Simplify complex codebases with Claude

Modern codebases are sprawling, dynamic, and interconnected. As software scales, even experienced teams struggle to manage complexity: unreadable abstractions, legacy modules, tangled dependencies, and logic that’s evolved far past its original design.

Claude has built two tools to help developers tame that complexity and make simplifying codebases not just possible, but productive:

• Start with Claude.ai for rapid prototyping, small refactors, or understanding unfamiliar code. It’s free to sign up and works on web, desktop, and mobile.
• Advance to Claude Code for deep, multi-file simplification work. This agentic tool lives in your terminal and connects directly to your repo.

Together, these tools help you reduce complexity, boost maintainability, and improve clarity, with far less manual effort.

Why simplifying complex code matters

Complex codebases increase risk and reduce velocity. They slow onboarding, complicate debugging, and create fragile systems that resist change.

Claude helps simplify codebases by:

• Clarifying intent: Explain what a function really does, so you can make it easier to read and change.
• Eliminating duplication: Identify repeated logic, similar modules, or patterns that could be abstracted.
• Reducing surface area: Spot functions that do too much, and split them into smaller, reusable components.
• Improving naming and structure: Suggest clearer variable names, more intuitive APIs, and logical folder organization.
• Handling legacy debt: Translate outdated or undocumented code into modern, idiomatic alternatives.

Whether you’re preparing for a handoff, rewriting a monolith, or building for long-term maintainability, Claude can simplify the hard parts.

Simplifying code in Claude.ai

Claude.ai is the fastest way to reduce complexity without needing terminal setup or repo access. Just paste in a function or file and ask Claude to:

• Identify overly complex logic
• Rename unclear variables or parameters
• Split long functions into helpers
• Suggest modern idioms or clearer constructs
• Remove unnecessary conditionals or nesting

Example: Simplifying a complex conditional block

Prompt Claude.ai to clarify a nested if/else logic:

This function has nested if/else logic and unclear conditions. Can you simplify and clarify it?

This function has nested if/else logic and unclear conditions. Can you simplify and clarify it?

def route_request(user):
    if user.is_authenticated:
        if user.has_permission("admin"):
            return admin_dashboard()
        else:
            return user_dashboard()
    else:
        return login_screen()

Claude explains that flipping the first condition and using a ternary operator improves readability while preserving behavior.

def route_request(user):
    if not user.is_authenticated:
        return login_screen()

    return admin_dashboard() if user.has_permission("admin") else user_dashboard()

Going deeper with Claude Code: repo-wide simplification

When simplification requires coordination across files, modules, or entire systems, Claude Code steps in. This terminal-based agent reads from and writes to your codebase, making it ideal for structural refactors.

Initialize it once in your terminal: 

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

Once initialized, Claude Code can:

• Summarize large classes or modules in plain English
• Find and remove redundant logic across files
• Extract shared helpers and reduce duplication
• Rename functions, variables, or files consistently
• Suggest module splits to reduce import chains or circular dependencies

Example: Untangling a utility module

Prompt Claude Code to simplify your utility module:

The utils.py file is over 600 lines and mixes unrelated functions. Can you group related functions and suggest how to split it?

Claude Code will: 

• Group 22 string manipulation functions together and recommends a new string_utils.py
• Identify 13 date/time helpers for datetime_utils.py
• Flag 8 unused functions for deletion
• Generate stub files with updated imports and usage paths

Tool-powered deep dives

Claude Code also offers specialized tools to simplify code structurally and safely.

Code execution tool

Use this sandboxed tool to test rewritten logic before applying it. You can:

• Time original vs refactored versions
• Verify behavior consistency
• Benchmark simplified alternatives

This profiles runtime performance without leaving the terminal.

claude.code_execution(
    code="""
def inefficient_sum(arr):
    total = 0
    for x in arr:
        total += x
    return total
""",
    test_input="[1, 2, 3, 4, 5]"
)

Text editor tool

Make in-place edits, undo changes, and run structural replacements. You can:

• Use str_replace to rename identifiers across files
• Review edit previews before committing
• Roll back entire sessions if needed

These features make multi-file simplification safer and more transparent.

Optimizing enormous repos

Claude Code can operate efficiently even on massive codebases, but you can guide it to focus context.

Try these practices:

• Add a CLAUDE.md file to describe project structure, entry points, and pain areas.
• Use subdirectory targeting (claude suggest --scope=src/components/) to limit focus.
• Reference Velox/GitHub issue #403 for advanced token budgeting and repo slicing.

These steps help Claude Code prioritize high-impact simplifications, without getting lost in boilerplate.

When to use Claude.ai vs Claude Code

Each of these two tools naturally fit into different stages of your codebase simplification: 

Claude.ai helps you navigate unfamiliar code, review PRs for clarity, and handle isolated refactors. Use it to simplify notebook logic, reduce cyclomatic complexity, and quickly onboard contributors to legacy code.

Claude Code take the next step. It scans entire folders, extracts shared components, removes cross-module dependencies, and enforces consistent style as it breaks down monoliths into clean, team-owned boundaries. You can run it from the terminal if you have API access or a Max plan subscription.

In general, start with Claude.ai for exploration and focused edits. Switch to Claude Code for sophisticated multi-file changes and architecture-level refactors. 

Sample prompts to simplify complex code

Try these prompts to accelerate simplification with Claude:

With Claude.ai: 

• Can you make this function easier to read?
• Suggest better variable names and remove redundant branches.
• Flatten this nested loop and simplify logic.
• Turn this long function into smaller reusable ones.

With Claude Code:

• Can you make this function easier to read?
• Suggest better variable names and remove redundant branches.
• Flatten this nested loop and simplify logic.
• Turn this long function into smaller reusable ones.

These prompts help you refactor gradually, without destabilizing your codebase.

Get started

Claude makes simplifying codebases more approachable and more powerful, whether you’re polishing a single file or re-architecting a repo.

• Start with Claude.ai and sign up for free. Use it to identify quick simplifications and improve code readability. 
• 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

By reducing friction, eliminating redundancy, and clarifying logic, Claude helps teams write software that’s easier to reason about, maintain, and extend.