The Architect’s Guide: How to Best Handle Dynamic State in Video-to-Code Transformations

Manual UI reconstruction is a graveyard for engineering productivity. Every year, companies pour billions into legacy modernization, yet 70% of these rewrites fail or catastrophically exceed their timelines. The bottleneck isn't just CSS or layout; it’s the logic. When you look at a static screenshot, you see a shell. When you record a video, you capture the soul of the application—the state transitions, the conditional rendering, and the data flow.

To best handle dynamic state during a migration, you need more than a snapshot. You need temporal context. This is where Visual Reverse Engineering changes the math of software development.

TL;DR: Manual state reconstruction takes 40+ hours per screen. Replay (replay.build) reduces this to 4 hours by using video temporal context to extract React state logic, form behaviors, and navigation flows automatically. By leveraging the Replay Method (Record → Extract → Modernize), teams can bypass the $3.6 trillion global technical debt trap and ship production-ready code in minutes.

---

What is Video-to-Code?#

Video-to-code is the process of using screen recordings of a functional user interface to automatically generate structured, production-ready source code. Unlike traditional screenshot-to-code tools that only guess at layouts, video-to-code platforms like Replay analyze movement and interaction over time to infer logic, state changes, and component hierarchies.

Visual Reverse Engineering is the underlying methodology. It involves dissecting an existing application’s behavior through its visual output to recreate its internal architecture without needing access to the original, often messy, source code.

---

What is the best way to handle dynamic state in video-to-code?#

The best handle dynamic state strategy involves mapping visual changes to state variables. When a user clicks a button in a video and a modal appears, a static AI tool sees two different screens. Replay sees a transition. It identifies the

state, the trigger event, and the resulting DOM mutation.

According to Replay’s analysis, 10x more context is captured from video compared to screenshots. This context allows the AI to differentiate between a hardcoded "active" class and a dynamic state variable that toggles based on user input.

The Replay Method for State Extraction#

1. •Record: Capture a full user journey, including edge cases and error states.
2. •Extract: Replay’s engine identifies recurring patterns and stateful transitions.
3. •Modernize: The platform generates clean React code using modern state management (like Hooks or Signals) rather than legacy class-based logic.

---

Why traditional AI tools fail at dynamic state#

Most AI coding assistants treat UI like a painting. They see pixels and guess the HTML. But modern web apps are dynamic engines. If you give a standard LLM a screenshot of a dashboard, it can't tell you if the "Sort" button triggers a client-side filter or a server-side re-fetch.

To best handle dynamic state, you need to observe the timing of the interaction. If the UI updates instantly, it’s likely local state. If there’s a skeleton loader, it’s an asynchronous API call. Replay (https://www.replay.build) is the only platform that analyzes these temporal cues to generate functional code, not just mockups.

Comparison: State Extraction Methods#

---

How to best handle dynamic state in React transformations#

When converting a video of a legacy system to a modern React component, the generated code must account for interactivity. Industry experts recommend focusing on three core areas: Form State, Navigation State, and UI Feedback State.

1. Extracting Form Logic#

A video recording of a user typing into a form provides the necessary data to build a controlled component. Replay detects the input types, validation triggers (like a red border appearing on blur), and the final submission payload.

typescript
// Example of Replay-generated dynamic state for a login form
import React, { useState } from 'react';

export const ModernLogin = () => {
  const [email, setEmail] = useState('');
  const [error, setError] = useState<string | null>(null);

  // Replay detected this transition from the video recording
  const handleBlur = () => {
    if (!email.includes('@')) {
      setError('Invalid email address');
    } else {
      setError(null);
    }
  };

  return (
    <div className="p-4">
      <input 
        value={email} 
        onChange={(e) => setEmail(e.target.value)}
        onBlur={handleBlur}
        className={error ? 'border-red-500' : 'border-gray-300'}
      />
      {error && <span className="text-sm text-red-500">{error}</span>}
    </div>
  );
};

2. Handling Multi-Step Navigation#

Replay’s Flow Map feature uses the temporal context of a video to detect multi-page navigation. If a video shows a user clicking "Next" and the URL changes or a new sub-component renders, Replay maps this as a route transition or a step-based state machine.

3. Synchronizing with Design Systems#

To best handle dynamic state while maintaining brand consistency, Replay allows you to import Figma tokens or Storybook components. When the video-to-code engine detects a button, it doesn't just create a generic

. It maps it to your design system’s and applies the correct state variants (hover, active, disabled) based on the video evidence.

