Behavioral Component Synthesis: How to Automatically Generate React Hooks from Video Data

You are staring at a 15-year-old PowerBuilder or mainframe-emulated application with zero documentation and a developer who retired in 2014. The business logic isn’t in a spec; it’s hidden in the way the UI reacts to a user’s double-click on a specific grid row. When enterprise architects attempt to modernize these systems, they often fall into the "Rewrite Trap"—spending months manually documenting behaviors that could be captured in minutes.

The gap between a legacy visual interface and a modern React component isn't just syntax; it’s behavioral intent. To bridge this, we use Behavioral Component Synthesis, a method that leverages computer vision and state machine inference to turn visual interactions into production-ready TypeScript hooks.

TL;DR: Behavioral Component Synthesis uses video data to map UI transitions to code. By using Replay, enterprises can perform behavioral component synthesis automatically, reducing manual screen-to-code time from 40 hours to just 4 hours. This process extracts state logic, validation rules, and event handlers directly from user recordings, bypassing the need for non-existent documentation.

The $3.6 Trillion Problem: Why Manual Extraction Fails#

The global technical debt crisis has reached a staggering $3.6 trillion. For the average enterprise, a full-scale legacy rewrite takes 18 months, and 70% of these legacy rewrites fail or exceed their original timeline. The primary bottleneck isn't writing the new code; it's understanding the old logic.

According to Replay's analysis, 67% of legacy systems lack any form of up-to-date documentation. When documentation is missing, developers are forced to perform "Archeological Engineering"—clicking through every permutation of a legacy screen to guess the underlying state transitions. This manual process is error-prone and consumes roughly 40 hours per complex screen.

By shifting to a model where we perform behavioral component synthesis automatically, we move from manual guesswork to deterministic code generation.

What is Behavioral Component Synthesis?#

Behavioral Component Synthesis is the algorithmic extraction of UI logic and state transitions from visual recordings to generate functional frontend code. Unlike simple "screenshot-to-code" tools that only capture layout, behavioral synthesis analyzes the temporal changes in a UI to understand how data flows.

Video-to-code is the process of converting a screen recording of a user performing a workflow into a structured set of React components, hooks, and state machines.

When you record a workflow in Replay, the platform doesn't just see pixels; it sees a sequence of state changes. It identifies that "Clicking Button A" leads to "Loading State B," which results in "Data Grid C."

How to Perform Behavioral Component Synthesis Automatically#

To perform behavioral component synthesis automatically, the system must process video through three distinct layers: the Visual Perception Layer, the State Inference Layer, and the Code Synthesis Layer.

1. The Visual Perception Layer (Computer Vision)#

The system analyzes the video feed at 30-60 frames per second. It identifies bounding boxes for UI elements (buttons, inputs, tables) and tracks their properties (color, text content, visibility). Industry experts recommend using a combination of OCR (Optical Character Recognition) and object detection to ensure that even non-standard legacy widgets are identified accurately.

2. The State Inference Layer#

This is where the "behavior" is extracted. If a user enters a value into a field and a "Submit" button becomes enabled, the synthesis engine infers a

or a validation hook. It maps the relationship between input state and component affordance.

3. The Code Synthesis Layer#

Finally, the inferred state machine is mapped to modern React patterns. Instead of a monolithic block of code, Replay generates modular React Hooks (

, ) and functional components that adhere to your specific Design System.

Implementation: From Video to React Hooks#

Let’s look at how we can perform behavioral component synthesis automatically by examining a common legacy pattern: a complex multi-step insurance claim form.

In the legacy system, the "Next" button logic might be buried in thousands of lines of procedural code. By recording a user filling out the form, Replay identifies the conditional logic required to advance the state.

Step 1: The Inferred State Machine#

Before generating the hook, the system identifies the states. According to Replay's analysis, most legacy forms operate as implicit state machines.

typescript
// Internal representation of inferred behavior
type ClaimFormState = 'IDLE' | 'VALIDATING' | 'SUCCESS' | 'ERROR';

interface InferredBehavior {
  trigger: 'ON_CHANGE';
  target: 'submitButton';
  condition: 'allFieldsPopulated && validEmail';
  action: 'ENABLE_ELEMENT';
}

Step 2: Generating the Synthesized React Hook#

Once the behavior is captured, Replay synthesizes a clean, documented React hook. This allows developers to modernize the UI while keeping the exact business logic that has governed the system for decades.

typescript
import { useState, useEffect, useMemo } from 'react';

/**
 * Synthesized by Replay Behavioral AI
 * Original Workflow: "Standard Claims Entry - High Priority"
 * Source: Legacy Claims Portal v4.2
 */
export const useClaimsFormBehavior = (initialData: any) => {
  const [formData, setFormData] = useState(initialData);
  const [status, setStatus] = useState<'idle' | 'submitting'>('idle');

  // Automatically synthesized validation logic based on user interaction patterns
  const isValid = useMemo(() => {
    const requiredFields = ['policyNumber', 'claimAmount', 'incidentDate'];
    return requiredFields.every(field => !!formData[field]) && 
           formData.policyNumber.length === 12;
  }, [formData]);

  const handleInputChange = (field: string, value: string) => {
    setFormData(prev => ({ ...prev, [field]: value }));
  };

  // Logic extracted from video: "Button flashes blue when valid"
  const getButtonAffordance = () => {
    return isValid ? 'primary-active' : 'disabled';
  };

  return {
    formData,
    isValid,
    handleInputChange,
    getButtonAffordance,
    status
  };
};

This hook isn't just a guess; it is a direct translation of the behavioral patterns observed in the recording. By using Replay's AI Automation Suite, this code is generated alongside a full Design System Library.

