software-crypto-web3

Blockchain & Web3 Development Skill — Quick Reference

This skill equips blockchain developers with execution-ready patterns for building secure, gas-optimized smart contracts and decentralized applications. Claude should apply these patterns when users ask for smart contract development, DeFi protocols, NFT implementations, security audits, or Web3 architecture.

Modern Best Practices: Security-first development, formal verification, comprehensive testing (unit, integration, fork, invariant), gas optimization, upgradeable contracts, multi-chain deployment, and battle-tested DeFi patterns.

Quick Reference

| Task | Tool/Framework | Command | When to Use | |------|----------------|---------|-------------| | Solidity Development | Hardhat/Foundry | npx hardhat init or forge init | Ethereum/EVM smart contracts | | Solana Programs | Anchor | anchor init | Solana blockchain development | | Cosmos Contracts | CosmWasm | cargo generate --git cosmwasm-template | Cosmos ecosystem contracts | | TON Contracts | Tact/FunC + Blueprint | npm create ton@latest | TON blockchain development | | Testing (Solidity) | Foundry/Hardhat | forge test or npx hardhat test | Unit, fork, invariant tests | | Security Audit | Slither/Mythril/Echidna | slither . | Static analysis, fuzzing | | Gas Optimization | Foundry Gas Snapshots | forge snapshot | Benchmark and optimize gas | | Deployment | Hardhat Deploy/Forge Script | npx hardhat deploy | Mainnet/testnet deployment | | Verification | Etherscan API | npx hardhat verify | Source code verification | | Upgradeable Contracts | OpenZeppelin Upgrades | @openzeppelin/hardhat-upgrades | Proxy-based upgrades |

When to Use This Skill

Claude should invoke this skill when a user requests:

• Smart contract development (Solidity, Rust, CosmWasm)
• DeFi protocol implementation (AMM, lending, staking, yield farming)
• NFT and token standards (ERC20, ERC721, ERC1155, SPL tokens)
• DAO governance systems
• Cross-chain bridges and interoperability
• Gas optimization and storage patterns
• Smart contract security audits
• Testing strategies (Foundry, Hardhat, Anchor)
• Oracle integration (Chainlink, Pyth)
• Upgradeable contract patterns (proxies, diamonds)
• Web3 frontend integration (ethers.js, web3.js, @solana/web3.js)
• Blockchain indexing (The Graph, subgraphs)
• MEV protection and flashbots
• Layer 2 scaling solutions (Optimism, Arbitrum, zkSync)
• Backend crypto integration (.NET/C#, multi-provider architecture, CQRS)
• Webhook handling and signature validation (Fireblocks, custodial providers)
• Event-driven architecture with Kafka for crypto payments
• Transaction lifecycle management and monitoring
• Wallet management (custodial vs non-custodial)

Decision Tree: Blockchain Platform Selection

Project needs: [Use Case]
    ├─ EVM-compatible smart contracts?
    │   ├─ Complex testing needs → Foundry (Solidity tests, fuzzing, gas snapshots)
    │   ├─ TypeScript ecosystem → Hardhat (plugins, TypeScript, Ethers.js)
    │   └─ Enterprise features → NestJS + Hardhat
    │
    ├─ High throughput/low fees?
    │   ├─ Rust-based → Solana (Anchor framework, 50k+ TPS)
    │   ├─ EVM L2 → Arbitrum/Optimism (Ethereum security, lower gas)
    │   └─ Telegram integration → TON (Tact/FunC contracts)
    │
    ├─ Interoperability across chains?
    │   ├─ Cosmos ecosystem → CosmWasm (IBC protocol)
    │   ├─ Multi-chain DeFi → LayerZero or Wormhole
    │   └─ Bridge development → Custom bridge contracts
    │
    ├─ Token standard implementation?
    │   ├─ Fungible tokens → ERC20 (OpenZeppelin), SPL Token (Solana)
    │   ├─ NFTs → ERC721/ERC1155 (OpenZeppelin), Metaplex (Solana)
    │   └─ Semi-fungible → ERC1155 (gaming, fractionalized NFTs)
    │
    ├─ DeFi protocol development?
    │   ├─ AMM/DEX → Uniswap V3 fork or custom (x*y=k, concentrated liquidity)
    │   ├─ Lending → Compound/Aave fork (collateralized borrowing)
    │   └─ Staking/Yield → Custom reward distribution contracts
    │
    ├─ Upgradeable contracts required?
    │   ├─ Transparent Proxy → OpenZeppelin (admin/user separation)
    │   ├─ UUPS → Gas-efficient (upgrade logic in implementation)
    │   └─ Diamond Standard → Modular functionality (EIP-2535)
    │
    └─ Backend integration?
        ├─ .NET/C# → Multi-provider architecture (see Backend Integration Patterns)
        ├─ Node.js → Ethers.js/Web3.js + Prisma
        └─ Python → Web3.py + FastAPI

