Gas Token Refund Pattern Detector (Deprecated)

WHAT IT DOES

Gas Token Refund Pattern Detector (Deprecated) analyzes smart contract bytecode to identify patterns associated with gas token implementations—contracts designed to leverage the now-deprecated gas refund mechanism that existed prior to EIP-161. It retrieves on-chain contract bytecode via eth_getCode and fetches verified source code and ABI from block explorer APIs. The tool scans bytecode for specific opcode sequences associated with gas token patterns, including SELFDESTRUCT (used to clear storage and claim refunds), DELEGATECALL (used to invoke gas token logic), and storage zeroing patterns (CHSSTORE and related operations). It also analyzes storage slot usage patterns and state variable layouts to detect characteristic gas token structures such as mint/burn loops and balance tracking mechanisms. The output includes a detection confidence score, a list of detected patterns with their status (found, partial, or not found), deprecated pattern indicators, and actionable recommendations for migrating away from gas token logic, which is now obsolete.

HOW TO USE

Connect your BGWallet to the target EVM chain. Paste the address of the contract you wish to scan for gas token refund patterns. Optionally supply a GitHub repository URL to pull known gas token implementations and refund pattern examples for reference. The tool fetches the contract's bytecode, performs opcode-level pattern matching, and analyzes storage slot usage to detect gas token patterns. Review the detection confidence score, the list of detected patterns, and the recommendations. Use the results to identify and remove any remaining gas token logic from your contracts, migrating to modern gas optimization techniques that comply with current EVM semantics.

OPCODE SEQUENCE AND STORAGE PATTERN MATCHING ENGINE

The real technical mechanism is the opcode sequence and storage pattern matching engine that combines bytecode analysis with historical context. The tool disassembles the deployed bytecode into its constituent opcodes and scans for known sequences associated with gas token implementations. Key patterns include the SELFDESTRUCT opcode followed by storage zeroing operations, which characterized the gas token refund mechanism; DELEGATECALL sequences that invoke gas token contracts; and loop structures that iterate through storage slots to zero them out. The tool also analyzes storage slot usage patterns, looking for the characteristic "balance" and "minted" tracking structures typical of gas token implementations such as GST2. The detection engine uses a weighted scoring system: SELFDESTRUCT detection contributes 40% of the score, storage zeroing patterns 30%, DELEGATECALL patterns 20%, and loop structures 10%. The engine also cross-references detected patterns against a database of known gas token implementations to increase detection confidence. This approach provides a reliable identification of deprecated gas token patterns, enabling developers to audit their contracts for obsolete logic that may cause unexpected behavior or increased gas costs.

WHAT IT CANNOT SEE

This tool cannot detect gas token refund patterns without access to contract bytecode or ABI. It is limited by your RPC provider's rate limits for bytecode retrieval, which may delay analysis on congested networks. It cannot definitively prove the presence of a gas token pattern without historical transaction data or source code verification; bytecode pattern matching alone may produce false positives or negatives. The detection relies on the completeness of the ABI and source code verification; unverified contracts or incomplete verification data will produce incomplete or inaccurate results. Detection is based on bytecode pattern matching and may produce false positives or negatives, particularly for contracts that use SELFDESTRUCT or DELEGATECALL for legitimate non-gas-token purposes. The tool cannot detect patterns that have been obfuscated or modified from known implementations, as sophisticated contract authors may disguise gas token logic. It does not execute the contract to validate refund behavior, so it cannot confirm whether the detected patterns actually result in gas refunds. The tool cannot account for network-specific gas dynamics or EIP changes that affect the effectiveness of gas tokens; some networks may have different gas accounting rules.

PLEASE NOTE

This tool works exclusively with EVM-compatible chains. It requires active internet connectivity to access block explorer APIs and RPC endpoints. Some block explorers may require API keys for high-volume bytecode retrieval. The tool is read-only and does not modify or deploy any code—it only produces detection results. Gas tokens are deprecated due to EIP-161, which eliminated the gas refund mechanism. Contracts that still rely on gas token logic may experience increased gas costs or revert behavior. Always verify detection results against your contract's source code and historical transaction data before taking any action.