v1.4.0-rc1

Foundry v1.4.0

This release brings up to 10.52% better performance for forge coverage and up to 11.41% for fuzzed tests, a new formatter built on Solar, enhanced handling of multiple chain configurations and deployments, and an improved testing and debugging experience with backtraces and custom network precompiles. Foundry v1.4 is Osaka-ready, comes with new Anvil endpoints, deprecates the Etherscan v1 API, and publishes forge as an npm package.

Performance Improvements

Foundry v1.4 leverages Solar API to analyze contracts and identify coverage items (#11565), and updates coverage implementation to align with that of forge test (#11801). It also completely removes the proptest runner from fuzzed tests (#11061), resulting in up to a 10.52% performance improvement for forge coverage and up to an 11.41% performance improvement in fuzzed tests execution speed on the same benchmarked projects as previous versions.

Forge Coverage

Repository	v1.3.6	v1.4.0	X Times Faster	% Improvement
ithacaxyz-account	14.91 s	13.34 s	x1.12	10.52%
Uniswap-v4-core	1m 34.8s	1m 30.3s	x1.05	4.74%
sparkdotfi-spark-psm	3m 49.3s	3m 40.2s	x1.04	3.97%

Forge Fuzz tests

Repository	v1.3.6	v1.4.0	X Times Faster	% Improvement
ithacaxyz-account	3.18 s	3.02 s	x1.05	5.03%
solady	2.39 s	2.24 s	x1.07	6.28%
Uniswap-v4-core	6.84 s	6.20 s	x1.10	9.36%
sparkdotfi-spark-psm	3.07 s	2.72 s	x1.13	11.41%

Enhanced configuration

Configuration inheritance

Foundry v1.4 supports configuration inheritance through the extends field in foundry.toml, making it easier to maintain a shared base configuration across multiple projects or profiles (#11284). This enables cleaner setups and reduces duplication by inheriting from a base configuration file:

[profile.default]
extends = "./base-config.toml"
src = "src"
test = "test"

For more details please refer to configuration inheritance docs.

Multi-chain configuration

The newly added forge-std config helper, built on top of Foundry v1.4 cheatcodes, provides a streamlined way to manage configuration for multi-chain environments in tests and scripts. It automatically loads and parses TOML configuration files, creates forks for specified chains, and provides type-safe access to configuration variables.
Loading configuration and creating forks for each chain specified in the config can be done by calling _loadConfigAndForks function, which also supports updating configurations on the fly.

function _loadConfigAndForks(string memory filePath, bool writeToFile) internal

Scripting workflows, in particular, gain significant advantages from the features of the Config contract. Please refer to config helper docs and scripting with config docs for more details.
For a complex, production-ready example, please see Ithaca's account deploy script and configuration.

We're continuously working to improve multi-chain support, please share your feedback on the current approach and suggest new features or enhancements in #11449.

Enhanced testing UX

Foundry v1.4 introduces backtraces (#11547) that include the exact line number in the Solidity source code corresponding to the compiled bytecode where the error or revert occurred.

[FAIL: ERC20: transfer amount exceeds allowance] testTransferFromWithoutApproval() (gas: 28771)
Traces:
  [28771] ForkBacktraceTest::testTransferFromWithoutApproval()
    ├─ [22928] ForkedERC20Wrapper::transferFromWithoutApproval(0x55FE002aefF02F77364de339a1292923A15844B8, 0x000000000000000000000000000000000000dEaD, 1000000 [1e6])
    │   ├─ [18884] FiatTokenProxy::fallback(0x55FE002aefF02F77364de339a1292923A15844B8, 0x000000000000000000000000000000000000dEaD, 1000000 [1e6])
    │   │   ├─ [11573] FiatTokenV2_2::transferFrom(0x55FE002aefF02F77364de339a1292923A15844B8, 0x000000000000000000000000000000000000dEaD, 1000000 [1e6]) [delegatecall]
    │   │   │   └─ ← [Revert] ERC20: transfer amount exceeds allowance
    │   │   └─ ← [Revert] ERC20: transfer amount exceeds allowance
    │   └─ ← [Revert] ERC20: transfer amount exceeds allowance
    └─ ← [Revert] ERC20: transfer amount exceeds allowance

Backtrace:
  at FiatTokenV2_2.transferFrom
  at FiatTokenProxy.fallback
  at ForkedERC20Wrapper.transferFromWithoutApproval (src/ForkedERC20Wrapper.sol:35:24)
  at ForkBacktraceTest.testTransferFromWithoutApproval (test/ForkBacktrace.t.sol:28:96)

Forge Formatter

Foundry v1.4 ships with a new Solidity formatter (forge fmt) built on top of Solar and replacing the previous Solang-based implementation and its limitations (#10907). This change enables faster support for new Solidity language features and allows us to address long-standing formatting bugs that were previously blocked by Solang dependency.