Chain-Specific Considerations:

• Ethereum/EVM: Security-first, higher gas costs, largest ecosystem
• Solana: Performance-first, Rust required, lower fees
• Cosmos: Interoperability-first, IBC native, growing ecosystem
• TON: Telegram-first, async contracts, unique architecture

See [resources/](resources/) for chain-specific best practices.

Navigation

Resources

• [resources/blockchain-best-practices.md](resources/blockchain-best-practices.md) — Universal blockchain patterns and security
• [resources/backend-integration-best-practices.md](resources/backend-integration-best-practices.md) — .NET/C# crypto integration patterns (CQRS, Kafka, multi-provider)
• [resources/solidity-best-practices.md](resources/solidity-best-practices.md) — Solidity/EVM-specific guidance
• [resources/rust-solana-best-practices.md](resources/rust-solana-best-practices.md) — Solana + Anchor patterns
• [resources/cosmwasm-best-practices.md](resources/cosmwasm-best-practices.md) — Cosmos/CosmWasm guidance
• [resources/ton-best-practices.md](resources/ton-best-practices.md) — TON contracts (Tact/Fift/FunC) and deployment
• [../software-security-appsec/resources/smart-contract-security-auditing.md](../software-security-appsec/resources/smart-contract-security-auditing.md) — Smart contract audit workflows and tools (see software-security-appsec skill)
• [README.md](README.md) — Folder overview and usage notes
• [data/sources.json](data/sources.json) — Curated external references per chain

Templates

• Ethereum/EVM: [templates/ethereum/template-solidity-hardhat.md](templates/ethereum/template-solidity-hardhat.md), [templates/ethereum/template-solidity-foundry.md](templates/ethereum/template-solidity-foundry.md)
• Solana: [templates/solana/template-rust-anchor.md](templates/solana/template-rust-anchor.md)
• Cosmos: [templates/cosmos/template-cosmwasm.md](templates/cosmos/template-cosmwasm.md)
• TON: [templates/ton/template-tact-blueprint.md](templates/ton/template-tact-blueprint.md), [templates/ton/template-func-blueprint.md](templates/ton/template-func-blueprint.md)
• Bitcoin: [templates/bitcoin/template-bitcoin-core.md](templates/bitcoin/template-bitcoin-core.md)

Related Skills

• [../software-security-appsec/SKILL.md](../software-security-appsec/SKILL.md) — Security hardening, threat modeling, OWASP vulnerabilities
• [../software-architecture-design/SKILL.md](../software-architecture-design/SKILL.md) — System decomposition, modularity, dependency design
• [../ops-devops-platform/SKILL.md](../ops-devops-platform/SKILL.md) — Infrastructure, CI/CD, observability for blockchain nodes
• [../software-backend/SKILL.md](../software-backend/SKILL.md) — API integration with smart contracts, RPC nodes, indexers
• [../quality-resilience-patterns/SKILL.md](../quality-resilience-patterns/SKILL.md) — Resilience, circuit breakers, retry logic for chains
• [../software-code-review/SKILL.md](../software-code-review/SKILL.md) — Code review patterns and quality gates
• [../foundation-api-design/SKILL.md](../foundation-api-design/SKILL.md) — RESTful design for Web3 APIs and dApp backends

Operational Playbooks

• [resources/operational-playbook.md](resources/operational-playbook.md) — Smart contract architecture, security-first workflows, and platform-specific patterns