Modernizing the Core: Converting Delphi-Based Banking Terminals to React Portals with 90% Code Accuracy

Your Delphi-based banking terminals are likely older than the engineers currently tasked with maintaining them. While these systems are the workhorses of the financial sector—handling millions of transactions with Pascal-driven stability—they have become "black boxes" of technical debt. The source code is often spaghetti, the original architects have retired, and the Visual Component Library (VCL) is a barrier to the web-first world your customers and employees demand.

Converting delphibased banking terminals is no longer a luxury; it is a survival tactic. However, the traditional approach of manual "rip and replace" is a suicide mission for most IT departments. With a global technical debt mountain reaching $3.6 trillion, the banking sector can no longer afford the 18-month average timeline for enterprise rewrites that often end in failure.

TL;DR: Manual migration of legacy Delphi terminals takes roughly 40 hours per screen and has a 70% failure rate. By using Replay for Visual Reverse Engineering, banks can achieve 90% code accuracy, reducing modernization timelines from years to weeks and cutting costs by 70%.

The Delphi Debt Crisis: Why Manual Rewrites Fail#

The banking industry is uniquely paralyzed by its legacy footprint. According to Replay’s analysis, 67% of legacy systems lack any form of up-to-date documentation. When you are converting delphibased banking terminals, you aren't just moving code; you are trying to rediscover business logic buried in decades of event-driven Pascal.

The "Big Bang" rewrite fails because it attempts to translate code line-by-line. Delphi’s tightly coupled UI and logic layers make this nearly impossible. If you try to manually recreate a complex commercial loan origination screen in React, your developers will spend 40 hours per screen just trying to map the state transitions and validation rules.

Industry experts recommend moving toward a "Visual Reverse Engineering" model. Instead of reading broken code, you record the application in action. Replay captures every state change, pixel movement, and user workflow, converting those recordings into documented React components and clean TypeScript.

Visual Reverse Engineering is the process of using computer vision and AI to analyze the UI/UX of a running legacy application and automatically generating equivalent modern code and documentation without needing access to the original source.

The Strategy for Converting Delphi-Based Banking Terminals#

To successfully move from a monolithic Delphi .EXE to a cloud-native React portal, you need a structured pipeline. You cannot simply "export" Delphi to the web. You must extract the intent, the design system, and the state machine.

1. Visual Capture and Flow Mapping#

The first step in converting delphibased banking terminals is documenting the "as-is" state. Since documentation is usually non-existent, Replay uses its "Flows" feature to map the architecture. By recording a teller performing a "New Account Opening" workflow, Replay identifies every modal, dropdown, and validation trigger.

2. Design System Extraction (The Library)#

Delphi apps are notorious for inconsistent UI components added over 20 years. Replay’s "Library" feature scans the recorded sessions to identify recurring UI patterns. It then generates a standardized Design System in React. This ensures that your new portal doesn't just look like a web version of a 1998 desktop app, but a modern, accessible interface.

3. Component Generation with Blueprints#

Once the visual patterns are identified, Replay’s "Blueprints" editor allows architects to refine the generated code. This is where you achieve that 90% accuracy. Instead of a developer guessing how a Delphi TGrid handles pagination, Replay generates the functional React equivalent.

Modernizing Legacy UI requires a shift from "code translation" to "behavioral replication."

Comparison: Manual Rewrite vs. Replay Automation#

Implementation: From VCL to React/TypeScript#

When converting delphibased banking terminals, the most difficult part is handling the complex data grids and nested forms typical of Delphi. Below is an example of how a legacy Delphi "Customer Search" component is transformed into a modern, type-safe React component using the output generated by Replay.

Example 1: The Generated React Component#

This code block represents a standardized banking component generated by Replay after analyzing a Delphi terminal's search functionality.

typescript
import React, { useState, useEffect } from 'react';
import { Button, TextField, DataGrid, Card } from '@your-org/banking-ui-library';

// Replay-generated interface based on Delphi TField definitions
interface CustomerRecord {
  id: string;
  accountNumber: string;
  fullName: string;
  status: 'Active' | 'Dormant' | 'Closed';
  lastTransactionDate: string;
}

export const CustomerSearchPortal: React.FC = () => {
  const [query, setQuery] = useState('');
  const [results, setResults] = useState<CustomerRecord[]>([]);
  const [loading, setLoading] = useState(false);

  // Replay captured the Delphi 'OnClick' event and mapped it to this handler
  const handleSearch = async () => {
    setLoading(true);
    try {
      const response = await fetch(`/api/v1/customers?search=${query}`);
      const data = await response.json();
      setResults(data);
    } catch (error) {
      console.error('Search failed - Replay captured this validation logic from legacy VCL Exception', error);
    } finally {
      setLoading(false);
    }
  };

  return (
    <Card title="Core Banking: Customer Inquiry">
      <div className="flex gap-4 mb-6">
        <TextField 
          label="Search by Name or Account" 
          value={query} 
          onChange={(e) => setQuery(e.target.value)} 
        />
        <Button onClick={handleSearch} loading={loading}>
          Execute Inquiry
        </Button>
      </div>
      <DataGrid 
        columns={[
          { field: 'accountNumber', header: 'Account #' },
          { field: 'fullName', header: 'Customer Name' },
          { field: 'status', header: 'Status' }
        ]}
        rows={results}
      />
    </Card>
  );
};

