fix(ui): skip markThreadRead for reply-less thread parents

[xsahil03x]

Summary

Opening a thread on a parent with no replies produced a guaranteed StreamChatNetworkError 404 (Can't find thread with id ...) every time. _maybeMarkMessagesAsRead unconditionally called channel.markThreadRead(parentId) when in a thread, but the server-side thread object only exists after the first reply lands.

Guard added to _maybeMarkMessagesAsRead in thread mode: skip when the parent's replyCount is 0. Matches the iOS SDK's precedent in ChatThreadVC.shouldMarkThreadRead (if messageController.replies.isEmpty { return false }, comment: "If there are no replies, no thread is yet created").

Fixes #2806.

Why replyCount on the parent

• replyCount is server-owned and populated via message.updated on the parent — nothing in the LLC bumps it locally, so it stays at 0 for optimistic-only replies too. Both "no replies" and "one local-only reply" produce the same replyCount == 0, and both cases want the same behavior: skip → no 404.
• Alternative (channel.state.threads[parentId]?.isEmpty) is less robust — the client's thread map is only populated once thread messages are paged in.

Test plan

• New regression test in mark_read_test.dart:
  • does NOT fire when parentMessage.replyCount is 0 — the load-bearing guard.
  • fires when parentMessage.replyCount > 0 — happy path.
  • does NOT fire markRead (channel-level) when in a thread — invariant guard.
• Verified the regression test fails on master without the guard (MockChannel.markThreadRead(parent-id) was called) and passes with the guard.
• dart analyze clean, dart format clean.

Follow-up

• v9 backport is in a parallel PR (branch bug/skip_mark_thread_read_when_no_replies_v9).
• Cross-SDK check: Android (MessageListController.markLastMessageReadInternal) has the same latent bug and no explicit guard — worth tracking as a separate ticket if not already.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Fixed thread read-status marking so parent messages with no replies are no longer updated, preventing repeatable errors when opening a thread before the first reply.
  • Ensured thread views still correctly mark replies as read once the thread is available.
  • Confirmed thread mode no longer triggers channel-level read updates when thread-specific unread counts are present.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: d52d7eca-2dcb-48c5-985c-28d6a66635cb

📥 Commits

Reviewing files that changed from the base of the PR and between b65a0c8 and fb21f13.

📒 Files selected for processing (3)

• packages/stream_chat_flutter/CHANGELOG.md
• packages/stream_chat_flutter/lib/src/message_list_view/message_list_view.dart
• packages/stream_chat_flutter/test/src/message_list_view/mark_read_test.dart

🚧 Files skipped from review as they are similar to previous changes (2)

• packages/stream_chat_flutter/CHANGELOG.md
• packages/stream_chat_flutter/lib/src/message_list_view/message_list_view.dart

---

📝 Walkthrough

Walkthrough

StreamMessageListView now skips markThreadRead when a thread parent has no replies. Mark-read tests add thread state and verify reply-count gating, thread-level marking, and channel-level read suppression.

Changes

Thread read gating

Layer / File(s)	Summary
Guard thread read marking packages/stream_chat_flutter/lib/src/message_list_view/message_list_view.dart, packages/stream_chat_flutter/CHANGELOG.md	Thread read marking returns early for reply-less parents, and the changelog records the fix.
Validate thread read gates packages/stream_chat_flutter/test/src/message_list_view/mark_read_test.dart	Tests configure thread state and verify markThreadRead behavior based on replyCount, while channel-level markRead remains unused in threads.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related issues

• #2806 — Directly tracks the markThreadRead 404 fixed by the reply-count guard and accompanying tests.

Suggested reviewers: velikovpetar, renefloor

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main fix: skipping markThreadRead for thread parents with no replies.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch bug/skip_mark_thread_read_when_no_replies

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.24%. Comparing base (3a8b672) to head (fb21f13).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2807      +/-   ##
==========================================
+ Coverage   71.08%   71.24%   +0.15%     
==========================================
  Files         429      429              
  Lines       26892    26893       +1     
==========================================
+ Hits        19117    19159      +42     
+ Misses       7775     7734      -41     

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