code-quality

Run the 7-phase workflow: explore the codebase architecture, research relevant documentation, analyze impact of each change via Grep usages, detect duplication with jscpd, run language-specific linters, apply corrections, then re-verify until linters, tests, and duplication are all clean.

Run npx jscpd ./src --threshold 5 --reporters console,json to scan for copy-pasted code across 150+ languages. Thresholds vary by language: 3% for TypeScript and Python, 5% for Go and PHP, 10% for Java and C/C++. Duplication above 10% requires mandatory refactoring.

For TypeScript run npx eslint . --fix, npx prettier --write ., and npx tsc --noEmit. For Python run ruff check . --fix, black ., mypy ., and isort . to cover linting, formatting, and type checking.

Run functional verification first to confirm the original problem was actually solved, then run code-quality validation. Code quality checks confirm the fix is clean but do not verify the fix works.

Split a file when its total line count reaches 200 or more. Files under 100 lines of actual code (excluding comments and blanks) are fine, and files between 100 LoC and 200 total lines are acceptable if well-documented.

It catches interfaces defined inside component files, business logic placed in components instead of hooks, monolithic components that should be sectioned, local state used for global data instead of stores, and files exceeding size limits.