HYPEREVM_CHAIN_IDS

Documentation for eth_defi.provider.anvil.HYPEREVM_CHAIN_IDS data.

HYPEREVM_CHAIN_IDS: set[int] = {998, 999}

HyperEVM mainnet/testnet chain ids.

HyperEVM RPCs are special when forking with Anvil: asking Anvil to fork the chain tip without an explicit --fork-block-number can fail even after eth_blockNumber succeeded against the upstream RPC.

The failure mode we have seen in production is:

  • Anvil launches with --fork-url <HyperEVM RPC> and no --fork-block-number

  • during genesis creation, Anvil asks the upstream RPC for the default Anvil deployer account state at latest

  • HyperEVM sometimes responds with HTTP 400 and JSON-RPC error {"message":"Unknown block","code":26}

  • Anvil aborts with Error: failed to create genesis

Because of this, HyperEVM forks must be pinned slightly behind the tip unless the caller already supplied an explicit, known-good block number.