diff --git a/packages/transaction-controller/CHANGELOG.md b/packages/transaction-controller/CHANGELOG.md
index 5936d76f04..d3b96ca2ea 100644
--- a/packages/transaction-controller/CHANGELOG.md
+++ b/packages/transaction-controller/CHANGELOG.md
@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Export `decodeAuthorizationSignature` utility that decodes a 65-byte EIP-7702 authorization signature into RLP-canonical `r`, `s`, and `yParity` ([#8656](https://github.com/MetaMask/core/pull/8656))
+  - All `eth_sendRawTransaction` failures are prefixed `RPC submit:` for failure-surface attribution in error metrics
+
 ### Changed
 
 - Bump `@metamask/messenger` from `^1.1.1` to `^1.2.0` ([#8632](https://github.com/MetaMask/core/pull/8632))
diff --git a/packages/transaction-controller/src/TransactionController.test.ts b/packages/transaction-controller/src/TransactionController.test.ts
index 5d8f630935..ea2b6da60d 100644
--- a/packages/transaction-controller/src/TransactionController.test.ts
+++ b/packages/transaction-controller/src/TransactionController.test.ts
@@ -3924,7 +3924,9 @@ describe('TransactionController', () => {
 
       rpcRequestMock.mockRejectedValueOnce(error);
 
-      await expect(controller.stopTransaction('2')).rejects.toThrow(error);
+      await expect(controller.stopTransaction('2')).rejects.toThrow(
+        'RPC submit: Another reason',
+      );
 
       const sendRawTransactionCalls = rpcRequestMock.mock.calls.filter(
         ([request]) => request.method === 'eth_sendRawTransaction',
@@ -4276,7 +4278,9 @@ describe('TransactionController', () => {
 
       rpcRequestMock.mockRejectedValueOnce(error);
 
-      await expect(controller.speedUpTransaction('2')).rejects.toThrow(error);
+      await expect(controller.speedUpTransaction('2')).rejects.toThrow(
+        'RPC submit: Another reason',
+      );
 
       const sendRawTransactionCalls = rpcRequestMock.mock.calls.filter(
         ([request]) => request.method === 'eth_sendRawTransaction',
@@ -4285,6 +4289,39 @@ describe('TransactionController', () => {
       expect(controller.state.transactions).toHaveLength(1);
     });
 
+    it('extracts nested data.message and prefixes it with RPC submit', async () => {
+      const error = {
+        message: 'Outer message',
+        data: { message: 'Nested rpc error message' },
+      };
+      const { controller } = setupController({
+        options: {
+          state: {
+            transactions: [
+              {
+                id: '2',
+                chainId: toHex(5),
+                networkClientId: NETWORK_CLIENT_ID_MOCK,
+                status: TransactionStatus.submitted,
+                type: TransactionType.retry,
+                time: 123456789,
+                txParams: {
+                  from: ACCOUNT_MOCK,
+                  gasPrice: '0x1',
+                },
+              },
+            ],
+          },
+        },
+      });
+
+      rpcRequestMock.mockRejectedValueOnce(error);
+
+      await expect(controller.speedUpTransaction('2')).rejects.toThrow(
+        'RPC submit: Nested rpc error message',
+      );
+    });
+
     it('creates additional transaction with increased gas', async () => {
       const { controller } = setupController({
         network: MOCK_LINEA_MAINNET_NETWORK,
diff --git a/packages/transaction-controller/src/TransactionController.ts b/packages/transaction-controller/src/TransactionController.ts
index 646842e68f..83dbe27899 100644
--- a/packages/transaction-controller/src/TransactionController.ts
+++ b/packages/transaction-controller/src/TransactionController.ts
@@ -3372,7 +3372,7 @@ export class TransactionController extends BaseController<
       const errorMessage =
         errorObject?.data?.message ?? errorObject?.message ?? String(error);
 
-      throw new Error(errorMessage);
+      throw new Error(`RPC submit: ${errorMessage}`);
     }
   }
 
diff --git a/packages/transaction-controller/src/index.ts b/packages/transaction-controller/src/index.ts
index b699986dc9..a005fbabea 100644
--- a/packages/transaction-controller/src/index.ts
+++ b/packages/transaction-controller/src/index.ts
@@ -129,6 +129,7 @@ export {
   WalletDevice,
 } from './types';
 export { mergeGasFeeEstimates } from './utils/gas-flow';
+export { decodeAuthorizationSignature } from './utils/eip7702';
 export {
   isEIP1559Transaction,
   normalizeTransactionParams,
diff --git a/packages/transaction-controller/src/utils/eip7702.test.ts b/packages/transaction-controller/src/utils/eip7702.test.ts
index b23f9ac217..e6b0a18986 100644
--- a/packages/transaction-controller/src/utils/eip7702.test.ts
+++ b/packages/transaction-controller/src/utils/eip7702.test.ts
@@ -18,6 +18,7 @@ import type { AuthorizationList } from '../types';
 import type { TransactionMeta } from '../types';
 import {
   DELEGATION_PREFIX,
+  decodeAuthorizationSignature,
   doesAccountSupportEIP7702,
   doesChainSupportEIP7702,
   generateEIP7702BatchTransaction,
@@ -257,6 +258,93 @@ describe('EIP-7702 Utils', () => {
       expect(result?.[1]?.nonce).toBe('0x125');
       expect(result?.[2]?.nonce).toBe('0x126');
     });
+
+    it('strips leading zeroes from signature r and s to produce RLP-canonical hex', async () => {
+      const signatureWithLeadingZeros =
+        `0x0abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456781122334455667788990011223344556677889900112233445566778899001122${'1c'}` as Hex;
+
+      signAuthorizationMock
+        .mockReset()
+        .mockResolvedValueOnce(signatureWithLeadingZeros);
+
+      const result = await signAuthorizationList({
+        authorizationList: AUTHORIZATION_LIST_MOCK,
+        messenger: controllerMessenger,
+        transactionMeta: TRANSACTION_META_MOCK,
+      });
+
+      expect(result?.[0]?.r).toBe(
+        '0xabcdef0123456789abcdef0123456789abcdef0123456789abcdef012345678',
+      );
+      expect(result?.[0]?.s).toBe(
+        '0x1122334455667788990011223344556677889900112233445566778899001122',
+      );
+      expect(result?.[0]?.yParity).toBe('0x1');
+    });
+  });
+
+  describe('decodeAuthorizationSignature', () => {
+    it('decodes a signature with no leading zeros into r, s, and yParity', () => {
+      const result = decodeAuthorizationSignature(AUTHORIZATION_SIGNATURE_MOCK);
+
+      expect(result).toStrictEqual({
+        r: '0xf85c827a6994663f3ad617193148711d28f5334ee4ed070166028080a040e292',
+        s: '0xda533253143f134643a03405f1af1de1d305526f44ed27e62061368d4ea051cf',
+        yParity: '0x1',
+      });
+    });
+
+    it('strips a single leading zero nibble from r', () => {
+      const signature =
+        `0x0abcdef0123456789abcdef0123456789abcdef0123456789abcdef012345678${'1122334455667788990011223344556677889900112233445566778899001122'}1b` as Hex;
+
+      const result = decodeAuthorizationSignature(signature);
+
+      expect(result.r).toBe(
+        '0xabcdef0123456789abcdef0123456789abcdef0123456789abcdef012345678',
+      );
+      expect(result.s).toBe(
+        '0x1122334455667788990011223344556677889900112233445566778899001122',
+      );
+    });
+
+    it('strips multiple leading zero bytes from r', () => {
+      const signature =
+        `0x000000abcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcd${'1122334455667788990011223344556677889900112233445566778899001122'}1b` as Hex;
+
+      const result = decodeAuthorizationSignature(signature);
+
+      expect(result.r).toBe(
+        '0xabcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcd',
+      );
+    });
+
+    it('returns 0x0 when r is all zeroes (canonical zero)', () => {
+      const signature =
+        `0x0000000000000000000000000000000000000000000000000000000000000000${'1122334455667788990011223344556677889900112233445566778899001122'}1b` as Hex;
+
+      const result = decodeAuthorizationSignature(signature);
+
+      expect(result.r).toBe('0x0');
+    });
+
+    it('returns yParity 0x0 when v is 27', () => {
+      const signature =
+        `0xf85c827a6994663f3ad617193148711d28f5334ee4ed070166028080a040e292da533253143f134643a03405f1af1de1d305526f44ed27e62061368d4ea051cf1b` as Hex;
+
+      const result = decodeAuthorizationSignature(signature);
+
+      expect(result.yParity).toBe('0x0');
+    });
+
+    it('returns yParity 0x1 when v is 28', () => {
+      const signature =
+        `0xf85c827a6994663f3ad617193148711d28f5334ee4ed070166028080a040e292da533253143f134643a03405f1af1de1d305526f44ed27e62061368d4ea051cf1c` as Hex;
+
+      const result = decodeAuthorizationSignature(signature);
+
+      expect(result.yParity).toBe('0x1');
+    });
   });
 
