Android - App crashes

[mitarachim]

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Version Number: 9.3.61-0
Reproducible in staging?: Yes
Reproducible in production?: No
If this was caught during regression testing, add the test name, ID and link from BrowserStack: #87387
Email or phone of affected tester (no customers): sdsodijnosdjoij@gmail.com
Issue reported by: Applause Internal Team
Bug source: Exploratory - Significant User Experience Deterioration
Device used: Samsung Galaxy S25 FE / Android 16
App Component: Other

Action Performed:

1. Launch Android Expensify app.

Expected Result:

App will not crash.

Actual Result:

App crashes.

Workaround:

Unknown

Platforms:

• Android: App
• Android: mWeb Chrome
• iOS: App
• iOS: mWeb Safari
• iOS: mWeb Chrome
• Windows: Chrome
• MacOS: Chrome / Safari

Screenshots/Videos

Bug7134831_1776772011726.az_recorder_20260421_194537_1.mp4

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[melvin-bot]

You have been assigned to this deploy blocker because you recently merged this PR: #87387

[melvin-bot]

💬 A slack conversation has been started in #expensify-open-source

[github-actions]

👋 Friendly reminder that deploy blockers are time-sensitive ⏱ issues! Check out the open `StagingDeployCash` deploy checklist to see the list of PRs included in this release, then work quickly to do one of the following:

1. Identify the pull request that introduced this issue and revert it.
2. Find someone who can quickly fix the issue.
3. Fix the issue yourself.

[OSBotify]

Investigation Summary

Classification: Frontend bug
Causing PR: #87387 - "[No QA] Enable Hermes V1" by @j-piasecki (High confidence)
Related Issues: #86792 (the original issue this PR was fixing)

Recommendation: REVERT

PR #87387 enables Hermes V1 (a new JavaScript engine version) on Android and iOS, and the deploy blocker is an Android app crash reproducible in staging but not in production. The crash only appears after this PR introduced Hermes V1 support, which is a deep runtime-level change that directly explains app-level crashes on Android.

Assigned: @j-piasecki (PR author), @roryabraham (approving reviewer)
Labels: Both DeployBlockerCash and DeployBlocker are present. This is a Frontend bug (the fix requires reverting an App PR). DeployBlockerCash is kept. DeployBlocker has been removed.

Detailed Analysis

Evidence

• The melvin-bot already identified PR [No QA] Enable Hermes V1 #87387 as the likely cause, since it was the most recently merged PR touching native Android/iOS configuration at the time the bug was reported.
• PR [No QA] Enable Hermes V1 #87387 enables Hermes V1 for Android by setting hermesV1Enabled=true in android/gradle.properties and ENV['RCT_HERMES_V1_ENABLED'] = '1' in ios/Podfile.
• The Hermes engine was upgraded from v0.14.0 to v250829098.0.4 (a major version jump). This is a significant change to the JavaScript runtime used by the React Native app on mobile.
• The bug is an Android app crash (on Samsung Galaxy S25 FE / Android 16) that is reproducible in staging but not in production. Production does not yet include this PR; staging does (it was merged on 2026-04-17 and appears as item Add unread message indicator to browser tab #91 in the StagingDeployCash chronological list).
• No other PRs in the staging list touch the Android JS engine configuration.

Verification

• android/gradle.properties now contains hermesV1Enabled=true — the exact change introduced by PR [No QA] Enable Hermes V1 #87387.
• PR [No QA] Enable Hermes V1 #87387 modifies: android/gradle.properties, ios/Podfile, ios/Podfile.lock, package.json, package-lock.json, rock.config.mjs, and scripts/compute-patches-hash.sh — all of which are build configuration files for the native Android and iOS apps.
• The change is directly to the JavaScript engine runtime layer, which is the most fundamental component of a React Native app. A bug in this layer would manifest as an app crash on launch.
• PR [No QA] Enable Hermes V1 #87387 also required a companion Mobile-Expensify PR (#13910) to also enable Hermes V1. Both landed in the same staging build cycle.

Root Cause

PR #87387 upgrades the Hermes JavaScript engine from v0.14.0 to v250829098.0.4 (Hermes V1) on Android and iOS. The Hermes V1 engine has a compatibility issue that causes the Android app to crash on launch. The crash is staging-only because production does not yet contain this engine upgrade. Reverting this PR (and the accompanying Mobile-Expensify PR #13910) should restore the app to a stable state on Android.