Description

Sentry reports show users crashing on v7.66.0 with Account Id "undefined" not found during Engine initialization. The root cause is a corrupted AccountsController.internalAccounts.selectedAccount that is either missing or undefined in persisted state.

Migration 059 attempted to fix this but has a critical gap: it uses hasProperty(internalAccounts, 'selectedAccount') which returns false when the key is entirely absent (the common case after a JSON.stringify/JSON.parse roundtrip strips undefined values). This means migration 059 silently skips the most common form of this corruption.

Migration 126 fixes this by:

• Detecting both a missing key and an explicit undefined value
• Reporting the exact corruption type (key_missing, value_undefined, wrong_type_*, empty_string) to Sentry for diagnostics
• Recovering by setting selectedAccount to the first account ID, or falling back to '' (which AccountsController auto-reconciles)

Since this is migration 126 (> 107), it runs after inflateFromControllers pulls the per-controller filesystem data into engine.backgroundState, so it operates on the actual corrupted data regardless of its origin.

Changelog

CHANGELOG entry: Fixed a crash caused by corrupted account selection state during app upgrade

Related issues

Fixes: #11488

Manual testing steps

Feature: Migration 126 repairs missing selectedAccount

  Scenario: user upgrades with corrupted AccountsController state
    Given the user has a persisted AccountsController state where selectedAccount key is missing from internalAccounts
    When the user upgrades to the new app version
    Then migration 126 detects the missing key and sets selectedAccount to the first account ID
    And the app starts successfully without crashing

  Scenario: user upgrades with valid AccountsController state
    Given the user has a persisted AccountsController state where selectedAccount is a valid account ID
    When the user upgrades to the new app version
    Then migration 126 is a no-op and the state is unchanged

Screenshots/Recordings

Before

N/A

After

N/A

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Mobile Coding Standards.
• I've completed the PR template to the best of my ability
• I've included tests if applicable
• I've documented my code using JSDoc format if applicable
• I've applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

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