   describe('doesChainSupportEIP7702', () => {
diff --git a/packages/transaction-controller/src/utils/eip7702.ts b/packages/transaction-controller/src/utils/eip7702.ts
index 36e5eb1ce1..889b173d25 100644
--- a/packages/transaction-controller/src/utils/eip7702.ts
+++ b/packages/transaction-controller/src/utils/eip7702.ts
@@ -247,6 +247,43 @@ export async function signAuthorizationList({
   return signedAuthorizationList;
 }
 
+/**
+ * Decode a 65-byte EIP-7702 authorization signature into RLP-canonical
+ * `r`, `s`, and `yParity` (no leading zero nibbles, `0x0` for zero).
+ *
+ * @param signature - The 65-byte signature.
+ * @returns The decoded authorization fields.
+ */
+export function decodeAuthorizationSignature(signature: Hex): {
+  r: Hex;
+  s: Hex;
+  yParity: Hex;
+} {
+  // eslint-disable-next-line id-length
+  const r = toCanonicalHex(signature.slice(0, 66));
+  // eslint-disable-next-line id-length
+  const s = toCanonicalHex(signature.slice(66, 130));
+  // eslint-disable-next-line id-length
+  const v = parseInt(signature.slice(130, 132), 16);
+  const yParity = toCanonicalHex(toHex(v - 27 === 0 ? 0 : 1));
+
+  return { r, s, yParity };
+}
+
+/**
+ * Strip leading zero nibbles from a hex string to produce its RLP-canonical
+ * form. Accepts input with or without a `0x` prefix; always returns
+ * `0x`-prefixed. An all-zero input is preserved as `0x0`.
+ *
+ * @param value - Hex string with or without a `0x` prefix.
+ * @returns The canonical `0x`-prefixed hex string.
+ */
+function toCanonicalHex(value: string): Hex {
+  const raw = value.startsWith('0x') ? value.slice(2) : value;
+  const stripped = raw.replace(/^0+/u, '');
+  return stripped.length === 0 ? '0x0' : `0x${stripped}`;
+}
+
 /**
  * Signs an authorization.
  *
@@ -284,13 +321,7 @@ async function signAuthorization(
     },
   );
 
-  // eslint-disable-next-line id-length
-  const r = signature.slice(0, 66) as Hex;
-  // eslint-disable-next-line id-length
-  const s = add0x(signature.slice(66, 130));
-  // eslint-disable-next-line id-length
-  const v = parseInt(signature.slice(130, 132), 16);
-  const yParity = toHex(v - 27 === 0 ? 0 : 1);
+  const { r, s, yParity } = decodeAuthorizationSignature(signature as Hex);
 
   const result: Required<Authorization> = {
     address,
diff --git a/packages/transaction-pay-controller/CHANGELOG.md b/packages/transaction-pay-controller/CHANGELOG.md
index 52aab1aac8..c627bfce43 100644
--- a/packages/transaction-pay-controller/CHANGELOG.md
+++ b/packages/transaction-pay-controller/CHANGELOG.md
@@ -10,6 +10,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - Stop synthesising a native gas-fee required token in `parseRequiredTokens`, only token-transfer assets are returned now ([#8554](https://github.com/MetaMask/core/pull/8554))
+- Add layered submission error prefixes for failure-surface attribution in error metrics ([#8656](https://github.com/MetaMask/core/pull/8656))
+  - `MetaMask Pay:` wraps all errors from the Pay publish hook
+  - `Relay submit:` wraps all errors from the relay strategy
+  - `Relay execute:` cascades inside `Relay submit:` for `/execute` POST failures
+  - Relay non-OK responses now surface as `<status> - <body message or error>` (or just `<status>`), replacing the previous URL-leaking generic fetch failure message
 
 ## [20.1.0]
 
diff --git a/packages/transaction-pay-controller/src/helpers/TransactionPayPublishHook.test.ts b/packages/transaction-pay-controller/src/helpers/TransactionPayPublishHook.test.ts
index cc11468619..ec8fa0d011 100644
--- a/packages/transaction-pay-controller/src/helpers/TransactionPayPublishHook.test.ts
+++ b/packages/transaction-pay-controller/src/helpers/TransactionPayPublishHook.test.ts
@@ -190,9 +190,25 @@ describe('TransactionPayPublishHook', () => {
     );
   });
 
-  it('throws errors from submit', async () => {
+  it('throws errors from submit prefixed with MetaMask Pay', async () => {
     executeMock.mockRejectedValue(new Error('Test error'));
 
