Fix messages appearing out of order when local time is not synced with server time

[VelikovPetar]

Goal

Fix messages appearing out of order when a user's device clock is not in sync with the server, or when multiple messages are sent in rapid succession and their server-assigned timestamps don't preserve the local send order.

Implementation

Introduced MessageSortComparator — a dedicated Comparator<Message> that uses a two-tier sorting strategy:

• Same user + both messages have createdLocallyAt: sort by createdLocallyAt to preserve the exact order the messages were composed, regardless of server-side timestamp assignment or network latency.
• All other pairs: sort by createdAt, falling back to createdLocallyAt when the server timestamp is not yet available. This handles cross-user messages and ensures clock-skewed messages land in the correct position on the timeline.

Replaced all existing .sortedBy { it.getCreatedAtOrNull() } call-sites in ChannelMutableState, ThreadMutableState, Channel.kt (extensions), and Thread.kt (extensions) with .sortedWith(MessageSortComparator).

Why sorting by createdLocallyAt is reliable for same-user messages:

ChatClient.sendMessage calls Message.ensureCreatedLocallyAt() before dispatching each message. That function sets createdLocallyAt to max(channel.lastMessageAt + 1ms, now()), which guarantees the timestamp is always strictly after the previous message in the channel. As a result, successive messages from the same user always have monotonically increasing createdLocallyAt values that reflect the exact order they were composed — making it safe to use as the sort key for same-user pairs.

UI Changes

Before	After

Testing

[github-actions]

PR checklist ❌

The following issues were detected:

• Section Testing is missing or empty.

What we check

1. Title is concise (5–18 words) unless labeled pr:ignore-for-release.
2. At least one pr: label exists (e.g., pr:bug, pr:new-feature).
3. Sections ### Goal, ### Implementation, and ### Testing contain content.

[github-actions]

SDK Size Comparison 📏

SDK	Before	After	Difference	Status
stream-chat-android-client	5.26 MB	5.26 MB	0.00 MB	🟢
stream-chat-android-offline	5.48 MB	5.48 MB	0.00 MB	🟢
stream-chat-android-ui-components	10.63 MB	10.63 MB	0.00 MB	🟢
stream-chat-android-compose	12.85 MB	12.85 MB	0.00 MB	🟢