We've aimed for feature parity with the legacy formatter, but there may still be some edge cases that aren’t fully covered yet, so please be aware and report any issues you encounter.

Coverage-Guided Fuzzing

In addition to extending coverage-guided fuzzing and time-based campaigns to stateless fuzz tests, this version introduces ABI mutations (such as bit-flip, interesting word, increment/decrement, and Gaussian noise mutators) to enhance test coverage and help uncover new execution paths by generating diverse and edge-case inputs (#11061).

Custom Network Precompiles

Beginning with the transfer precompile contributed by the Celo team for Anvil (#11209), we have extended support to forge and cast components, making it simpler for external contributions. If you want to contribute support for a custom network, please check out documentation and Celo example within foundry-evm-networks crate.

Anvil Improvements

With this release, Anvil adds support for JS and prestate tracers, and print traces and logs when using --print-traces switch, enabling more powerful and customizable debugging capabilities. Additionally, several new RPC endpoints have been introduced:

• eth_config: exposes Anvil's current configuration, such as chain ID, fork settings, and feature flags (#11591).
• anvil_impersonateSignature: allows simulating transactions as if they were signed by a given address, useful for testing signature-based flows (#11195).
• anvil_getBlobSidecarsByBlockId: returns the blobs for a given transaction hash (#11828).

Other

• forge lint improvements: mixed case exceptions lint, ERC20 transfer check
• improve state diffs cheatcodes by adding nonce and balance diffs and by using storage layout to decode values
• addition of native vm.bound cheatcode that enables log-uniform sampling
• updated Sourcify integration to support API v2

Performance improvements

• feat(forge): Remove proptest runner from fuzzed tests (#11061) by @grandizzy
• perf: box inspectors in InspectorStack (#11100) by @DaniPopes
• perf: use fxhash for coverage hitmap (#11155) by @DaniPopes
• perf: parallelize remappings provider (#11536) by @DaniPopes
• perf: avoid project output clone (#11707) by @DaniPopes
• perf: lazy cheatcodes SignaturesIdentifier, save only if online (#11708) by @DaniPopes
• perf: link in parallel (#11710) by @DaniPopes
• perf(coverage): reserve some space for hits early (#11793) by @DaniPopes
• fix(coverage): sync implementation with forge test (#11801) by @DaniPopes

Anvil Features

• feat(anvil): improve historic state access (#10420) by @naijauser
• feat(anvil): added js tracer (#11052) by @Soubhik-10
• feat(anvil): add option to disable pool balance checks in EVM configuration (#11242) by @mablr
• feat(anvil): added anvil_impersonateSignature (#11195) by @Soubhik-10
• feat: add missing eip7702 support (#11490) by @ongyimeng
• feat(anvil): support celo transfer precompile (#11491) by @mattsse
• feat(anvil): add eth_config rpc endpoint (#11591) by @zerosnacks
• feat(anvil): calculate max_transactions based on block gas capacity (#11670) by @forkfury
• feat(anvil): add PreStateTracer support for debug_traceTransaction (#11709) by @w1tcher
• feat: print traces and logs in calltracer (#11722) by @mattsse
• feat(anvil): add support for anvil_getBlobSidecarsByBlockId (#11828) by @mablr

Anvil Fixes

• fix(anvil): specialize eth_getAccountInfo in fork mode (#11634) by @mattsse
• fix: use existing functions for accountinfo (#11134) by @mattsse
• fix(anvil): unwrap panic in eth/backend/mem/mod.rs (#11141) by @zerosnacks
• fix(anvil): v1.2 state load compatibility (#11179) by @zerosnacks
• fix(anvil): print traces for eth_simulateV1 (#11253) by @klkvr
• fix(anvil): deterministic block production (#11415) by @fubhy
• Fix: invalid tx input error in anvil component (#114...