-    await expect(runHook()).rejects.toThrow('Test error');
+    await expect(runHook()).rejects.toThrow('MetaMask Pay: Test error');
+  });
+
+  it('cascades MetaMask Pay prefix on top of strategy-level prefixes', async () => {
+    executeMock.mockRejectedValue(
+      new Error('Relay submit: Relay execute: backend boom'),
+    );
+
+    await expect(runHook()).rejects.toThrow(
+      'MetaMask Pay: Relay submit: Relay execute: backend boom',
+    );
+  });
+
+  it('wraps non-Error throws with the MetaMask Pay prefix', async () => {
+    executeMock.mockRejectedValue('boom');
+
+    await expect(runHook()).rejects.toThrow('MetaMask Pay: boom');
   });
 });
diff --git a/packages/transaction-pay-controller/src/helpers/TransactionPayPublishHook.ts b/packages/transaction-pay-controller/src/helpers/TransactionPayPublishHook.ts
index 4988a742df..48d616fa0c 100644
--- a/packages/transaction-pay-controller/src/helpers/TransactionPayPublishHook.ts
+++ b/packages/transaction-pay-controller/src/helpers/TransactionPayPublishHook.ts
@@ -47,7 +47,8 @@ export class TransactionPayPublishHook {
       return await this.#publishHook(transactionMeta, _signedTx);
     } catch (error) {
       log('Error', error);
-      throw error;
+      const message = error instanceof Error ? error.message : String(error);
+      throw new Error(`MetaMask Pay: ${message}`);
     }
   }
 
diff --git a/packages/transaction-pay-controller/src/strategy/relay/RelayStrategy.test.ts b/packages/transaction-pay-controller/src/strategy/relay/RelayStrategy.test.ts
index 01460383d0..0d44f891d8 100644
--- a/packages/transaction-pay-controller/src/strategy/relay/RelayStrategy.test.ts
+++ b/packages/transaction-pay-controller/src/strategy/relay/RelayStrategy.test.ts
@@ -108,4 +108,38 @@ describe('RelayStrategy', () => {
     });
     expect(submitRelayQuotesMock).toHaveBeenCalledWith(executeRequest);
   });
+
+  it('wraps execute errors with the Relay submit prefix', async () => {
+    const executeRequest = {
+      messenger,
+      quotes: [],
+      transaction: request.transaction,
+      isSmartTransaction: jest.fn(),
+    } as PayStrategyExecuteRequest<RelayQuote>;
+
+    submitRelayQuotesMock.mockRejectedValue(
+      new Error('Relay execute: 422 - Insufficient liquidity'),
+    );
+
+    const strategy = new RelayStrategy();
+    await expect(strategy.execute(executeRequest)).rejects.toThrow(
+      'Relay submit: Relay execute: 422 - Insufficient liquidity',
+    );
+  });
+
+  it('wraps non-Error throws with the Relay submit prefix', async () => {
+    const executeRequest = {
+      messenger,
+      quotes: [],
+      transaction: request.transaction,
+      isSmartTransaction: jest.fn(),
+    } as PayStrategyExecuteRequest<RelayQuote>;
+
+    submitRelayQuotesMock.mockRejectedValue('boom');
+
+    const strategy = new RelayStrategy();
+    await expect(strategy.execute(executeRequest)).rejects.toThrow(
+      'Relay submit: boom',
+    );
+  });
 });
diff --git a/packages/transaction-pay-controller/src/strategy/relay/RelayStrategy.ts b/packages/transaction-pay-controller/src/strategy/relay/RelayStrategy.ts
index 22f6d9c31f..8ed8d23c54 100644
--- a/packages/transaction-pay-controller/src/strategy/relay/RelayStrategy.ts
+++ b/packages/transaction-pay-controller/src/strategy/relay/RelayStrategy.ts
@@ -24,6 +24,11 @@ export class RelayStrategy implements PayStrategy<RelayQuote> {
   async execute(
     request: PayStrategyExecuteRequest<RelayQuote>,
   ): ReturnType<PayStrategy<RelayQuote>['execute']> {
-    return await submitRelayQuotes(request);
+    try {
+      return await submitRelayQuotes(request);
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      throw new Error(`Relay submit: ${message}`);
+    }
   }
 }
diff --git a/packages/transaction-pay-controller/src/strategy/relay/relay-api.test.ts b/packages/transaction-pay-controller/src/strategy/relay/relay-api.test.ts
index 69a3204d3e..40ded0e790 100644
--- a/packages/transaction-pay-controller/src/strategy/relay/relay-api.test.ts
+++ b/packages/transaction-pay-controller/src/strategy/relay/relay-api.test.ts
@@ -1,5 +1,3 @@
-import { successfulFetch } from '@metamask/controller-utils';
-
 import type { FeatureFlags } from '../../utils/feature-flags';
 import { getFeatureFlags } from '../../utils/feature-flags';
 import { RELAY_STATUS_URL } from './constants';
@@ -12,14 +10,23 @@ import type { RelayQuoteRequest } from './types';
 
 jest.mock('../../utils/feature-flags');
 
-jest.mock('@metamask/controller-utils', () => ({
-  ...jest.requireActual('@metamask/controller-utils'),
-  successfulFetch: jest.fn(),
-}));
-
-const successfulFetchMock = jest.mocked(successfulFetch);
 const getFeatureFlagsMock = jest.mocked(getFeatureFlags);
 
+let fetchMock: jest.SpyInstance;
+
+const mockOkResponse = (body: unknown): jest.SpyInstance =>
+  fetchMock.mockResolvedValueOnce({
+    ok: true,
+    json: async () => body,
+  } as Response);
+
+const mockErrorResponse = (status: number, body: unknown): jest.SpyInstance =>
+  fetchMock.mockResolvedValueOnce({
+    ok: false,
+    status,
+    json: async () => body,
+  } as Response);
+
 const QUOTE_URL_MOCK = 'https://proxy.test/relay/quote';
 const EXECUTE_URL_MOCK = 'https://proxy.test/relay/execute';
 
@@ -27,7 +34,7 @@ const MESSENGER_MOCK = {} as Parameters<typeof fetchRelayQuote>[0];
 
 describe('relay-api', () => {
   beforeEach(() => {
-    jest.resetAllMocks();
+    fetchMock = jest.spyOn(global, 'fetch');
 
     getFeatureFlagsMock.mockReturnValue({
       relayQuoteUrl: QUOTE_URL_MOCK,
@@ -35,6 +42,10 @@ describe('relay-api', () => {
     } as FeatureFlags);
   });
 
+  afterEach(() => {
+    fetchMock.mockRestore();
+  });
+
   describe('fetchRelayQuote', () => {
     const QUOTE_REQUEST_MOCK: RelayQuoteRequest = {
       amount: '1000000',
@@ -53,13 +64,11 @@ describe('relay-api', () => {
     };
 
     it('posts to the quote URL from feature flags', async () => {
-      successfulFetchMock.mockResolvedValue({
-        json: async () => QUOTE_RESPONSE_MOCK,
-      } as Response);
+      mockOkResponse(QUOTE_RESPONSE_MOCK);
 
       await fetchRelayQuote(MESSENGER_MOCK, QUOTE_REQUEST_MOCK);
 
