diff --git a/src/__tests__/chaos/horizonDuplicateHash.test.ts b/src/__tests__/chaos/horizonDuplicateHash.test.ts
new file mode 100644
index 00000000..a50d8a81
--- /dev/null
+++ b/src/__tests__/chaos/horizonDuplicateHash.test.ts
@@ -0,0 +1,144 @@
+import * as StellarSdk from '@stellar/stellar-sdk';
+import { StellarSubmissionService } from '../../services/stellarSubmissionService';
+import { globalMetrics } from '../../lib/metrics';
+
+// Mock logger
+jest.mock('../../lib/logger', () => ({
+  globalLogger: {
+    child: jest.fn().mockReturnValue({
+      info: jest.fn(),
+      warn: jest.fn(),
+      error: jest.fn(),
+      debug: jest.fn(),
+    }),
+  },
+  logger: {
+    child: jest.fn().mockReturnValue({
+      info: jest.fn(),
+      warn: jest.fn(),
+      error: jest.fn(),
+      debug: jest.fn(),
+    }),
+  }
+}));
+
+// Mock environment
+jest.mock('../../config/env', () => ({
+  env: {
+    STELLAR_NETWORK: 'testnet',
+    STELLAR_NETWORK_PASSPHRASE: 'Test SDF Network ; September 2015',
+    STELLAR_SERVER_SECRET: 'SABERIntegrationTestSecretKey1234567890ABCDEF',
+  },
+}));
+
+describe('Horizon Duplicate Hash Chaos Tests', () => {
+  let service: StellarSubmissionService;
+  let mockServer: any;
+  let metricsIncrementSpy: jest.SpyInstance;
+
+  beforeEach(() => {
+    process.env.STELLAR_SERVER_SECRET = 'SABERIntegrationTestSecretKey1234567890ABCDEF';
+    jest.clearAllMocks();
+    
+    metricsIncrementSpy = jest.spyOn(globalMetrics, 'increment');
+    
+    mockServer = {
+      getAccount: jest.fn().mockResolvedValue({
+        accountId: () => 'G-MOCK-PUBLIC-KEY',
+        sequenceNumber: () => '1',
+        incrementSequenceNumber: jest.fn(),
+      }),
+      sendTransaction: jest.fn(),
+    };
+    
+    StellarSdk.rpc.Server = jest.fn(() => mockServer) as any;
+    StellarSdk.Keypair.fromSecret = jest.fn(() => ({
+      publicKey: () => 'G-MOCK-PUBLIC-KEY',
+      sign: jest.fn(),
+    })) as any;
+    
+    StellarSdk.Asset.native = jest.fn(() => ({ code: 'XLM', issuer: undefined })) as any;
+    
+    StellarSdk.TransactionBuilder = jest.fn(() => ({
+      addOperation: jest.fn().mockReturnThis(),
+      setTimeout: jest.fn().mockReturnThis(),
+      build: jest.fn().mockReturnValue({
+        hash: () => Buffer.from('mock-hash'),
+        sign: jest.fn(),
+      }),
+    })) as any;
+    
+    StellarSdk.Operation.payment = jest.fn() as any;
+    (StellarSdk as any).BASE_FEE = '100';
+    
+    service = new StellarSubmissionService();
+  });
+
+  afterEach(() => {
+    metricsIncrementSpy.mockRestore();
+  });
+
+  it('should treat first-attempt duplicate as success (retry recovery scenario)', async () => {
+    mockServer.sendTransaction.mockResolvedValueOnce({
+      hash: 'mock-hash',
+      status: 'DUPLICATE',
+      latestLedger: 12345,
+      latestLedgerCloseTime: 1234567890,
+    });
+
+    const result = await service.submitPayment('G-DEST', '10.0');
+
+    expect(result.status).toBe('DUPLICATE');
+    expect(metricsIncrementSpy).toHaveBeenCalledWith('submission.duplicate.recovered', 1);
+  });
+
+  it('should treat true-duplicate as success without double persisting (client bug)', async () => {
+    mockServer.sendTransaction.mockResolvedValueOnce({
+      hash: 'mock-hash',
+      status: 'DUPLICATE',
+      latestLedger: 12345,
+      latestLedgerCloseTime: 1234567890,
+    });
+
+    const result = await service.submitPayment('G-DEST', '10.0');
+
+    expect(result.status).toBe('DUPLICATE');
+    expect(metricsIncrementSpy).toHaveBeenCalledWith('submission.duplicate.recovered', 1);
+    
+    expect(result).toBeDefined();
+    
+    expect(service.getTransactionCacheSize()).toBe(1);
+  });
+
+  it('Concurrent duplicate submissions from two workers coalesce', async () => {
+    mockServer.sendTransaction
+      .mockResolvedValueOnce({
+        hash: 'mock-hash',
+        status: 'PENDING',
+        latestLedger: 12345,
+        latestLedgerCloseTime: 1234567890,
+      })
+      .mockResolvedValueOnce({
+        hash: 'mock-hash',
+        status: 'DUPLICATE',
+        latestLedger: 12345,
+        latestLedgerCloseTime: 1234567890,
+      });
+
+    const worker1 = service;
+    const worker2 = new StellarSubmissionService();
+
+    const [res1, res2] = await Promise.all([
+      worker1.submitPayment('G-DEST', '10.0'),
+      worker2.submitPayment('G-DEST', '10.0'),
+    ]);
+
+    expect(res1.status).toBe('PENDING');
+    expect(res2.status).toBe('DUPLICATE');
+
+    expect(metricsIncrementSpy).toHaveBeenCalledWith('submission.duplicate.recovered', 1);
+    
+    expect(res1).toBeDefined();
+    expect(res2).toBeDefined();
+  });
+});
diff --git a/src/services/stellarSubmissionService.ts b/src/services/stellarSubmissionService.ts
index bd17d639..56ba1d7f 100644
--- a/src/services/stellarSubmissionService.ts
+++ b/src/services/stellarSubmissionService.ts
@@ -10,6 +10,7 @@ import {
   shouldRetryStellarRPCFailure,
   createStellarErrorResponse
 } from '../lib/stellarRpcFailure';
+import { globalMetrics } from '../lib/metrics';
 
 const logger = globalLogger.child({ service: 'stellar-submission' });
 
@@ -265,10 +266,13 @@ export class StellarSubmissionService {
         if (result.status === 'PENDING') {
           return result;
         } else if (result.status === 'DUPLICATE') {
-          throw Errors.conflict('Transaction already submitted', {
-            hash: result.hash,
+          globalMetrics.increment('submission.duplicate.recovered', 1);
+          logger.info('Recovered duplicate transaction submission', {
             transactionHash,
+            attemptCount,
+            operation: 'send_transaction',
           });
+          return result;
         } else if (result.status === 'TRY_AGAIN_LATER') {
           throw Errors.serviceUnavailable('Transaction rate limited, try again later');
         } else {