A Sway audit is a security review of Fuel Network contracts written in Sway, covering the UTXO-based execution model, predicates and scripts, native asset handling, and the storage and access-control semantics that differ from account-model chains.
Sway looks like Rust and executes nothing like Ethereum. Fuel uses a UTXO model with predicates and scripts alongside contracts, native multi-asset support instead of token contracts, and a strict separation between what a script may do and what a contract may do. Reviewers who read Sway as "Rust for the EVM" miss the bugs, because the bugs live in exactly the places the models differ.
We maintain SwayScan, an open-source static analyser for Sway published on crates.io, which means our review starts from a codified list of Sway-specific patterns rather than from first principles each time. Manual review then covers what no analyser can: whether your predicate can be satisfied by an input you did not intend, whether your asset accounting survives a multi-asset transfer, and whether your storage access control holds under the call patterns Fuel permits.
We fix a commit hash, agree the in-scope contracts and read your architecture docs, then build a threat model: who the actors are, what the trust boundaries are, and which invariants must never break. Nothing is reviewed against assumptions we have not written down.
Line-by-line review by at least two auditors working independently, focused on authorisation, accounting, upgrade paths, external integrations and the gap between what the code does and what the documentation claims it does. Most critical findings come from this phase, not from tooling.
Static analysers appropriate to the language, plus property-based fuzzing and invariant testing to push the system into states no unit test covers. Tooling is used to widen coverage, never to replace the manual pass.
Candidate findings are proven on a forked network with a working proof of concept. We report what an attacker can actually do and what it costs them, not a theoretical severity label.
Every finding gets a severity rating, reproduction steps, the affected code, the impact in concrete terms and a specific remediation. You get a draft for discussion before anything is finalised.
We re-test every remediation against the original proof of concept and check that the fix has not opened a new path. The final report is yours to publish.
Very few firms. We built and maintain SwayScan, the open-source Sway static analyser, which is publicly verifiable on crates.io — that is the honest signal of depth here, rather than a claim about experience you cannot check.
The execution model. Fuel is UTXO-based with predicates and scripts and native assets, so input validation, asset attribution and the predicate boundary replace most of the ERC-20 and account-model bug classes you would look for on the EVM.
Yes — predicates, scripts and contracts, because a system is only as strong as the weakest of the three and predicates are where the least review attention usually goes.
Yes, it is open source and installable from crates.io. Run it yourself before you engage anyone, including us.
A repository or contract address, a commit hash to freeze the scope, whatever architecture or spec documentation exists, and a point of contact who can answer design questions. If documentation is thin we will write our understanding of the system back to you and ask you to confirm it — that step alone catches design-level bugs.
A single token contract is 24–48 hours. A typical dApp or mid-sized protocol runs one to two weeks. Large DeFi systems, L2s, bridges and ZK circuits are scoped per project after we have seen the code. We will give you a fixed timeline with the quote, not an estimate that moves.
Yes. Fix review is part of the engagement, not an upsell. We re-run the original proof of concept against your patched code and confirm the fix has not introduced a new path.
Send the repository and a commit hash through the contact form, message @bugtester25 on Telegram, or book a 30-minute scoping call. 200+ protocols audited · $4B+ secured · 0 hacks post-audit. Prefer email? info@safeedges.in.