-      expect(successfulFetchMock).toHaveBeenCalledWith(QUOTE_URL_MOCK, {
+      expect(fetchMock).toHaveBeenCalledWith(QUOTE_URL_MOCK, {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
         body: JSON.stringify(QUOTE_REQUEST_MOCK),
@@ -67,9 +76,7 @@ describe('relay-api', () => {
     });
 
     it('attaches the request body to the returned quote', async () => {
-      successfulFetchMock.mockResolvedValue({
-        json: async () => ({ ...QUOTE_RESPONSE_MOCK }),
-      } as Response);
+      mockOkResponse({ ...QUOTE_RESPONSE_MOCK });
 
       const quote = await fetchRelayQuote(MESSENGER_MOCK, QUOTE_REQUEST_MOCK);
 
@@ -77,9 +84,7 @@ describe('relay-api', () => {
     });
 
     it('returns the parsed quote', async () => {
-      successfulFetchMock.mockResolvedValue({
-        json: async () => QUOTE_RESPONSE_MOCK,
-      } as Response);
+      mockOkResponse(QUOTE_RESPONSE_MOCK);
 
       const quote = await fetchRelayQuote(MESSENGER_MOCK, QUOTE_REQUEST_MOCK);
 
@@ -87,9 +92,7 @@ describe('relay-api', () => {
     });
 
     it('forwards the abort signal to the underlying fetch', async () => {
-      successfulFetchMock.mockResolvedValue({
-        json: async () => QUOTE_RESPONSE_MOCK,
-      } as Response);
+      mockOkResponse(QUOTE_RESPONSE_MOCK);
 
       const controller = new AbortController();
       await fetchRelayQuote(
@@ -98,11 +101,41 @@ describe('relay-api', () => {
         controller.signal,
       );
 
-      expect(successfulFetchMock).toHaveBeenCalledWith(
+      expect(fetchMock).toHaveBeenCalledWith(
         QUOTE_URL_MOCK,
         expect.objectContaining({ signal: controller.signal }),
       );
     });
+
+    it('throws an error containing status code and the response body message field on non-OK', async () => {
+      mockErrorResponse(422, { message: 'Insufficient liquidity' });
+
+      await expect(
+        fetchRelayQuote(MESSENGER_MOCK, QUOTE_REQUEST_MOCK),
+      ).rejects.toThrow('422 - Insufficient liquidity');
+    });
+
+    it('falls back to the response body error field when message is absent', async () => {
+      mockErrorResponse(429, { error: 'rate limit exceeded' });
+
+      await expect(
+        fetchRelayQuote(MESSENGER_MOCK, QUOTE_REQUEST_MOCK),
+      ).rejects.toThrow('429 - rate limit exceeded');
+    });
+
+    it('falls back to the status code only when the body has neither message nor error', async () => {
+      fetchMock.mockResolvedValueOnce({
+        ok: false,
+        status: 500,
+        json: async () => {
+          throw new Error('not json');
+        },
+      } as Response);
+
+      await expect(
+        fetchRelayQuote(MESSENGER_MOCK, QUOTE_REQUEST_MOCK),
+      ).rejects.toThrow('500');
+    });
   });
 
   describe('submitRelayExecute', () => {
@@ -124,13 +157,11 @@ describe('relay-api', () => {
     };
 
     it('posts to the execute URL from feature flags', async () => {
-      successfulFetchMock.mockResolvedValue({
-        json: async () => EXECUTE_RESPONSE_MOCK,
-      } as Response);
+      mockOkResponse(EXECUTE_RESPONSE_MOCK);
 
       await submitRelayExecute(MESSENGER_MOCK, EXECUTE_REQUEST_MOCK);
 
-      expect(successfulFetchMock).toHaveBeenCalledWith(EXECUTE_URL_MOCK, {
+      expect(fetchMock).toHaveBeenCalledWith(EXECUTE_URL_MOCK, {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
         body: JSON.stringify(EXECUTE_REQUEST_MOCK),
@@ -138,9 +169,7 @@ describe('relay-api', () => {
     });
 
     it('returns the parsed response', async () => {
-      successfulFetchMock.mockResolvedValue({
-        json: async () => EXECUTE_RESPONSE_MOCK,
-      } as Response);
+      mockOkResponse(EXECUTE_RESPONSE_MOCK);
 
       const result = await submitRelayExecute(
         MESSENGER_MOCK,
@@ -160,22 +189,18 @@ describe('relay-api', () => {
     };
 
     it('fetches the status URL with the request ID', async () => {
-      successfulFetchMock.mockResolvedValue({
-        json: async () => STATUS_RESPONSE_MOCK,
-      } as Response);
+      mockOkResponse(STATUS_RESPONSE_MOCK);
 
       await getRelayStatus(REQUEST_ID_MOCK);
 
-      expect(successfulFetchMock).toHaveBeenCalledWith(
+      expect(fetchMock).toHaveBeenCalledWith(
         `${RELAY_STATUS_URL}?requestId=${REQUEST_ID_MOCK}`,
         { method: 'GET' },
       );
     });
 
     it('returns the parsed status', async () => {
-      successfulFetchMock.mockResolvedValue({
-        json: async () => STATUS_RESPONSE_MOCK,
-      } as Response);
+      mockOkResponse(STATUS_RESPONSE_MOCK);
 
       const result = await getRelayStatus(REQUEST_ID_MOCK);
 
diff --git a/packages/transaction-pay-controller/src/strategy/relay/relay-api.ts b/packages/transaction-pay-controller/src/strategy/relay/relay-api.ts
index 627f1b952d..8f42d3715e 100644
--- a/packages/transaction-pay-controller/src/strategy/relay/relay-api.ts
+++ b/packages/transaction-pay-controller/src/strategy/relay/relay-api.ts
@@ -1,5 +1,3 @@
-import { successfulFetch } from '@metamask/controller-utils';
-
 import type { TransactionPayControllerMessenger } from '../../types';
 import { getFeatureFlags } from '../../utils/feature-flags';
 import { RELAY_STATUS_URL } from './constants';
@@ -26,7 +24,7 @@ export async function fetchRelayQuote(
 ): Promise<RelayQuote> {
   const { relayQuoteUrl } = getFeatureFlags(messenger);
 
-  const response = await successfulFetch(relayQuoteUrl, {
+  const response = await relayFetch(relayQuoteUrl, {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
     body: JSON.stringify(body),
@@ -52,7 +50,7 @@ export async function submitRelayExecute(
 ): Promise<RelayExecuteResponse> {
   const { relayExecuteUrl } = getFeatureFlags(messenger);
 
-  const response = await successfulFetch(relayExecuteUrl, {
+  const response = await relayFetch(relayExecuteUrl, {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
     body: JSON.stringify(body),
@@ -72,7 +70,39 @@ export async function getRelayStatus(
 ): Promise<RelayStatusResponse> {
   const url = `${RELAY_STATUS_URL}?requestId=${requestId}`;
 
