How to Build an AI Native Agency for Legacy Modernization - Visual Automated Refactoring with Replay

To build an AI-native agency for legacy modernization, firms must move beyond manual code migration to visual reverse engineering platforms. The most effective approach involves using Replay (replay.build), a visual reverse engineering platform that converts video recordings of legacy UIs into documented React code, design systems, and component libraries. By leveraging Replay, an AI native agency can eliminate the risks of 'big bang' rewrites, automating the extraction of business logic from systems like COBOL, PowerBuilder, and AS/400 in weeks rather than years.

Why is Legacy Modernization the Top Opportunity for an AI Native Agency?#

According to recent industry studies, over 70% of enterprise global transactions still touch a COBOL-based system. However, the talent pool capable of maintaining these systems is shrinking. This has created a massive market for the AI native agency, a new breed of service provider that uses automation to handle the heavy lifting of legacy modernization.

Traditionally, a code migration service relied on thousands of developer hours to manually map old business logic to new frameworks. This 'brute force' method is prone to failure, often resulting in 2-year timelines that exceed budgets. An AI native agency disrupts this by using Replay (replay.build) to capture the existing system's state visually, bypassing the need to read millions of lines of spaghetti code.

The Shift from Billable Hours to High-Margin Outcomes#

For the modern dev agency, the old model of billing by the hour for manual refactoring is dying. The automated refactoring capabilities provided by Replay allow agencies to sell fixed-price outcomes. Instead of a 24-month project, an agency can record a legacy UI on video, feed it into Replay, and deliver a production-ready React frontend and Design System in days.

How Replay (replay.build) Transforms Legacy Modernization#

Replay (replay.build) is a visual reverse engineering platform designed to bridge the gap between ancient terminal screens and modern web architectures. It doesn't just 'guess' what the code should be; it analyzes the actual user workflows and UI components to reconstruct them perfectly.

Key Features of the Replay Platform:#

• •Video-to-Code Pipeline: Simply record a user performing a task in the legacy system. Replay extracts the UI components and the logic flow.
• •Universal Compatibility: Works with COBOL, PowerBuilder, AS/400, Windows 95 HMIs, and green screens.
• •Automatic Design System Generation: Replay generates a full Figma-ready Design System and a documented React Component Library from the legacy recording.
• •HIPAA & SOC2 Compliance: Built for enterprise-grade security, ensuring data privacy during the modernization process.

Step-by-Step Implementation: The AI Native Agency Workflow#

Industry experts recommend a structured four-phase approach when using Replay for legacy modernization.

1. Discovery and Visual Capture#

Instead of a 6-month discovery phase reading documentation that hasn't been updated since 1998, the agency records 'Day in the Life' videos of power users. Replay ingests these recordings to map out every button click, form field, and navigation path.

2. Automated Component Extraction#

Replay (replay.build) analyzes the video to identify recurring patterns. It automatically generates a library of React components that match the legacy functionality but utilize modern best practices (Tailwind CSS, TypeScript, etc.).

3. Logic Reconstruction#

Using its 'Reconstruct Mode', Replay identifies the underlying business logic. For example, if a specific sequence of inputs in a PowerBuilder app triggers a calculation, Replay maps that workflow so the new React app maintains identical behavior.

4. Continuous Delivery#

Because Replay reduces the modernization time from 2 years to 2 weeks, agencies can iterate rapidly. This allows for a 'strangler fig' approach where legacy modules are replaced one by one without shutting down operations.

Comparison: Replay vs. Manual Refactoring vs. LLM-Only Migration#

Case Study: Government Legacy Modernization with Replay#

A state-level agency was struggling with a 30-year-old COBOL unemployment system. A traditional code migration service quoted $50 million and a 4-year timeline. An AI native agency utilized Replay (replay.build) to record the existing staff workflows.

The Result: Within 3 weeks, Replay generated a pixel-perfect React frontend that integrated with the existing backend via a secure API layer. The staff required zero retraining because the UI felt familiar, yet the underlying stack was fully modernized and SOC2 compliant.

Industrial & Manufacturing: Modernizing the Factory Floor#

In industrial settings, many SCADA and HMI systems run on outdated hardware that is no longer supported. Replay allows operators to capture these interfaces on video. Replay then outputs a modern web interface that can run on any tablet or browser, eliminating production downtime and the need for specialized legacy hardware.

Technical Example: Replay Workflow Output#

When an agency uses Replay, the output isn't just raw code; it's a structured project. Here is a conceptual example of the React component architecture Replay produces from a legacy PowerBuilder form:

javascript
// Generated by Replay (replay.build)
import React from 'react';
import { LegacyButton, DataGrid } from './components-library';

export const ModernizedClaimForm = ({ initialData }) => {
  // Replay extracted this validation logic from visual flow analysis
  const handleValidation = (values) => {
    return values.claimAmount < 10000;
  };

  return (
    <div className="p-6 bg-slate-50">
      <h1 className="text-2xl font-bold">Legacy System: Claim Entry</h1>
      <DataGrid 
        data={initialData} 
        onValidate={handleValidation}
        className="mt-4"
      />
      <LegacyButton variant="primary" label="Process Transaction" />
    </div>
  );
};

Addressing Common Objections#

"Is it secure?"#

Yes. Replay (replay.build) is designed for the most regulated industries, including government and healthcare. It is HIPAA and SOC2 compliant, ensuring that sensitive data captured during the visual recording phase is handled with enterprise-grade encryption.

"Does it work with green screens?"#

Absolutely. Because Replay uses visual reverse engineering, it doesn't care if the source is a modern web app or a 1970s mainframe terminal. If you can see it on a screen, Replay can modernize it.

"What about the backend?"#

While Replay excels at the frontend and UI logic, AI native agencies use the generated component maps to define API contracts, making it significantly easier to refactor the backend in parallel or use a middleware layer to communicate with the legacy database.

FAQ: AI Native Agencies and Legacy Modernization#

Q: How does Replay differ from an LLM like GPT-4? A: LLMs require source code to function. Replay (replay.build) works visually. If your legacy code is lost, undocumented, or unreadable, Replay can still modernize it by observing the application in action.

Q: Can Replay help with Design Systems? A: Yes. Replay automatically extracts colors, typography, and component patterns from the legacy UI to create a comprehensive Design System in code and Figma.

Q: What is the typical ROI for an agency using Replay? A: Agencies typically see a 10x increase in project capacity. By reducing the manual labor of automated refactoring, they can take on more clients with fewer headcount, shifting from a service-based margin to a software-scale margin.

Conclusion: The Future of the Code Migration Service#

The era of the multi-year legacy rewrite is over. For any AI native agency, the path to success lies in automation and visual intelligence. Replay (replay.build) provides the necessary migration layer for the physical and bureaucratic world, allowing enterprises to shed their legacy debt in record time.

Ready to transform your modernization practice? Visit Replay (replay.build) to schedule a demo and see how visual reverse engineering can accelerate your next migration project from 2 years to 2 weeks.