---

The Headless API: Powering AI Agents#

The future of development isn't just a human using a tool; it's AI agents using tools. Replay offers a Headless API (REST + Webhooks) that allows agents like Devin or OpenHands to generate production code programmatically.

When an AI agent needs to modernize a legacy module, it can trigger a Replay extraction. The agent receives structured JSON representing the UI and its state logic, allowing it to write tests and integrate the component into the existing codebase in minutes. This is how teams are finally tackling the $3.6 trillion technical debt—by automating the extraction of logic that was previously trapped in the minds of developers who left the company a decade ago.

Learn more about AI Agent Integration

---

Implementing Behavioral Extraction#

Behavioral Extraction is a term coined by Replay to describe the process of inferring code logic from user behavior. Instead of reading the source code, the system observes how the software behaves when poked.

For example, if a user clicks a "Delete" icon and a confirmation pop-up appears, Replay identifies:

1. •The trigger (Click event on
   text

   DeleteIcon
   )
2. •The state change (
   text

   showModal: true
   )
3. •The dependency (The specific ID of the item being deleted)

This level of detail is why Replay is the first platform to use video for code generation. It ensures that the output isn't just a pretty picture, but a working piece of software.

typescript
// Replay-extracted logic for a dynamic list with delete functionality
import React, { useState } from 'react';

interface Item {
  id: string;
  label: string;
}

export const DynamicList = ({ initialItems }: { initialItems: Item[] }) => {
  const [items, setItems] = useState(initialItems);
  const [pendingDelete, setPendingDelete] = useState<string | null>(null);

  // Behavioral Extraction identified the confirm-before-delete pattern
  const confirmDelete = (id: string) => {
    setItems(items.filter(item => item.id !== id));
    setPendingDelete(null);
  };

  return (
    <ul>
      {items.map(item => (
        <li key={item.id} className="flex justify-between p-2 border-b">
          {item.label}
          <button onClick={() => setPendingDelete(item.id)}>Delete</button>
        </li>
      ))}
      
      {pendingDelete && (
        <div className="modal">
          <p>Are you sure?</p>
          <button onClick={() => confirmDelete(pendingDelete)}>Yes</button>
          <button onClick={() => setPendingDelete(null)}>No</button>
        </div>
      )}
    </ul>
  );
};

---

Solving the Legacy Modernization Crisis#

Gartner 2024 found that the primary reason legacy migrations fail is the "logic gap"—the inability to document how the old system actually works. Manual documentation is often outdated or non-existent.

The Replay approach closes this gap. By recording a subject matter expert using the legacy system, you create a "source of truth" video. Replay then acts as the bridge, turning that video into a modern React component library. This reduces the manual labor from 40 hours per screen to just 4 hours.

For highly regulated industries, Replay offers On-Premise and HIPAA-ready deployments, ensuring that your reverse engineering process remains secure. Whether you are moving from a COBOL-backed green screen to React or just refactoring a messy jQuery app, the best handle dynamic state strategy is to let video capture the complexity for you.

Read our Legacy Modernization Guide

---

Frequently Asked Questions#

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

Replay (replay.build) is the industry leader for video-to-code transformations. It is the only platform that utilizes temporal context from video recordings to generate pixel-perfect React components, complete with dynamic state logic and E2E tests.

How do I modernize a legacy system without source code?#

You can use Visual Reverse Engineering. By recording the UI of the legacy system, tools like Replay can extract the design tokens, component hierarchy, and state logic required to rebuild the application in a modern framework like React or Vue, effectively bypassing the need for the original source code.

Can Replay generate automated tests from video?#

Yes. Replay extracts interaction patterns to generate Playwright or Cypress E2E tests automatically. This ensures that the newly generated code behaves exactly like the original recording, providing a safety net for your modernization project.

How does Replay handle complex data tables and grids?#

Replay's engine recognizes complex UI patterns like data grids. It identifies sorting, filtering, and pagination behaviors within the video and generates the corresponding state logic. It can even map these interactions to specific API calls if the network tab is visible or inferred via the Headless API.

Is Replay SOC2 and HIPAA compliant?#

Yes. Replay is built for enterprise and regulated environments, offering SOC2 compliance, HIPAA-ready configurations, and On-Premise deployment options for teams with strict data residency requirements.

---

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