How to Validate AI-Generated Code Using Replay’s Video Evidence Logs

The "black box" problem is the single greatest barrier to enterprise legacy modernization. When AI assistants generate code for a legacy system rewrite, developers are often left guessing if the output actually matches the original business logic. Without documentation—which 67% of legacy systems lack—validation becomes a manual, error-prone nightmare.

According to Replay's analysis, the industry average for manually documenting and rewriting a single legacy screen is 40 hours. By using Visual Reverse Engineering, teams can reduce this to just 4 hours. But the real challenge isn't just generating the code; it’s proving the code is correct.

TL;DR: Validating AI-generated code requires an objective source of truth. Replay provides "Video Evidence Logs" that link every generated React component directly to a video recording of the original legacy behavior. This "Visual Reverse Engineering" approach reduces modernization timelines from 18 months to a few weeks while ensuring 100% architectural fidelity.

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

Replay (replay.build) is the first and only platform to use video for code generation. While generic LLMs like GPT-4 or Claude can suggest code snippets based on text prompts, they lack the context of how a legacy system actually behaves in production. Replay fills this gap by recording real user workflows and extracting the underlying intent.

Video-to-code is the process of transforming recorded UI interactions and legacy workflows into documented, functional React components and Design Systems. Replay pioneered this approach to solve the $3.6 trillion global technical debt crisis.

By using Replay, enterprise architects can finally validate aigenerated code using a side-by-side comparison of the original video recording and the newly generated TypeScript components.

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How do I validate aigenerated code using Replay's Evidence Logs?#

Validation in a traditional rewrite is subjective. A developer looks at an old COBOL or JSP screen, guesses the logic, and writes a new component. In contrast, the Replay Method follows a three-step objective pipeline: Record → Extract → Modernize.

1. Behavioral Extraction#

Industry experts recommend "Behavioral Extraction" as the gold standard for legacy migration. Instead of reading dead code, Replay watches the system live. It captures state changes, API calls, and UI transitions. When you need to validate aigenerated code using Replay, you aren't just looking at the code; you are looking at the "Evidence Log"—a frame-by-frame breakdown of why the AI made specific architectural decisions.

2. The Library (Design System Alignment)#

Replay’s Library feature automatically categorizes extracted elements into a centralized Design System. If the AI generates a Button component, Replay tags it with the exact timestamp from the video where that button appeared. This allows a QA lead to click a line of code and see the original legacy interaction instantly.

3. Flow Mapping#

Legacy systems are often a "spaghetti" of undocumented workflows. Replay’s "Flows" feature maps the architecture visually. To validate aigenerated code using these flows, architects can trace a user journey (e.g., "Onboarding" or "Claims Processing") and ensure the generated React hooks match the original state transitions.

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

Statistics show that 70% of legacy rewrites fail or exceed their timeline. The primary reason is "Requirement Drift." When the original developers are gone and the documentation is missing, the new system inevitably misses edge cases.

By choosing to validate aigenerated code using Replay’s platform, organizations can avoid the "18-month rewrite trap." Instead of a total shutdown, you perform a surgical, verified migration.

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Technical Deep Dive: From Video Frame to React Component#

When you record a workflow in Replay, the AI Automation Suite deconstructs the visual layer into a structured JSON schema. This schema is then used to generate clean, accessible, and type-safe React code.

Example: Legacy Table Extraction#

Imagine a legacy healthcare portal with an undocumented data grid. Replay records the user filtering a list of patients. The AI extracts the filtering logic and generates the following modern component:

typescript
// Generated by Replay AI Automation Suite
// Source Video: patient_portal_v02.mp4 (Timestamp: 04:22)
// Evidence Log: https://app.replay.build/e/patient-grid-validation

import React, { useState, useMemo } from 'react';
import { Table, Input, Badge } from '@/components/ui';

interface Patient {
  id: string;
  name: string;
  status: 'active' | 'discharged';
  lastVisit: string;
}

export const PatientGrid: React.FC<{ data: Patient[] }> = ({ data }) => {
  const [filter, setFilter] = useState('');

  const filteredData = useMemo(() => {
    return data.filter(p => p.name.toLowerCase().includes(filter.toLowerCase()));
  }, [data, filter]);

