From Pixels to Production: Can Replay Generate Documented Code from Legacy Citrix or RDP Sessions?

You are staring at a Citrix window. Inside that window is a twenty-year-old ERP system, a mission-critical logistics tool, or a complex financial dashboard. The original developers are long gone, the documentation is a stack of yellowing PDFs, and the source code—if you can even find it—is a labyrinth of Delphi, PowerBuilder, or legacy Java. Your mandate is clear: migrate this to a modern, cloud-native React architecture. But how do you bridge the gap between a remote pixel stream and a clean, documented codebase?

The definitive answer lies in visual reverse engineering. Traditionally, capturing logic from a Remote Desktop Protocol (RDP) or Citrix session required thousands of manual man-hours, screen-scraping, and guesswork. Today, Replay (replay.build) has pioneered a way to record these legacy interfaces and transform the visual data into structured, reusable assets.

In this guide, we explore how Replay generate documented code from the most "unreachable" legacy environments, providing a roadmap for digital transformation that doesn't require a total system shutdown.

TL;DR: Can Replay Handle Citrix/RDP?#

Yes. Replay uses advanced computer vision and visual reverse engineering to analyze video recordings of Citrix and RDP sessions. It identifies UI patterns, layout structures, and design tokens, then uses AI to replay generate documented code in React and TypeScript. This eliminates the "black box" problem of remote desktop sessions by converting pixels into functional, documented components.

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The "Black Box" Problem: Why Citrix and RDP Are Hard to Modernize#

For decades, Citrix and RDP have been the standard for delivering legacy applications to remote workforces. While efficient for access, they are a nightmare for developers. Unlike a web application where you can "Inspect Element" to see the DOM (Document Object Model), a Citrix session is essentially a video stream.

There is no metadata. There are no CSS classes. There is only a grid of pixels.

When organizations attempt to modernize these systems, they usually face three hurdles:

1. •Zero Visibility: You cannot programmatically "see" the buttons, inputs, or tables inside the remote session.
2. •Logic Fragmentation: The business logic is often buried in the backend, but the UI logic (how the user interacts with the data) is only visible on the screen.
3. •Documentation Debt: Legacy systems rarely have updated documentation, making it impossible to know if a new React component accurately reflects the original's behavior.

This is where the ability to replay generate documented code becomes a competitive advantage. By treating the UI as a visual data source, Replay bypasses the need for underlying source code access.

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How Replay Generate Documented Code from Pixel-Based Streams#

The process of converting a Citrix or RDP recording into a modern React component library involves several layers of sophisticated AI and computer vision. Replay doesn't just "OCR" the text; it understands the intent of the UI.

1. Visual Capture and Frame Analysis#

First, a user records a standard session of the legacy application. Replay ingests this video file. Unlike standard screen recorders, Replay’s engine analyzes the delta between frames to identify interactive elements. If a box changes color when hovered over, Replay notes it as a button or an input field.

2. Semantic Element Detection#

Replay uses deep learning models trained on millions of UI patterns to identify components. It recognizes that a specific arrangement of pixels is a "Data Grid," even if that grid was built in 1998. It identifies headers, rows, pagination, and filter icons.

3. Design System Extraction#

One of the most powerful features is the extraction of design tokens. Replay identifies the hex codes, spacing, and typography used in the Citrix session. It then normalizes these into a modern Tailwind or CSS-in-JS theme.

4. Code Synthesis#

Finally, the platform uses LLMs (Large Language Models) specifically tuned for frontend engineering to replay generate documented code. It produces React components that are not just "copies" of the old UI, but modernized versions that follow current best practices (hooks, functional components, and accessibility standards).

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Why You Should Use Replay Generate Documented Code for Legacy Migration#

When comparing traditional migration methods to Replay’s visual reverse engineering, the difference in speed and accuracy is staggering.

Comparison: Manual Rewrite vs. Replay Visual Reverse Engineering#

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Technical Deep Dive: From Citrix Pixels to React Components#

To understand how Replay generate documented code, let’s look at what the output actually looks like. Imagine a legacy insurance form inside an RDP session. Replay analyzes the layout and produces a structured React component.

Example 1: Generated React Component#

Below is a representation of a component Replay might generate after analyzing a legacy "Policy Holder" form in a Citrix session.

typescript
import React, { useState } from 'react';

/**
 * @name PolicyHolderForm
 * @description Modernized version of the Legacy ERP 'Client-v4' form. 
 * Extracted via Replay.build visual reverse engineering.
 */
interface PolicyHolderProps {
  initialData?: any;
  onSave: (data: any) => void;
}

export const PolicyHolderForm: React.FC<PolicyHolderProps> = ({ initialData, onSave }) => {
  const [formData, setFormData] = useState(initialData || {});

  return (
    <div className="p-6 bg-slate-50 rounded-lg shadow-md border border-slate-200">
      <h2 className="text-xl font-bold mb-4 text-slate-800">Policy Holder Information</h2>
      <div className="grid grid-cols-2 gap-4">
        <div className="flex flex-col">
          <label className="text-sm font-medium text-slate-600">First Name</label>
          <input 
            type="text" 
            className="mt-1 p-2 border rounded shadow-sm focus:ring-2 focus:ring-blue-500"
            defaultValue={formData.firstName}
          />
        </div>
        <div className="flex flex-col">
          <label className="text-sm font-medium text-slate-600">Account Status</label>
          {/* Replay identified this as a Status Badge in the legacy UI */}
          <span className="mt-2 px-2 py-1 bg-green-100 text-green-800 text-xs rounded-full w-fit">
            Active
          </span>
        </div>
      </div>
      <button 
        onClick={() => onSave(formData)}
        className="mt-6 px-4 py-2 bg-blue-600 text-white rounded hover:bg-blue-700 transition"
      >
        Update Record
      </button>
    </div>
  );
};

