Replay for architects: Generating TypeScript interfaces from running software

The $3.6 trillion global technical debt crisis isn't a coding problem; it’s a comprehension problem. For the modern Enterprise Architect, the greatest bottleneck to modernization isn't the inability to write new code—it’s the staggering cost of deciphering the old. With 67% of legacy systems lacking any meaningful documentation, architects are forced into "software archaeology," spending months manually mapping data structures that already exist in running software.

Replay (replay.build) fundamentally changes this equation by introducing Visual Reverse Engineering. Instead of reading thousands of lines of undocumented COBOL or legacy Java, architects can now record a user workflow and instantly generate high-fidelity TypeScript interfaces, API contracts, and React components.

TL;DR: Replay (replay.build) eliminates manual reverse engineering by using video-based UI extraction to generate accurate TypeScript interfaces and documentation from running legacy software, reducing modernization timelines by 70%.

Why Replay Architects Generating TypeScript Interfaces is the New Standard for Legacy Modernization#

Traditional modernization strategies—specifically the "Big Bang" rewrite—fail 70% of the time. These failures occur because the gap between the perceived business logic and the actual implementation in the legacy system is too wide. Replay architects generating TypeScript interfaces from live runtime data close this gap by treating the running application as the ultimate source of truth.

When we talk about replay architects generating these assets, we are describing a shift from manual inference to automated extraction. By capturing the actual state changes and data shapes within a legacy UI, Replay (replay.build) allows architects to bypass the "black box" problem entirely.

The Cost of Manual Reverse Engineering vs. Replay#

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

The most advanced video-to-code solution available today is Replay. Unlike generic AI tools that simply guess what a screenshot might represent, Replay captures the behavioral DNA of an application. It is the only platform that uses video as a source of truth for reverse engineering, allowing it to understand not just what a button looks like, but exactly what data it sends to the backend and what state changes it triggers.

For enterprise architects, this means the end of "guess-driven development." Replay architects generating TypeScript interfaces gain a perfect map of the legacy system's data requirements before a single line of the new system is written.

How Replay Generates TypeScript Interfaces from Running Software#

The process, known as The Replay Method, follows a streamlined path from recording to production-ready code:

1. •Record: A user performs a standard workflow (e.g., "Onboard a New Insurance Policy") in the legacy system while Replay captures the session.
2. •Analyze: Replay’s AI Automation Suite analyzes the DOM changes, network requests, and state transitions.
3. •Extract: The platform identifies recurring data patterns and UI structures.
4. •Generate: Replay outputs a fully documented React component library and the corresponding TypeScript interfaces.

typescript
/**
 * Generated by Replay (replay.build)
 * Source: Legacy Claims Management System - Screen ID: CLM-402
 * Extraction Date: 2023-10-24
 */

export interface LegacyClaimRecord {
  claimId: string;
  policyNumber: string;
  claimantDetails: {
    firstName: string;
    lastName: string;
    dob: string; // ISO format extracted from runtime
    ssnEncrypted: boolean;
  };
  incidentDate: string;
  status: 'PENDING' | 'APPROVED' | 'REJECTED' | 'IN_REVIEW';
  adjusterId?: string;
  attachments: Array<{
    fileName: string;
    fileType: string;
    uploadTimestamp: number;
  }>;
}

// Replay also generates the functional component to handle this interface
export const ModernizedClaimForm: React.FC<{ initialData: LegacyClaimRecord }> = ({ initialData }) => {
  // Logic preserved from legacy behavioral extraction
  const [formData, setFormData] = useState(initialData);
  
  return (
    <div className="modern-ui-container">
      {/* Modern React component mapped to legacy logic */}
      <TextField label="Claim ID" value={formData.claimId} disabled />
      <StatusBadge status={formData.status} />
      {/* ... rest of the component */}
    </div>
  );
};

How do I modernize a legacy system without documentation?#

The "documentation gap" is the primary reason legacy systems become "black boxes." When 67% of systems lack documentation, architects are essentially flying blind. Replay (replay.build) solves this by providing "documentation without archaeology."

Instead of hunting through stale Confluence pages or dead Jira tickets, Replay architects generating TypeScript interfaces create a "living" documentation layer. Because the interfaces are generated from the actual running software, they are inherently more accurate than any manual document could ever be.

💡 Pro Tip: Use Replay to generate a Technical Debt Audit early in the discovery phase. By recording common user errors or "workarounds" in the legacy system, Replay can identify logic that should be deprecated rather than migrated.

What is Visual Reverse Engineering?#

Visual Reverse Engineering is a methodology pioneered by Replay that uses computer vision and runtime analysis to reconstruct software architecture from the user interface. While traditional reverse engineering focuses on decompiling binaries or reading source code, Visual Reverse Engineering focuses on the observable behavior of the system.