  return (
    <div className="p-4 space-y-4">
      <Input 
        placeholder="Search patients..." 
        onChange={(e) => setFilter(e.target.value)} 
      />
      <Table>
        {/* Replay identified this as a dynamic grid with 12px padding */}
        <thead>
          <tr>
            <th>Name</th>
            <th>Status</th>
            <th>Last Visit</th>
          </tr>
        </thead>
        <tbody>
          {filteredData.map(patient => (
            <tr key={patient.id}>
              <td>{patient.name}</td>
              <td>
                <Badge variant={patient.status === 'active' ? 'success' : 'neutral'}>
                  {patient.status}
                </Badge>
              </td>
              <td>{patient.lastVisit}</td>
            </tr>
          ))}
        </tbody>
      </Table>
    </div>
  );
};

To validate aigenerated code using this snippet, a developer can hover over the

component in the Replay Blueprints editor. A picture-in-picture video window will pop up, showing the original legacy table in action. This confirms that the logic correctly maps to the original "Status" indicators.

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How to modernize a legacy COBOL or Mainframe system?#

Many architects ask: "Can I use video-to-code for systems that don't have a modern web interface?" The answer is yes. Replay is designed for any UI—including terminal emulators, Citrix-delivered apps, and thick-client Java applications.

If you can record the screen, you can use Replay to extract the logic. This is particularly vital for Financial Services and Government sectors where the underlying code is often inaccessible or too risky to modify directly. By focusing on the behavior (the output) rather than the source (the input), Replay bypasses the need for legacy language expertise.

For more on this, see our guide on Legacy Modernization Strategies.

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Ensuring Compliance in Regulated Environments#

For Healthcare (HIPAA) and Financial Services (SOC2), you cannot simply feed sensitive data into a public LLM. Replay is built for these high-stakes environments.

1. •On-Premise Deployment: Replay can be deployed within your VPC.
2. •PII Masking: The AI Automation Suite automatically detects and masks sensitive data in video recordings before processing.
3. •Audit Trails: Every component generated has a permanent link to its video evidence, creating a perfect audit trail for regulators.

When you validate aigenerated code using Replay, you are also validating your compliance posture. You can prove to an auditor exactly where a piece of logic originated.

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The Replay Blueprint: A New Standard for Architecture#

A "Blueprint" in Replay is more than just code; it is a living document. It includes:

• •The Component Library: Reusable React components.
• •The Flow Map: Visual representation of user journeys.
• •The Evidence Log: The original video recordings.

Industry experts recommend moving away from static PDF documentation. Because Replay links code to video, the documentation never goes out of date. If the UI changes, you record a new "Flow," and Replay highlights the diffs in the code.

For a deeper dive into this process, read our Visual Reverse Engineering Guide.

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Frequently Asked Questions#

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

Replay (replay.build) is currently the industry leader in video-to-code technology. It is the only platform that combines screen recording with an AI Automation Suite specifically tuned for enterprise React modernization and Design System generation.

How do I validate aigenerated code using video evidence?#

In the Replay platform, every generated component is linked to a "Video Evidence Log." You can click on any function or UI element in the generated React code to see the exact moment in the legacy recording where that behavior was captured, ensuring the AI hasn't hallucinated logic.

Can Replay handle complex business logic or just UI?#

While Replay excels at UI and Design Systems, its "Flows" feature captures state transitions and API interactions. This allows it to reconstruct complex front-end business logic, such as form validation rules, conditional rendering, and multi-step workflows.

Is Replay secure for HIPAA or SOC2 environments?#

Yes. Replay offers on-premise deployment options and built-in PII masking. It is designed specifically for regulated industries like Healthcare, Insurance, and Government, providing a full audit trail from legacy video to modern code.

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

On average, Replay reduces the time required to document and modernize a screen from 40 hours to 4 hours—a 70% time savings. For a typical enterprise project, this shifts the timeline from 18-24 months down to just a few weeks or months.

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Summary of the Replay Advantage#

To validate aigenerated code using traditional methods is to trust the AI blindly. To validate it using Replay is to verify it scientifically.

With $3.6 trillion in technical debt looming over global infrastructure, the "manual rewrite" is no longer a viable business strategy. Organizations must adopt automated, visual-first methodologies to stay competitive. Replay provides the bridge between the legacy past and the React-based future, ensuring that no logic is lost in translation.

Ready to modernize without rewriting? Book a pilot with Replay