feat: zero network fees in relay execute flow (#8181)

## Explanation

When using the Relay execute flow (EIP-7702 + execute enabled), network
fees are subsidized by the relayer for cross-chain transactions. This
change zeroes out the displayed source network fees in the quote
normalization step so users see the correct zero cost.

relayer.

## References

- Builds on top of #8133

## 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 fee calculation and submit-path selection for Relay
transactions based on `quote.metamask.isExecute`, which could impact gas
estimation/fee display and which submission mechanism is used. Risk is
moderate due to user-visible fee outputs and execution-path branching,
but scope is limited to Relay strategy.
> 
> **Overview**
> **Relay execute quotes now drive fee display and submission behavior
via `metamask.isExecute`.** When a Relay quote indicates execute flow,
quote normalization zeroes `fees.sourceNetwork` and clears
`metamask.gasLimits` since the relayer subsidizes origin gas.
> 
> `relay-submit` now chooses the `/execute` submission path solely based
on `quote.original.metamask.isExecute` (removing EIP-7702/feature-flag
gating in this decision), with corresponding test updates. Types and
changelog are updated to include the optional `metamask.isExecute` flag.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
91323fc. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: matthewwalsh0

packages/transaction-pay-controller/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- Zero out source network fees in Relay strategy when quote indicates execute flow ([#8181](https://github.com/MetaMask/core/pull/8181))
+
 ## [16.5.0]
 
 ### Added

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

@@ -2163,6 +2163,81 @@ describe('Relay Quotes Utils', () => {
       });
     });
 
+    describe('zeroes source network fees for execute flow', () => {
+      const ZERO_AMOUNT = { fiat: '0', human: '0', raw: '0', usd: '0' };
+
+      it('sets source network fees to zero when quote has isExecute', async () => {
+        const quoteMock = cloneDeep(QUOTE_MOCK);
+        quoteMock.metamask.isExecute = true;
+
+        successfulFetchMock.mockResolvedValue({
+          json: async () => quoteMock,
+        } as never);
+
+        const result = await getRelayQuotes({
+          messenger,
+          requests: [QUOTE_REQUEST_MOCK],
+          transaction: TRANSACTION_META_MOCK,
+        });
+
+        expect(result[0].fees.sourceNetwork).toStrictEqual({
+          estimate: ZERO_AMOUNT,
+          max: ZERO_AMOUNT,
+        });
+      });
+
+      it('preserves isExecute from quote response on normalized quote', async () => {
+        const quoteMock = cloneDeep(QUOTE_MOCK);
+        quoteMock.metamask.isExecute = true;
+
+        successfulFetchMock.mockResolvedValue({
+          json: async () => quoteMock,
+        } as never);
+
+        const result = await getRelayQuotes({
+          messenger,
+          requests: [QUOTE_REQUEST_MOCK],
+          transaction: TRANSACTION_META_MOCK,
+        });
+
+        expect(result[0].original.metamask.isExecute).toBe(true);
+      });
+
+      it('does not zero source network fees when quote does not have isExecute', async () => {
+        successfulFetchMock.mockResolvedValue({
+          json: async () => QUOTE_MOCK,
+        } as never);
+
+        const result = await getRelayQuotes({
+          messenger,
+          requests: [QUOTE_REQUEST_MOCK],
+          transaction: TRANSACTION_META_MOCK,
+        });
+
+        expect(result[0].fees.sourceNetwork).not.toStrictEqual({
+          estimate: ZERO_AMOUNT,
+          max: ZERO_AMOUNT,
+        });
+      });
+
+      it('returns empty gas limits when quote has isExecute', async () => {
+        const quoteMock = cloneDeep(QUOTE_MOCK);
+        quoteMock.metamask.isExecute = true;
+
+        successfulFetchMock.mockResolvedValue({
+          json: async () => quoteMock,
+        } as never);
+
+        const result = await getRelayQuotes({
+          messenger,
+          requests: [QUOTE_REQUEST_MOCK],
+          transaction: TRANSACTION_META_MOCK,
+        });
+
+        expect(result[0].original.metamask.gasLimits).toStrictEqual([]);
+      });
+    });
+
     it('includes target network fee in quote', async () => {
       successfulFetchMock.mockResolvedValue({
         json: async () => QUOTE_MOCK,

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

@@ -473,6 +473,7 @@ async function normalizeQuote(
   const targetAmount = getFiatValueFromUsd(targetAmountUsd, usdToFiatRate);
 
   const metamask = {
+    ...quote.metamask,
     gasLimits,
   };
 
@@ -566,6 +567,9 @@ function getFiatRates(
  * transaction's params so that gas estimation and gas-fee-token logic handle
  * both transactions together.
  *
+ * When the execute flow is active (indicated by `quote.metamask.isExecute`),
+ * network fees are zeroed because the relayer covers them.
+ *
  * @param quote - Relay quote.
  * @param messenger - Controller messenger.
  * @param request - Quote request.
@@ -585,6 +589,14 @@ async function calculateSourceNetworkCost(
 > {
   const { from, sourceChainId, sourceTokenAddress } = request;
 
