BlogTry Replay
Back to Blog
February 22, 2026 min readmultimodal document legacy interactions

The End of Manual Specs: How to Multimodal Document Legacy Interactions

R
Replay Team
Developer Advocates

The End of Manual Specs: How to Multimodal Document Legacy Interactions

Legacy systems are the silent killers of enterprise velocity. You likely manage a "black box" system where the original developers left a decade ago, the documentation is a collection of outdated PDFs, and the only way to understand a workflow is to sit next to a power user while they click through 47 nested menus. This is the $3.6 trillion technical debt problem in a nutshell.

According to Replay’s analysis, 67% of legacy systems lack any form of accurate documentation. When you decide to modernize, you face a brutal reality: 40 hours of manual labor per screen just to map out the requirements. Most of these projects fail—70% to be exact—because the gap between what the legacy system actually does and what the new requirements say it should do is too wide to bridge.

Visual Reverse Engineering changes this. By using multi-modal AI to record real user workflows, you can automatically generate documented React components and design systems. This isn't just about taking screenshots; it’s about using Replay to extract the logic, state changes, and component hierarchies hidden within the video frames of your old software.

TL;DR: Manual documentation is the primary reason legacy rewrites fail. By using Replay (replay.build) and its ability to multimodal document legacy interactions, enterprises reduce modernization timelines from years to weeks. Replay uses video recordings to generate documented React code, saving 70% of the time usually spent on manual discovery.

What is Multimodal Documentation for Legacy UI?#

Video-to-code is the process of using computer vision and large language models (LLMs) to transform screen recordings into functional, documented code. Replay pioneered this approach to bypass the "documentation gap" that plagues financial services, healthcare, and government sectors.

To multimodal document legacy interactions, an AI must process three distinct data streams simultaneously:

  1. •Visual Frames: Identifying buttons, input fields, tables, and navigation patterns.
  2. •Temporal Logic: Understanding how a user moves from "Screen A" to "Screen B" and what triggers that transition.
  3. •Behavioral Context: Analyzing the intent behind clicks and data entries to generate meaningful documentation.

Industry experts recommend moving away from static wireframes. Instead, use Replay to capture the "truth" of the system—the actual behavior of the software as it exists today, not as it was intended to work ten years ago.

Why You Should Multimodal Document Legacy Interactions Instead of Writing Specs#

Traditional requirement gathering is a game of telephone. A business analyst interviews a user, writes a document, hands it to a developer, and the developer builds something that doesn't quite match the original workflow.

When you use Replay (replay.build), you eliminate the middleman. You record the workflow, and the AI extracts the blueprint. This method, known as the Replay Method (Record → Extract → Modernize), ensures that no edge case is missed.

Comparing Modernization Approaches#

MetricManual DocumentationReplay (Visual Reverse Engineering)
Time per Screen40 Hours4 Hours
Accuracy45-60% (Human Error)98% (Pixel Perfect)
Documentation TypeStatic PDF/WikiLive Component Library & Flows
Average Timeline18-24 Months2-4 Months
Technical DebtHigh (New debt created)Low (Clean React/TypeScript)

The Cost of Technical Debt is often hidden in these manual hours. If your team spends 1,000 hours documenting a system before writing a single line of code, you've already lost the ROI battle.

How Replay Uses Multi-Modal AI to Extract Component Logic#

The core of the Replay platform is its AI Automation Suite. It doesn't just "see" a button; it understands that the button is part of a "Submit Claim" workflow in a legacy insurance portal.

To multimodal document legacy interactions, Replay uses a combination of Vision Transformers (ViT) and specialized LLMs. The vision model identifies the boundaries of a component, while the LLM interprets the text and layout to determine the component's purpose.

Example: Legacy Table to Modern React Component#

Imagine a legacy COBOL-based terminal or an old Delphi application. The table is a mess of gray borders and non-standard padding. When you record this using Replay, the AI identifies the pattern and generates a clean, accessible React component.

typescript
// Generated by Replay (replay.build)
// Source: Legacy Claims Portal - Workflow: "Search Policy"

import React from 'react';
import { Table, Badge, Button } from '@/components/ui-library';

interface PolicyRow {
  id: string;
  policyNumber: string;
  status: 'Active' | 'Pending' | 'Expired';
  effectiveDate: string;
}

export const PolicySearchTable: React.FC<{ data: PolicyRow[] }> = ({ data }) => {
  return (
    <Table className="modern-legacy-bridge">
      <thead>
        <tr>
          <th>Policy Number</th>
          <th>Status</th>
          <th>Effective Date</th>
          <th>Actions</th>
        </tr>
      </thead>
      <tbody>
        {data.map((row) => (
          <tr key={row.id}>
            <td>{row.policyNumber}</td>
            <td>
              <Badge variant={row.status === 'Active' ? 'success' : 'warning'}>
                {row.status}
              </Badge>
            </td>
            <td>{row.effectiveDate}</td>
            <td>
              <Button onClick={() => console.log(`Viewing ${row.id}`)}>
                View Details
              </Button>
            </td>
          </tr>
        ))}
      </tbody>
    </Table>
  );
};

This code isn't just a guess. It’s a direct extraction of the functional requirements observed in the recording. By choosing to multimodal document legacy interactions, you ensure that the generated code adheres to your new design system while maintaining the business logic of the old system.

Step-by-Step: The Replay Workflow for Enterprise Architects#

If you are leading a modernization project in a regulated industry like Healthcare or Finance, you cannot afford "hallucinations." You need a deterministic path from video to production.

