How I use Claude Code to implement new features in an existing complex codebase

9 months ago

The article provides a comprehensive guide on using Claude Code, an AI coding tool, for implementing new features in complex codebases.
It emphasizes the importance of maintaining clean, production-grade code and reducing bugs introduced by AI.
The guide includes a detailed CLAUDE.md file with coding rules and best practices for implementation, testing, database handling, and code organization.
Key practices include following Test-Driven Development (TDD), using branded types for IDs, and preferring simple, testable functions.
Testing best practices highlight the importance of parameterized inputs, strong assertions, and testing edge cases.
The article outlines a structured AI coding process involving planning, coding, reviewing, and committing changes with specific shortcuts like qnew, qplan, qcode, qcheck, and qgit.
It warns about the limitations of AI tools in 2025, stressing the need for active oversight to avoid technical debt and suboptimal solutions.
The guide concludes with resources for further learning and support in AI coding and business scaling.

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