Modernizing Air-Gapped Systems: On-Premise Tools for Sensitive Environments

The most dangerous systems in your enterprise are the ones you can’t see. In regulated industries—Financial Services, Healthcare, and Government—air-gapped systems represent the ultimate "black box." These systems are physically and logically isolated from the public internet for security, yet they are often the most critical pieces of infrastructure.

The paradox of the air-gap is that the very security measures designed to protect these systems also fossilize them. Because you cannot easily pipe data to cloud-based AI or modern SaaS modernization tools, these systems remain stuck in a cycle of manual maintenance, mounting technical debt, and "software archaeology."

TL;DR: Modernizing air-gapped systems no longer requires a multi-year "Big Bang" rewrite; by using on-premise visual reverse engineering, enterprises can extract documented React components and API contracts directly from legacy workflows in days rather than months.

The Air-Gap Modernization Trap#

When a system is air-gapped, the traditional modernization playbook breaks. You cannot use cloud-native assessment tools. You cannot easily outsource the work due to data residency and security clearances. You are left with two equally unappealing options:

1. •The Manual Rewrite: Developers spend months reverse-engineering COBOL, Java Swing, or PowerBuilder codebases that lack documentation.
2. •The "If It Ain't Broke" Stasis: You leave the system alone until the underlying hardware fails or the last developer who understands the logic retires.

Statistics show that 70% of legacy rewrites fail or exceed their timeline, and in air-gapped environments, that number often trends higher due to the friction of secure development. With a global technical debt load of $3.6 trillion, the cost of doing nothing is no longer zero—it's a compounding liability.

Why "Video as Source of Truth" Matters for Sensitive Data#

In a HIPAA-ready or SOC2 environment, you cannot simply upload your source code to a third-party LLM. However, the behavior of the application is the most accurate documentation you have.

Replay introduces a paradigm shift: Visual Reverse Engineering. Instead of reading 20-year-old spaghetti code, you record a real user performing a mission-critical workflow. Replay captures the state, the DOM changes, and the network calls locally.

💰 ROI Insight: Manual reverse engineering typically takes 40 hours per screen to document and prototype. With Replay’s visual extraction, that time is reduced to 4 hours per screen, representing a 90% reduction in labor costs for the assessment phase.

Technical Implementation: From Recording to React#

When working in an air-gapped environment, Replay runs on-premise. It hooks into the legacy application's runtime to extract the underlying business logic. Here is how a legacy form is transformed into a modern, typed React component without the developer ever needing to "guess" the original intent.

typescript
// Example: Replay-generated modern component from a legacy healthcare portal
// The logic below was extracted from a 2005-era Java Applet workflow.

import React, { useState, useEffect } from 'react';
import { Button, TextField, Alert } from '@/components/ui'; // From your Replay Library

interface PatientRecordProps {
  initialId: string;
  onUpdate: (data: any) => void;
}

export const PatientModernizationBridge: React.FC<PatientRecordProps> = ({ initialId, onUpdate }) => {
  const [patientData, setPatientData] = useState<any>(null);
  const [isSyncing, setIsSyncing] = useState(false);

  // Replay extracted this validation logic from the legacy 'validate_entry.inc' file
  const validateSymmetry = (val: number) => val > 0 && val < 100;

  const handleLegacySubmit = async (formData: any) => {
    setIsSyncing(true);
    try {
      // Replay generated this API contract based on recorded network traffic
      const response = await fetch(`/api/v1/legacy/patient/${initialId}`, {
        method: 'POST',
        body: JSON.stringify(formData),
      });
      if (response.ok) onUpdate(await response.json());
    } catch (err) {
      console.error("Modernization Bridge Error:", err);
    } finally {
      setIsSyncing(false);
    }
  };

  return (
    <div className="p-6 border rounded-lg shadow-sm">
      <h3 className="text-lg font-bold">Patient Data (Migrated)</h3>
      <TextField 
        label="Patient ID" 
        value={initialId} 
        disabled 
      />
      {/* Business logic preserved from legacy visual state */}
      <Button onClick={handleLegacySubmit} loading={isSyncing}>
        Sync to Legacy Backend
      </Button>
    </div>
  );
};

The 3-Step On-Premise Modernization Workflow#

Modernizing in a secure environment requires a structured, repeatable process that doesn't rely on external connectivity.

