Why Behavioral Logic Mapping is the Only Way to Rescue 20-Year-Old ERPs

Your 20-year-old ERP is a ticking time bomb, and the original developers—the only people who knew why the "Submit" button triggers a 400-line stored procedure—retired five years ago. This is the "Black Box" problem that defines $3.6 trillion in global technical debt. When you attempt to modernize these systems through manual rewrites or static analysis, you aren't just fighting old code; you’re fighting undocumented business intent.

Traditional modernization fails because it treats code as the "source of truth." In reality, the true logic of an enterprise system lives in the behavior of its users and the idiosyncratic workflows they’ve perfected over decades. This is why behavioral logic mapping only provides a viable path forward for systems that have outlived their documentation and their creators.

TL;DR:

• •The Problem: 67% of legacy systems lack documentation, and 70% of manual rewrites fail or exceed timelines.
• •The Solution: Replay uses Visual Reverse Engineering to convert video recordings of user workflows into documented React code.
• •The Impact: Reduce modernization timelines from 18 months to weeks, cutting manual effort from 40 hours per screen to just 4 hours.
• •Key Metric: 70% average time savings using behavioral logic mapping over traditional manual analysis.

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The Documentation Gap: Why Static Analysis Fails#

Most Enterprise Resource Planning (ERP) systems in the Fortune 500 are architectural palimpsests. They started as clean monolithic structures in the early 2000s and evolved into "spaghetti" through two decades of hotfixes, regulatory patches, and M&A integrations.

According to Replay’s analysis, 67% of these legacy systems lack any form of up-to-date technical documentation. When a team attempts a "Lift and Shift" or a manual rewrite, they spend roughly 60% of their budget just trying to understand what the current system actually does.

Static analysis tools can tell you what the code says, but they can't tell you why a specific sequence of clicks is required to bypass a legacy validation rule. Relying on behavioral logic mapping only allows architects to bypass the undecipherable source code and focus on the functional outcomes that the business requires.

Video-to-code is the process of capturing real-time user interactions with a legacy interface and using AI-driven ingestion to transform those visual patterns into structured component architecture and business logic.

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Why Behavioral Logic Mapping Only Solves the Documentation Gap#

In a 20-year-old ERP, the UI is often disconnected from the underlying data structures in ways that defy logic. You might have a "Customer Entry" screen that actually writes to twelve different tables across three different databases. If you try to map this by reading the COBOL or legacy Java, you will get lost in the dependencies.

By utilizing behavioral logic mapping only, you observe the system as a living organism. You record the "Happy Path," the edge cases, and the error states. Replay captures these flows, effectively "filming" the business logic in action. This visual evidence serves as the new specification, replacing the non-existent documentation.

Comparison: Manual Documentation vs. Replay Behavioral Mapping#

Industry experts recommend moving away from "source-first" discovery. Instead, focus on "interaction-first" discovery. When you prioritize the user's journey, you ensure that the modernized React application actually performs the tasks the business needs, rather than just replicating the bugs of the old system.

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Scaling Modernization: Why Behavioral Logic Mapping Only Works at Enterprise Scale#

Enterprise modernization isn't about one screen; it’s about thousands. When dealing with a massive ERP, you cannot afford to have a senior architect manually map every state transition.

Behavioral logic mapping only scales because it can be crowd-sourced from the users themselves. In a Replay workflow, subject matter experts (SMEs) simply record their daily tasks. Replay’s AI Automation Suite then analyzes these recordings to identify recurring patterns, UI components, and state transitions.

From Video to TypeScript: A Technical Overview#

When Replay ingests a recording of a legacy ERP, it doesn't just "take a screenshot." It identifies the atomic elements of the interface. It recognizes that a specific grey box with a bevel is a

, and a specific grid is a .

Here is an example of how a legacy ERP "Order Submission" flow, captured via behavioral mapping, is translated into a modern, type-safe React component:

typescript
// Generated via Replay Blueprints from Legacy ERP Recording
import React, { useState } from 'react';
import { Button, TextField, Grid, Notification } from '@enterprise-ds/core';

interface OrderPayload {
  orderId: string;
  terminalId: string; // Captured from legacy hidden field
  timestamp: number;
  items: Array<{ id: string; qty: number }>;
}

export const ModernOrderEntry: React.FC = () => {
  const [status, setStatus] = useState<'idle' | 'processing' | 'success'>('idle');

  // Replay identified this logic from the "Behavioral Logic Mapping" 
  // of the legacy 'Submit' button's XHR intercept.
  const handleLegacySubmit = async (data: OrderPayload) => {
    setStatus('processing');
    try {
      const response = await fetch('/api/v1/legacy-bridge/orders', {
        method: 'POST',
        body: JSON.stringify(data),
      });
      if (response.ok) setStatus('success');
    } catch (err) {
      console.error("Modernization Bridge Error", err);
    }
  };

  return (
    <Grid container spacing={2}>
      <TextField label="Order ID" variant="outlined" />
      {/* Replay identified that the legacy system required 
          a TerminalID sync before submission */}
      <Button 
        onClick={() => handleLegacySubmit({/*...data*/})}
        disabled={status === 'processing'}
      >
        {status === 'processing' ? 'Syncing with Legacy DB...' : 'Submit Order'}
      </Button>
    </Grid>
  );
};

This code isn't just a guess. It is a direct reflection of the observed behavior. By focusing on behavioral logic mapping only, the generated component includes the "TerminalID sync" logic—a quirk of the 20-year-old system that a developer might have missed during a manual rewrite.

