By itself, nothing. That is not a dodge — it is the actual answer, and it is why you have read 6 pages about this and still do not feel any better.
"k" is 1 character. There is nothing inside it to analyse. Everything you are reacting to is coming from somewhere else.
Free to try. We never store your chats.
"What does k mean from a guy." "What does k mean from a girl." Those are the questions the internet decided to answer, and they are the wrong unit. Gender is not what is carrying the signal here.
The person is. The same character means something completely different depending on who typed it, and no list can know that.
What does he normally send?
If he has answered in 1 or 2 words since the day you met, "k" is Tuesday. It is not cold, it is his baseline, and reading it as a signal will start an argument about nothing.
If he usually writes 3 lines and sends a voice note when he is annoyed, then "k" is genuinely different, and the difference is the message. Not the letter. The drop.
Look at the 5 messages before it, not the 1 in front of you. Did the length fall off gradually over the last few weeks, or did it fall off in this conversation? Those have completely different answers.
A gradual fade is usually about the relationship. A sudden drop inside 1 conversation is usually about the thing that was just said, and it is often not the thing you think it is.
And check what you sent immediately before. A short reply frequently answers a message that did not leave room for a long one.
Do not ask "are you mad at me". It reads as a request to be reassured, it puts the work on him, and if he was not annoyed before, the question is the thing that makes it a subject.
Match the register instead. Something short and easy, no reference to the tone, no verdict. If it was nothing, the conversation just continues. If it was something, it will come up on its own with more than 1 letter attached to it.
And if you are asking this question at 3am, the honest read is usually that you already know it is not about the letter.
You paste it and it reads it against him rather than against a list — what his normal length is, whether this is his baseline or a change, and what it usually means when it changes.
Then it writes the reply in 4 tones, and tells you if the better move today is not to answer it at all.
Try it on your conversation