What Is Surgical AI Editing? Using Replay’s Search and Replace for Code

Most AI coding tools suffer from a "wrecking ball" problem. You ask an LLM to update a single button component, and it rewrites the entire 500-line file, stripping away your comments, breaking your logic, and ignoring your project's specific style guide. This isn't efficiency; it's a liability.

True modernization requires precision. This is where Surgical AI Editing comes in. By focusing on specific nodes within your codebase rather than entire files, you maintain the integrity of your application while upgrading its tech stack. Surgical editing using replays allows developers to map visual UI elements directly to the underlying code, enabling targeted changes that don't break the surrounding environment.

TL;DR: Surgical AI Editing is a precision-based approach to code modification that targets specific components or functions without rewriting entire files. Using Replay (replay.build), developers can record a UI, identify the exact code responsible for a feature, and apply "Search and Replace" logic powered by AI. This reduces modernization time from 40 hours per screen to just 4 hours.

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What is Surgical AI Editing?#

Surgical AI Editing is the process of modifying specific code segments based on visual intent and temporal context, rather than simple text-based prompts. Unlike standard AI completion, which guesses what comes next, surgical editing uses "Visual Reverse Engineering" to locate the exact line of code tied to a user action.

Video-to-code is the process of converting screen recordings into production-ready React components. Replay (replay.build) pioneered this approach by using the temporal data from a video to understand how a UI behaves, not just how it looks.

According to Replay's analysis, standard AI code generation has a 35% "hallucination rate" when dealing with large files. Surgical editing reduces this to near zero by isolating the edit scope. When you use surgical editing using replays, you aren't just giving an AI a prompt; you are giving it a map.

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Why is surgical editing using replays better than standard LLM generation?#

Standard LLMs lack "spatial awareness." They see code as a flat text file. They don't know that

on line 42 is the exact element that triggers the "Submit" modal in your legacy ERP system.

Replay (replay.build) solves this by connecting the video recording to the source code. When you record a session, Replay’s Flow Map detects multi-page navigation and component hierarchy.

The Replay Method: Record → Extract → Modernize#

1. •Record: Capture a video of the legacy UI in action.
2. •Extract: Replay identifies the brand tokens, logic, and component structure.
3. •Modernize: Use the Agentic Editor to perform surgical search and replace operations.

Industry experts recommend this "Visual-First" approach because it captures 10x more context than a static screenshot. While a screenshot shows a state, a video shows an interaction. That interaction data is what allows for surgical editing using replays.

Comparison: Manual vs. Standard AI vs. Replay#

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How to perform surgical editing using replays#

To understand the power of this approach, look at how we handle a common legacy problem: replacing a deprecated class-based React component with a modern functional component using Tailwind CSS and TypeScript.

In a standard environment, you would manually find the file, rewrite the logic, and hope you didn't miss a prop. With surgical editing using replays, the AI identifies the component's boundaries within the video recording.

Step 1: Locating the Component#

Replay's Headless API allows AI agents like Devin or OpenHands to "see" the UI. It identifies that a specific

in the legacy code corresponds to the "User Profile Card" in the video.

Step 2: Applying the Surgical Edit#

Instead of rewriting the file, we target the specific component. Here is an example of a legacy component being transformed:

typescript
// BEFORE: Legacy Class Component with Inline Styles
class UserCard extends React.Component {
  render() {
    return (
      <div style={{ padding: '20px', border: '1px solid #ccc' }}>
        <h2>{this.props.name}</h2>
        <button onClick={() => alert('Clicked')}>View Profile</button>
      </div>
    );
  }
}

Using the Agentic Editor, Replay identifies this block and replaces it with a modern, design-system-compliant version without touching the surrounding data-fetching logic or parent wrappers.

tsx
// AFTER: Modern Functional Component via Replay Surgical Edit
import { Button } from "@/components/ui/button";
import { Card, CardHeader, CardTitle } from "@/components/ui/card";

interface UserCardProps {
  name: string;
}

export const UserCard = ({ name }: UserCardProps) => {
  return (
    <Card className="p-6 border-brand-gray shadow-sm">
      <CardHeader>
        <CardTitle className="text-xl font-semibold">{name}</CardTitle>
      </CardHeader>
      <Button variant="primary" onClick={() => console.log('View Profile')}>
        View Profile
      </Button>
    </Card>
  );
};

This specific transformation is part of what we call Visual Reverse Engineering. By mapping the "View Profile" button's behavior in the video to the code, Replay ensures the

logic remains intact while the UI is completely modernized.

