What to do if he only reaches out for hookups (and what to say)

Look at the shape of the whole thread, not one message. If nearly all his messages land between 11pm and 2am, if he never asks what you did that day, and if every plan you suggest gets a soft 'maybe later,' he has already told you what he's offering. Check whether he has ever suggested a daytime plan with no sex attached. If he hasn't, that tells you more than any single compliment he's paid you.

Also notice what he does when you show interest in something other than sex. Does he match it, change the subject, or go quiet for a day? A guy who is open to more usually takes an interest in your life without being prompted. A guy who only wants the arrangement tends to treat anything outside it as friction.

The move here is to reply to the real thing in front of you. You can either tell him what you're looking for and ask whether he's on the same page, or tell him you're not up for casual meetups and leave the door open only if he wants something different. Both work. Hinting doesn't, because hints let him keep the ambiguity that suits him.

Keep the message short and concrete. Name what you want in plain words, then give him one specific option to respond to, like a daytime coffee or a plan that doesn't involve his place. Ask one question at most. You're not trying to sound clever. You're trying to make his answer easy to read.

Don't answer a 1am message at 1am. Waiting until the next day gives you time to decide what you want instead of reacting to his timing, and it shows you're not on call. Aim to reply within the same working day, not an hour later, so it doesn't look like a game.

If he doesn't respond to your clear message within about three days, send one short follow up that's easy to answer, then stop. Don't send a third message asking why he's gone quiet. If he comes back with another late night invitation, that's your answer. Stop once it's clear the only thing on offer is the arrangement you've already said you don't want.