Example 2: State Management and Business Logic#

In Delphi, business logic is often tied directly to the

. When converting delphibased banking terminals, Replay’s AI Automation Suite extracts this logic into custom hooks, ensuring a clean separation of concerns.

typescript
// Replay extracted the validation logic from the Delphi 'OnBeforePost' event
import { create } from 'zustand';

interface TransactionState {
  amount: number;
  isAuthorized: boolean;
  setAmount: (val: number) => void;
  validateTransaction: () => boolean;
}

export const useTransactionStore = create<TransactionState>((set, get) => ({
  amount: 0,
  isAuthorized: false,
  setAmount: (val) => set({ amount: val }),
  validateTransaction: () => {
    const { amount } = get();
    // Logic extracted from legacy Delphi: Ensure amount doesn't exceed daily teller limit
    const TELLER_LIMIT = 10000;
    if (amount > TELLER_LIMIT) {
      alert("Transaction exceeds teller limit. Manager override required.");
      return false;
    }
    return true;
  }
}));

Security and Compliance in Regulated Environments#

For Financial Services and Insurance, "cloud-ready" isn't enough. You need "compliance-ready." Converting delphibased banking terminals involves handling Sensitive Personal Information (SPI).

According to Replay’s analysis, manual migrations often introduce security vulnerabilities because developers forget to implement the obscure, hard-coded security checks found in legacy Pascal code. Replay mitigates this by documenting every "Flow" and "Blueprint," ensuring that security logic is surfaced during the reverse engineering process.

Replay is built for these high-stakes environments:

• •SOC2 & HIPAA Ready: Your modernization data is handled with enterprise-grade security.
• •On-Premise Availability: For banks that cannot send data to the cloud, Replay can be deployed entirely within your own infrastructure.
• •Audit Trails: Every component generated has a lineage back to the recording of the legacy system, providing a clear audit trail for regulators.

Enterprise React Architecture requires this level of rigor to pass internal security reviews.

The Replay Workflow: From Recording to React#

The process of converting delphibased banking terminals with Replay follows a refined four-step cycle:

1. •Record: A subject matter expert (SME) records themselves using the Delphi terminal. They perform standard tasks like wire transfers, loan approvals, or account lookups.
2. •Analyze: Replay’s AI Automation Suite analyzes the video, identifying UI components (buttons, grids, inputs) and the logical flows between screens.
3. •Generate: Replay produces a "Blueprint"—a high-fidelity React representation of the system. It builds a "Library" of reusable components that follow your new brand guidelines while maintaining legacy functionality.
4. •Deploy: Developers take the 90% accurate code, connect it to modern APIs (perhaps replacing the old COM+ or SOAP backends), and deploy the new React portal.

Industry experts recommend this "visual-first" approach because it bypasses the "Documentation Gap." When 67% of your systems have no manual, the application itself becomes the source of truth.

Frequently Asked Questions#

How does Replay handle complex Delphi logic that isn't visible on the screen?#

While Replay is a visual reverse engineering tool, it captures the behavioral output of that logic. By observing how the UI reacts to different inputs (e.g., error messages, field masking, or conditional visibility), Replay can infer the underlying business rules. For deep backend logic, Replay provides the architectural "Flows" that tell your backend team exactly what APIs need to be built to support the new React frontend.

Can we use Replay if we don't have the Delphi source code?#

Yes. This is one of the primary advantages of converting delphibased banking terminals with Replay. Because it uses visual reverse engineering, it only needs to "see" the application running. It does not require access to the original Pascal source code, making it ideal for systems where the code has been lost or is too convoluted to read.

What is the typical time savings when using Replay?#

According to Replay's analysis, the average manual modernization project takes 40 hours per screen. With Replay, that is reduced to approximately 4 hours per screen—a 90% reduction in manual labor and a 70% overall time saving for the project.

Is the generated React code maintainable?#

Absolutely. Replay does not produce "spaghetti code" or "machine code." It generates clean, documented TypeScript and React components that follow modern best practices. The code is structured to be used with popular libraries like Tailwind CSS, MUI, or your own internal design system.

Does Replay support on-premise deployments for highly regulated banks?#

Yes. Replay offers an on-premise version of its platform specifically for industries like Government, Healthcare, and Financial Services. This ensures that no sensitive banking data or screen recordings ever leave your secure network during the conversion process.

Moving Forward: The End of Technical Debt#

The $3.6 trillion technical debt problem won't be solved by hiring more developers to write code manually. It will be solved by automation. Converting delphibased banking terminals is the perfect use case for Visual Reverse Engineering. It allows financial institutions to preserve their proven business logic while shedding the constraints of 32-bit desktop environments.

By moving to a React-based portal architecture, you open the door to mobile accessibility, cloud scalability, and a significantly better developer experience. You turn a "legacy liability" into a "digital asset."

Ready to modernize without rewriting? Book a pilot with Replay and see how we can convert your legacy terminals into modern React portals in weeks, not years.