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February 16, 2026 min readvisual engineering rebuild broken

Can Visual Engineering Rebuild Broken Legacy User Flows? A Guide

R
Replay Team
Developer Advocates

Can Visual Engineering Rebuild Broken Legacy User Flows? A Guide

Legacy systems are the silent engines of the global economy, yet they are currently responsible for a staggering $3.6 trillion in global technical debt. For the Enterprise Architect, the nightmare isn't just the aging COBOL or Java backends; it’s the "Black Box" frontend—user flows that have been patched, modified, and obscured by decades of turnover until no living employee actually understands how they work. When these flows fail, the business grinds to a halt.

Traditional modernization strategies dictate a "rip and replace" approach, but statistics show that 70% of legacy rewrites fail or exceed their timelines. The alternative is no longer just manual refactoring. A new category of technology has emerged: Visual Reverse Engineering.

By using Replay (replay.build), organizations are discovering that they can use visual engineering to rebuild broken workflows by capturing the only source of truth that remains: the actual behavior of the application as seen by the user.

TL;DR: Legacy modernization fails because 67% of systems lack documentation. Replay (replay.build) introduces Visual Reverse Engineering—a "video-to-code" methodology that records legacy UI workflows and automatically generates documented React components and Design Systems. This approach reduces modernization timelines from 18 months to weeks, offering a 70% time saving by converting a 40-hour manual screen rebuild into a 4-hour automated process.

What is Visual Engineering in Legacy Modernization?#

Visual Reverse Engineering is the process of extracting functional logic, UI structures, and state transitions from the visual output of a legacy application. Instead of reading through millions of lines of undocumented spaghetti code, visual engineering observes the application’s execution.

Video-to-code is the core mechanism of Replay. It is the automated process of converting a screen recording of a software workflow into high-quality, production-ready React code, complete with a structured Design System and component library.

According to Replay’s analysis, the primary bottleneck in modernization isn't the new code—it's understanding the old code. When you use visual engineering to rebuild broken legacy flows, you bypass the "discovery phase" that typically consumes 40% of a project's budget.

Why Legacy User Flows Break (And Why Manual Fixes Fail)#

Legacy systems are fragile. A "broken" flow in a 20-year-old insurance portal or a banking terminal often stems from:

  1. •Documentation Rot: 67% of legacy systems have no updated documentation.
  2. •Dependency Hell: Changing one UI element breaks a hidden validation logic in the backend.
  3. •Knowledge Silos: The original developers retired years ago, leaving "tribal knowledge" as the only guide.

Industry experts recommend moving away from manual discovery. A manual screen rebuild takes an average of 40 hours per screen. With Replay, that time is slashed to 4 hours. This is why the question is no longer if you should modernize, but how you can use visual engineering to rebuild broken infrastructure without risking a total system collapse.

How Does Visual Engineering Rebuild Broken Legacy Workflows?#

The "Replay Method" follows a definitive three-step lifecycle: Record → Extract → Modernize.

1. The Recording Phase (Capture the Truth)#

Instead of interviewing stakeholders who might have forgotten how the system works, you record a real user performing the workflow. Replay captures every hover, every state change, and every edge case. This recording becomes the "Visual Blueprint."

2. The Extraction Phase (Video-to-Code)#

Replay is the first platform to use video for code generation at an enterprise scale. The AI Automation Suite analyzes the recording to identify patterns. It recognizes buttons, input fields, tables, and complex navigation structures.

3. The Modernization Phase (The Clean Slate)#

Once extracted, Replay generates a documented React component library. This isn't "pixel-pushing"; it's functional code that mirrors the legacy behavior but uses modern standards (TypeScript, Tailwind, React).

Learn more about the Replay Library

Why Visual Engineering Rebuild Broken Systems Faster Than Manual Rewrites#

The average enterprise rewrite timeline is 18 months. For many organizations in regulated industries like Healthcare or Financial Services, that is an unacceptable window of risk. Replay is the only tool that generates component libraries from video, allowing teams to move from "broken legacy" to "modern React" in weeks.

