Description

The Shield announcement modal uses a cohort strategy (wallet_home / post_tx) to determine when to show users the entry modal. Users assigned to the post_tx cohort were never seeing the modal due to multiple issues in the evaluation flow:

1. pendingShieldCohort was not persisted - With persist: false, the POST_TX cohort value set by #assignPostTxCohort after a swap/transfer was lost whenever the MV3 service worker restarted. On the next Home page visit, componentDidMount would overwrite it with WALLET_HOME, causing the evaluation to return early for pending-but-not-expired users. Changed to persist: true so the value survives service worker restarts.

2. Pending cohort cleared before evaluation completed - setPendingShieldCohort(null) was called synchronously before evaluateCohortEligibility had a chance to finish. If the evaluation failed, the pending cohort was permanently lost with no retry. Now the pending cohort is only cleared after the evaluation promise resolves successfully.

3. Timeout event fired incorrectly for non-expired cohorts - When entrypointCohort === POST_TX, the guard entrypointCohort !== POST_TX && !hasExpired was always false, causing the ShieldEligibilityCohortTimeout event to fire even when the assigned cohort had not actually expired. Added a hasExpired guard so the timeout event only fires when the cohort has genuinely expired.

4. Missing error observability - Failures in evaluateCohortEligibility were only logged with log.warn. Added Sentry error capture so cohort evaluation failures surface in monitoring.

5. post_tx could not overwrite an existing wallet_home pending cohort - #assignPostTxCohort only set POST_TX when pendingShieldCohort was falsy (!pendingShieldCohort). If the user had already visited Home (setting it to WALLET_HOME), a subsequent swap would not overwrite it. Now the guard checks specifically for pendingShieldCohort === POST_TX instead, allowing POST_TX to take priority over WALLET_HOME.

Ref: cohort technical details

Changelog

CHANGELOG entry: Fixed a bug where users assigned to the post-transaction Shield cohort would never see the Shield announcement modal

Related issues

Fixes:

Manual testing steps

1. Build and load the extension with Shield feature enabled
2. For post_tx cohort, sign in and navigate to the Home pageverify no modal appears (initial cohort assignment happens silently for post_tx users)
3. Perform a swap or token transfer transaction
4. Navigate back to the Home page
5. Verify the Shield entry modal appears for users assigned to the post_tx cohort
6. Close the extension completely, reopen it, and repeat steps 3-5, verify the pendingShieldCohort value persists across restarts and the modal still appears
7. For wallet_home cohort users: verify the modal still appears immediately on first Home page visit (no regression)

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Extension 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.