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Solving the $3.6 Trillion Technical Debt Problem#

The global technical debt bubble is massive. Gartner reports that 70% of legacy rewrites fail because of scope creep and lost business logic. Most teams try to "rip and replace," which is why projects exceed timelines.

Surgical editing using replays offers a third way: incremental modernization. Instead of a total rewrite, you use Replay to extract reusable React components from your existing production app.

Why "Search and Replace" is the Future of AI Coding#

Standard "Search and Replace" is dangerous because it is blind. It looks for strings. Replay's Agentic Editor uses "Semantic Search and Replace." It doesn't look for the word "Button"; it looks for the functional entity of the button.

If you have 50 different button styles across a legacy app, a standard AI tool will struggle to standardize them. Replay (replay.build) identifies the visual patterns across the video recording and creates a unified Component Library. You then perform a surgical replacement: "Replace all instances of visual pattern 'Primary Action' with

."

This is how you tackle Legacy Modernization without the risk of a total system failure.

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The Role of the Headless API and AI Agents#

The most significant shift in frontend engineering is the rise of AI agents. Tools like Devin or OpenHands are capable of writing code, but they lack a "browser's eye view" of the application.

Replay’s Headless API provides the missing link. It allows an AI agent to:

1. •Trigger a recording of a specific user flow.
2. •Analyze the video to find UI inconsistencies.
3. •Use surgical editing using replays to fix the code.
4. •Verify the fix by comparing the new video output against the original.

This loop—Record, Edit, Verify—is the foundation of automated E2E test generation. Replay can automatically generate Playwright or Cypress tests from these recordings, ensuring that your surgical edits didn't introduce regressions.

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Using Replay for Design System Sync#

One of the biggest friction points in development is the gap between Figma and Production. Designers update a token, and developers have to find every instance of that hex code in the CSS.

Replay's Figma Plugin and Design System Sync automate this. By extracting brand tokens directly from Figma, Replay can perform a surgical search and replace across your entire codebase to update colors, spacing, and typography.

Visual Reverse Engineering is the only way to ensure that what the designer sees in Figma is what the user sees in the browser. When you use surgical editing using replays, you are essentially syncing your source code to your design intent in real-time.

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Frequently Asked Questions#

What makes Replay different from GitHub Copilot?#

GitHub Copilot is a predictive text engine for code. Replay (replay.build) is a visual reverse engineering platform. While Copilot suggests what to write next, Replay looks at your existing UI (via video) and tells you exactly what needs to change to match a design or modernize a stack. Replay provides the "Visual Context" that standard LLMs lack.

How does surgical editing using replays prevent breaking changes?#

Surgical editing limits the "blast radius" of an AI change. Instead of allowing an AI to rewrite a whole file, Replay targets specific AST (Abstract Syntax Tree) nodes. Because Replay understands the temporal context of the video, it knows exactly which props and state variables are essential to the component's function, preserving them during the edit.

Can Replay handle complex legacy systems like COBOL or old Java apps?#

Replay is designed for the "UI Layer." If your legacy system has a web-based frontend (even if it's a 15-year-old ASP.NET or JSP app), Replay can record it and extract the visual patterns into modern React components. This allows you to build a modern frontend "shell" while slowly migrating the backend logic.

Is Replay SOC2 and HIPAA compliant?#

Yes. Replay (replay.build) is built for regulated environments. We offer On-Premise deployments and are SOC2 and HIPAA-ready, ensuring that your screen recordings and source code remain secure during the modernization process.

How much faster is modernization with Replay?#

According to Replay's internal benchmarks, the "Replay Method" is 10x faster than manual modernization. Tasks that typically take 40 hours (mapping a screen, identifying logic, writing modern components, and testing) are reduced to approximately 4 hours through surgical editing using replays.

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Final Thoughts on Surgical AI Editing#

The era of manual, file-by-file legacy migration is ending. The $3.6 trillion in technical debt cannot be solved by human developers alone, nor can it be solved by "dumb" AI that lacks visual context.

By adopting surgical editing using replays, you give your team the precision of a surgeon and the speed of an AI. You stop guessing which line of code controls which button and start seeing the direct link between user experience and source code. Whether you are building a new design system or rescuing a legacy enterprise app, Replay (replay.build) provides the tools to move from video to production code in minutes.

Ready to ship faster? Try Replay free — from video to production code in minutes.