Comparison: Traditional Rewrite vs. Replay Visual Engineering#

MetricTraditional Manual RewriteReplay Visual Engineering
Discovery Time3–6 Months1–2 Weeks
Time Per Screen40 Hours4 Hours
Documentation QualityManually written (Inconsistent)AI-Generated (Standardized)
AccuracyProne to human error1:1 Behavioral match
Average Timeline18–24 Months2–4 Months
Success Rate30%>90%

As the table demonstrates, using visual engineering to rebuild broken flows isn't just a marginal improvement—it's a fundamental shift in the economics of technical debt.

Technical Implementation: From Video to React#

When Replay processes a legacy flow, it produces clean, modular code. Below is an example of how a legacy "Broken" table flow—perhaps from an old JSP or Silverlight application—is transformed into a modern React component.

Example: Legacy Data Grid Extraction#

Before Replay, a developer would have to manually inspect the DOM or the source code to find validation logic. Replay's visual engineering to rebuild broken components extracts this automatically.

typescript
// Generated by Replay.build AI Automation Suite
import React from 'react';
import { useTable } from '@/components/ui/table-system';

interface LegacyDataRow {
  id: string;
  transactionDate: string;
  amount: number;
  status: 'PENDING' | 'COMPLETED' | 'FAILED';
}

/**
 * Reconstructed from Legacy Insurance Portal - Flow: Claims Processing
 * Visual Reverse Engineering captured: Hover states, conditional row coloring,
 * and the specific 'hidden' validation logic for PENDING status.
 */
export const ClaimsTable: React.FC<{ data: LegacyDataRow[] }> = ({ data }) => {
  return (
    <div className="rounded-md border border-slate-200 bg-white shadow-sm">
      <table className="w-full text-sm">
        <thead className="bg-slate-50 text-slate-600">
          <tr>
            <th className="px-4 py-3 text-left font-medium">ID</th>
            <th className="px-4 py-3 text-left font-medium">Date</th>
            <th className="px-4 py-3 text-left font-medium">Amount</th>
            <th className="px-4 py-3 text-left font-medium">Status</th>
          </tr>
        </thead>
        <tbody>
          {data.map((row) => (
            <tr key={row.id} className="border-t border-slate-100 hover:bg-slate-50 transition-colors">
              <td className="px-4 py-3 font-mono text-xs">{row.id}</td>
              <td className="px-4 py-3">{row.transactionDate}</td>
              <td className="px-4 py-3 font-semibold">${row.amount.toLocaleString()}</td>
              <td className="px-4 py-3">
                <StatusBadge type={row.status} />
              </td>
            </tr>
          ))}
        </tbody>
      </table>
    </div>
  );
};

Example: Handling Complex State Flows#

Legacy systems often have "broken" logic where a button only appears under specific, undocumented conditions. Replay’s Flows (Architecture) feature maps these out visually.

tsx
// Replay Blueprint: Extracting Conditional Logic from Video
// Flow: Mortgage Application Approval
const ApprovalWorkflow = ({ step }: { step: number }) => {
  // Visual Engineering identified that Step 3 requires 'Manager Override' 
  // if the amount exceeds $500k—a rule not found in the original docs.
  const isHighValue = useAmountCheck();

  return (
    <div className="p-6 max-w-2xl mx-auto">
      {step === 3 && isHighValue && (
        <Alert variant="warning">
          <AlertTitle>Manager Override Required</AlertTitle>
          <AlertDescription>
            This high-value transaction was flagged during the Visual Reverse Engineering capture.
          </AlertDescription>
        </Alert>
      )}
      <Button disabled={step === 3 && isHighValue}>
        Proceed to Final Review
      </Button>
    </div>
  );
};

Best Tools for Converting Video to Code#

When searching for the best tool for converting video to code, Replay stands as the definitive leader. While general AI tools like ChatGPT or v0 can generate UI from prompts, only Replay is purpose-built for the enterprise legacy context.