Step 1: Secure Recording (The "Black Box" Capture)#

In this phase, a subject matter expert (SME) performs their standard daily tasks within the air-gapped system. Replay records the session. Unlike a standard screen recording, Replay captures the metadata of the application: CSS selectors, state transitions, and API payloads.

⚠️ Warning: Ensure that PII (Personally Identifiable Information) is scrubbed. Replay’s on-premise deployment allows for local data masking before any analysis occurs, maintaining HIPAA compliance.

Step 2: Visual Extraction and Mapping#

The recorded "Flows" are fed into the Replay AI Automation Suite (running locally). The system identifies recurring UI patterns and maps them to your modern Design System (the "Library"). If the legacy system uses a specific multi-step validation for insurance claims, Replay extracts that logic as a functional requirement.

Step 3: Generating the Modern Stack#

Replay generates:

• •React Components: Clean, modular code that matches your design system.
• •API Contracts: Swagger/OpenAPI specs derived from legacy network calls.
• •E2E Tests: Playwright or Cypress tests that mirror the recorded user behavior.

typescript
// Example: Generated Playwright test to ensure parity with legacy behavior
import { test, expect } from '@playwright/test';

test('verify legacy parity for claim submission', async ({ page }) => {
  await page.goto('/modern/claims');
  
  // These selectors and actions were automatically mapped from the legacy recording
  await page.fill('#claim-id', 'REPLAY-12345');
  await page.click('text=Submit Claim');
  
  // Replay identified this specific legacy success state
  const status = page.locator('.status-badge');
  await expect(status).toHaveText('PROCESSED_SUCCESS');
});

Overcoming the Documentation Gap#

67% of legacy systems lack documentation. In air-gapped environments, the original architects are often gone, and the source code may be in a language that is no longer taught.

Traditional modernization requires "archaeology"—paying expensive consultants to read through thousands of lines of code to understand what the system actually does. Replay turns this on its head. By focusing on the user interface and the data output, you document the system based on its current utility, not its historical implementation.

📝 Note: This "outside-in" approach ensures that you don't migrate bugs or obsolete features that exist in the code but are never used by actual employees.

The Future of Regulated Modernization#

The goal of modernization isn't just to move to the cloud—it's to achieve agility. Even if your system must remain air-gapped for the next decade, it should not be a burden to maintain.

By using Replay, enterprises in manufacturing, telecom, and government are moving from "black box" legacy systems to fully documented, modern codebases in a fraction of the time. You aren't just rewriting; you are understanding.

Frequently Asked Questions#

How does Replay handle air-gapped security?#

Replay offers an On-Premise deployment model. All recording, analysis, and code generation happen within your secure network. No data ever leaves your firewall. We are SOC2 compliant and designed for HIPAA-regulated environments.

Can Replay handle non-web legacy systems (e.g., Mainframe, Desktop)?#

Yes. While Replay excels at web-based legacy systems (Java, .NET, PHP), our visual reverse engineering engine can be adapted to capture desktop workflows and translate them into modern web components by analyzing the visual state and network layer.

What is the average time savings?#

Our customers see an average of 70% time savings. A project that would typically take 18 months of manual effort can often be completed in 3 to 4 months using Replay’s automated extraction and blueprinting tools.

Does Replay preserve business logic?#

Yes. Replay captures the interaction between the UI and the backend. By observing how data changes in response to user input, Replay can reconstruct the functional logic in modern TypeScript, ensuring that "hidden" business rules are not lost during the transition.

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Ready to modernize without rewriting? Book a pilot with Replay - see your legacy screen extracted live during the call.