regression: Ephemeral messages not showing on threads

[jessicaschelly]

Proposed changes (including videos or screenshots)

Fixes non-member mention warnings not appearing inside thread replies.

Fixes ephemeral messages (e.g. non-member mention warnings) not appearing inside thread replies.
The root cause was that the notify-user stream — which delivers user-scoped ephemeral messages — was not feeding into the thread message cache. The fix adds a check in incomingMessages.ts: when an incoming ephemeral message has a tmid, it is forwarded to upsertThreadMessageInCache so it gets inserted into the correct thread, in addition to being stored in the regular message store.

This PR also adds/updates e2e coverage for message mention warnings:

• Adds a thread scenario that mentions a non-member and verifies the warning actions are visible inside the thread.
• Reuses page-object helpers for warning action buttons in regular messages and thread messages.
• Keeps the existing permission-specific warning action assertions for room messages.

Issue(s)

CORE-2278
Root cause: #39859

Steps to test or reproduce

1. Create or open a channel where the target user is not a member.
2. Send a message and open its thread.
3. Send a thread reply mentioning the non-member user.
4. Verify the non-member mention warning appears inside the thread with the expected actions:
   • Do nothing
   • Add them
   • Let them know

Automated coverage: apps/meteor/tests/e2e/message-mentions.spec.ts includes the should show non-member mention warning inside threads scenario.

Further comments

Summary by CodeRabbit

• Bug Fixes

  • Improved thread message caching for ephemeral incoming messages.

• Tests

  • Added test coverage for message mention warnings triggered within thread conversations.
  • Refactored mention warning tests with improved helper utilities.

[dionisio-bot]

Looks like this PR is ready to merge! 🎉
If you have any trouble, please check the PR guidelines

[changeset-bot]

⚠️ No Changeset found

Latest commit: 3b33a8b

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[coderabbitai]

Walkthrough

Thread messages are now upserted into the client cache when incoming ephemeral messages contain a thread ID. E2E tests are refactored to use new page-object helper methods that simplify action-button locator assertions, with a new test validating mention warnings inside threads.

Changes

Thread Message Caching and E2E Validation

Layer / File(s)	Summary
Thread message cache integration apps/meteor/client/startup/incomingMessages.ts	Import of upsertThreadMessageInCache and conditional call when msg.tmid is present to store thread message data in the client cache.
Test helper methods for message action buttons apps/meteor/tests/e2e/page-objects/fragments/home-content.ts	getLastMessageActionButton(name) and getLastThreadMessageActionButton(name) locator getters enable consistent action-button target queries in tests.
E2E test refactoring and thread mention validation apps/meteor/tests/e2e/message-mentions.spec.ts	Message-mention warning test cases refactored to use new helpers across non-member @all/@here action flows (Do nothing, Add them, Let them know); new test validates mention warnings and action buttons inside threads.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested labels

type: bug

Suggested reviewers

• MartinSchoeler
• tassoevan

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title directly addresses the main issue fixed in the PR: ephemeral messages (non-member mention warnings) not appearing in threads, which is the primary change across all modified files.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (release-8.5.0@8d6fad5). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.5.0   #40776   +/-   ##
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  Coverage                 ?   69.93%           
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  Files                    ?     3327           
  Lines                    ?   126586           
  Branches                 ?    21970           
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  Hits                     ?    88526           
  Misses                   ?    34779           
  Partials                 ?     3281           

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[cubic-dev-ai]

1 issue found across 3 files

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