Improve code maintainability using Claude

Writing clean code is hard. Keeping it that way is even harder.

As teams grow, features evolve, and product deadlines compress, codebases often become sprawling collections of quick fixes, duplicated logic, and brittle edge cases. This results in a system that’s difficult to extend, debug, or even understand.

Code maintainability isn’t just about elegance. It directly affects developer productivity, onboarding time, and long-term system resilience. That’s where Claude comes in.

Claude helps engineering teams refactor and maintain better code using two powerful tools:

• Claude.ai: Anthropic’s AI coding tool, available in your browser, that’s perfect for structured code generation, architectural planning, and small-scale refactors. It offers a fast feedback loop for improving naming conventions, simplifying functions, or designing modular interfaces.
• Claude Code: Anthropic’s agentic coding tool that integrates directly with your local repo to audit files, detect anti-patterns, and propose clean, testable updates at scale. It supports multi-file reasoning, semantic code search, and user-guided diffs.

In this article, we’ll explore how both tools help you improve code maintainability, from one-off cleanups to organization-wide refactors.

Why maintainability matters

Poorly maintained code leads to:

• Longer ramp-up time for new engineers
• Increased bug rates due to implicit dependencies and unclear logic
• Slow feature velocity, as devs spend more time navigating the system than building
• Technical debt creep, where each new feature adds more entropy

Conversely, well-maintained code makes teams faster and more resilient. You ship features with fewer regressions. You spend less time debugging. You onboard new engineers in weeks, not months.

Claude helps teams bake maintainability into their daily workflows.

Start with Claude.ai: small changes, fast loops

Claude.ai is ideal for early-stage cleanup, architectural brainstorming, and interface design. It’s available via web, desktop, and mobile, and free to use. 

Improve naming, modularity, and structure

Prompt Claude with a code snippet and ask for maintainability improvements:

Refactor this function to improve readability and follow single-responsibility principles.

Claude will return a cleaned-up version with:

• More descriptive variable and function names
• Logical separation of side effects
• Extracted helper methods
• Inline comments for clarity

This is especially useful for:

• Reviewing pull requests before merge
• Teaching junior devs clean code patterns
• Planning large-scale architecture changes

Refactor boilerplate into reusable modules

Many teams struggle with duplicated logic, especially in utility files, database queries, and form validation. Claude.ai can identify patterns and propose reusable abstractions.

Prompt example:

Here are three data validation functions. Can you extract shared logic into a common helper and simplify the rest?

Claude will return modularized code with well-scoped helpers, saving time across files and improving consistency.

Explain legacy or opaque code

Sometimes, the first step to maintainability is just understanding what you're looking at.

Paste in a legacy function and ask:

Explain what this code is doing, and suggest how to modernize it using async/await and error handling.

Claude will also walk through the logic line-by-line, highlight performance bottlenecks, and suggest replacements. 

Scale up with Claude Code: agentic terminal refactoring

While Claude.ai shines for lightweight and conceptual tasks, Claude Code is built for deep integration. 

Install it in your terminal via:

npm install -g @anthropic-ai/claude-code

Claude Code runs in your terminal and connects directly to your repo. Once initialized, it understands your full project context—including directory structure, code semantics, and test outputs.

What makes Claude Code different?

• One-time initialization: You only need to launch Claude Code once per session. No need to call it per prompt.
• Multi-file awareness: Claude tracks dependencies, file structure, and naming conventions across your codebase.
• Guided diffs: Claude shows you proposed changes before applying them, so you stay in control.
• Project memory: With CLAUDE.md, you can store preferred patterns, linter rules, and architecture principles.

Refactoring workflows with Claude Code

Here’s how Claude Code helps you improve code maintainability across the lifecycle.

Audit for code smells and anti-patterns

Run:

find all functions over 50 lines and recommend splits

Claude will return a list of long functions with inline suggestions to extract helpers, move logic to services, or isolate side effects. You can then selectively apply those suggestions.

Other prompts to try:

find unused imports across the repo and remove them
list all duplicate functions and propose a shared utility module
identify inconsistent naming conventions for React hooks

These audits reduce entropy and enforce consistency across your team.

Enforce modularity and DRY principles

Claude Code is particularly helpful for refactoring repetitive logic spread across files.

Try:

create a reusable fetch wrapper with error handling, then update all direct fetch() calls

Claude will scan the repo, refactor each instance, and show diffs for approval.

This is good for:

• Centralizing HTTP logic
• Consolidating logging or error formatting
• Replacing ad hoc date manipulation with a utility like date-fns

Improve test coverage and structure

Well-tested code is easier to maintain. Claude Code can scaffold tests or refactor brittle suites:

refactor this Jest test file to use beforeEach hooks and async/await

Or:

generate unit tests for the `calculateDiscount` function using edge case inputs

You can even ask Claude to detect redundant tests or identify gaps in coverage based on conditional branches.

Use case: cleaning up a payment module

Let’s walk through a real-world scenario.

The setup

You have a payment.js file with 600+ lines of spaghetti logic. It handles:

• Pricing calculations
• Tax rules per region
• API calls to a payment gateway
• UI string formatting
• Analytics events

It’s fragile. Every new feature risks breaking something else.

Step 1: Audit with Claude Code

Run:

analyze payment.js and recommend how to split it into smaller modules

Claude suggests:

• Moving tax logic to tax-utils.js
• Separating gateway code into payment-api.js
• Extracting analytics to a dedicated trackEvent utility

It proposes a new file structure and shows line-specific diffs.

Step 2: Apply targeted refactors

Approve the suggested diffs, and Claude Code automatically updates the imports, ensures tests pass, and documents each change in commit messages.

Step 3: Maintain with Claude.md

Add project conventions to CLAUDE.md:

• Use formatCurrency()from lib/currency for all price displays
• All API calls must use the apiClient wrapper
• Prefer named exports over default exports

Claude will now follow these rules in future prompts.

When to use Claude.ai vs Claude Code

Improving code maintainability is a mindset. Claude helps you build that muscle across your workflows with its two tools.

Claude.ai handles lightweight transformations, such as renaming variables, explaining logic, and generating scaffolds. 

Claude Code takes the next step by handling sophisticated edits across entire codebases. It executes multi-file refactors, audits your codebase for inconsistencies, and applies diffs aligned with your version control system that you’ve approved.

In general, use Claude.ai to clean up fast, explain clearly, and scaffold smart. Switch to Claude Code to refactor deeply, scale consistency, and enforce structure.

Get started

Claude is ready to help you maintain your codebase—whether you’re planning your next architecture revamp or just fixing a confusing function. Here’s how to begin:

1. Visit Claude.ai and sign up for free. Use it to refactor functions, clean up naming, or explain legacy code. 
2. When you're ready to dive into code, install Claude Code and run it in your terminal if you have a Max plan or API access. 

npm install -g @anthropic-ai/claude-code
claude init

Both tools act as co-maintainers — accelerating good habits, reducing tech debt, and giving your team more time to build. Whether you're cleaning up a legacy module or designing a new service from scratch, Claude is ready to help you make your codebase healthier, one refactor at a time.