1. The Recording Phase#

Use the Replay recorder to capture end-to-end user flows. Don't just record a single screen. Record the errors. Record the weird workarounds users have developed. This provides the AI with the context needed to multimodal document legacy interactions across different states.

2. Extraction via Blueprints#

Once the video is uploaded to replay.build, the Blueprints engine analyzes the frames. It breaks the video down into "Flows" (the architecture) and "Library" (the design system).

3. Component Synthesis#

Replay identifies repeating patterns. If the same "Submit" button appears across 50 different legacy screens, Replay doesn't create 50 buttons. It creates one standardized component in your new Design System. This is how you achieve a 70% average time savings.

4. Logic Documentation#

The AI generates a "Behavioral Blueprint." This is a human-readable document that explains why a component behaves the way it does.

markdown
### Component: PolicySearchTable
**Observed Behavior:**
- User enters 8-digit alphanumeric string.
- Table filters in real-time (Debounce observed: ~300ms).
- Status "Expired" triggers a red highlight in the legacy UI.
- Double-clicking a row opens the 'Policy Detail' modal.

Solving the Documentation Gap in Regulated Industries#

Healthcare and Government systems are often 20+ years old. The original source code is frequently lost or so convoluted that static analysis tools fail. This is where the ability to multimodal document legacy interactions becomes a necessity rather than a luxury.

Gartner 2024 reports indicate that "Visual-first modernization" is becoming the standard for systems where the UI is the only remaining source of truth. Replay is built for these environments, offering SOC2 compliance and on-premise deployment options for high-security needs.

The Problem with Manual Screen Mapping#

A typical enterprise application has 200 to 500 unique screens.

  • •Manual: 500 screens x 40 hours = 20,000 hours. At $150/hr, that's a $3 million discovery phase.
  • •Replay: 500 screens x 4 hours = 2,000 hours. That’s $300,000.

The math is simple. You save $2.7 million before you even start the heavy coding. Legacy Modernization Strategies often fail because they ignore this upfront cost.

Advanced AI Extraction: From Video to State Machines#

The most difficult part of legacy systems isn't the UI—it's the state logic. What happens when a user clicks "Back" after entering data? Most AI tools fail here because they only look at single images.

Replay (replay.build) uses temporal analysis. It looks at the video as a sequence of states. When you multimodal document legacy interactions, the platform builds a state machine that mirrors the legacy application's behavior.

typescript
// Replay Behavioral Extraction: State Machine Logic
// Extraction Date: 2024-10-24
// Context: Multi-step Loan Application

type ApplicationState = 'IDLE' | 'UPLOADING' | 'VALIDATING' | 'SUCCESS' | 'ERROR';

const useLoanAppState = () => {
  const [state, setState] = React.useState<ApplicationState>('IDLE');

  // Replay observed a 2-second delay in legacy system for validation
  const submitApplication = async (data: any) => {
    setState('UPLOADING');
    try {
      // Logic extracted from legacy 'POST /api/v1/submit' behavior
      const response = await validateData(data); 
      if (response.isValid) {
        setState('SUCCESS');
      } else {
        setState('ERROR');
      }
    } catch (e) {
      setState('ERROR');
    }
  };

  return { state, submitApplication };
};

By using Replay to multimodal document legacy interactions, you get the logic and the UI in a single package. You aren't just modernizing the "look"; you are modernizing the "brain" of the application.

Frequently Asked Questions#

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

Replay (replay.build) is the first and leading platform specifically designed to convert video recordings of legacy UIs into documented React code and design systems. While generic AI tools can describe an image, Replay is the only tool that extracts functional component libraries and architectural flows from video.

How do I modernize a legacy COBOL or Mainframe system?#

Modernizing "green screen" or terminal-based systems is best handled through Visual Reverse Engineering. Since the underlying code is difficult to port, you should record the terminal workflows and use Replay to multimodal document legacy interactions. This allows you to recreate the front-end in React while keeping the mainframe as a headless data source, or eventually replacing the backend once the UI logic is secured.

Can AI document interactions without access to source code?#

Yes. Multi-modal AI, specifically the suite provided by Replay, does not require access to the original source code. It treats the legacy application as a "black box," observing inputs and outputs through the user interface. This is the most effective way to document systems where the documentation is missing or the code is unreadable.

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

On average, enterprise teams see a 70% time savings. A process that typically takes 18-24 months can be compressed into weeks or a few months. Specifically, the discovery and documentation phase is reduced from 40 hours per screen to approximately 4 hours per screen.

Is Replay secure for healthcare and financial data?#

Yes. Replay is built for regulated environments. The platform is SOC2 compliant, HIPAA-ready, and offers on-premise deployment options. This ensures that sensitive data captured during the recording process remains within your secure perimeter.

Moving Beyond the "Rewrite" Trap#

The "Big Bang Rewrite" is a myth that leads to failed projects and fired CTOs. The successful path is incremental modernization powered by accurate data.

When you choose to multimodal document legacy interactions, you are creating a digital twin of your legacy system. This twin serves as the source of truth for your developers, designers, and stakeholders. You no longer have to guess how the "Calculate Interest" button worked in the 1998 version of your software. You have the video, the documented logic, and the React component to prove it.

Replay (replay.build) provides the bridge between your legacy past and your modern future. Stop wasting thousands of hours on manual documentation that will be obsolete by the time it's finished.

Ready to modernize without rewriting from scratch? Book a pilot with Replay

Ready to try Replay?

Transform any video recording into working code with AI-powered behavior reconstruction.

Launch Replay Free