fix(backend): round owed amounts via half-even policy in loanController.ts roundToCents (#1372)

.gitattributes

@@ -0,0 +1,8 @@
+* text=auto eol=lf
+*.ts text eol=lf
+*.tsx text eol=lf
+*.js text eol=lf
+*.jsx text eol=lf
+*.json text eol=lf
+*.md text eol=lf
+*.css text eol=lf

backend/src/__tests__/loanConfig.test.ts

@@ -1,3 +1,4 @@
+import { jest } from '@jest/globals';
 import { validateLoanConfig, validateLoanConfigOnStartup } from '../config/loanConfig.js';
 
 describe('Loan config startup validation', () => {

backend/src/__tests__/roundToCents.test.ts

@@ -0,0 +1,23 @@
+import { roundToCents } from '../controllers/loanController.js';
+
+describe('roundToCents half-even rounding', () => {
+  it('applies banker rounding (half-even) for .5 cent cases', () => {
+    expect(roundToCents(0.125)).toBe(0.12);
+    expect(roundToCents(0.135)).toBe(0.14);
+    expect(roundToCents(10.005)).toBe(10.0);
+    expect(roundToCents(10.015)).toBe(10.02);
+  });
+
+  it('handles negative half-even rounding symmetrically', () => {
+    expect(roundToCents(-0.125)).toBe(-0.12);
+    expect(roundToCents(-0.135)).toBe(-0.14);
+  });
+
+  it('rounds non-tie values to nearest cent', () => {
+    expect(roundToCents(10.004)).toBe(10.0);
+    expect(roundToCents(10.006)).toBe(10.01);
+    expect(roundToCents(12.3456)).toBe(12.35);
+    expect(roundToCents(12.3412)).toBe(12.34);
+    expect(roundToCents(0.0049)).toBe(0);
+  });
+});

backend/src/controllers/loanController.ts

@@ -12,6 +12,7 @@
 import { cacheService } from '../services/cacheService.js';
 import { notificationService } from '../services/notificationService.js';
 import { invalidateOnRepay, invalidateOnLoanRequest } from '../utils/cacheKeys.js';
+import { roundToCents } from '../money/decimal.js';
 
 // ─── Test/Dev Only ────────────────────────────────────────────────────────────
 
@@ -52,7 +53,7 @@
   try {
     const { loanId } = req.params;
 
     const borrower = (req as any).user?.publicKey as string;
 
     const result = await query('SELECT * FROM loans WHERE id = $1', [loanId]);
     const loan = result.rows[0] as Record<string, unknown> | undefined;
@@ -225,7 +226,7 @@
   return result.rows[0]?.last_indexed_ledger ?? 0;
 };
 
-const roundToCents = (value: number): number => Math.floor((value + Number.EPSILON) * 100) / 100;
+export { roundToCents };
 
 const addDays = (date: Date, days: number): Date => {
   const result = new Date(date);

backend/src/money/__tests__/decimal.test.ts

@@ -3,6 +3,7 @@ import {
   toStroops,
   fromStroops,
   splitProRata,
+  roundToCents,
   RoundingMode,
   MoneyError,
   STROOP_SCALE,
@@ -168,3 +169,17 @@ describe('splitProRata', () => {
     expect(() => splitProRata(1n, [-1n])).toThrow(MoneyError);
   });
 });
+
+describe('roundToCents', () => {
+  it('rounds via half-even rounding mode (bankers rounding)', () => {
+    expect(roundToCents(0.125)).toBe(0.12);
+    expect(roundToCents(0.135)).toBe(0.14);
+    expect(roundToCents(10.005)).toBe(10.0);
+    expect(roundToCents(10.015)).toBe(10.02);
+  });
+
+  it('handles negative numbers symmetrically', () => {
+    expect(roundToCents(-0.125)).toBe(-0.12);
+    expect(roundToCents(-0.135)).toBe(-0.14);
+  });
+});

backend/src/money/decimal.ts

@@ -154,6 +154,17 @@ export function fromStroops(value: bigint): string {
   return `${negative ? '-' : ''}${whole.toString()}.${fraction}`;
 }
 
+/**
+ * Round a numeric amount to 2 decimal places (cents) using the policy's
+ * default half-even rounding mode.
+ */
+export function roundToCents(value: number, mode: RoundingMode = DEFAULT_MODE): number {
+  if (!Number.isFinite(value)) return value;
+  const stroops = toStroops(value.toFixed(7), mode);
+  const cents = roundDiv(stroops, 100_000n, mode);
+  return Number(cents) / 100;
+}
+
 /**
  * Split `total` stroops across `weights` proportionally using the
  * largest-remainder method, guaranteeing the returned parts sum *exactly*

frontend/src/app/[locale]/activity/page.tsx

@@ -84,7 +84,10 @@ export default function ActivityPage() {
     const remittanceEvents: ActivityItem[] = remittances.map((remittance) => ({
       id: `remittance-${remittance.id}`,
       type: "Remittance",
-      description: `To ${remittance.recipientAddress.slice(0, 6)}...${remittance.recipientAddress.slice(-4)}`,
+      description: `To ${remittance.recipientAddress.slice(
+        0,
+        6,
+      )}...${remittance.recipientAddress.slice(-4)}`,
       amount: `-${formatCurrency(remittance.amount)}`,
       timestamp: new Date(remittance.createdAt).toISOString(),
       status: remittance.status,

