Foundry projects

If your contracts already live in a Foundry project, you do not need to restate its remappings and library paths. Turn on foundryProject and Tevm asks forge for them.

{
	"foundryProject": true
}

At config-resolution time this runs:

forge config --json

and merges the resulting remappings and libs into the Tevm config. Your own remappings in tevm.config.json are layered on top and win on conflict.

Pointing at a specific forge binary

Set foundryProject to a path instead of true:

{
	"foundryProject": "/opt/homebrew/bin/forge"
}

This is worth doing in CI, where forge may not be on PATH for the process that runs your bundler.

A complete Foundry + Vite project

my-dapp/
├── foundry.toml
├── remappings.txt
├── lib/
│   └── openzeppelin-contracts/
├── src/
│   └── Token.sol
├── tevm.config.json
├── tsconfig.json
├── vite.config.ts
└── app/
    └── main.ts

[profile.default]
src = "src"
out = "out"
libs = ["lib"]

@openzeppelin/=lib/openzeppelin-contracts/

{
	"foundryProject": true
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;
 
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
 
contract Token is ERC20 {
    constructor() ERC20("Token", "TKN") {
        _mint(msg.sender, 1_000_000e18);
    }
}

import { vitePluginTevm } from '@tevm/vite-plugin'
import { defineConfig } from 'vite'
 
export default defineConfig({
	plugins: [vitePluginTevm()],
})

import { createMemoryClient } from 'tevm'
import { Token } from '../src/Token.sol'
 
const client = createMemoryClient()
 
const token = Token.withAddress('0x1234567890123456789012345678901234567890')
 
await client.setCode({
	address: token.address,
	bytecode: token.deployedBytecode,
})
 
console.log(await client.readContract(token.read.symbol()))

Note that src/Token.sol is a plain .sol file, so the import carries the ABI but no creation bytecode. If you want to deploy it from JavaScript, rename it to Token.s.sol or add a separate .s.sol wrapper — Foundry ignores the extra extension segment and still compiles it.

Living alongside forge build

The two toolchains do not share an artifact directory. Foundry writes to out/, Tevm writes to .tevm/. They can both be present; they simply compile the same sources independently.

If you want a single source of truth for the solc version, set it in both places:

[profile.default]
solc = "0.8.30"

vitePluginTevm({ solc: '0.8.30' })

Tevm does not read foundry.toml's solc field — the compiler version is a plugin option, so it must be set explicitly.

Errors you might see

• FoundryNotFoundError — forge config --json could not be executed. Either install Foundry, point foundryProject at the binary, or drop foundryProject and list remappings and libs in tevm.config.json yourself.
• FoundryConfigError — forge ran but its output could not be parsed. Run forge config --json by hand to see what it emitted.
• InvalidRemappingsError — the remappings from forge (or from remappings.txt) were not in prefix=target form.