In their kitchen there is probably a corner that looks like a small laboratory, with a grinder, scales and a kettle that shows the water temperature. This person has built a system for making coffee. That gives you the first rule of buying for them: do not add to the system. They chose every piece of it carefully, and they will politely leave your new gadget unused.
Buy something for the coffee ritual instead, not for the equipment. There are many good choices.
The safest choice: good beans, chosen with care
Coffee is the one part of the system that gets used up and bought again, so a gift fits in easily there. But there is a right and a wrong way. The wrong way is a random "premium" bag from a supermarket shelf. They can taste the difference, which is the reason for all that equipment. The right way is coffee from a real roaster, ideally one they have not tried. Discovering a new roaster is the gift. A subscription from a good roaster turns this into months of small deliveries, which is close to ideal for this person.
If you know how they make their coffee, one sentence to a roaster gets you the right bag. Espresso drinkers and filter drinkers want different roasts. If you do not know, the safest guess is a lighter single-origin roast for filter coffee.
Things that go with the coffee
A serious coffee person has put great care into making coffee, but usually very little into drinking it. That is where your gift can help.
The cup. They own precise equipment, but they drink from whatever mug survived their last house move. A really beautiful cup, handmade and the right size for how they drink, will be used, and noticed, every day.
The accompaniment. The right biscuit, or the piece of chocolate that goes well with an espresso. It gets eaten, it is modest, and it fits the interest exactly.
The morning around the coffee. A tray, a small carafe for the second cup, or anything that makes the ten-minute ritual feel calm and chosen rather than rushed. This is a gift for why they love the hobby, not for how they do it.
What to avoid
Novelty mugs, for this person more than anyone. The all-in-one machine, which replaces the system they enjoy using. Flavoured syrups. And general coffee-themed merchandise. An object that says "but first, coffee" turns a real craft interest into a slogan about their personality.
Look at the whole person
An interest this obvious is a useful place to start. But it is only one fact about a whole person, and the most thoughtful gift often comes from a second fact. Their coffee habit tells you that they value ritual, craft and well-made everyday things. That taste goes far beyond the corner of their kitchen, and it is exactly what we match on. Tell us who they are, including the coffee, and set a budget. Then swipe through gifts that fit the whole person, not just their equipment.