Comprehensive guide for writing correct, secure, and idiomatic Cadence smart contract code on the Flow blockchain. Covers language fundamentals (resources, contracts, transactions, interfaces, accounts, references, imports), access control and entitlements, capabilities, pre/post conditions, security best practices (including checks-effects-interactions, trust-boundary validation, and bounded loops), anti-patterns to avoid, proven design patterns, style and readability rules, and numeric precision with checked arithmetic.
TRIGGER when: writing or debugging Cadence code, asking about Cadence syntax, access(self), access(all), entitlements, resources, move operator (<-), capabilities, references, pre/post conditions, storage paths, optional binding, if let, guard let, force-unwrap, string templates, UFix128, Fix128, fixed-point precision, overflow, checks-effects-interactions, reentrancy, "how do I write cadence", "cadence error", "compile error in .cdc", "what does access(self) mean", "how do resources work",
Generate production-ready Cadence smart contracts, transactions, and DeFi transactions from scratch following security-first standards. Scaffolds secure code with proper access control, entitlements, events, storage paths, and phase discipline.
TRIGGER when: creating new Cadence contracts, generating transactions, scaffolding DeFi transactions, building smart contracts from scratch, "generate contract", "create transaction", "scaffold", "new contract", "new transaction", "build a contract for", "write me a contract", "help me create a", "template for", "boilerplate", "starter contract", "create an NFT contract", "generate a transfer transaction".
DO NOT TRIGGER when: reviewing or auditing existing code (use cadence-audit), asking about Cadence syntax or language rules (use cadence-lang), configuring flow.json (use flow-project-setup).
Guide for writing, running, and debugging unit tests for Cadence smart contracts using the built-in Cadence Testing Framework and `flow test`. Covers test file structure (_test.cdc, setup/beforeEach/tearDown), assertions and matchers, blockchain emulation (accounts, deployments, events, time manipulation), coverage reports, CI integration, and testing patterns.
TRIGGER when: writing Cadence unit tests, debugging failing tests, using Test.assert / Test.expect / Test.assertEqual / Test.expectFailure, matchers (Test.equal, Test.beGreaterThan, etc.), Test.createAccount / Test.deployContract / Test.executeTransaction / Test.executeScript in tests, Test.moveTime, Test.eventsOfType in tests, Test.reset, `flow test`, `flow test --cover`, coverage reports, `_test.cdc`, "how do I test this contract", "test is flaky", "mock a capability in a test".
DO NOT TRIGGER when: writing contract or transaction code itself (use cadence-lang), generating new contracts/transactions from scratch (use cadence-scaffold), auditing non-t