Nightly (2025-10-01)

Other

• fix(fmt): return formatted code when stdin and --raw (#11900) by @grandizzy

Full Changelog:

nightly...nightly-f240c459d3345353df7c7769a7bd7d5043b0770c

Nightly (2025-10-02)

Other

• fix(coverage): filter out vyper sources (#11899) by @grandizzy
• fix(evm): correct favored threshold comparison (#11902) by @MozirDmitriy
• fix(fmt): avoid blank line before identifiers (#11908) by @0xrusowsky
• fix(coverage): filter vy and vyi (#11909) by @0xrusowsky
• ci: remove name from sccache action (#11912) by @DaniPopes
• chore(chisel): remove unused EtherscanABIResponse and serde import (#11911) by @radik878
• fix(fmt): rustfmt-like blank lines in stmt blocks (#11914) by @0xrusowsky
• chore: restore openchain support (#11915) by @grandizzy
• feat(fmt): solar bump + handle cmnts in non-informed params (#11901) by @0xrusowsky
• fix(forge): do not warn on backward compatible solc_version config (#11916) by @grandizzy

Full Changelog:

nightly...nightly-bd0e4a729d28ff677c0aaa8ba8c1c409a2366faa

Nightly (2025-10-01)

Other

• fix(verify): handle missing optimizer_runs mismatch message (#11885) by @Bilogweb3
• fix(common): avoid panic on invalid calldata selector by propagating parse error (#11888) by @radik878
• fix(fmt): always return formatted when source read from stdin (#11876) by @grandizzy
• fix(forge): same way to flatten for all commands (#11873) by @grandizzy
• fix(fmt): fn estimate_size() account for opening brackets (#11887) by @0xrusowsky
• refactor: move breakpoints to foundry-evm-core (#11889) by @onbjerg
• fix: use sourcify for selector lookups (#11757) by @onbjerg
• chore: rm duplicate install tests (#11890) by @grandizzy
• Improve remote wallet --help commands (#11891) by @albertlai431
• docs: explicitly mark forge geiger deprecated (#11893) by @onbjerg
• feat: struct initializer lint (#11892) by @onbjerg
• fix: normalize path separators in git submodule URL lookup (#11826) by @wellnana
• feat(config): warn on unknown config keys in foundry.toml (#11816) by @TropicalDog17
• fix: only include item's source in docs (#11895) by @onbjerg

Full Changelog:

nightly...nightly-fe10724f648a9e034f00e67dbd96539721b44bfe

Nightly (2025-09-30)

Other

• fix(fmt): don't break exprs that overflow but fit assignement (#11837) by @0xrusowsky
• fix(fmt): indent calls with single member that fits but breaks when args (#11854) by @0xrusowsky
• fix(lint): allow custom types in "constant fn getters" (#11866) by @0xrusowsky
• fix(forge): support broadcast from vm.deployCode (#11864) by @grandizzy
• feat(anvil): improve historic state access (#10420) by @naijauser
• Update to soldeer 0.8.0 (#11863) by @mario-eth
• fix(fs): flush BufWriter after GzEncoder::finish() in write_json_gzip_file (#11827) by @sashass1315
• feat(forge): no warning on external config sections (#11869) by @grandizzy
• fix(fmt): account for CRLF when handling cursor (#11874) by @0xrusowsky
• fix(prevrandao not set): support gnosis network (#11877) by @chen4903
• chore: clean up fmt debugging (#11878) by @DaniPopes
• chore: clean up fmt entry point (#11879) by @DaniPopes
• chore(deps): bump taiki-e/install-action from 2.62.2 to 2.62.13 (#11882) by @dependabot[bot]
• chore(deps): bump crate-ci/typos from 1.36.2 to 1.36.3 (#11880) by @dependabot[bot]
• chore(deps): bump docker/login-action from 3.5.0 to 3.6.0 (#11881) by @dependabot[bot]
• fix: inline config locations (#11883) by @DaniPopes

Full Changelog:

nightly...nightly-918eb6aadb1bfd506c64d57ae3dfa21ed87f4e52

Nightly (2025-09-29)

Other

• chore: remove feature(doc_auto_cfg) (#11852) by @DaniPopes
• chore(deps): weekly cargo update (#11851) by @github-actions[bot]
• chore(anvil): fixed broken link (#11858) by @cypherpepe
• anvil: return JoinHandle from TaskManager::spawn_blocking for proper task control (#11857) by @viktorking7
• fix(forge): use global json arg everywhere (#11860) by @mablr

Full Changelog:

nightly...nightly-78ce479d54879f3e03ed8895053a156b58261df6

Nightly (2025-09-26)

Other

• fix(fmt): estimate size + account for all blocks (#11824) by @0xrusowsky
• chore: revert evm version / solc incompat warning (#11831) by @grandizzy

Full Changelog:

nightly...nightly-f8dd6aef21a7a02a6b7471ee06427f155c03a3b3

Nightly (2025-09-28)

• No changes

Nightly (2025-09-25)

• No changes

Nightly (2025-09-25)

Other

• ci: update release runners (#11810) by @DaniPopes

Full Changelog:

nightly...nightly-bd96c5723bb3c7c53839f599369abf45aaaba80e