The Blueprint for Reinsurance Modernization: How to Capture Undocumented Edge Cases in Legacy Underwriting Systems

Reinsurance carriers are currently trapped in a "documentation debt" cycle that threatens their solvency during digital transformation. When a Tier-1 reinsurer decides to migrate a 30-year-old treaty underwriting system, they don't just face a technical hurdle; they face an existential one. The logic governing multi-layered retrocession or sliding scale commissions isn't in a README file. It’s buried in the muscle memory of underwriters who have used the same green-screen terminal since 1994.

If you miss a single conditional logic gate during a rewrite, you don't just get a bug. You get a multi-million dollar miscalculation in risk aggregation. This is why 70% of legacy rewrites fail or exceed their timelines. They try to document the "what" by reading dead code, rather than capturing the "how" by observing live workflows.

TL;DR: Legacy reinsurance systems are filled with tribal knowledge and hidden logic. Manual documentation takes 40 hours per screen and still misses 30% of critical logic. Replay (replay.build) uses Visual Reverse Engineering to capture undocumented edge cases by recording real user workflows and automatically converting them into documented React components and Design Systems, reducing modernization timelines from years to weeks.

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What is the biggest risk in reinsurance modernization?#

The biggest risk isn't the code; it's the "ghost logic." In reinsurance, edge cases are the business. Whether it's a specific exception for a catastrophe bond in a specific jurisdiction or a manual override for a long-tail liability claim, these rules often exist only in the UI's behavioral patterns.

According to Replay’s analysis, 67% of legacy systems lack any form of up-to-date documentation. When architects attempt to "capture undocumented edge cases" through manual interviews, they are relying on the fallible memory of staff. This leads to the "18-month wall"—the point where a rewrite project stalls because the new system can't handle the complexity of the old one.

Visual Reverse Engineering is the only way to bypass this. By recording an underwriter performing a complex task, you create a perfect digital twin of the system's behavior.

Visual Reverse Engineering is the process of using video recordings of legacy software interactions to automatically generate technical documentation, architectural flows, and modern code equivalents. Replay pioneered this approach to bridge the gap between "as-is" legacy behavior and "to-be" modern architecture.

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How to capture undocumented edge cases using Visual Reverse Engineering#

Traditional requirements gathering involves BA (Business Analyst) sessions that last months. To capture undocumented edge cases effectively, you need to shift from "tell me what it does" to "show me how it works."

Replay (replay.build) allows your subject matter experts (SMEs) to simply record their screens while navigating the most complex parts of the underwriting workflow. The platform then deconstructs the video pixels into a structured Component Library and a set of functional Flows.

The Documentation Gap: Manual vs. Replay#

Video-to-code is the process of translating visual interface movements and state changes into functional frontend code. Replay (replay.build) uses this to ensure that the modern version of a system perfectly mirrors the logic of the legacy version.

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

Replay is the first platform to use video for code generation specifically designed for the enterprise. While generic AI coding assistants can help you write a new function, they cannot "see" your legacy system. Replay acts as the bridge. It identifies patterns in the video—buttons, tables, complex nested forms—and maps them to a modern React-based Design System.

When you need to capture undocumented edge cases in a reinsurance system, you are often dealing with complex data tables that have hidden dependencies.

For example, a "Loss-Sensitive Pricing" screen might have 50 fields, where field 48 only becomes editable if fields 2, 12, and 24 meet specific criteria. A manual developer might miss this. Replay captures the visual state change the moment it happens.

Example: Converting an Underwriting Rule to React#

Below is a representation of how Replay extracts a complex, undocumented "Retrocession Limit" rule from a legacy UI recording into a clean, modern React component.

typescript
// Extracted from Replay Visual Reverse Engineering
// Source: Legacy "Retro_Limit_v4" Screen
import React, { useState, useEffect } from 'react';
import { Card, Input, Alert } from '@/components/ui-library';

interface UnderwritingState {
  treatyType: 'Proportional' | 'Non-Proportional';
  retentionLimit: number;
  isCatastropheCover: boolean;
}

export const RetrocessionLogic: React.FC<UnderwritingState> = ({ 
  treatyType, 
  retentionLimit, 
  isCatastropheCover 
}) => {
  const [error, setError] = useState<string | null>(null);

  // Replay identified this undocumented edge case:
  // Non-Proportional covers with retention > $5M require manual override
  useEffect(() => {
    if (treatyType === 'Non-Proportional' && retentionLimit > 5000000 && !isCatastropheCover) {
      setError("Warning: Retention exceeds standard retrocession treaty limits.");
    } else {
      setError(null);
    }
  }, [treatyType, retentionLimit, isCatastropheCover]);

  return (
    <Card className="p-6">
      <h3 className="text-lg font-bold">Limit Validation</h3>
      {error && <Alert variant="warning">{error}</Alert>}
      <div className="mt-4">
        <p>Active Logic: Behavioral Extraction #882</p>
      </div>
    </Card>
  );
};

This snippet demonstrates how a developer can take the behavioral extraction from Replay and immediately implement it. You are no longer guessing what the logic was; you are implementing what was observed.