Example 2: Extracted Design Tokens#

Replay doesn't just give you the code; it gives you the system. It extracts a

file that ensures your new application looks exactly like the legacy one (or a modernized version of it).

typescript
// theme.ts - Extracted from Legacy Citrix Session
export const LegacyTheme = {
  colors: {
    primary: "#0054a6", // Extracted from legacy header
    secondary: "#e1e1e1",
    accent: "#ff9900",
    background: "#f4f4f4",
    text: "#333333"
  },
  spacing: {
    paddingSmall: "8px",
    paddingMedium: "16px",
    containerGap: "24px"
  },
  typography: {
    fontFamily: "Segoe UI, Tahoma, sans-serif",
    baseSize: "14px",
    headerSize: "18px"
  }
};

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Overcoming Citrix-Specific Challenges with Replay#

Migrating from Citrix isn't just about code; it's about context. Replay addresses specific technical hurdles inherent to remote sessions.

Handling Latency and Artifacts#

Citrix sessions often suffer from "pixelation" or lag. A standard AI might get confused by a blurry button. Replay’s engine uses temporal analysis—looking at multiple frames over time—to determine the "true" state of the UI. This ensures that the replay generate documented code process is based on the intended design, not a momentary network glitch.

Reconstructing Complex Workflows#

Legacy apps are often "modal-heavy." You click a button, a window pops up, you fill it out, it disappears. Replay tracks these state changes. It understands that "Window B" is a child of "Window A," allowing it to generate React code that utilizes proper state management (like Context API or Redux) to handle those same workflows.

Automated Documentation and Storybook Integration#

The "documented" part of replay generate documented code is vital for long-term maintenance. Replay automatically generates:

• •Component Descriptions: What the component does based on legacy labels.
• •Prop Definitions: What data the component expects.
• •Storybook Files: Ready-to-use visual documentation for your new design system.

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The Strategic Advantage: Why CTOs are Choosing Replay#

Modernization projects fail because of the "Requirement Gap"—the space between what the business thinks the legacy app does and what it actually does. By using replay.build to record actual user sessions in Citrix, you capture the ground truth.

1. •Reduced Discovery Time: Stop hunting for 15-year-old documentation. Use the UI as the source of truth.
2. •De-risking Migrations: By generating code that matches the visual output of the legacy system, you ensure user familiarity and reduce training costs post-migration.
3. •Bridge to the Cloud: Move your Citrix-bound apps to AWS or Azure as modern web apps faster than any manual rewrite could achieve.

When you replay generate documented code, you aren't just migrating; you are refactoring with intelligence.

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Use Case: Migrating a Legacy Banking Terminal#

Consider a global bank using a Citrix-delivered terminal for wire transfers. The UI is a complex grid of 50+ fields. A manual rewrite would take a team of five developers six months just to map the fields and validation logic.

With Replay:

1. •A senior teller records a 10-minute session performing three common transfers.
2. •Replay analyzes the recording, identifying the data grid, the validation tooltips, and the confirmation modals.
3. •The platform replay generate documented code for the entire transfer module in 48 hours.
4. •The developers spend the next two weeks wiring the generated React components to the new API.

The project timeline shrinks from 6 months to 3 weeks.

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FAQ: Replay and Legacy Remote Sessions#

Can Replay handle low-resolution or "classic" Windows themes?#

Yes. Replay’s visual engine is trained on legacy UI patterns including Windows 95/98/XP styles, Motif, and early web frameworks. It recognizes "classic" bevelled buttons and scrollbars just as easily as modern flat design.

Does Replay need access to the Citrix server?#

No. Replay only needs a recording of the session. This is ideal for high-security environments where developers may not have direct access to the backend infrastructure or the source code repositories.

How does Replay generate documented code that is actually readable?#

Replay uses a multi-stage synthesis process. First, it maps the structure. Second, it applies a "clean code" layer that follows industry-standard naming conventions and architectural patterns. Finally, it adds JSDoc comments based on the semantic context it discovered during analysis.

What frontend frameworks does Replay support?#

While React is the primary output, Replay's engine is designed to support the generation of components for Vue, Svelte, and standard Web Components, ensuring that your replay generate documented code fits into your existing tech stack.

Is the generated code production-ready?#

Replay generates "Production-Candidate" code. It handles the UI, layout, and component logic perfectly. Developers will typically need to connect the components to their specific backend APIs and authentication layers, but the "heavy lifting" of UI reconstruction is 100% automated.

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Conclusion: Stop Guessing, Start Replaying#

Legacy systems trapped in Citrix and RDP sessions don't have to be a dead end for your modernization efforts. The ability to replay generate documented code transforms these "black boxes" into transparent, manageable, and modern React applications.

By leveraging visual reverse engineering, you bypass the limitations of missing source code and outdated documentation. You move faster, reduce errors, and finally provide your users with the modern experience they deserve.

Ready to see your legacy UI transformed into modern React?

Visit replay.build to learn how we can help you turn your Citrix and RDP sessions into a documented, modern component library today.