+    #[account(
+        init,
+        payer = payer,
+        mint::decimals = 9,
+        mint::authority = mint_authority,
+        mint::token_program = token_program,
+    )]
+    pub mint: InterfaceAccount<'info, Mint>,
+
+    /// CHECK: Mint authority
+    pub mint_authority: UncheckedAccount<'info>,
+
+    #[account(mut)]
+    pub payer: Signer<'info>,
+
+    pub token_program: Program<'info, Token2022>,
+    pub system_program: Program<'info, System>,
+}
+```
+
+**Note:** The `anchor-spl` crate includes the `token_2022_extensions` module for working with extensions, but not all extension instructions are fully implemented yet. You may need to manually implement CPI calls for some extensions.
+
+---
+
+## Using Token-2022 in Native Rust
+
+```rust
+use spl_token_2022::{
+    extension::ExtensionType,
+    instruction::initialize_mint2,
+};
+
+pub fn create_token_2022_mint(
+    payer: &AccountInfo,
+    mint: &AccountInfo,
+    mint_authority: &Pubkey,
+    decimals: u8,
+    extensions: &[ExtensionType],
+) -> ProgramResult {
+    // Calculate space needed for extensions
+    let mut space = 82; // Base mint size
+    for extension in extensions {
+        space += extension.get_account_len();
+    }
+
+    // Create account with proper size
+    // ... (similar to regular mint creation)
+
+    // Initialize extensions
+    // Each extension has its own initialization instruction
+
+    // Finally initialize mint
+    invoke(
+        &initialize_mint2(
+            &spl_token_2022::ID,
+            mint.key,
+            mint_authority,
+            None,
+            decimals,
+        )?,
+        &[mint.clone()],
+    )?;
+
+    Ok(())
+}
+```
+
+---
+
+## Transfer Hook Extension Example (Anchor)
+
+```rust
+use anchor_lang::prelude::*;
+use anchor_spl::token_interface::{TokenAccount, TokenInterface};
+
+#[program]
+pub mod transfer_hook {
+    use super::*;
+
+    #[interface(spl_transfer_hook_interface::execute)]
+    pub fn execute_transfer_hook(
+        ctx: Context<TransferHook>,
+        amount: u64,
+    ) -> Result<()> {
+        msg!("Transfer hook called! Amount: {}", amount);
+        // Custom transfer logic here
+        Ok(())
+    }
+}
+
+#[derive(Accounts)]
+pub struct TransferHook<'info> {
+    pub source: InterfaceAccount<'info, TokenAccount>,
+    pub destination: InterfaceAccount<'info, TokenAccount>,
+    /// CHECK: authority
+    pub authority: UncheckedAccount<'info>,
+}
+```
+
+---
+
+## Next Steps
+
+- **Common Patterns**: See [tokens-patterns.md](tokens-patterns.md) for escrow, staking, NFT creation patterns
+- **Security**: See [tokens-patterns.md](tokens-patterns.md) for comprehensive security best practices