Bug Fixes

1. Compression index bounds check - Added validation preventing array index out-of-bounds in transfer2 token inputs
2. Decompress amount validation - Added check that ATA/compress_to_pubkey decompress amount matches input token data amount
3. MAX_COMPRESSIONS boundary fix - Changed >= to > to allow exactly MAX_COMPRESSIONS items in transfer2
4. Explicit ATA derivation error - Added InvalidAtaDerivation error instead of silent fallback when ATA derivation fails or mismatches
5. Rent exemption stability - Made rent calculations read CompressionInfo directly from bytes rather than relying on sysvar
6. CompressedMintMetadata change - Added compressed_address field (32 bytes) directly to mint struct, reduced reserved from 49 to 17 bytes; unifies compressed address source

Error Handling

7. New error types - Added 6 errors to CTokenError: MissingPayer, BorrowFailed, InvalidCTokenOwner, DecompressAmountMismatch, CompressionIndexOutOfBounds, InvalidAtaDerivation
8. SPL Token error mapping - Changed from raw SPL Token error codes to Anchor ErrorCode mappings (+6000 offset)

Refactoring

9. Program folder restructure - Reorganized compressed-token/program/src/ into compressed_token/ (mint_action, transfer2), compressible/ (claim, withdraw), and ctoken/ (approve, burn, close, create, freeze_thaw, mint_to, transfer) subdirectories
10. File renaming - Removed ctoken_ prefix from files (e.g., ctoken_burn.rs -> ctoken/burn.rs, create_associated_token_account.rs -> ctoken/create_ata.rs)
11. Added top-up modules - New top_up.rs files for ctoken and mint in ctoken-interface with optimized lamports calculation from account bytes
12. TypeScript layout alignment - Moved compressedAddress from instruction-level to mint.metadata, removed tokenPoolBump and tokenPoolIndex fields, added rentExemptionPaid and reserved fields to CompressionInfo (88 -> 96 bytes)
13. Removed CreateSplMint action - Deleted CreateSplMint action type and related code from both Rust and TypeScript

Documentation

14. Documentation restructure - Moved docs from flat instructions/ to categorized ctoken/, compressed_token/, compressible/ directories; added new INSTRUCTIONS.md with discriminator reference table

Tests

15. New test coverage - Added ata_decompress.rs (532 lines), check_extensions.rs (744 lines), mint_validation.rs (358 lines), create_ata.rs, create.rs, failing.rs for comprehensive validation testing

Summary by CodeRabbit

• New Features

  • Added rent exemption tracking in compressed accounts.
  • Introduced ATA (Associated Token Account) support for compressed-only extensions.
  • Added compress-and-close functionality for managing compressed token lifecycles.

• Bug Fixes

  • Improved error handling with new error codes for better diagnostics.
  • Fixed account validation for compressed account operations.

• Documentation

  • Reorganized architecture documentation with clearer instruction references and examples.

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