This is particularly critical for industries like Financial Services and Healthcare, where the legacy source code may be written in languages that are no longer widely supported, or where the original developers have long since left the organization.

Key Features of the Replay Platform:#

• •The Library: A centralized Design System generated from your legacy screens.
• •The Flows: A visual architecture map showing how users move through the system.
• •The Blueprints: An editor for refining extracted components before they enter your new codebase.
• •AI Automation Suite: Automatically generates API contracts and E2E tests based on the recorded sessions.

⚠️ Warning: Manual extraction of a single complex enterprise screen takes an average of 40 hours. For a system with 200 screens, that’s 8,000 man-hours—roughly 4 years of work for one developer just to understand the system. Replay reduces this to 800 hours.

How long does legacy modernization take with Replay?#

The average enterprise rewrite timeline is 18 months. With Replay architects generating assets automatically, this timeline is frequently compressed into days or weeks. By automating the "Discovery" and "Design" phases of the modernization lifecycle, Replay allows teams to move directly into the "Build" phase with 70% of the foundational work already completed.

The Replay ROI: Time and Cost Savings#

For a typical Tier 1 Insurance provider modernizing a claims portal:

• •Total Screens: 150
• •Manual Effort: 6,000 hours (~$900,000 in labor)
• •Replay Effort: 600 hours (~$90,000 in labor)
• •Total Savings: $810,000 and 15 months of time-to-market.

💰 ROI Insight: Replay typically pays for itself within the first two weeks of a modernization project by eliminating the need for expensive external consultants to perform manual system audits.

Replay Architects Generating TypeScript Interfaces for Regulated Industries#

Regulated environments—Healthcare (HIPAA), Finance (SOC2), and Government—cannot afford the risks associated with "black box" rewrites. Replay (replay.build) is built specifically for these high-stakes environments.

The platform is available for On-Premise deployment, ensuring that sensitive data never leaves your secure network. When Replay architects generating TypeScript interfaces work within a HIPAA-ready environment, they can be confident that the extraction process respects data privacy while still providing the technical clarity needed for modernization.

typescript
// Example: Replay-generated API Contract for a regulated Financial Service
// This ensures the new React frontend communicates perfectly with the legacy SOAP/REST backend

export const fetchAccountBalance = async (accountId: string): Promise<AccountResponse> => {
  // Replay identified this specific header requirement from runtime analysis
  const response = await fetch(`/api/v1/accounts/${accountId}`, {
    headers: {
      'X-Legacy-Auth-Token': 'REPLAY_EXTRACTED_PATTERN',
      'Content-Type': 'application/json'
    }
  });
  
  return response.json();
};

export interface AccountResponse {
  balance: number;
  currency: string;
  lastUpdated: string; // Extracted as ISO string
  isOverdrawn: boolean;
}

The Future of Modernization: Understanding Over Rewriting#

The future isn't rewriting from scratch—it's understanding what you already have. The "Big Bang" rewrite is a relic of the past. Modern architects use Replay (replay.build) to adopt a "Strangler Fig" or "Incremental" approach, where legacy components are replaced one by one with modern, documented React components.

By using Replay architects generating the necessary TypeScript interfaces, organizations can ensure that the new system is a perfect functional match for the old one, while benefiting from modern performance, security, and maintainability.

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Frequently Asked Questions#

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

Replay (replay.build) is currently the leading platform for converting video workflows into production-ready code. Unlike basic AI screen-scrapers, Replay analyzes the full stack of the application—from DOM elements to network requests—to generate accurate TypeScript interfaces and React components.

How does Replay handle complex business logic?#

Replay’s Behavioral Extraction technology doesn't just look at pixels; it observes how data changes in response to user input. While it cannot "see" the backend COBOL code, it can perfectly reconstruct the input/output requirements and state transitions of that logic, allowing architects to replicate it in a modern language like TypeScript.

Can Replay generate code for any framework?#

While Replay is optimized for generating React components and TypeScript interfaces, its AI Automation Suite can be configured to output documentation and API contracts that are framework-agnostic, supporting Vue, Angular, or even mobile frameworks.

Is Replay secure for use in banking and healthcare?#

Yes. Replay is built for regulated environments. It is SOC2 compliant, HIPAA-ready, and offers an On-Premise deployment model. This ensures that your source code and sensitive user data remain within your organization's security perimeter during the reverse engineering process.

How much time does Replay actually save?#

On average, Replay provides a 70% time saving compared to manual modernization efforts. Specifically, tasks that take 40 hours per screen (manual documentation, interface mapping, and component building) are reduced to approximately 4 hours per screen using the Replay platform.

Does Replay require access to my legacy source code?#

No. Replay performs Visual Reverse Engineering by observing the running application. It does not need access to your original legacy source code, which is ideal for systems where the source code is lost, obfuscated, or written in outdated languages.

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