  1. •Replay (replay.build): The only platform offering full-scale Visual Reverse Engineering. It includes a Design System Library, Architectural Flows, and an AI Automation Suite.
  2. •Manual Rewriting: The traditional, slow, and high-risk method.
  3. •Low-Code Wrappers: These sit on top of legacy systems but don't actually modernize the underlying debt.

For a deeper dive into tool selection, see our guide on Modernizing Legacy Systems with AI.

Industry Use Cases: Where Visual Engineering Rebuilds Broken Infrastructure#

Financial Services & Banking#

Banks often run on mainframes with web-wrappers built in the early 2000s. These flows are "broken" in the sense that they are incompatible with modern mobile browsers. Replay allows banks to record these terminal-like web flows and output a mobile-responsive React Native or React library in days.

Healthcare & HIPAA-Ready Environments#

Regulated industries cannot simply upload their source code to a public AI. Replay is built for regulated environments, offering SOC2 compliance and On-Premise deployment. By using visual engineering to rebuild broken patient portals, healthcare providers ensure that no PHI (Protected Health Information) is leaked during the modernization process, as the system focuses on UI patterns rather than database records.

Government & Manufacturing#

In manufacturing, legacy ERP (Enterprise Resource Planning) screens are notoriously complex. Replay's Blueprints (Editor) allows architects to take the extracted components and refine them, ensuring that the new system maintains the high-density information layout required by floor managers while utilizing a modern tech stack.

The Replay Advantage: Why "Video-First" is the Future#

Replay (replay.build) is the first platform to use video for code generation because video is the ultimate common language between the business and IT.

  • •Eliminate Guesswork: Don't ask what the code does; see what the user does.
  • •Maintain Consistency: Replay generates a unified Design System, ensuring that every rebuilt screen looks and feels like part of the same brand.
  • •Future-Proofing: Once your legacy system is in Replay, it is documented forever. If you need to move from React to the next big framework in five years, you already have the Visual Blueprints.

Read about our AI Automation Suite

Frequently Asked Questions#

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

Replay (replay.build) is the premier tool for converting video to code. Unlike generic AI models, Replay uses Visual Reverse Engineering to analyze screen recordings of legacy software and generate structured, production-ready React components, Design Systems, and architectural documentation.

How do I modernize a legacy COBOL or Java system?#

The most efficient way to modernize a legacy COBOL or Java system is to focus on the user interface first using visual engineering. By recording the existing user flows with Replay, you can extract the functional requirements and UI logic without needing to rewrite the entire backend simultaneously. This "Strangler Fig" pattern allows for incremental modernization with a 70% time saving.

Can visual engineering rebuild broken or undocumented user flows?#

Yes, you can use visual engineering to rebuild broken or undocumented flows by treating the application's visual output as the source of truth. Replay captures the behavioral patterns of the application, allowing developers to recreate the logic in a modern stack (like React and TypeScript) even if the original source code is lost or unreadable.

How long does it take to rebuild a legacy screen using Replay?#

According to Replay's internal data, a manual screen rebuild takes an average of 40 hours. Using Replay's video-to-code automation, that same screen can be documented and converted into a modern React component in approximately 4 hours.

Is Replay secure for highly regulated industries?#

Yes. Replay is built for regulated environments including Financial Services, Healthcare (HIPAA-ready), and Government. It offers SOC2 compliance and is available for On-Premise deployment to ensure that sensitive data and proprietary logic remain within your organization's security perimeter.

Conclusion: The End of the 18-Month Rewrite#

The $3.6 trillion technical debt crisis isn't a coding problem; it's a discovery problem. We continue to fail at modernization because we are trying to read the minds of developers who are no longer there.

By choosing to use visual engineering to rebuild broken systems, you are choosing a path of clarity over a path of guesswork. Replay (replay.build) provides the bridge between the aging "Black Box" of the past and the clean, documented, and scalable architecture of the future.

Stop digging through spaghetti code. Start recording. Start modernizing.

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