v6.6.0 is a MANDATORY upgrade for all Pacific-1 Mainnet node operators and validators. Nodes that do not upgrade will halt at the upgrade height and fall out of consensus.
RPC / API Changes eth_blobBaseFee added New EVM RPC method to query the current blob base fee. eth_getBlockTransactionCountByHash modified Fixed hash lookup consistency; now returns null for unknown/empty block hashes instead of an error or wrong value. eth_getBlockTransactionCountByNumber modified Fixed inconsistency between transaction count returned here vs eth_getBlockByNumber. eth_call modified Fixed EIP-1559 call handling so maxFeePerGas and related fields are correctly processed. eth_getBlockByNumber / eth_getBlockByHash (genesis block) modified Genesis block handling aligned across all block-fetching RPC methods. debug_traceBlock / debug_traceTransaction modified Debug trace speedup implemented; profiled block tracing is now opt-in (disabled by default). tx_search / block_search modified Results are now capped by MaxTxSearchResults to prevent unbounded result sets. sei_* (legacy RPC namespace) deprecated The sei_ legacy RPC namespace is being deprecated. Operators and clients should migrate to standard eth_ methods. Various unsupported EVM RPC methods modified Methods that were previously silently unimplemented now return explicit 'unsupported' error responses.