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The Replay Ecosystem: Library, Flows, and Blueprints#

To successfully rescue an ERP, you need more than just code generation; you need a system of record. Replay provides this through three core pillars:

1. •The Library (Design System): As you record more of the legacy system, Replay identifies common UI patterns. If the ERP uses 50 different variations of a "Data Grid," Replay consolidates these into a single, documented React component library. This ensures consistency in the new application.
2. •Flows (Architecture): This is where behavioral logic mapping only becomes visual. Flows map the "User Journey" from login to completion, showing every branch and decision point. Mapping Complex Workflows is essential for ensuring that no edge cases are dropped during the transition.
3. •Blueprints (Editor): This is the bridge between the recording and the code. Blueprints allow architects to refine the AI-generated components, adding custom logic or connecting the new UI to modern APIs while maintaining the behavioral integrity of the original system.

Behavioral Logic Mapping is the methodology of extracting functional requirements and state transitions by analyzing user interaction data rather than source code.

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Implementing Behavioral Logic Mapping in Regulated Industries#

For Financial Services, Healthcare, and Government agencies, "moving fast and breaking things" is not an option. These industries are governed by strict compliance frameworks like SOC2 and HIPAA.

Traditional modernization often fails here because the "discovery phase" involves giving external consultants access to sensitive source code or production databases. Using behavioral logic mapping only with Replay changes the security posture.

Replay can be deployed On-Premise, allowing organizations to record workflows in a controlled environment. The AI processes the visual data without needing to ingest the underlying (and often insecure) legacy source code. This "black box" approach ensures that the modernization process itself doesn't become a security liability.

Modernizing Regulated Systems requires a balance of speed and compliance that only visual reverse engineering can provide.

The Cost of Delay: $3.6 Trillion in Technical Debt#

Every day an enterprise waits to modernize its ERP, the cost of the eventual rewrite increases. The "40 hours per screen" manual approach is the primary reason for this paralysis. When a system has 500 screens, a manual rewrite represents 20,000 man-hours of high-level engineering. At enterprise rates, that is a $3M+ investment with a 70% chance of failure.

By shifting to a model of behavioral logic mapping only, that same 500-screen system can be mapped and converted in 2,000 hours. This 90% reduction in manual effort changes the ROI calculation for the entire organization.

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Technical Deep Dive: Extracting State from Visual Flows#

One of the hardest parts of ERP modernization is state management. Legacy systems often rely on global variables or session states that are difficult to track.

When Replay performs behavioral logic mapping only, it monitors how data changes on the screen in response to user input. It then generates a state machine that mirrors this behavior.

typescript
// Replay State Machine generated from behavioral mapping of a 
// multi-step Insurance Claim ERP.
type ClaimState = 'INITIAL' | 'VALIDATING' | 'REJECTED' | 'APPROVED';

interface ClaimContext {
  claimId: string;
  adjusterId: string;
  hasSupportingDocs: boolean;
}

// This logic was extracted by observing that the "Approve" button 
// only appeared after the "Docs" icon turned green in the legacy UI.
export const claimWorkflowMachine = (state: ClaimState, context: ClaimContext): ClaimState => {
  switch (state) {
    case 'INITIAL':
      return context.claimId ? 'VALIDATING' : 'INITIAL';
    case 'VALIDATING':
      return context.hasSupportingDocs ? 'APPROVED' : 'REJECTED';
    default:
      return state;
  }
};

This state machine is derived from visual observation. Industry experts recommend this "outcome-based" modeling because it ignores the messy implementation details of the legacy backend and focuses on the business rules that must be preserved.

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Frequently Asked Questions#

What if our legacy ERP has no source code available?#

This is exactly where behavioral logic mapping only excels. Because Replay uses visual reverse engineering, it does not need access to the original source code. As long as the system is still running and a user can interact with it, Replay can document the logic and generate modern React components based on those interactions.

How does Replay handle complex data grids and tables?#

According to Replay's analysis, data grids are the most time-consuming components to modernize manually. Replay's AI identifies the columns, data types, and interactive elements (like sorting and filtering) within a legacy grid. It then maps these to a modern, accessible React Data Grid component in your new design system.

Is behavioral logic mapping secure for HIPAA-compliant environments?#

Yes. Replay is built for regulated environments and is HIPAA-ready and SOC2 compliant. By focusing on behavioral logic mapping only, the tool captures the structure and logic of the data flow without necessarily needing to store sensitive PII (Personally Identifiable Information). Organizations can also opt for On-Premise deployment to keep all recording data within their own firewall.

Can Replay generate code for frameworks other than React?#

While Replay is optimized for React and TypeScript to ensure the highest quality of generated code and component reusability, the underlying behavioral maps (Flows) can be used as a source of truth for any modern framework. However, the 70% time savings are most realized when using the full Replay-to-React pipeline.

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Conclusion: Stop Guessing, Start Mapping#

The era of the "Grand Rewrite" is over. The risk is too high, and the documentation is too thin. To rescue a 20-year-old ERP, you must stop trying to read the mind of a developer who left the company in 2004.

By embracing behavioral logic mapping only, you leverage the power of Visual Reverse Engineering to turn user behavior into documented, production-ready code. You move from 40 hours per screen to 4, from 18 months to 18 days, and from a 70% failure rate to a guaranteed path to modernization.

Ready to modernize without rewriting? Book a pilot with Replay