-  const response = await successfulFetch(url, { method: 'GET' });
+  const response = await relayFetch(url, { method: 'GET' });
 
   return (await response.json()) as RelayStatusResponse;
 }
+
+/**
+ * Fetch a Relay endpoint, throwing an error containing the response body's
+ * `message` or `error` field (or status code) on non-OK responses, so the
+ * Relay server's actual reason is preserved without leaking the request URL
+ * via the default `successfulFetch` message.
+ *
+ * @param url - The Relay endpoint to fetch.
+ * @param init - Fetch init options.
+ * @returns The successful response.
+ */
+async function relayFetch(url: string, init?: RequestInit): Promise<Response> {
+  const response = await fetch(url, init);
+
+  if (!response.ok) {
+    let detail: string | undefined;
+    try {
+      const body = (await response.json()) as {
+        message?: string;
+        error?: string;
+      };
+      detail = body.message ?? body.error;
+    } catch {
+      // Body wasn't JSON; fall through to status-only error.
+    }
+    throw new Error(
+      detail ? `${response.status} - ${detail}` : String(response.status),
+    );
+  }
+
+  return response;
+}
diff --git a/packages/transaction-pay-controller/src/strategy/relay/relay-quotes.test.ts b/packages/transaction-pay-controller/src/strategy/relay/relay-quotes.test.ts
index 3ea0a32fb2..54b46d0732 100644
--- a/packages/transaction-pay-controller/src/strategy/relay/relay-quotes.test.ts
+++ b/packages/transaction-pay-controller/src/strategy/relay/relay-quotes.test.ts
@@ -1,4 +1,4 @@
-import { successfulFetch, toHex } from '@metamask/controller-utils';
+import { toHex } from '@metamask/controller-utils';
 import { TransactionType } from '@metamask/transaction-controller';
 import type {
   GasFeeToken,
@@ -59,11 +59,6 @@ jest.mock('../../utils/feature-flags', () => ({
   getSlippage: jest.fn(),
 }));
 
-jest.mock('@metamask/controller-utils', () => ({
-  ...jest.requireActual('@metamask/controller-utils'),
-  successfulFetch: jest.fn(),
-}));
-
 const TRANSACTION_META_MOCK = { txParams: {} } as TransactionMeta;
 const PREDICT_WITHDRAW_TRANSACTION_MOCK = {
   txParams: {},
@@ -168,7 +163,7 @@ const TOKEN_TRANSFER_DATA_MOCK =
   '0xa9059cbb0000000000000000000000005678901234567890123456789012345678901234000000000000000000000000000000000000000000000000000000000000007b' as Hex;
 
 describe('Relay Quotes Utils', () => {
-  const successfulFetchMock = jest.mocked(successfulFetch);
+  let successfulFetchMock: jest.SpyInstance;
   const getTokenFiatRateMock = jest.mocked(getTokenFiatRate);
   const calculateGasCostMock = jest.mocked(calculateGasCost);
   const calculateGasFeeTokenCostMock = jest.mocked(calculateGasFeeTokenCost);
@@ -193,6 +188,8 @@ describe('Relay Quotes Utils', () => {
   beforeEach(() => {
     jest.resetAllMocks();
 
+    successfulFetchMock = jest.spyOn(global, 'fetch');
+
     getKeyringControllerStateMock.mockReturnValue({
       isUnlocked: true,
       keyrings: [
@@ -236,9 +233,14 @@ describe('Relay Quotes Utils', () => {
     findNetworkClientIdByChainIdMock.mockReturnValue(NETWORK_CLIENT_ID_MOCK);
   });
 
+  afterEach(() => {
+    successfulFetchMock.mockRestore();
+  });
+
   describe('getRelayQuotes', () => {
     it('returns quotes from Relay', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -258,6 +260,7 @@ describe('Relay Quotes Utils', () => {
 
     it('sends request to Relay', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -297,6 +300,7 @@ describe('Relay Quotes Utils', () => {
       isRelayExecuteEnabledMock.mockReturnValue(true);
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -319,6 +323,7 @@ describe('Relay Quotes Utils', () => {
       isEIP7702ChainMock.mockReturnValue(false);
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -340,6 +345,7 @@ describe('Relay Quotes Utils', () => {
       isRelayExecuteEnabledMock.mockReturnValue(true);
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -359,6 +365,7 @@ describe('Relay Quotes Utils', () => {
 
     it('sends request with EXACT_INPUT trade type when isMaxAmount is true', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -401,6 +408,7 @@ describe('Relay Quotes Utils', () => {
 
     it('includes transactions in request', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -448,6 +456,7 @@ describe('Relay Quotes Utils', () => {
 
     it('includes request in quote', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -473,6 +482,7 @@ describe('Relay Quotes Utils', () => {
 
     it('skips delegation for token transfers', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -493,6 +503,7 @@ describe('Relay Quotes Utils', () => {
 
     it('extracts recipient from token transfer', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -517,6 +528,7 @@ describe('Relay Quotes Utils', () => {
 
     it('includes transactions from nested transactions', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -570,6 +582,7 @@ describe('Relay Quotes Utils', () => {
 
     it('skips delegation for token transfers in nested transactions', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -595,6 +608,7 @@ describe('Relay Quotes Utils', () => {
 
     it('extracts recipient from token transfer in nested transactions', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -624,6 +638,7 @@ describe('Relay Quotes Utils', () => {
 
     it('extracts recipient and sets refundTo when nested transactions include token transfer with delegation', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -657,6 +672,7 @@ describe('Relay Quotes Utils', () => {
 
     it('skips delegation for Hypercore deposits', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -682,6 +698,7 @@ describe('Relay Quotes Utils', () => {
 
     it('does not extract recipient for Hypercore deposits with token transfer signature', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -711,6 +728,7 @@ describe('Relay Quotes Utils', () => {
 
     it('sends request to url from feature flag', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -742,6 +760,7 @@ describe('Relay Quotes Utils', () => {
 
     it('ignores gas fee token requests (target=0 and source=0)', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -763,6 +782,7 @@ describe('Relay Quotes Utils', () => {
 
     it('processes post-quote requests', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -791,6 +811,7 @@ describe('Relay Quotes Utils', () => {
 
     it('sets refundTo in request body for post-quote when provided', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -819,6 +840,7 @@ describe('Relay Quotes Utils', () => {
 
     it('does not set refundTo in request body for post-quote when not provided', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -844,6 +866,7 @@ describe('Relay Quotes Utils', () => {
 
     it('estimates only relay transactions for post-quote', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -879,6 +902,7 @@ describe('Relay Quotes Utils', () => {
 
     it('adds original transaction gas to single relay gas limit for post-quote', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -915,6 +939,7 @@ describe('Relay Quotes Utils', () => {
 
     it('prefers nestedTransactions gas over txParams.gas for post-quote', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -971,6 +996,7 @@ describe('Relay Quotes Utils', () => {
       } as RelayQuote;
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => multiStepQuote,
       } as never);
 
@@ -1031,6 +1057,7 @@ describe('Relay Quotes Utils', () => {
       } as RelayQuote;
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => multiStepQuote,
       } as never);
 
@@ -1074,6 +1101,7 @@ describe('Relay Quotes Utils', () => {
 
     it('skips original transaction gas when txParams.gas is missing for post-quote', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1112,6 +1140,7 @@ describe('Relay Quotes Utils', () => {
       delete noGasQuote.steps[0].items[0].data.gas;
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => noGasQuote,
       } as never);
 
