Custom EVM Networks

The evm-networks crate defines custom network features that are shared across Foundry's tooling (anvil, forge and cast). Currently, it supports custom precompiles, with planned support for custom transaction types.

Adding a Custom Network

To add configuration support for a custom network (e.g. my_network), add a new field to the NetworkConfigs struct:

    /// Enable my custom network features.
    #[arg(help_heading = "Networks", long)]
    #[serde(default)]
    pub my_network: bool,

This automatically enables:

• my_network = true in foundry.toml
• --my-network anvil CLI flag

Networks:
      --my-network
          Enable my custom network features

If you'd like network features to be enabled automatically based on the chain ID, update NetworkConfigs::with_chain_id:

impl NetworkConfigs {
    pub fn with_chain_id(chain_id: u64) -> Self {
        // Enable custom network features here
    }
}

Adding a custom precompile

• Create a module for your network-specific logic, e.g., my_network/transfer.
• Implement the precompile logic as a function that accepts a PrecompileInput containing execution context and hooks for interacting with EVM state, and returns a PrecompileResult:

pub fn custom_precompile(
  input: alloy_evm::precompiles::PrecompileInput<'_>
) -> revm::precompile::PrecompileResult {
  // Your logic here
}

• Enable the precompile in the NetworkConfigs implementation by conditionally applying it to an address:

if self.my_network {
    precompiles.apply_precompile(&MY_NETWORK_TRANSFER_ADDRESS, move |_| {
        Some(my_network::transfer::custom_precompile())
    });
}