fix: MM pay request amount used when both paymentProvider and isPostQuote is defined (MetaMask#9070)

## Explanation

Fix MM pay request amount used when both paymentOverride and isPostQuote
is defined.

## References

Related to https://consensyssoftware.atlassian.net/browse/CONF-1520

## Checklist

- [X] I've updated the test suite for new or updated code as appropriate
- [X] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [X] I've communicated my changes to consumers by [updating changelogs
for packages I've
changed](https://github.com/MetaMask/core/tree/main/docs/processes/updating-changelogs.md)
- [X] I've introduced [breaking
changes](https://github.com/MetaMask/core/tree/main/docs/processes/breaking-changes.md)
in this PR and have prepared draft pull requests for clients and
consumer packages to resolve them

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Changes payment quote amounts sent to the relay API for a specific MM
Pay path; wrong amounts could affect funding quotes, though scope is
narrow and well-tested.
> 
> **Overview**
> Fixes **MetaMask Pay** relay quote bodies when **`paymentOverride` is
Money Account** and **`isPostQuote`** is true: the relay request
**`amount`** for **`EXACT_OUTPUT`** now comes from
**`transactionData.tokens[0].amountRaw`** instead of
**`request.sourceTokenAmount`**, so the quoted output matches the
destination token’s units when decimals differ.
> 
> Missing token data falls back to **`'0'`**. Tests cover the new amount
source, decimal mismatch, and empty/missing **`transactionData`**; the
package changelog records the fix.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
6d89828. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: jpuri

packages/transaction-pay-controller/CHANGELOG.md

@@ -11,6 +11,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Bump `@metamask/bridge-controller` from `^75.0.0` to `^75.1.0` ([#9072](https://github.com/MetaMask/core/pull/9072))
 
+### Fixed
+
+- Fix request amount used for cases when paymentOverride is defined and also isPostQuote is true ([#9070](https://github.com/MetaMask/core/pull/9070))
+
 ## [23.4.0]
 
 ### Changed

packages/transaction-pay-controller/src/strategy/relay/relay-quotes.test.ts

@@ -3073,19 +3073,21 @@ describe('Relay Quotes Utils', () => {
 
       function setupMoneyAccountMocks({
         amountHuman = AMOUNT_HUMAN_MOCK,
+        amountRaw = AMOUNT_RAW_MOCK,
         overrideCalls = [OVERRIDE_CALL_MOCK],
         recipient,
         authorizationList = DELEGATION_RESULT_MOCK.authorizationList,
       }: {
         amountHuman?: string;
+        amountRaw?: string;
         overrideCalls?: { to: Hex; data: Hex; value: Hex }[];
         recipient?: Hex;
         authorizationList?: typeof DELEGATION_RESULT_MOCK.authorizationList;
       } = {}): void {
         getControllerStateMock.mockReturnValue({
           transactionData: {
             [TRANSACTION_ID_MOCK]: {
-              tokens: [{ amountHuman }],
+              tokens: [{ amountHuman, amountRaw }],
             },
           },
         } as never);
@@ -3097,7 +3099,7 @@ describe('Relay Quotes Utils', () => {
         });
       }
 
-      it('sets tradeType to EXACT_OUTPUT and amount from request sourceTokenAmount', async () => {
+      it('sets tradeType to EXACT_OUTPUT and amount from transactionData amountRaw', async () => {
         setupMoneyAccountMocks();
         successfulFetchMock.mockResolvedValue({
           ok: true,
@@ -3116,7 +3118,95 @@ describe('Relay Quotes Utils', () => {
         );
 
         expect(body.tradeType).toBe('EXACT_OUTPUT');
-        expect(body.amount).toBe(QUOTE_REQUEST_MOCK.sourceTokenAmount);
+        expect(body.amount).toBe(AMOUNT_RAW_MOCK);
+      });
+
+      it('uses amountRaw rather than sourceTokenAmount when decimals differ', async () => {
+        const destinationAmountRaw = '100000';
+        const sourceTokenAmountWithDifferentDecimals = '10000000';
+
+        setupMoneyAccountMocks({ amountRaw: destinationAmountRaw });
+        successfulFetchMock.mockResolvedValue({
+          ok: true,
+          json: async () => QUOTE_MOCK,
+        } as never);
+
+        await getRelayQuotes({
+          accountSupports7702: true,
+          messenger,
+          requests: [
+            {
+              ...MONEY_ACCOUNT_REQUEST_MOCK,
+              sourceTokenAmount: sourceTokenAmountWithDifferentDecimals,
+            },
+          ],
+          transaction: MONEY_ACCOUNT_TX_MOCK,
+        });
+
+        const body = JSON.parse(
+          successfulFetchMock.mock.calls[0][1]?.body as string,
+        );
+
+        expect(body.amount).toBe(destinationAmountRaw);
+        expect(body.amount).not.toBe(sourceTokenAmountWithDifferentDecimals);
+      });
+
+      it('defaults amount to 0 when transactionData has no tokens', async () => {
+        getControllerStateMock.mockReturnValue({
+          transactionData: {
+            [TRANSACTION_ID_MOCK]: {},
+          },
+        } as never);
+
+        getPaymentOverrideDataMock.mockResolvedValue({
+          calls: [OVERRIDE_CALL_MOCK],
+        });
+
+        successfulFetchMock.mockResolvedValue({
+          ok: true,
+          json: async () => QUOTE_MOCK,
+        } as never);
+
+        await getRelayQuotes({
+          accountSupports7702: true,
+          messenger,
+          requests: [MONEY_ACCOUNT_REQUEST_MOCK],
+          transaction: MONEY_ACCOUNT_TX_MOCK,
+        });
+
+        const body = JSON.parse(
+          successfulFetchMock.mock.calls[0][1]?.body as string,
+        );
+
+        expect(body.amount).toBe('0');
+      });
+
+      it('defaults amount to 0 when transactionData is missing', async () => {
+        getControllerStateMock.mockReturnValue({
+          transactionData: {},
+        } as never);
+
+        getPaymentOverrideDataMock.mockResolvedValue({
+          calls: [OVERRIDE_CALL_MOCK],
+        });
+
+        successfulFetchMock.mockResolvedValue({
+          ok: true,
+          json: async () => QUOTE_MOCK,
+        } as never);
+
+        await getRelayQuotes({
+          accountSupports7702: true,
+          messenger,
+          requests: [MONEY_ACCOUNT_REQUEST_MOCK],
+          transaction: MONEY_ACCOUNT_TX_MOCK,
+        });
+
+        const body = JSON.parse(
+          successfulFetchMock.mock.calls[0][1]?.body as string,
+        );
+
+        expect(body.amount).toBe('0');
       });
 
       it('includes token transfer and override calls in txs', async () => {

packages/transaction-pay-controller/src/strategy/relay/relay-quotes.ts

@@ -464,7 +464,7 @@ async function processMoneyAccountPostQuote(
 
   requestBody.authorizationList = normalizeAuthorizationList(authorizationList);
   requestBody.tradeType = 'EXACT_OUTPUT';
-  requestBody.amount = request.sourceTokenAmount;
+  requestBody.amount = transactionData?.tokens?.[0]?.amountRaw ?? '0';
   requestBody.txs = [
     {
       to: request.targetTokenAddress,