chore: update default bridge slippage to 2% (#37367)

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## **Description**

Update default slippage value for bridge quotes from 0.5 to 2%.
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CHANGELOG entry: chore: update default bridge slippage to 2%

## **Related issues**

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Sets bridge default slippage to 2% via SlippageValue enum and updates
UI logic and tests accordingly.
> 
> - **Bridge logic**:
> - Replace `BRIDGE_DEFAULT_SLIPPAGE` with `SlippageValue` enum; set
`BridgeDefault = 2` and use in `ui/ducks/bridge/bridge.ts` initial
state.
> - Update slippage calculation to treat cross-chain as `2%` in
`ui/pages/bridge/utils/slippage-service.ts`.
> - **UI**:
> - Use `SlippageValue` in `bridge-transaction-settings-modal.tsx`;
hardcoded options now `[EvmStablecoin(0.5), BridgeDefault(2)]` and
default selection uses `BridgeDefault`.
> - **Tests**:
> - Update unit tests in `ui/ducks/bridge/bridge.test.ts` to expect
`SlippageValue.BridgeDefault`.
> - Adjust e2e analytics assertion in
`test/e2e/tests/metrics/bridge.spec.ts` to expect `18`
`SwapBridgeInputChanged` events.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
5bf8097. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: SteP-n-s

test/e2e/tests/metrics/bridge.spec.ts

@@ -115,8 +115,8 @@ describe('Bridge tests', function (this: Suite) {
          */
 
         assert(
-          swapBridgeInputChanged.length === 22,
-          'Should have 22 input change events',
+          swapBridgeInputChanged.length === 18,
+          `Should have 18 input change events, but got ${swapBridgeInputChanged.length}`,
         );
 
         const swapBridgeInputChangedKeys = new Set(

ui/ducks/bridge/bridge.test.ts

@@ -4,7 +4,6 @@ import { zeroAddress } from 'ethereumjs-util';
 import {
   BridgeBackgroundAction,
   BridgeUserAction,
-  BRIDGE_DEFAULT_SLIPPAGE,
   formatChainIdToCaip,
   getNativeAssetForChainId,
 } from '@metamask/bridge-controller';
@@ -14,6 +13,7 @@ import { toAssetId } from '../../../shared/lib/asset-utils';
 import { CHAIN_IDS } from '../../../shared/constants/network';
 import { setBackgroundConnection } from '../../store/background-connection';
 import { MultichainNetworks } from '../../../shared/constants/multichain/networks';
+import { SlippageValue } from '../../pages/bridge/utils/slippage-service';
 import bridgeReducer from './bridge';
 import {
   setFromToken,
@@ -141,7 +141,7 @@ describe('Ducks - Bridge', () => {
         toChainId: null,
         fromToken: null,
         toToken: null,
-        slippage: BRIDGE_DEFAULT_SLIPPAGE,
+        slippage: SlippageValue.BridgeDefault,
         fromTokenInputValue: null,
         sortOrder: 'cost_ascending',
         toTokenExchangeRate: null,
@@ -240,7 +240,7 @@ describe('Ducks - Bridge', () => {
         fromTokenExchangeRate: null,
         fromTokenInputValue: null,
         selectedQuote: null,
-        slippage: BRIDGE_DEFAULT_SLIPPAGE,
+        slippage: SlippageValue.BridgeDefault,
         sortOrder: 'cost_ascending',
         toChainId: null,
         toToken: null,

ui/ducks/bridge/bridge.ts

@@ -1,7 +1,6 @@
 import { createAsyncThunk, createSlice } from '@reduxjs/toolkit';
 import {
   SortOrder,
-  BRIDGE_DEFAULT_SLIPPAGE,
   formatChainIdToCaip,
   getNativeAssetForChainId,
   calcLatestSrcBalance,
@@ -15,6 +14,7 @@ import {
 import { zeroAddress } from 'ethereumjs-util';
 import { fetchTxAlerts } from '../../../shared/modules/bridge-utils/security-alerts-api.util';
 import { endTrace, TraceName } from '../../../shared/lib/trace';
+import { SlippageValue } from '../../pages/bridge/utils/slippage-service';
 import { getTokenExchangeRate, toBridgeToken } from './utils';
 import type { BridgeState, ChainIdPayload, TokenPayload } from './types';
 
@@ -31,7 +31,7 @@ const initialState: BridgeState = {
   sortOrder: SortOrder.COST_ASC,
   selectedQuote: null,
   wasTxDeclined: false,
-  slippage: BRIDGE_DEFAULT_SLIPPAGE,
+  slippage: SlippageValue.BridgeDefault,
   txAlert: null,
 };
 

ui/pages/bridge/prepare/bridge-transaction-settings-modal.tsx

@@ -1,6 +1,5 @@
 import React, { useState, useEffect } from 'react';
 import { useDispatch, useSelector } from 'react-redux';
-import { BRIDGE_DEFAULT_SLIPPAGE } from '@metamask/bridge-controller';
 import {
   Button,
   ButtonSize,
@@ -30,9 +29,13 @@ import {
 } from '../../../helpers/constants/design-system';
 import { getIsSolanaSwap, getSlippage } from '../../../ducks/bridge/selectors';
 import { setSlippage } from '../../../ducks/bridge/actions';
+import { SlippageValue } from '../utils/slippage-service';
 import { Column, Row, Tooltip } from '../layout';
 
-const HARDCODED_SLIPPAGE_OPTIONS = [BRIDGE_DEFAULT_SLIPPAGE, 2];
+const HARDCODED_SLIPPAGE_OPTIONS = [
+  SlippageValue.EvmStablecoin,
+  SlippageValue.BridgeDefault,
+];
 
 export const BridgeTransactionSettingsModal = ({
   onClose,
@@ -69,7 +72,7 @@ export const BridgeTransactionSettingsModal = ({
         if (!slippage || slippage === 0) {
           // Default to first option if no slippage set, null, or 0
           // This handles undefined, null, 0, and other falsy values
-          setLocalSlippage(BRIDGE_DEFAULT_SLIPPAGE);
+          setLocalSlippage(SlippageValue.BridgeDefault);
           setCustomSlippage(undefined);
         } else if (HARDCODED_SLIPPAGE_OPTIONS.includes(slippage)) {
           setLocalSlippage(slippage);

ui/pages/bridge/utils/slippage-service.ts

@@ -8,7 +8,7 @@ import { STABLECOINS_BY_CHAIN_ID } from './stablecoins';
 export enum SlippageValue {
   EvmStablecoin = 0.5,
   EvmDefault = 2,
-  BridgeDefault = 0.5,
+  BridgeDefault = 2,
 }
 
 /**
@@ -70,7 +70,7 @@ function isStablecoinPair(
  * Calculates the appropriate slippage based on the transaction context
  *
  * Rules:
- * - Bridge (cross-chain): Always 0.5%
+ * - Bridge (cross-chain): Always 2%
  * - Swap on Solana: Always undefined (AUTO mode)
  * - Swap on EVM stablecoin pairs (same chain only): 0.5%
  * - Swap on EVM other pairs: 2%
@@ -87,7 +87,7 @@ export function calculateSlippage(
     return SlippageValue.BridgeDefault;
   }
 
-  // 1. Cross-chain (bridge) → 0.5%
+  // 1. Cross-chain (bridge) → 2%
   if (!isSwap || fromChain.chainId !== toChain.chainId) {
     return SlippageValue.BridgeDefault;
   }