They’re about to lose you. They know it. So they offer money.
Not a raise — a bonus. One-time. With a clawback clause. If you leave within eighteen months, you pay it back. The retention bonus is a golden handcuff presented as a gift.
“We want to show you how much we value you.” They value you at exactly the amount that makes leaving mathematically painful for eighteen months. Not a dollar more.
If they valued you, they’d fix the thing making you want to leave. The retention bonus is cheaper than fixing the problem.