[Bug]: Max button not working for money account deposit

[bschorchit]

Describe the bug

We're getting several reports about the max button not working for money account deposit.

Expected behavior

No response

Screenshots/Recordings

Steps to reproduce

1. Start a money account deposit with a fixed spread token
2. Click max
3. Notice this blocking alert will appear sometimes

Not super consistent repro steps.

Error messages or log output

Where was this bug found?

Internal release testing

Version

8.3.0

Build number

Build type

None

Device

Operating system

iOS

Additional context

No response

Severity

No response

[metamask-ci]

Triage Agent -- Classification

Severity: Sev2 (confidence: 0.72) ⚠️ Advisory

The max button in the money account deposit flow is partially broken - it intermittently shows a blocking alert that prevents users from completing a deposit. This blocks a key flow (depositing max amount) but has inconsistent reproduction, suggesting it affects a subset of interactions rather than being universally broken. A workaround exists (manually entering the amount instead of using max).
Not auto-applied -- confidence below threshold.

Size: size-M (confidence: 0.65) ⚠️ Advisory

The issue involves the interaction between the deposit flow, the max button logic (likely in the confirmation/custom amount component), and the BlockingActionModal. The inconsistent reproduction suggests a race condition or state management issue that may span multiple components. Investigation is needed to identify the exact trigger, likely involving the confirmation flow's AdvancedCustomAmount loader and how it interacts with fixed spread tokens.
Not auto-applied -- confidence below threshold.

Team: team-earn ✅

Matched via CODEOWNERS: @MetaMask/earn

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Root Cause Analysis

Affected component: Money account deposit confirmation flow - likely the AdvancedCustomAmount loader and max amount calculation for fixed spread tokens

The deposit flow in useMoneyAccount.ts navigates to a confirmation screen with ConfirmationLoader.AdvancedCustomAmount and initializes the transaction batch with amount BigInt(0), expecting the confirmation UI to allow the user to set the actual amount. When the user clicks 'max', the confirmation component needs to calculate the maximum depositable amount. For fixed spread tokens, this calculation likely involves fetching the exchange rate or checking allowances, and a race condition or error in this async operation appears to trigger the BlockingActionModal (or a similar blocking alert). The inconsistency suggests a timing issue - perhaps the exchange rate fetch via MoneyAccountBalanceService:getExchangeRate sometimes fails or returns stale data, or the gas estimation for the max amount encounters an error that surfaces as a blocking modal rather than being handled gracefully. The requiredAssets in the batch are set with amount '0x0', and when the max button recalculates the actual required amount for a fixed spread token, the spread calculation or balance check may intermittently fail.

Evidence:

• Deposit initiates with amount BigInt(0) and navigates to ConfirmationLoader.AdvancedCustomAmount
• requiredAssets amount is set to '0x0' initially, requiring recalculation when max is clicked
• BlockingActionModal component exists and shows a modal with spinner that blocks interaction
• Issue is specific to 'fixed spread tokens' suggesting the spread/rate calculation is involved
• Inconsistent reproduction points to a race condition or async timing issue
• The deposit flow uses isGasFeeSponsored for Monad chain which may affect max calculation differently

Suggested Fix

Confidence: medium: likely but needs investigation - the exact confirmation component handling the max button and the specific blocking alert trigger are not in the provided code context. The root cause hypothesis is based on the deposit flow architecture and the mention of fixed spread tokens.

Investigate the confirmation flow's max amount calculation for fixed spread tokens. The issue likely resides in the component loaded by ConfirmationLoader.AdvancedCustomAmount where the max button triggers an async operation (balance check, exchange rate fetch, or gas estimation) that either fails or triggers a blocking modal incorrectly. The fix should: 1) Add proper error handling around the max amount calculation to prevent the blocking modal from appearing on transient failures, 2) Ensure the exchange rate and spread calculations for fixed spread tokens are properly awaited before enabling the max button, 3) Add a fallback or retry mechanism if the rate fetch fails.

Target files: app/components/UI/Money/hooks/useMoneyAccount.ts, app/components/Views/confirmations/components/confirm
Target functions: AdvancedCustomAmount max button handler, initiateDeposit, max amount calculation for fixed spread tokens

Approach:

1. Locate the AdvancedCustomAmount confirmation loader component (referenced in ConfirmationLoader.AdvancedCustomAmount) and find the max button click handler. 2. Trace the code path when max is clicked for a fixed spread token - identify where the blocking alert/modal is triggered. 3. Check if there's a race condition between the exchange rate fetch and the max amount calculation. 4. Add proper error handling to gracefully handle failures in the max calculation without showing a blocking modal. 5. If the blocking alert is intentional (e.g., insufficient balance after spread), ensure the condition is correctly evaluated and doesn't trigger on valid max amounts. 6. Consider caching the exchange rate or pre-fetching it when the deposit flow opens to avoid timing issues when max is clicked.

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Confidence threshold: 0.85. Labels marked ✅ were auto-applied. Labels marked ⚠️ are advisory only (below threshold).
To re-triage, remove the ta-bot-triage label and re-apply ta-needs-triage.
⚠️ Some dimensions could not be confidently classified. An engineer should review this issue.