You are looking for a change, and once you start looking you find 1 every day.
Some of them mean something. Most of them are Tuesday.
Free to try. We never store your chats.
A slow reply, a short answer, a cancelled plan — on their own that is noise, and everybody produces it.
3 changes in the same direction inside the same stretch is a different object. That is the threshold worth reacting to.
Not volume. Volume is the last thing to go and the easiest to keep up out of habit.
Initiation moves first — who opens the thread, who suggests the thing, who asks the follow-up question.
Scroll back through the last 10 exchanges and count who started them. That number is usually the whole answer.
Reply speed. It tracks somebody's week far more closely than it tracks their feelings.
If it is a real decline, more messages will not reverse it, and "is something wrong?" over text almost always returns "no, just tired."
The conversation that works here happens out loud, and it is short.
It watches the direction rather than the day — what this person used to do, and what changed in the last few weeks.
It will say "this seems to be changing" before it says anything stronger, because 1 week is not evidence.
Try it on your conversation