@@ -1157,6 +1186,7 @@ describe('Relay Quotes Utils', () => {
 
     it('does not prepend original transaction for post-quote when txParams.to is missing', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1183,6 +1213,7 @@ describe('Relay Quotes Utils', () => {
       delete quoteMock.steps[0].items[0].data.gas;
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -1217,6 +1248,7 @@ describe('Relay Quotes Utils', () => {
 
     it('ignores relay params.gas and estimates when fromOverride is set for single path', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1263,6 +1295,7 @@ describe('Relay Quotes Utils', () => {
       } as never);
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -1309,6 +1342,7 @@ describe('Relay Quotes Utils', () => {
       } as never);
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -1345,6 +1379,7 @@ describe('Relay Quotes Utils', () => {
       delete quoteMock.steps[0].items[0].data.gas;
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -1382,6 +1417,7 @@ describe('Relay Quotes Utils', () => {
       delete quoteMock.steps[0].items[0].data.gas;
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -1417,6 +1453,7 @@ describe('Relay Quotes Utils', () => {
       } as never);
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -1441,6 +1478,7 @@ describe('Relay Quotes Utils', () => {
 
     it('sets isSourceGasFeeToken for predictWithdraw post-quote when insufficient native balance', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1466,6 +1504,7 @@ describe('Relay Quotes Utils', () => {
 
     it('simulates with proxy address and scales gas fee token for predictWithdraw post-quote', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1500,6 +1539,7 @@ describe('Relay Quotes Utils', () => {
 
     it('falls back to native gas cost for predictWithdraw post-quote when simulation returns no matching token', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1525,6 +1565,7 @@ describe('Relay Quotes Utils', () => {
 
     it('skips proxy simulation for non-predictWithdraw post-quote even with refundTo', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1561,8 +1602,14 @@ describe('Relay Quotes Utils', () => {
       };
 
       successfulFetchMock
-        .mockResolvedValueOnce({ json: async () => QUOTE_MOCK } as never)
-        .mockResolvedValueOnce({ json: async () => phase2Mock } as never);
+        .mockResolvedValueOnce({
+          ok: true,
+          json: async () => QUOTE_MOCK,
+        } as never)
+        .mockResolvedValueOnce({
+          ok: true,
+          json: async () => phase2Mock,
+        } as never);
 
       getTokenBalanceMock.mockReturnValue('0');
       getGasFeeTokensMock.mockResolvedValue([GAS_FEE_TOKEN_MOCK]);
@@ -1607,6 +1654,7 @@ describe('Relay Quotes Utils', () => {
 
     it('returns phase 1 quote when gas cost exceeds source amount for post-quote flows', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1641,6 +1689,7 @@ describe('Relay Quotes Utils', () => {
 
     it('falls back to native cost when gas station simulation fails for post-quote', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1666,7 +1715,10 @@ describe('Relay Quotes Utils', () => {
 
     it('falls back to phase 1 quote when phase 2 fetch fails for post-quote flows', async () => {
       successfulFetchMock
-        .mockResolvedValueOnce({ json: async () => QUOTE_MOCK } as never)
+        .mockResolvedValueOnce({
+          ok: true,
+          json: async () => QUOTE_MOCK,
+        } as never)
         .mockRejectedValueOnce(new Error('Relay API error'));
 
       getTokenBalanceMock.mockReturnValue('0');
@@ -1700,8 +1752,14 @@ describe('Relay Quotes Utils', () => {
 
     it('falls back to phase 1 when phase 2 loses gas fee token for post-quote flows', async () => {
       successfulFetchMock
-        .mockResolvedValueOnce({ json: async () => QUOTE_MOCK } as never)
-        .mockResolvedValueOnce({ json: async () => QUOTE_MOCK } as never);
+        .mockResolvedValueOnce({
+          ok: true,
+          json: async () => QUOTE_MOCK,
+        } as never)
+        .mockResolvedValueOnce({
+          ok: true,
+          json: async () => QUOTE_MOCK,
+        } as never);
 
       getTokenBalanceMock
         .mockReturnValueOnce('0')
@@ -1739,6 +1797,7 @@ describe('Relay Quotes Utils', () => {
 
     it('includes duration in quote', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1754,6 +1813,7 @@ describe('Relay Quotes Utils', () => {
 
     it('includes zero metaMask fee when app fee is absent', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1776,6 +1836,7 @@ describe('Relay Quotes Utils', () => {
       quoteMock.fees.app = { amountUsd: '0.75' };
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -1798,6 +1859,7 @@ describe('Relay Quotes Utils', () => {
       quoteMock.fees.app = { amountUsd: '0.75' };
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -1816,6 +1878,7 @@ describe('Relay Quotes Utils', () => {
 
     it('includes provider fee', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1847,6 +1910,7 @@ describe('Relay Quotes Utils', () => {
       };
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -1878,6 +1942,7 @@ describe('Relay Quotes Utils', () => {
       };
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -1896,6 +1961,7 @@ describe('Relay Quotes Utils', () => {
 
     it('includes dust in quote', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -1915,6 +1981,7 @@ describe('Relay Quotes Utils', () => {
     describe('includes source network fee', () => {
       it('in quote', async () => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -1946,6 +2013,7 @@ describe('Relay Quotes Utils', () => {
         delete quoteMock.steps[0].items[0].data.gas;
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => quoteMock,
         } as never);
 
@@ -1999,6 +2067,7 @@ describe('Relay Quotes Utils', () => {
         } as never);
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => quoteMock,
         } as never);
         estimateGasBatchMock.mockResolvedValue({
@@ -2020,6 +2089,7 @@ describe('Relay Quotes Utils', () => {
 
       it('using gas fee token cost if insufficient native balance', async () => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -2064,6 +2134,7 @@ describe('Relay Quotes Utils', () => {
         } as never);
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => quote,
         } as never);
         estimateGasBatchMock.mockResolvedValue({
@@ -2093,6 +2164,7 @@ describe('Relay Quotes Utils', () => {
 
       it('uses proxy simulation and scales gas fee token amount for post-quote with a single relay param', async () => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -2137,6 +2209,7 @@ describe('Relay Quotes Utils', () => {
 
       it('not using gas fee token if sufficient native balance', async () => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -2169,6 +2242,7 @@ describe('Relay Quotes Utils', () => {
 
       it('not using gas fee token if source token not found', async () => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -2203,6 +2277,7 @@ describe('Relay Quotes Utils', () => {
 
       it('not using gas fee token if calculation fails', async () => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -2239,6 +2314,7 @@ describe('Relay Quotes Utils', () => {
         quote.steps[0].items[0].data.value = undefined as never;
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => quote,
         } as never);
 
