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Foundry v1.0 migration guide

Foundry v1.0 introduced breaking changes that may require updates in existing projects. Use this checklist to migrate safely.

Compiler defaults

The optimizer is disabled by default in v1.0. Explicitly enable it in foundry.toml:

foundry.toml
[profile.default]
optimizer = true
optimizer_runs = 200

vm.expectRevert behavior

vm.expectRevert no longer applies to internal calls by default. If you were testing internal functions directly, move the call behind a public wrapper or enable revert checking on internal calls.

testFail tests removed

testFail-prefixed tests are no longer supported. Replace them with explicit revert tests:

function test_RevertWhen_Unauthorized() public {
    vm.expectRevert("Not authorized");
    target.doSomething();
}

Legacy console.sol signatures removed

Upgrade to the latest forge-std and use the current console.sol signatures. Old signatures fail to compile.

Conflicting remappings now error

Foundry fails when remappings collide between root and dependencies. Make the root remapping explicit in foundry.toml and avoid duplicating it in dependencies.

Coverage artifacts no longer persist

forge coverage does not write artifacts anymore. If you depended on those artifacts, run forge build after coverage.

Other changes

  • FORGE_SNAPSHOT_CHECK requires a boolean value
  • forge inspect --pretty removed; use forge inspect
  • forge bind --ethers removed; use forge bind
  • forge debug removed; use forge test --debug or forge script --debug
  • cast etherscan-source replaced by cast source
  • foundryup installs stable by default; use foundryup -i nightly for nightly
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