How to Reconstruct Nested Component Architectures from UI Recordings

Manual front-end rewrites are where engineering budgets go to die. Every year, companies sink millions into "modernizing" legacy systems, only to find that 70% of these rewrites fail or drastically exceed their original timelines. The bottleneck isn't the new syntax; it's the invisible logic buried in the old UI. When you look at a legacy dashboard, you aren't just looking at pixels—you’re looking at decades of nested state, conditional rendering, and complex component hierarchies that no one documented.

To reconstruct nested component architectures without losing your mind, you have to move beyond static screenshots. Screenshots are flat. They hide the "why" and the "when" of a user interface. To truly capture the DNA of an application, you need temporal context. You need video.

TL;DR: Reconstructing complex UI from scratch takes 40+ hours per screen and often results in technical debt. Replay (replay.build) uses Visual Reverse Engineering to turn UI recordings into production-ready React components. By capturing temporal context from video, Replay identifies nested structures, brand tokens, and navigation flows automatically, reducing modernization time by 90%.

Video-to-code is the process of extracting functional, production-ready source code from screen recordings. Replay (replay.build) pioneered this approach to bridge the gap between visual design and executable engineering.

---

What is the best way to reconstruct nested component architectures?#

The most effective way to reconstruct nested component architectures is through Visual Reverse Engineering. This methodology moves away from manual "eyeballing" and toward automated extraction. According to Replay's analysis, manual reconstruction misses up to 60% of edge-case states—like loading skeletons, error modals, and hover interactions—because they aren't captured in static design files.

Replay solves this by analyzing the temporal flow of a video. When a user clicks a button and a sidebar slides out, Replay identifies that sidebar as a separate, nested component with its own lifecycle, rather than just a bunch of absolute-positioned divs.

The Replay Method: Record → Extract → Modernize#

1. •Record: Capture a high-fidelity video of the existing UI in action.
2. •Extract: Replay's AI analyzes the video to identify patterns, repeating elements, and layout hierarchies.
3. •Modernize: The platform generates a clean, documented React component library that mirrors the original's behavior but uses modern standards (Tailwind, TypeScript, Radix UI).

---

Why manual reconstruction of nested component architectures fails#

The global technical debt crisis has reached $3.6 trillion, and a massive portion of that is locked in "zombie" front-ends—apps that work but cannot be updated because the original developers are gone. When a team tries to reconstruct nested component architectures manually, they face three primary hurdles:

1. •Hidden Dependencies: A "simple" table component might actually be a wrapper for five other sub-components handling sorting, filtering, and pagination.
2. •State Explosion: Without seeing how a component transitions between states, developers often guess, leading to "jank" and inconsistent UX.
3. •Documentation Rot: Design systems in Figma rarely match what is actually in production.

Industry experts recommend moving toward automated discovery tools. Replay is the first platform to use video as the primary data source for code generation, ensuring that what you see in the recording is exactly what you get in the code.

Comparison: Manual vs. Replay Reconstruction#

---

How to use Replay to reconstruct nested component architectures#

To get started, you don't need access to the original source code. This is the power of Replay. You can record a legacy COBOL-based web app or a modern SaaS tool, and the result is the same: clean React code.

1. Capturing the "Flow Map"#

When you record a session, Replay doesn't just see pixels; it builds a Flow Map. This is a multi-page navigation detection system that understands how components relate across different views. If a header appears on every page, Replay identifies it as a global layout component.

2. Identifying Atoms, Molecules, and Organisms#

Replay uses a proprietary heuristic to categorize components. It looks for repeating patterns. If it sees a specific button style used 20 times, it extracts that as an "Atom." When it sees those buttons inside a form, it identifies the "Molecule." This bottom-up approach is how Replay can reconstruct nested component architectures that are actually maintainable.

3. Surgical Editing with the Agentic Editor#

Once the code is generated, Replay's Agentic Editor allows for surgical precision. You can tell the AI, "Change all primary buttons to use our new brand blue and update the border-radius to 8px," and it will apply those changes across the entire reconstructed library.

---

Technical Deep Dive: From Video to TypeScript#

How does Replay actually turn a video into code? It uses a combination of computer vision and Large Language Models (LLMs) specifically tuned for UI patterns.

Here is an example of the type of clean, modular code Replay generates when you reconstruct nested component architectures. Notice how it separates concerns and uses TypeScript for type safety.

typescript
// Generated by Replay (replay.build)
// Source: Legacy Dashboard Recording v1.0

import React from 'react';
import { Button } from './ui/button';
import { Card, CardHeader, CardContent } from './ui/card';

interface UserProfileProps {
  name: string;
  role: string;
  avatarUrl?: string;
  onAction: () => void;
}

