Hardhat

Hardhat now lets you test against the upcoming Amsterdam hardfork, adding experimental support for EIP-7976, EIP-7981, EIP-7997, EIP-8024 and EIP-8037, including the new DUPN, SWAPN and EXCHANGE opcodes and the separated execution/state gas metering in block gasUsed.Because EIP-8037 significantly changes the gas cost of state creation, existing gas assumptions in tests should be re-verified early; separately, sending an EIP-4844 transaction from a locally managed account without blobs now throws an error instead of silently dropping them.

Matters for: Relevant for teams writing gas-sensitive contract tests and those forking Sepolia or mainnet state who need to account for the Amsterdam hardfork activation and new opcode behavior.

Hardhat now supports test profiles for Solidity tests, letting test settings differ between environments like local development and CI, and hardhat-mocha has been updated to mocha@12. This release also removes support for pre-Byzantium hardforks (chainstart, homestead, dao, tangerineWhistle, spuriousDragon) from the accepted hardfork and hardforkHistory values since EDR cannot execute them, so any config or test referencing those hardfork names must be updated to a supported hardfork.

Matters for: Teams running Solidity test suites across multiple environments (local dev vs CI) and projects whose Hardhat network configs reference early Ethereum hardforks for chain history simulation.

Hardhat now defaults to a new eth_estimateGas mode called noInternalOutOfGas that prevents misleading gas estimates when internal calls run out of gas, and it speeds up ethers-based test suites by using EDR's native Keccak-256 instead of the pure-JS implementation. It also fixes configuration variables from printing their values in error messages and improves the error message shown when an HD key cannot be derived.

Matters for: Teams running large ethers.js test suites on EDR-based Hardhat networks and projects relying on eth_estimateGas for contracts with internal calls.

Hardhat now supports compiling contracts with the new slang-solx compiler via the hardhat-slang-solx plugin.This is an additive change, so existing setups are unaffected and no migration is required.

Matters for: Solidity developers evaluating alternative compilers for their Hardhat-based contract build pipelines.