Rules - Workspace rule system message shown instead of personal rule system message

[jponikarchuk]

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Version Number: 9.3.22-1
Reproducible in staging?: Yes
Reproducible in production?: N/A - new feature, doesn't exist in prod
If this was caught during regression testing, add the test name, ID and link from BrowserStack: #82438
Email or phone of affected tester (no customers): ndk.2303+246@gmail.com
Issue reported by: Applause Internal Team
Bug source: Pull Request QA execution
Device used: Windows 11 Home/Chrome
App Component: Money Requests

Action Performed:

Preconditions:

• Admin create a workspace, invite member to ws, create a merchant rules: Merchant match: "Uber" → Category: "Travel"
• Member creates a personal expense rule for Mechant match: "Uber" → Category: "Meals & Entertainment"

1. Open https://staging.new.expensify.com/
2. Login as Member
3. Navigate to workspace chat
4. Create an expense with "Merchant: Uber"

Expected Result:

Verify the system message says "Applied a personal rule:"

Actual Result:

Category is updated to "Meals & Entertainment", but the system msg is "set the category to "Travel" via workspace rule"

Workaround:

Unknown

Platforms:

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

Screenshots/Videos

1.mp4

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[melvin-bot]

You have been assigned to this deploy blocker because you recently merged this PR: #82438

[melvin-bot]

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

[melvin-bot]

Triggered auto assignment to @greg-schroeder (Bug), see https://stackoverflow.com/c/expensify/questions/14418 for more details. Please add this bug to a GH project, as outlined in the SO.

[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: Backend bug
Causing PR: #82438 - "Enable merchant rules v2" by @luacmartins (High confidence)
Related Issues: None

Recommendation: NEEDS INVESTIGATION (Backend team required)

This is a backend bug in the rule priority/message generation logic. The PR that enabled merchant rules v2 exposed an existing backend issue where personal expense rules correctly take precedence over workspace merchant rules (the category is updated correctly), but the system message incorrectly indicates a workspace rule was applied.

Labels: Keep DeployBlocker (backend issue). Remove DeployBlockerCash since the fix requires backend changes, not App PR revert.

Detailed Analysis

Evidence

PR #82438 simply removed a feature flag check that prevented merchant rules from displaying in production:

- if (isProduction) {
-     return null;
- }

This enabled the merchant rules feature for all users. The bug was discovered during QA testing of this new feature.

Verification

The bug manifests as follows:

1. Admin creates workspace merchant rule: "Uber" → Category: "Travel"
2. Member creates personal expense rule: "Uber" → Category: "Meals & Entertainment"
3. Member creates expense with merchant "Uber"
4. Expected: Category set to "Meals & Entertainment" with message "Applied a personal rule"
5. Actual: Category correctly set to "Meals & Entertainment", BUT message says "set the category to "Travel" via workspace rule"

The frontend code in ModifiedExpenseMessage.ts displays system messages based on the policyRulesModifiedFields property in the report action. When this field is present, it shows "via workspace rules". The backend is incorrectly populating this field even when a personal rule takes precedence.

Root Cause

This is a backend bug in the rule application logic. The backend correctly applies personal rules with higher priority, but the system message generation incorrectly attributes the change to workspace rules.

Personal rules should use a different field or source indicator (not policyRulesModifiedFields) since that field specifically triggers "via workspace rules" messages in the frontend.

From documentation: "Your Personal Expense Rule takes precedence. Workspace Merchant Rules apply only if no personal rule overrides the expense."

Why Backend Fix Required

• The App frontend correctly displays messages based on data structure received from backend
• No App code determines rule priority or generates system messages
• The backend needs to either:
  1. Use a different field for personal rule modifications, OR
  2. Add a rule source indicator (personal vs workspace) to the message data