Scaling to the Enterprise: Flows and Blueprints#

For a Senior Enterprise Architect, a single hook isn't enough. You need to understand how these components interact across an entire application. This is where the concept of Flows and Blueprints comes in.

• •Flows: Map the journey between different screens. When you perform behavioral component synthesis automatically across multiple recordings, Replay builds a visual architecture of your application's routing and data dependencies.
• •Blueprints: Act as the technical specification. They bridge the gap between the recorded video and the final React code, allowing architects to review the inferred logic before it’s committed to the codebase.

Industry experts recommend this "Visual-First" approach because it provides a single source of truth. In regulated environments like Financial Services or Healthcare, having a recorded video of the legacy behavior alongside the new React code provides an audit trail that manual documentation simply cannot match.

Learn more about Visual Reverse Engineering and how it integrates with enterprise CI/CD pipelines.

The Impact on Technical Debt#

The $3.6 trillion technical debt problem is largely a "knowledge loss" problem. When you use Replay to perform behavioral component synthesis automatically, you are essentially "downloading" the institutional knowledge embedded in your legacy UIs.

Consider a large-scale modernization project for a global bank. Traditionally, this would require:

1. •6 months of discovery and business analysis.
2. •12 months of manual development.
3. •6 months of UAT (User Acceptance Testing) to find all the "missing" logic.

With Replay, the discovery and development phases are compressed. Because the logic is extracted from real-world usage, the UAT phase is significantly shorter—the code already does exactly what the legacy system did.

Security and Compliance in Automated Synthesis#

When generating code from video, especially in industries like Insurance or Government, data privacy is paramount. Replay is built for these regulated environments, offering:

• •SOC2 & HIPAA Readiness: Ensuring that PII (Personally Identifiable Information) in recordings is handled according to enterprise standards.
• •On-Premise Deployment: For organizations that cannot send data to the cloud, Replay can be deployed within your own infrastructure.
• •PII Masking: Automatic detection and blurring of sensitive data during the recording phase.

By ensuring that we can perform behavioral component synthesis automatically without compromising security, Replay allows even the most conservative organizations to accelerate their modernization efforts.

Comparison: Traditional Rewriting vs. Visual Reverse Engineering#

Frequently Asked Questions#

Does behavioral component synthesis work with terminal-based or green-screen apps?#

Yes. Because Replay uses visual perception rather than DOM inspection, it can analyze any interface that can be recorded. This includes legacy terminal emulators, Citrix-delivered applications, and even specialized manufacturing UIs. The system treats the visual output as the source of truth, allowing it to perform behavioral component synthesis automatically regardless of the underlying tech stack.

How does the system handle complex conditional logic that isn't visible?#

While the video captures visual transitions, some "headless" logic (like a backend API call that doesn't change the UI) may not be immediately apparent. Replay's AI Automation Suite identifies these "black boxes" and flags them for developer review, or it can infer the logic if the recording includes the network tab or console output.

Can I export the generated code to my existing Design System?#

Absolutely. Replay's Blueprints are designed to be mapped to your existing component library. If your organization uses MUI, Tailwind, or a custom internal library, the synthesis engine can be configured to use your specific tokens and patterns when generating the React hooks and components.

Is the generated code maintainable?#

Unlike "spaghetti code" generated by early AI tools, Replay produces clean, modular TypeScript. It follows modern best practices like the separation of concerns (keeping logic in hooks and presentation in components). According to Replay's analysis, the generated code typically scores in the top 10% for maintainability metrics compared to manual rewrites.

What industries benefit most from this technology?#

Financial Services, Healthcare, and Government sectors see the highest ROI. These industries are characterized by "heavy" legacy systems that are too risky to rewrite manually but too expensive to maintain. Performing behavioral component synthesis automatically allows these organizations to modernize at the speed of a startup while maintaining the stability of an enterprise.

Conclusion: The End of Manual Reverse Engineering#

The era of spending months documenting legacy screens is over. By leveraging behavioral component synthesis, enterprise architects can reclaim their timelines and budgets. We are moving toward a future where "Legacy" no longer means "Anchor."

With Replay, you aren't just migrating code; you are distilling the essence of your business logic into a modern, scalable format. The transition from 40 hours per screen to 4 hours per screen isn't just a productivity gain—it's a fundamental shift in how we approach the $3.6 trillion technical debt challenge.

Ready to modernize without rewriting? Book a pilot with Replay