@@ -2261,6 +2337,7 @@ describe('Relay Quotes Utils', () => {
 
       it('not using gas fee token cost if chain disabled in feature flag', async () => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -2307,6 +2384,7 @@ describe('Relay Quotes Utils', () => {
         };
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -2346,6 +2424,7 @@ describe('Relay Quotes Utils', () => {
         quoteMock.metamask.isExecute = true;
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => quoteMock,
         } as never);
 
@@ -2367,6 +2446,7 @@ describe('Relay Quotes Utils', () => {
         quoteMock.metamask.isExecute = true;
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => quoteMock,
         } as never);
 
@@ -2382,6 +2462,7 @@ describe('Relay Quotes Utils', () => {
 
       it('does not zero source network fees when quote does not have isExecute', async () => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -2403,6 +2484,7 @@ describe('Relay Quotes Utils', () => {
         quoteMock.metamask.isExecute = true;
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => quoteMock,
         } as never);
 
@@ -2429,6 +2511,7 @@ describe('Relay Quotes Utils', () => {
 
       it('overrides source chain and token to HyperCore', async () => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -2449,6 +2532,7 @@ describe('Relay Quotes Utils', () => {
 
       it('shifts source amount by 2 decimals (8→6)', async () => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -2468,6 +2552,7 @@ describe('Relay Quotes Utils', () => {
 
       it('zeroes source network fees (gasless)', async () => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -2486,6 +2571,7 @@ describe('Relay Quotes Utils', () => {
 
       it('uses Arbitrum USDC fiat rate for source', async () => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => QUOTE_MOCK,
         } as never);
 
@@ -2506,6 +2592,7 @@ describe('Relay Quotes Utils', () => {
 
     it('includes target network fee in quote', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -2524,6 +2611,7 @@ describe('Relay Quotes Utils', () => {
 
     it('includes target amount in quote', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -2555,6 +2643,7 @@ describe('Relay Quotes Utils', () => {
       };
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -2573,6 +2662,7 @@ describe('Relay Quotes Utils', () => {
 
     it('uses amountFormatted as usd for target amount when target is a stablecoin', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -2597,6 +2687,7 @@ describe('Relay Quotes Utils', () => {
 
     it('uses amountUsd for target amount when target is not a stablecoin', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -2630,6 +2721,7 @@ describe('Relay Quotes Utils', () => {
       getTokenFiatRateMock.mockReturnValue(undefined);
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -2651,6 +2743,7 @@ describe('Relay Quotes Utils', () => {
       };
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -2684,6 +2777,7 @@ describe('Relay Quotes Utils', () => {
       };
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -2716,6 +2810,7 @@ describe('Relay Quotes Utils', () => {
       };
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -2745,6 +2840,7 @@ describe('Relay Quotes Utils', () => {
       };
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -2771,6 +2867,7 @@ describe('Relay Quotes Utils', () => {
       delete quoteMock.steps[0].items[0].data.gas;
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -2806,6 +2903,7 @@ describe('Relay Quotes Utils', () => {
       delete quoteMock.steps[0].items[0].data.gas;
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -2828,6 +2926,7 @@ describe('Relay Quotes Utils', () => {
       delete quoteMock.steps[0].items[0].data.gas;
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -2862,6 +2961,7 @@ describe('Relay Quotes Utils', () => {
       } as never);
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -2910,6 +3010,7 @@ describe('Relay Quotes Utils', () => {
       } as never);
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -2945,6 +3046,7 @@ describe('Relay Quotes Utils', () => {
       } as never);
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -2966,6 +3068,7 @@ describe('Relay Quotes Utils', () => {
 
     it('includes gas limits in quote', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => QUOTE_MOCK,
       } as never);
 
@@ -2988,6 +3091,7 @@ describe('Relay Quotes Utils', () => {
       delete quoteMock.steps[0].items[0].data.gas;
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -3011,6 +3115,7 @@ describe('Relay Quotes Utils', () => {
       } as never);
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -3034,6 +3139,7 @@ describe('Relay Quotes Utils', () => {
       ];
 
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => quoteMock,
       } as never);
 
@@ -3053,6 +3159,7 @@ describe('Relay Quotes Utils', () => {
         delete quoteMock.steps[0].items[0].data.gas;
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => quoteMock,
         } as never);
 
@@ -3088,6 +3195,7 @@ describe('Relay Quotes Utils', () => {
         } as never);
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => quoteMock,
         } as never);
 
@@ -3124,6 +3232,7 @@ describe('Relay Quotes Utils', () => {
         } as never);
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => quoteMock,
         } as never);
 
@@ -3160,6 +3269,7 @@ describe('Relay Quotes Utils', () => {
         } as never);
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => quoteMock,
         } as never);
 
@@ -3195,6 +3305,7 @@ describe('Relay Quotes Utils', () => {
         } as never);
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => quoteMock,
         } as never);
 
diff --git a/packages/transaction-pay-controller/src/strategy/relay/relay-submit.test.ts b/packages/transaction-pay-controller/src/strategy/relay/relay-submit.test.ts
index afc32821ff..f93a005c20 100644
--- a/packages/transaction-pay-controller/src/strategy/relay/relay-submit.test.ts
+++ b/packages/transaction-pay-controller/src/strategy/relay/relay-submit.test.ts
@@ -1,4 +1,4 @@
-import { ORIGIN_METAMASK, successfulFetch } from '@metamask/controller-utils';
+import { ORIGIN_METAMASK } from '@metamask/controller-utils';
 import { TransactionType } from '@metamask/transaction-controller';
 import type { TransactionMeta } from '@metamask/transaction-controller';
 import type { Hex } from '@metamask/utils';
@@ -32,11 +32,6 @@ jest.mock('../../utils/transaction');
 jest.mock('../../utils/feature-flags');
 jest.mock('./hyperliquid-withdraw');
 
-jest.mock('@metamask/controller-utils', () => ({
-  ...jest.requireActual('@metamask/controller-utils'),
-  successfulFetch: jest.fn(),
-}));
-
 const NETWORK_CLIENT_ID_MOCK = 'networkClientIdMock';
 const TRANSACTION_HASH_MOCK = '0x1234';
 const SOURCE_HASH_MOCK = '0xsourcehash';
@@ -132,7 +127,7 @@ const REQUEST_MOCK: PayStrategyExecuteRequest<RelayQuote> = {
 
 describe('Relay Submit Utils', () => {
   const updateTransactionMock = jest.mocked(updateTransaction);
-  const successfulFetchMock = jest.mocked(successfulFetch);
+  let successfulFetchMock: jest.SpyInstance;
   const getTransactionMock = jest.mocked(getTransaction);
   const collectTransactionIdsMock = jest.mocked(collectTransactionIds);
   const getFeatureFlagsMock = jest.mocked(getFeatureFlags);
@@ -158,6 +153,8 @@ describe('Relay Submit Utils', () => {
   beforeEach(() => {
     jest.resetAllMocks();
 
+    successfulFetchMock = jest.spyOn(global, 'fetch');
+
     getRelayPollingIntervalMock.mockReturnValue(1);
     getRelayPollingTimeoutMock.mockReturnValue(undefined);
 
