fix: enable EXACT_INPUT Max for Money Account Send to Perps

app/components/Views/confirmations/hooks/transactions/useTransactionCustomAmount.test.ts

@@ -1434,6 +1434,37 @@ describe('useTransactionCustomAmount', () => {
       expect(result.current.amountFiat).toBe('750.50');
     });
 
+    it('sets isMaxAmount for Max when payment override is MoneyAccount (e.g. Send to Perps)', async () => {
+      // With TPC MoneyAccount max support (MetaMask/core#9707), isMaxAmount=true
+      // uses the typed required amount (full withdrawable) rather than the pay
+      // token's bare on-chain mUSD balance, enabling EXACT_INPUT Max quotes.
+      useMoneyAccountBalanceMock.mockReturnValue({
+        withdrawableFiatRaw: '4.70',
+      } as ReturnType<typeof useMoneyAccountBalance>);
+
+      const { result } = runHook({
+        transactionMeta: {
+          type: TransactionType.perpsDeposit,
+          id: transactionIdMock,
+          chainId: '0x1' as Hex,
+          txParams: { from: '0xabc' },
+        } as unknown as Partial<TransactionMeta>,
+        stateOverrides: moneyAccountStateOverrides,
+      });
+
+      await act(async () => {
+        result.current.updatePendingAmountPercentage(100);
+      });
+
+      // Full withdrawable balance is shown, not the reduced bare-mUSD figure.
+      expect(result.current.amountFiat).toBe('4.70');
+      expect(setTransactionConfigMock).toHaveBeenCalledTimes(1);
+
+      const config = { isMaxAmount: false };
+      setTransactionConfigMock.mock.calls[0][1](config);
+      expect(config.isMaxAmount).toBe(true);
+    });
+
     it('returns 0 when payment override is MoneyAccount but withdrawableFiatRaw is undefined', async () => {
       useMoneyAccountBalanceMock.mockReturnValue({
         withdrawableFiatRaw: undefined,

app/components/Views/confirmations/hooks/transactions/useTransactionCustomAmount.ts

@@ -292,12 +292,16 @@ export function useTransactionCustomAmount({
         },
       });
 
-      // Do NOT set isMaxAmount=true for perps or money-account withdraw. TPC's
-      // calculatePostQuoteSourceAmounts substitutes `token.balanceRaw` when
-      // isMaxAmount is true: wrong for HyperLiquid (wallet USDC vs typed HL
-      // balance) and wrong for money account (on-chain mUSD only vs mUSD +
-      // vmUSD fiat total). Keeping isMaxAmount false routes the typed
-      // amount through as token.amountRaw.
+      // Do NOT set isMaxAmount=true for perps/money-account withdraw or money
+      // account deposit flows. For those, TPC would substitute an on-chain
+      // balanceRaw that does not match the typed balance (HyperLiquid wallet
+      // USDC vs HL balance; money-account on-chain mUSD vs mUSD + vmUSD).
+      //
+      // Deposits funded from the money account (e.g. Send to Perps) DO set
+      // isMaxAmount=true so quotes use EXACT_INPUT. That is safe once TPC uses
+      // the typed required amount for MoneyAccount max instead of the pay
+      // token's bare mUSD balance (MetaMask/core#9707). Mobile still types the
+      // full withdrawableFiatRaw amount into the required token.
       const shouldSetMax =
         percentage === 100 &&
         !isPerpsWithdraw &&