Secure DeFi Smart Contract Development

I’m looking for a senior-level smart-contract engineer who can own the full lifecycle of a new vault-based DeFi protocol that will launch first on Ethereum mainnet and other EVM-compatible networks. The immediate focus is getting deposits, withdrawals, and overall fund custody right for a single ERC-20 token (think USDC or WETH) while laying the groundwork for future extensions. Here’s what I need you to drive: • Contract architecture in Solidity and Hardened JavaScript, with least-privilege remote account control baked in from day one. • Thorough threat models, upgrade plans, and a mainnet-ready checklist for every material change. • Comprehensive test coverage—unit, integration, fuzz, and mainnet-fork—plus swift remediation of any auditor findings. • Continuous review of internal and partner pull requests to spot re-entrancy, privilege escalation, or unbounded-state risks before they merge. • Collaboration with the broader Web3 and product teams to define events, error surfaces, and safe defaults for end users. • Clear reasoning around multiblock and eventual cross-chain failure modes, even when timers and messaging protocols get involved. • Knowledge transfer: mentor other engineers on secure patterns and help refine our hiring bar as we scale. Acceptance criteria: • Vault contracts let users deposit and withdraw the chosen ERC-20 seamlessly, preserve accounting to the wei, and expose on-chain proofs of solvency. • All critical paths achieve >95% code coverage and pass differential fuzzing for at least 48 hours with no invariant breaks. • Threat model, upgrade plan, and deployment checklist are reviewed and signed off by both me and an external auditor before mainnet deploy. Additionally: We aim to complete the base project by April next year to transition into product finalization. Preference will be given to candidates open to a long-term development period of at least five years. If this sounds like your wheelhouse, tell me how you’d approach the vault core and what tooling you prefer for fuzzing and fork testing.