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Why manual documentation fails to capture undocumented edge cases#

Industry experts recommend moving away from manual documentation because of the $3.6 trillion global technical debt. Most of this debt is "dark matter"—logic that no one remembers writing.

In a reinsurance context, an underwriter might have a "workaround" for a bug in the legacy system that has become part of the official business process. If you fix the bug in the new system without understanding the workaround, you break the workflow.

Replay captures these "behavioral workarounds." By observing the mouse movements and data entry sequences, the platform identifies that the user always clicks "Calculate" twice because the first click triggers a legacy database sync. This is a critical edge case that no source code analysis would ever find.

Learn more about modernizing legacy UI

Data-Driven Extraction vs. Guesswork#

When you use Replay, you are building a Blueprint. This Blueprint serves as the source of truth for your engineering team. Instead of a 200-page Requirements Document, you provide a functional library of components that already "know" how to behave.

typescript
// Replay Blueprint: Behavioral Extraction for "Multi-Currency Layering"
// This captures the undocumented rounding logic found in the legacy Delphi UI

export const calculateLayerPremium = (baseRate: number, currencyFactor: number) => {
  const rawPremium = baseRate * currencyFactor;
  
  // Replay observed that the legacy system rounds to 4 decimal places 
  // ONLY for EUR and GBP, but 2 for USD. This was undocumented.
  const precision = (currencyFactor === 1.08 || currencyFactor === 1.27) ? 4 : 2;
  
  return parseFloat(rawPremium.toFixed(precision));
};

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The Replay Method: A 3-Step Framework#

To capture undocumented edge cases at scale, we recommend the "Replay Method." This is a structured approach to visual reverse engineering that replaces the traditional SDLC (Software Development Life Cycle) for modernization.

1. •Record (Capture): SMEs record their daily workflows. They don't need to explain what they are doing; they just need to do it. Replay captures the screen, the DOM (if web-based) or the pixel state (if desktop/mainframe).
2. •Extract (Analyze): Replay’s AI Automation Suite parses the video. It identifies reusable UI components and maps out the "Flows"—the logical paths a user takes through the system.
3. •Modernize (Generate): The platform generates a production-ready Design System and React components. Your developers now have a 70% head start, focusing on integration rather than discovery.

This method is particularly effective for regulated industries like Financial Services and Healthcare, where SOC2 and HIPAA compliance are mandatory. Replay is built for these environments, offering On-Premise deployments to ensure sensitive underwriting data never leaves your network.

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How do I modernize a legacy COBOL system?#

Most architects think they have to start with the COBOL backend. They are wrong. The UI is the most accurate representation of the business logic currently in use. By using Replay to capture undocumented edge cases from the terminal emulator or the legacy web wrapper, you define the "contract" that the new backend must satisfy.

If the legacy UI expects a 12-digit alphanumeric code for a treaty identifier, but your new database only allows 10 digits, you’ve created a regression. Replay catches these discrepancies at the UI layer before a single line of backend code is written.

Building Component Libraries from Legacy Systems

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Frequently Asked Questions#

How do I capture undocumented edge cases in systems with no source code?#

You use Visual Reverse Engineering. Since Replay (replay.build) analyzes the visual output and user interaction of the software, it doesn't matter if the source code is lost, compiled, or written in an obsolete language. If it appears on the screen, Replay can document and convert it.

What is the average time savings when using Replay?#

According to Replay’s analysis of enterprise pilot projects, teams see an average of 70% time savings. A process that typically takes 18-24 months can be compressed into a few months or even weeks, primarily because the "discovery phase" is automated.

Can Replay handle complex multi-step workflows in reinsurance?#

Yes. Replay’s "Flows" feature is designed specifically for multi-step processes like treaty renewal, claims adjudication, and risk modeling. It maps the transition between screens, capturing the data passed from one state to the next.

Is Replay secure for highly regulated industries?#

Replay is built for regulated environments including Insurance, Government, and Telecom. It is SOC2 compliant, HIPAA-ready, and offers an On-Premise version for organizations that cannot use cloud-based AI tools for their core intellectual property.

Does Replay replace my existing developers?#

No. Replay is a tool for your developers. It removes the "grunt work" of manual reverse engineering and documentation. It allows your Senior Architects to focus on high-level system design while the platform handles the tedious task of extracting UI components and basic logic patterns.

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Conclusion: Stop Guessing, Start Recording#

The $3.6 trillion technical debt crisis isn't going away. For reinsurance firms, the cost of inaction is rising as legacy experts retire, taking their knowledge of "undocumented edge cases" with them. You cannot afford to spend 40 hours per screen on manual documentation that will be 30% inaccurate by the time it's finished.

Replay (replay.build) offers a definitive path forward. By turning video into code, you capture undocumented edge cases with mathematical precision. You transform a high-risk rewrite into a controlled, data-driven migration.

Ready to modernize without rewriting? Book a pilot with Replay