Using Claude Code and Aider to Refactor Large Projects: Enhancing Maintainability and Scalability

Modern software projects often grow into sprawling, complex codebases that challenge even the most seasoned developers. As technical debt accumulates, maintenance becomes a burden, and enhancing features or onboarding new team members gets harder. Enter AI-powered tools like Claude Code and Aider, which are transforming how teams refactor and maintain large-scale projects.

Why Refactor Large Projects?

• Improve code readability and structure
• Reduce bugs and technical debt
• Facilitate onboarding and collaboration
• Enable faster feature development

Traditional refactoring is labor-intensive, especially across hundreds or thousands of files. AI-powered tools promise to automate repetitive, error-prone tasks, freeing developers to focus on higher-level design and problem-solving.

Claude Code: Agentic Coding for Real-World Refactoring

Claude Code, developed by Anthropic, is an agentic coding tool designed to integrate deeply with your coding workflow. Unlike traditional code assistants, Claude Code can:

• Search and read code across your repository
• Edit files, write and run tests
• Commit and push code to GitHub
• Use command-line tools, all while keeping you informed at every step ^{^5}.

This agentic approach means Claude Code acts as a collaborative partner, not just a code generator. It’s especially effective for large-scale refactoring, as it can process many files in a single pass—tasks that might take hours manually can be done in minutes ^{^5}.

Best Practices:

• Organize your repository and create a CLAUDE.md to guide the assistant’s actions and understanding of your codebase ^{^1}.
• Break down large refactoring tasks into smaller, focused prompts to improve accuracy and avoid unintended changes ^{^3}.
• Use iterative refinement: let Claude propose changes, review them, and provide feedback for further improvement ^{^2}.

Aider: Complementary AI for Code Transformation

While less detailed documentation exists for Aider compared to Claude Code, Aider is another AI-driven code assistant that excels at understanding context and making targeted changes across multiple files. Used together, these tools can:

• Batch-remove deprecated code patterns
• Standardize APIs or interfaces
• Update documentation and comments project-wide

Real-World Results: Case Studies and Insights

A recent case study using Claude 3.7 Sonnet and GPT-4o demonstrated the power of AI-driven batch refactoring. The task: remove deprecated arguments and feature flags across 64 test files. Key takeaways included ^{^4}:

• Efficiency: AI handled tedious, repetitive edits with minimal manual intervention.
• Consistency: Splitting complex changes into smaller, focused steps reduced errors and unintended side effects.
• Limitations: AI sometimes missed edge cases or made inconsistent changes, so human review remains essential.

Another developer reported using Claude Sonnet within the Zed editor to refactor a blog codebase, highlighting the tool’s ability to understand project context and make meaningful improvements ^{^6}.

Infographic: The AI-Powered Refactoring Workflow

+-------------------------+
| 1. Prepare Repository   |
| - Organize files        |
| - Add CLAUDE.md         |
+-----------+-------------+
            |
            v
+-------------------------+
| 2. Define Refactoring   |
|    Goals & Prompts      |
+-----------+-------------+
            |
            v
+-------------------------+
| 3. Run AI Tools         |
| - Claude Code           |
| - Aider                 |
+-----------+-------------+
            |
            v
+-------------------------+
| 4. Review & Iterate     |
| - Human-in-the-loop     |
| - Refine prompts        |
+-----------+-------------+
            |
            v
+-------------------------+
| 5. Commit & Test        |
| - Push changes          |
| - Run test suites       |
+-------------------------+

Flow Chart: AI Refactoring Process

flowchart TD
    A[Start: Large Codebase] --> B[Organize & Document (CLAUDE.md)]
    B --> C[Define Refactoring Tasks]
    C --> D[Run Claude Code / Aider]
    D --> E[Review AI Suggestions]
    E --> F{Changes OK?}
    F -- Yes --> G[Commit & Push]
    F -- No --> H[Refine Prompts & Re-run]
    H --> D
    G --> I[Run Tests & Deploy]
    I --> J[End]

Conclusion

AI-powered tools like Claude Code and Aider are revolutionizing large-scale code refactoring. By automating repetitive changes, improving consistency, and integrating with your workflow, these tools dramatically boost maintainability and scalability. While human oversight remains crucial, the future of software engineering is increasingly collaborative—between developers and intelligent, agentic AI assistants ^{^1^5}.

“AI is already a powerful tool for large-scale code modifications, allowing for efficient batch refactoring with minimal manual oversight.” ^{^4}