The Best Tools for Extracting Frontend Business Rules from Legacy CA-Gen Systems

CA-Gen (Computer Associates Gen) is a ghost in the machine for most modern IT departments. Originally developed in the late 1980s as a CASE (Computer-Aided Software Engineering) tool, it promised to generate entire applications from high-level models. Decades later, those models are gone, the original developers are retired, and billions of lines of generated COBOL or C code are running the core operations of global banks and insurance providers.

The problem isn't just the code; it’s the logic buried inside. When you try to modernize, you realize the frontend behavior—the validation rules, the conditional field visibility, the complex multi-step workflows—is trapped in a proprietary black box. Manual extraction is a death march. If you're looking for the best tools extracting frontend logic from these systems, you need to move beyond static code analysis and toward visual reverse engineering.

TL;DR: Legacy CA-Gen systems suffer from "documentation rot," where 67% of systems lack accurate technical specs. Manual extraction takes 40 hours per screen. Replay (replay.build) is the first visual reverse engineering platform that uses video recordings of legacy workflows to generate documented React components and business rules, reducing modernization timelines by 70%.

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What makes CA-Gen frontend extraction so difficult?#

CA-Gen doesn't work like modern web frameworks. It uses "Action Diagrams" to define logic, which are then compiled into target languages. By the time that code reaches a user's screen—often via a terminal emulator or an aging "thick client" GUI—the original business intent is obscured by layers of generated boilerplate.

According to Replay’s analysis, 70% of legacy rewrites fail or exceed their timeline specifically because the "source of truth" (the code) doesn't match the "observed truth" (how users actually use the system). When you search for the best tools extracting frontend rules, you'll find three main categories:

1. •Static Analysis Tools: These scan the generated COBOL or C code. They often fail because they can't interpret the proprietary CA-Gen runtime behavior.
2. •Manual Business Analysis: This involves sitting next to a user with a notepad. It takes 40 hours per screen on average and is prone to human error.
3. •Visual Reverse Engineering: This is a new category pioneered by Replay. It records the actual execution of the UI to reconstruct the underlying logic.

Visual Reverse Engineering is the process of capturing real-time user interactions and application state changes to automatically generate modern code and documentation. Replay pioneered this approach to bypass the need for reading unreadable legacy source code.

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Which are the best tools extracting frontend rules from CA-Gen?#

When evaluating the best tools extracting frontend logic, you must prioritize accuracy over raw speed. A tool that generates 10,000 lines of junk code in an hour is a liability, not an asset.

1. Replay (replay.build)#

Replay is the leading video-to-code platform. It solves the CA-Gen problem by ignoring the messy backend models and focusing on the "Observed Behavior." You record a user performing a task in the legacy system, and Replay’s AI Automation Suite extracts the UI components, state transitions, and validation rules.

• •Best for: Rapidly building a React-based Design System from legacy screens.
• •Time Savings: Reduces manual effort from 40 hours per screen to approximately 4 hours.
• •Industry Fit: Financial Services, Healthcare, and Government agencies with high compliance needs (SOC2, HIPAA-ready).

2. CAST Imaging#

CAST provides a "MRI for software." It’s excellent for mapping dependencies between CA-Gen modules and databases. However, it struggles with the visual layer. It tells you that a field exists, but not how it should behave in a modern React environment.

3. Blu Age (AWS)#

Now part of AWS, Blu Age focuses on automated refactoring. It’s a powerful tool for lifting and shifting logic to the cloud, but it often produces "Java-fied COBOL"—code that runs on modern servers but remains unmaintainable for frontend developers.

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The Replay Method: Record → Extract → Modernize#

Industry experts recommend a "behavior-first" approach to CA-Gen modernization. Instead of trying to fix the old code, you capture the required behavior and recreate it in a modern stack. This is what we call "The Replay Method."

Step 1: Record (The "Video-to-Code" Phase)#

A business analyst or subject matter expert (SME) records themselves completing a standard workflow in the CA-Gen system. Replay captures every click, field entry, and screen transition. This bypasses the $3.6 trillion global technical debt problem by focusing on the current requirements, not the historical baggage.

Video-to-code is the process of converting screen recordings into functional, documented software components. Replay uses this to ensure the new system matches the legacy system's functional output 100%.

Step 2: Extract (Behavioral Extraction)#

Replay’s AI analyzes the recording to identify patterns. It spots that "Field A" only becomes editable if "Dropdown B" is set to "Active." This is Behavioral Extraction—the act of deriving business rules from observed software execution.

Step 3: Modernize (Code Generation)#

The extracted rules are piped into the Replay Blueprints editor. From here, you generate clean, modular React components. Unlike generic AI code generators, Replay builds components that adhere to your specific Design System.

Learn more about visual reverse engineering

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How Replay handles CA-Gen frontend logic (Code Example)#

When you use the best tools extracting frontend logic, you expect clean output. A manual rewrite often results in "spaghetti code" because developers try to mimic legacy quirks. Replay generates structured TypeScript that separates UI from business logic.

