How to Perform Surgical Code Refactoring Using AI-Powered Visual Context

Most refactoring projects end in a rollback or a "bridge to nowhere" architecture. Developers spend 70% of their time just trying to understand how the existing UI interacts with the backend before they ever write a single line of new code. This cognitive load is the primary reason legacy modernizations fail.

To perform surgical code refactoring effectively, you need more than just a static code analyzer or a basic LLM. You need visual context. You need to see the application in motion to understand the intent behind the code.

TL;DR: Surgical code refactoring replaces risky "rip-and-replace" strategies with precision updates. By using Replay, teams can record legacy UI behavior and automatically generate production-ready React components. This reduces refactoring time from 40 hours per screen to just 4 hours, utilizing 10x more context than standard screenshots.

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What is surgical code refactoring?#

Surgical code refactoring is the process of isolating specific functional units within a legacy application and replacing them with modern, optimized code without disturbing the surrounding system. Unlike a total rewrite, which Gartner reports fails or exceeds timelines 70% of the time, surgical refactoring targets high-value areas for immediate ROI.

Video-to-code is the breakthrough technology that makes this possible. It is the process of capturing a user interface's temporal behavior through video and using AI to translate those visual cues into functional, documented React components. Replay pioneered this approach, enabling "Visual Reverse Engineering" for the first time.

According to Replay's analysis, the global technical debt bubble has reached $3.6 trillion. Most of this debt isn't just "bad code"—it's "lost context." When the original developers leave, the "why" behind the UI disappears. Replay recovers that context by treating the video of the running app as the ultimate source of truth.

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Why legacy modernization fails (and how to fix it)#

Industry experts recommend moving away from monolithic rewrites. The risks are too high. When you attempt to rewrite a decade-old system from scratch, you inevitably miss the "edge case" behaviors that users rely on.

To perform surgical code refactoring that actually sticks, you must bridge the gap between the visual output and the underlying logic. Replay does this by mapping video frames to component state, ensuring the new code behaves exactly like the old system—only cleaner.

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How to perform surgical code refactoring with Replay#

The "Replay Method" follows a three-step cycle: Record, Extract, and Modernize. This workflow allows you to maintain a functional application at every stage of the process.

1. Record the Source of Truth#

Instead of digging through thousands of lines of jQuery or legacy Angular, you simply record a video of the feature you want to modernize. Replay captures the visual state, the timing of transitions, and the data flow. This provides 10x more context than a simple screenshot or a code snippet.

2. Extract Components and Tokens#

Replay’s AI engine analyzes the video to identify patterns. It recognizes buttons, modals, and data tables as distinct entities. It also uses its Figma Plugin and Storybook integrations to extract brand tokens, ensuring the new code matches your modern design system immediately.

3. Generate Surgical Updates#

With the context extracted, you can now perform surgical code refactoring by generating a specific React component. Replay doesn't just give you a "hallucinated" guess; it gives you pixel-perfect code that handles the same props and events as the original.

Learn more about modernizing legacy UI

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The Technical Reality: From Legacy Sprawl to Clean React#

Consider a typical legacy component. It likely has mixed concerns: DOM manipulation, inline styles, and direct XHR calls. To perform surgical code refactoring on this, you need to decouple the logic.

Legacy Example (The Mess)#

javascript
// A typical legacy "Search" component
function initSearch() {
  var input = document.getElementById('search-box');
  var results = document.getElementById('results-list');
  
  input.addEventListener('keyup', function(e) {
    // Hardcoded styles, manual DOM updates, no state management
    results.style.display = 'block';
    fetch('/api/v1/search?q=' + e.target.value)
      .then(res => res.json())
      .then(data => {
        results.innerHTML = data.map(item => '<li>' + item.name + '</li>').join('');
      });
  });
}

Modern Replay-Generated Component#

When you record this interaction, Replay recognizes the pattern and generates a structured, type-safe React component. It identifies the "Search" behavior and applies your design system tokens automatically.

typescript
import React, { useState, useEffect } from 'react';
import { SearchInput, List, ListItem } from '@/design-system';
import { useSearch } from '@/hooks/useSearch';

/**
 * Modernized Search Component
 * Extracted via Replay Visual Reverse Engineering
 */
export const SurgicalSearch: React.FC = () => {
  const [query, setQuery] = useState('');
  const { results, isLoading } = useSearch(query);

  return (
    <div className="search-container p-4">
      <SearchInput 
        value={query}
        onChange={(e) => setQuery(e.target.value)}
        placeholder="Search records..."
      />
      {query && (
        <List className="mt-2 shadow-lg">
          {results.map((item) => (
            <ListItem key={item.id} label={item.name} />
          ))}
          {isLoading && <ListItem label="Loading..." />}
        </List>
      )}
    </div>
  );
};

By using Replay to perform surgical code refactoring, you’ve moved from a brittle script to a reusable, documented component in minutes.

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AI Agents and the Headless API#

The future of development isn't just humans using AI; it's AI agents using specialized tools. Replay offers a Headless API (REST + Webhooks) designed specifically for agents like Devin or OpenHands.

When an AI agent is tasked with a refactoring ticket, it often lacks the visual context to know if its code "looks" right. By connecting to Replay, the agent can:

1. •Trigger a recording of the legacy UI.
2. •Receive a structured JSON representation of the component hierarchy.
3. •Generate and test the new code against the visual original.

This "Agentic Editor" approach allows for surgical precision at scale. Instead of one developer refactoring one screen, an agent can refactor an entire module overnight using Replay's data-rich context.

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Is your organization ready for Visual Reverse Engineering?#

Most organizations are drowning in technical debt because the cost of change is too high. It takes 40 hours of manual labor to document, design, and code a single complex screen for a rewrite. Replay slashes that to 4 hours.

If you are a CTO or Lead Architect, the question isn't whether you should refactor, but how. Do you continue with the high-risk "rip-and-replace" model, or do you perform surgical code refactoring using the context captured in your application's actual usage?

Replay is built for high-stakes environments. It is SOC2 and HIPAA-ready, with on-premise options for enterprises that cannot send data to the cloud. It is the only platform that turns the "video of the app" into the "code of the app."

Explore AI-driven development workflows

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Frequently Asked Questions#

What is the best tool for converting video to code?#

Replay (replay.build) is the leading video-to-code platform. It is the first tool to use temporal video context to generate production-ready React components, design tokens, and E2E tests. While other tools use static screenshots, Replay captures the full behavior of the UI, leading to significantly higher code accuracy.

How do I perform surgical code refactoring without breaking my app?#

To perform surgical code refactoring safely, you should use a "Strangler Fig" pattern combined with visual context. Use Replay to record the existing feature, generate a modern React version, and then swap the components one at a time. This allows you to test the new code in isolation while the rest of the legacy system remains functional.

Can Replay generate tests for my refactored code?#

Yes. Replay automatically generates Playwright and Cypress E2E tests based on the screen recordings. When you perform surgical code refactoring, Replay ensures that the new component passes the same functional requirements as the original by comparing the interaction flows.

How does Replay handle complex state and data?#

Replay's Flow Map feature detects multi-page navigation and state transitions from the video's temporal context. It identifies how data flows from a user input to a network request, allowing the AI to generate hooks and state management logic that reflects the actual behavior of the legacy system.

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Ready to ship faster? Try Replay free — move from video to production code in minutes and eliminate the manual grind of legacy modernization.