+  if (quote.metamask?.isExecute) {
+    log('Zeroing network fees for execute flow');
+
+    const zeroAmount = { fiat: '0', human: '0', raw: '0', usd: '0' };
+
+    return { estimate: zeroAmount, max: zeroAmount, gasLimits: [] };
+  }
+
   const relayParams = quote.steps
     .flatMap((step) => step.items)
     .map((item) => item.data);

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

@@ -14,11 +14,7 @@ import type {
   TransactionPayQuote,
 } from '../../types';
 import type { FeatureFlags } from '../../utils/feature-flags';
-import {
-  isEIP7702Chain,
-  isRelayExecuteEnabled,
-  getFeatureFlags,
-} from '../../utils/feature-flags';
+import { getFeatureFlags } from '../../utils/feature-flags';
 import { getLiveTokenBalance, normalizeTokenAddress } from '../../utils/token';
 import {
   collectTransactionIds,
@@ -135,9 +131,6 @@ describe('Relay Submit Utils', () => {
   const getLiveTokenBalanceMock = jest.mocked(getLiveTokenBalance);
   const normalizeTokenAddressMock = jest.mocked(normalizeTokenAddress);
 
-  const isEIP7702ChainMock = jest.mocked(isEIP7702Chain);
-  const isRelayExecuteEnabledMock = jest.mocked(isRelayExecuteEnabled);
-
   const {
     addTransactionMock,
     addTransactionBatchMock,
@@ -155,9 +148,6 @@ describe('Relay Submit Utils', () => {
   beforeEach(() => {
     jest.resetAllMocks();
 
-    isEIP7702ChainMock.mockReturnValue(false);
-    isRelayExecuteEnabledMock.mockReturnValue(false);
-
     getLiveTokenBalanceMock.mockResolvedValue('9999999999');
     normalizeTokenAddressMock.mockImplementation(
       (tokenAddress) => tokenAddress,
@@ -1022,8 +1012,7 @@ describe('Relay Submit Utils', () => {
       } as FeatureFlags;
 
       beforeEach(() => {
-        isEIP7702ChainMock.mockReturnValue(true);
-        isRelayExecuteEnabledMock.mockReturnValue(true);
+        request.quotes[0].original.metamask.isExecute = true;
         getDelegationTransactionMock.mockResolvedValue(DELEGATION_RESULT_MOCK);
         getFeatureFlagsMock.mockReturnValue(FEATURE_FLAGS_MOCK);
 
@@ -1113,6 +1102,10 @@ describe('Relay Submit Utils', () => {
           ...request.quotes[0],
           original: {
             ...ORIGINAL_QUOTE_MOCK,
+            metamask: {
+              ...ORIGINAL_QUOTE_MOCK.metamask,
+              isExecute: true,
+            },
             steps: [
               {
                 ...ORIGINAL_QUOTE_MOCK.steps[0],
@@ -1261,17 +1254,8 @@ describe('Relay Submit Utils', () => {
         });
       });
 
-      it('uses TransactionController path when chain is not EIP-7702', async () => {
-        isEIP7702ChainMock.mockReturnValue(false);
-
-        await submitRelayQuotes(request);
-
-        expect(getDelegationTransactionMock).not.toHaveBeenCalled();
-        expect(addTransactionMock).toHaveBeenCalledTimes(1);
-      });
-
-      it('uses TransactionController path when executeEnabled is false', async () => {
-        isRelayExecuteEnabledMock.mockReturnValue(false);
+      it('uses TransactionController path when isExecute is not set', async () => {
+        request.quotes[0].original.metamask.isExecute = undefined;
 
         await submitRelayQuotes(request);
 

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

@@ -22,11 +22,7 @@ import type {
   TransactionPayControllerMessenger,
   TransactionPayQuote,
 } from '../../types';
-import {
-  getFeatureFlags,
-  isEIP7702Chain,
-  isRelayExecuteEnabled,
-} from '../../utils/feature-flags';
+import { getFeatureFlags } from '../../utils/feature-flags';
 import {
   getLiveTokenBalance,
   normalizeTokenAddress,
@@ -320,12 +316,7 @@ async function submitTransactions(
         ]
       : normalizedParams;
 
-  const { sourceChainId } = quote.request;
-
-  if (
-    isRelayExecuteEnabled(messenger) &&
-    isEIP7702Chain(messenger, sourceChainId)
-  ) {
+  if (quote.original.metamask.isExecute) {
     return await submitViaRelayExecute(
       quote,
       transaction,

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

@@ -74,6 +74,7 @@ export type RelayQuote = {
   };
   metamask: {
     gasLimits: number[];
+    isExecute?: boolean;
     isMaxGasStation?: boolean;
   };
   request: RelayQuoteRequest;