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/ for chain-specific best practices.

Navigation

Resources

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

Templates

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

Related Skills

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

Operational Playbooks