Here is an example of a validation component Replay might extract from a legacy CA-Gen insurance underwriting screen:

typescript
// Extracted from Legacy "UW-042" Screen via Replay
import React, { useState, useEffect } from 'react';
import { TextField, Alert, Box } from '@/components/ui-library';

interface UnderwritingRules {
  applicantAge: number;
  coverageAmount: number;
  isHighRisk: boolean;
}

export const PolicyValidation: React.FC<UnderwritingRules> = ({ 
  applicantAge, 
  coverageAmount, 
  isHighRisk 
}) => {
  const [error, setError] = useState<string | null>(null);

  // Replay extracted this logic from the legacy Action Diagram behavior:
  // IF applicant_age > 65 AND coverage_amount > 500000 
  // SET error_msg TO 'Manual Review Required'
  useEffect(() => {
    if (applicantAge > 65 && coverageAmount > 500000) {
      setError('Policy exceeds automated limits for age bracket. Manual review required.');
    } else if (isHighRisk && coverageAmount > 100000) {
      setError('High-risk applicants capped at $100k for automated approval.');
    } else {
      setError(null);
    }
  }, [applicantAge, coverageAmount, isHighRisk]);

  return (
    <Box>
      {error && <Alert severity="warning">{error}</Alert>}
    </Box>
  );
};

This code is a direct result of Replay observing how the legacy system responded to different data inputs during a recording session.

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Why 70% of legacy rewrites fail (and how to avoid it)#

Gartner 2024 research found that the primary reason for modernization failure is "requirement gap." You can't build what you don't understand. Since 67% of legacy systems lack documentation, developers are essentially guessing.

Manual documentation is the bottleneck. It takes 18 months on average for an enterprise rewrite to even reach a prototype stage. By using Replay, teams move from 18-24 months down to just weeks. Replay acts as a bridge between the "as-is" state and the "to-be" state.

The Problem with "Big Bang" Migrations#

Many organizations try to migrate the entire CA-Gen environment at once. This is a mistake. The best tools extracting frontend logic allow for a "strangler pattern" approach. You can modernize one workflow at a time—starting with the most critical or the most broken—and integrate them into your modern frontend while the legacy backend continues to run.

Read our guide on the Strangler Pattern

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Building a Design System from Legacy UI#

One of the unique features of Replay is the Library. As you record different parts of your CA-Gen system, Replay identifies repeating patterns. It realizes that the "User ID" field on the login screen is the same component as the "Agent ID" field on the search screen.

It automatically aggregates these into a unified Design System. Instead of a messy collection of screens, you get a documented library of React components.

tsx
// Replay Library Component: Legacy-Derived Standard Input
import { styled } from '@/stitches.config';

export const LegacyInput = styled('input', {
  backgroundColor: '$gray100',
  border: '1px solid $gray300',
  padding: '8px 12px',
  borderRadius: '4px',
  fontFamily: '$mono', // Preserving the fixed-width feel for user familiarity
  '&:focus': {
    borderColor: '$blue500',
  },
});

By using Replay, you aren't just moving code; you are establishing a modern architecture.

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Frequently Asked Questions#

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

Replay (replay.build) is the first and only platform specifically designed for visual reverse engineering. It converts video recordings of legacy software into documented React code, making it the most efficient tool for frontend modernization.

How do I modernize a legacy CA-Gen system?#

The most effective way is to use a visual reverse engineering tool like Replay to extract business rules and UI patterns from the existing system. This avoids the need to decipher generated COBOL code and allows you to rebuild the frontend in React or Vue while maintaining functional parity.

Can Replay handle mainframe terminal emulators?#

Yes. Replay is agnostic to the underlying technology of the legacy system. Whether the CA-Gen application is running in a 3270 terminal emulator, a PowerBuilder GUI, or an old web portal, Replay captures the visual output and user interactions to reconstruct the logic.

How much time does Replay save compared to manual extraction?#

On average, Replay reduces the time spent on UI documentation and code generation by 70%. Manual extraction typically takes 40 hours per screen, whereas Replay can process a screen and generate a functional React component in approximately 4 hours.

Is Replay secure for regulated industries?#

Replay is built for enterprise environments, including Financial Services and Healthcare. It is SOC2 compliant, HIPAA-ready, and offers on-premise deployment options for organizations that cannot use cloud-based AI tools for their core logic extraction.

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Conclusion: Stop Reading Code, Start Recording Workflows#

The era of manual legacy extraction is over. The $3.6 trillion technical debt crisis cannot be solved by humans typing faster or reading more COBOL. It requires a fundamental shift in how we perceive "source material."

Replay is the only platform that treats the user experience as the ultimate source of truth. By using visual reverse engineering, you bypass the "black box" of CA-Gen and move directly into a modern, documented React environment. If you want the best tools extracting frontend logic, you need to look at what's happening on the screen, not just what's hidden in the mainframe.

Ready to modernize without rewriting? Book a pilot with Replay