frontend/src/app/components/borrower/LoanCard.tsx

@@ -150,7 +150,9 @@ export function LoanCard({ loan, variant = "compact" }: LoanCardProps) {
         <div className={`p-4 rounded-lg ${deadlineBg}`}>
           <p className="text-sm text-gray-600 mb-1">Next Payment</p>
           <p
-            className={`${variant === "compact" ? "text-lg" : "text-sm"} font-semibold ${deadlineTextColor}`}
+            className={`${
+              variant === "compact" ? "text-lg" : "text-sm"
+            } font-semibold ${deadlineTextColor}`}
           >
             {formatDate(loan.nextPaymentDeadline)}
           </p>

frontend/src/app/components/dashboards/FinancialPerformanceDashboard.tsx

@@ -354,7 +354,9 @@ export function FinancialPerformanceDashboard({
             <StatCard
               title="On-time Rate"
               value={`${displayLoanStats.onTimeRate}%`}
-              sub={`${displayLoanStats.repaid} of ${displayLoanStats.repaid + displayLoanStats.defaulted} resolved`}
+              sub={`${displayLoanStats.repaid} of ${
+                displayLoanStats.repaid + displayLoanStats.defaulted
+              } resolved`}
               colorClass="bg-purple-50 text-purple-900 dark:bg-purple-950/30 dark:text-purple-200"
             />
           </div>
@@ -417,7 +419,11 @@ export function FinancialPerformanceDashboard({
               value={fmt(displayDepositorStats.currentValue)}
               sub={
                 displayDepositorStats.depositAmount > 0
-                  ? `+${(((displayDepositorStats.currentValue - displayDepositorStats.depositAmount) / displayDepositorStats.depositAmount) * 100).toFixed(2)}% growth`
+                  ? `+${(
+                      ((displayDepositorStats.currentValue - displayDepositorStats.depositAmount) /
+                        displayDepositorStats.depositAmount) *
+                      100
+                    ).toFixed(2)}% growth`
                   : undefined
               }
               colorClass="bg-blue-50 text-blue-900 dark:bg-blue-950/30 dark:text-blue-200"

frontend/src/app/components/loan-wizard/StepAmountAsset.tsx

@@ -152,7 +152,9 @@ export function StepAmountAsset({ data, onChange, onNext, error, onError }: Step
                 helperText ||
                 (data.maxAmount === 0
                   ? "Not eligible"
-                  : `Eligible range: ${formatMoney(minAmount)} – ${formatMoney(data.maxAmount)} • Max ${decimals} decimal places`)
+                  : `Eligible range: ${formatMoney(minAmount)} – ${formatMoney(
+                      data.maxAmount,
+                    )} • Max ${decimals} decimal places`)
               }
               error={precisionError || undefined}
             />

frontend/src/app/components/ui.tsx

@@ -1 +1 @@
-export { COPY_FEEDBACK_RESET_MS } from './ui/CopyButton';
+export { COPY_FEEDBACK_RESET_MS } from "./ui/CopyButton";

frontend/src/app/components/ui/OperationProgress.tsx

@@ -88,7 +88,10 @@ export function OperationProgress({ transaction, type = "generic" }: OperationPr
               href={`https://stellar.expert/explorer/testnet/tx/${txHash}`}
               target="_blank"
               rel="noopener noreferrer"
-              aria-label={`View transaction ${txHash.slice(0, 8)}… on Stellar Explorer (opens in new tab)`}
+              aria-label={`View transaction ${txHash.slice(
+                0,
+                8,
+              )}… on Stellar Explorer (opens in new tab)`}
               className="text-xs text-blue-600 hover:text-blue-700 dark:text-blue-400 hover:underline flex items-center gap-1"
             >
               <Clock className="h-3 w-3" />

frontend/src/app/components/ui/Toaster.tsx

@@ -57,7 +57,9 @@ function ToastCard({ toast }: { toast: ToastItem }) {
       animate={{ opacity: 1, x: 0, scale: 1 }}
       exit={{ opacity: 0, x: 20, scale: 0.96 }}
       transition={{ duration: 0.2, ease: "easeOut" }}
-      className={`w-full rounded-xl border p-4 shadow-lg shadow-zinc-900/5 ${getToastStyles(toast.type)}`}
+      className={`w-full rounded-xl border p-4 shadow-lg shadow-zinc-900/5 ${getToastStyles(
+        toast.type,
+      )}`}
       role="alert"
     >
       <div className="flex items-start gap-3">

frontend/src/app/hooks/useReveal.test.tsx

@@ -125,12 +125,10 @@ describe("useReveal", () => {
 
   it("does not expose the value before the request resolves", async () => {
     let resolveFetch!: (val: unknown) => void;
-    global.fetch = jest.fn(
-      () =>
-        new Promise((resolve) => {
-          resolveFetch = resolve;
-        }),
-    ) as unknown as typeof fetch;
+    const fetchPromise = new Promise((resolve) => {
+      resolveFetch = resolve;
+    });
+    global.fetch = jest.fn(() => fetchPromise) as unknown as typeof fetch;
 
     const { result } = renderHook(() => useReveal(), { wrapper: createWrapper() });
 

frontend/src/app/utils/transactionFormatter.ts

@@ -186,7 +186,10 @@ export function formatRemittanceSend(params: {
   const operations: TransactionOperation[] = [
     {
       type: "Send Remittance",
-      description: `You are sending ${params.amount} ${params.token} to ${params.recipient.slice(0, 8)}...${params.recipient.slice(-6)}`,
+      description: `You are sending ${params.amount} ${params.token} to ${params.recipient.slice(
+        0,
+        8,
+      )}...${params.recipient.slice(-6)}`,
       amount: params.amount.toString(),
       token: params.token,
       details: {