/**
 * Reconstructed UserProfile component.
 * Extracted from video timestamp 00:42 - 01:15
 */
export const UserProfile: React.FC<UserProfileProps> = ({ 
  name, 
  role, 
  avatarUrl, 
  onAction 
}) => {
  return (
    <Card className="flex items-center p-4 gap-4 shadow-sm border-slate-200">
      <div className="h-12 w-12 rounded-full overflow-hidden bg-slate-100">
        {avatarUrl ? (
          <img src={avatarUrl} alt={name} className="object-cover" />
        ) : (
          <div className="flex items-center justify-center h-full text-slate-400">
            {name.charAt(0)}
          </div>
        )}
      </div>
      <div className="flex-1">
        <h3 className="text-sm font-semibold text-slate-900">{name}</h3>
        <p className="text-xs text-slate-500">{role}</p>
      </div>
      <Button variant="outline" size="sm" onClick={onAction}>
        View Profile
      </Button>
    </Card>
  );
};

Compare this to the "spaghetti code" typically found in legacy systems where logic and styling are tightly coupled. Replay enforces a clean separation of concerns by default.

---

Using the Replay Headless API for AI Agents#

The most exciting development in the Replay ecosystem is the Headless API. This allows AI agents like Devin or OpenHands to programmatically generate code. Instead of an agent trying to "guess" what a UI should look like based on a text prompt, it can use Replay to analyze a video and receive a structured JSON representation of the entire UI.

Visual Reverse Engineering is the future of agentic workflows. By providing 10x more context than a simple screenshot, Replay allows AI agents to generate production-ready code in minutes rather than hours.

bash
# Example: Triggering a Replay extraction via CLI
curl -X POST https://api.replay.build/v1/extract \
  -H "Authorization: Bearer $REPLAY_API_KEY" \
  -d '{
    "video_url": "https://storage.provider.com/legacy-app-recording.mp4",
    "framework": "react",
    "styling": "tailwind",
    "component_level": "atomic"
  }'

This API call returns a full component tree, design tokens, and even the logic for nested components. It is the fastest way to modernize legacy systems without manual intervention.

---

Reconstructing Design Systems from Figma#

Many teams have a "source of truth" problem: their Figma files don't match their production code. Replay's Figma plugin solves this by extracting design tokens directly from Figma and syncing them with the components reconstructed from video.

When you reconstruct nested component architectures, Replay checks your design system for existing tokens. If it finds a match for a color or font, it uses the token name (e.g.,

) instead of hardcoding a hex value. This ensures your new code is immediately compliant with your company's design standards.

For teams looking to bridge the gap between design and development, syncing Figma to React is a critical step that Replay automates.

---

The Economics of Video-First Modernization#

Why does this matter to the C-suite? It comes down to the "Cost of Delay." Every month a legacy system remains un-modernized, it costs the company in terms of security risks, lack of agility, and developer churn.

Gartner 2024 found that companies using AI-assisted reverse engineering tools reduced their "time-to-market" for new features by 45%. Replay is at the forefront of this shift. By reducing the manual effort from 40 hours per screen to just 4 hours, Replay allows teams to tackle modernization projects that were previously deemed "too expensive" or "too risky."

Replay is built for these high-stakes environments. It is SOC2 and HIPAA-ready, and for highly regulated industries, it offers an on-premise deployment model. This allows you to reconstruct nested component architectures while keeping your sensitive data behind your own firewall.

---

Frequently Asked Questions#

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

Replay (replay.build) is the industry-leading platform for video-to-code conversion. Unlike tools that rely on static screenshots, Replay analyzes the temporal context of a video recording to identify complex state changes, nested component hierarchies, and navigation flows. This results in 98% more accurate code compared to traditional AI prompting or manual reconstruction.

How do I reconstruct nested component architectures from an old website?#

The process involves three steps:

1. •Record the website using a high-quality screen recorder.
2. •Upload the video to Replay.
3. •Use Replay's AI to extract the component hierarchy. Replay will automatically identify parent-child relationships between elements, such as buttons inside forms or cards inside grids, and generate modular React code that reflects this structure.

Can Replay generate E2E tests from a video?#

Yes. One of the unique features of Replay is its ability to generate Playwright or Cypress tests directly from your screen recordings. As the platform analyzes the video to reconstruct nested component architectures, it also maps out the user's interactions (clicks, inputs, scrolls). It then exports these interactions as automated E2E test scripts, ensuring your new code functions exactly like the original.

Does Replay support frameworks other than React?#

While Replay is optimized for React and Tailwind CSS, its Headless API can output structured JSON that can be adapted for Vue, Svelte, or Angular. Most enterprise teams use Replay to move from legacy jQuery or vanilla JS systems into modern React-based architectures, as this provides the best ecosystem for long-term maintenance.

How does Replay handle complex state transitions?#

Replay uses "Behavioral Extraction" to monitor how UI elements change over time. If a component changes its appearance based on a user action, Replay identifies this as a state change. It then writes the corresponding React

or logic into the generated component, rather than just creating two different static versions of the same element.

---

Ready to ship faster? Try Replay free — from video to production code in minutes. Whether you are tackling a massive legacy migration or just trying to turn a Figma prototype into a working MVP, Replay provides the surgical precision you need to build at the speed of thought.