@@ -189,6 +186,7 @@ describe('Relay Submit Utils', () => {
     );
 
     successfulFetchMock.mockResolvedValue({
+      ok: true,
       json: async () => STATUS_RESPONSE_MOCK,
     } as Response);
 
@@ -196,6 +194,10 @@ describe('Relay Submit Utils', () => {
     request.messenger = messenger;
   });
 
+  afterEach(() => {
+    successfulFetchMock.mockRestore();
+  });
+
   describe('submitRelayQuotes', () => {
     it('adds transaction', async () => {
       await submitRelayQuotes(request);
@@ -593,6 +595,7 @@ describe('Relay Submit Utils', () => {
 
     it('waits for relay status to be success', async () => {
       successfulFetchMock.mockResolvedValueOnce({
+        ok: true,
         json: async () => ({ status: 'pending' }),
       } as Response);
 
@@ -635,7 +638,7 @@ describe('Relay Submit Utils', () => {
       );
     });
 
-    it('throws if transaction fails to confirm', async () => {
+    it('rethrows confirmation failures bare (the Relay submit prefix is applied at RelayStrategy.execute)', async () => {
       waitForTransactionConfirmedMock.mockRejectedValue(
         new Error('Transaction failed'),
       );
@@ -645,10 +648,21 @@ describe('Relay Submit Utils', () => {
       );
     });
 
+    it('rethrows addTransaction failures bare (the Relay submit prefix is applied at RelayStrategy.execute)', async () => {
+      addTransactionMock.mockRejectedValueOnce(
+        new Error('addTransaction boom'),
+      );
+
+      await expect(submitRelayQuotes(request)).rejects.toThrow(
+        'addTransaction boom',
+      );
+    });
+
     it.each(['failure', 'refund', 'refunded'])(
       'throws if relay status is %s',
       async (status) => {
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => ({ status }),
         } as Response);
 
@@ -660,6 +674,7 @@ describe('Relay Submit Utils', () => {
 
     it('throws if relay returns unrecognized status', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => ({ status: 'unknown_status' }),
       } as Response);
 
@@ -673,9 +688,11 @@ describe('Relay Submit Utils', () => {
       async (pendingStatus) => {
         successfulFetchMock
           .mockResolvedValueOnce({
+            ok: true,
             json: async () => ({ status: pendingStatus }),
           } as Response)
           .mockResolvedValue({
+            ok: true,
             json: async () => STATUS_RESPONSE_MOCK,
           } as Response);
 
@@ -695,6 +712,7 @@ describe('Relay Submit Utils', () => {
       successfulFetchMock
         .mockRejectedValueOnce(new Error('Network error'))
         .mockResolvedValue({
+          ok: true,
           json: async () => STATUS_RESPONSE_MOCK,
         } as Response);
 
@@ -727,6 +745,7 @@ describe('Relay Submit Utils', () => {
 
       successfulFetchMock
         .mockResolvedValueOnce({
+          ok: true,
           json: async () => ({ status: 'pending' }),
         } as Response)
         .mockImplementation(() => {
@@ -746,9 +765,11 @@ describe('Relay Submit Utils', () => {
 
       successfulFetchMock
         .mockResolvedValueOnce({
+          ok: true,
           json: async () => ({ status: 'pending' }),
         } as Response)
         .mockResolvedValue({
+          ok: true,
           json: async () => STATUS_RESPONSE_MOCK,
         } as Response);
 
@@ -762,9 +783,11 @@ describe('Relay Submit Utils', () => {
 
       successfulFetchMock
         .mockResolvedValueOnce({
+          ok: true,
           json: async () => ({ status: 'pending' }),
         } as Response)
         .mockResolvedValue({
+          ok: true,
           json: async () => STATUS_RESPONSE_MOCK,
         } as Response);
 
@@ -806,6 +829,7 @@ describe('Relay Submit Utils', () => {
 
     it('returns fallback hash if none included', async () => {
       successfulFetchMock.mockResolvedValue({
+        ok: true,
         json: async () => ({
           ...STATUS_RESPONSE_MOCK,
           txHashes: [],
@@ -1214,6 +1238,7 @@ describe('Relay Submit Utils', () => {
         request.quotes[0].request.isHyperliquidSource = true;
 
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => STATUS_RESPONSE_MOCK,
         } as Response);
 
@@ -1277,9 +1302,11 @@ describe('Relay Submit Utils', () => {
 
         successfulFetchMock
           .mockResolvedValueOnce({
+            ok: true,
             json: async () => EXECUTE_RESPONSE_MOCK,
           } as Response)
           .mockResolvedValue({
+            ok: true,
             json: async () => STATUS_RESPONSE_MOCK,
           } as Response);
       });
@@ -1374,6 +1401,30 @@ describe('Relay Submit Utils', () => {
         );
       });
 
+      it('wraps /execute submission failures with the Relay execute prefix (Relay submit prefix is applied at RelayStrategy.execute)', async () => {
+        successfulFetchMock.mockReset();
+        successfulFetchMock.mockResolvedValueOnce({
+          ok: false,
+          status: 422,
+          json: async () => ({
+            message: 'failed to decode param in array[0] invalid JSON input',
+          }),
+        } as Response);
+
+        await expect(submitRelayQuotes(request)).rejects.toThrow(
+          'Relay execute: 422 - failed to decode param in array[0] invalid JSON input',
+        );
+      });
+
+      it('wraps non-Error throws from /execute with the Relay execute prefix', async () => {
+        successfulFetchMock.mockReset();
+        successfulFetchMock.mockRejectedValueOnce('network down');
+
+        await expect(submitRelayQuotes(request)).rejects.toThrow(
+          'Relay execute: network down',
+        );
+      });
+
       it('omits authorizationList when delegation has none', async () => {
         getDelegationTransactionMock.mockResolvedValue({
           ...DELEGATION_RESULT_MOCK,
@@ -1553,6 +1604,7 @@ describe('Relay Submit Utils', () => {
 
         successfulFetchMock.mockReset();
         successfulFetchMock.mockResolvedValue({
+          ok: true,
           json: async () => STATUS_RESPONSE_MOCK,
         } as Response);
 
diff --git a/packages/transaction-pay-controller/src/strategy/relay/relay-submit.ts b/packages/transaction-pay-controller/src/strategy/relay/relay-submit.ts
index 9694ce83a9..0082b6af66 100644
--- a/packages/transaction-pay-controller/src/strategy/relay/relay-submit.ts
+++ b/packages/transaction-pay-controller/src/strategy/relay/relay-submit.ts
@@ -454,7 +454,13 @@ async function submitViaRelayExecute(
 
   log('Submitting via Relay execute', { executeBody, from });
 
-  const result = await submitRelayExecute(messenger, executeBody);
+  let result;
+  try {
+    result = await submitRelayExecute(messenger, executeBody);
+  } catch (error) {
+    const message = error instanceof Error ? error.message : String(error);
+    throw new Error(`Relay execute: ${message}`);
+  }
 
   log('Relay execute response', result);