He went from long texts to just "cool yeah"? What to do

A sudden or gradual move from long texts to clipped ones is most often about his bandwidth, not a verdict on you. People who text in full paragraphs usually have a lot of attention to give during a slow week, and that attention shifts when work, family, or stress takes over. Look at the timing. If the change started around a particular event, a busy stretch at work or a plan that fell through, the cause is probably outside the conversation.

The content of his short replies matters too. A reply like "cool yeah" to a question about his plans reads differently from the same words to a joke you made. Short answers to questions that asked him to share something personal can mean he is tired of carrying the conversation, or that he felt exposed by what he shared earlier. Notice whether he still asks anything back. If he has stopped asking questions entirely, the momentum is clearly on your side of the chat.

Your reply has to do three jobs. It should answer whatever he actually said, so he does not feel ignored. It should give him one clear, easy hook, such as a specific question he can answer in a few words or a small piece of your life he can react to. And it should carry no pressure about the change itself. Naming his short replies makes him defensive and makes the exchange about the texting rather than about the two of you.

Keep your message shorter than his used to be and lighter in tone. If you were both sending long messages before, a short, specific message from you reads as relaxed rather than as withdrawing. Make the hook something he can answer without thinking, like a photo, a small plan, or a question with a clear answer. Avoid questions that require him to explain his feelings or his week in depth, because that is exactly the effort he is currently not offering.

Send your reply when you would send it on any ordinary day, not in a burst of late-night feeling. A message sent at 2am reads as urgent and tends to pull the conversation in an intense direction. Mid-afternoon or early evening, when you are not already thinking about the change, gives you a calmer message and a better chance of a natural reply.

After you send it, give him a real window before you do anything else. A day is a reasonable baseline for a casual thread, and two or three days if the last few exchanges were slow. If he replies in kind, let the conversation grow back at its own pace. If he does not reply, do not follow up with a second message asking whether he is still interested. Stop there. A single unanswered message is itself your answer for now, and sending more shifts the thread into chasing, which almost always makes the drop-off worse.