Barkoe
Ask a manager why someone left and you will usually hear one reason: the offer was too good to refuse, or the commute, or a difficult project. Ask the person who left and the answer has several parts, most of which had been true for a year.
That gap is why retention works better as design than as mood management. You decide in advance, with the person, what would have to be true for them to stay, and you revisit it as things change.
Start with the shape of the job
Most jobs are set at the point of hire and then left alone. The description covers what the last person did, and the new one inherits it, including the parts they will outgrow within a year. Someone who is learning quickly and doing the same tasks in month fourteen as in month two is already halfway out the door, whatever their engagement score says.
Build a rotation into the role. Give the person a piece of work that belongs to the next level before they have the title, and write down what you both expect to change by the following review. It costs an hour to set up, and it gives the person a reason to look ahead inside your team rather than outside it.
Ask early, and act on the answer
A stay conversation is the opposite of an exit interview: you ask someone who works for you what would make them leave. It works in the first ninety days, when the answers are still cheap to act on. It works poorly in year four, when the honest answer is a list of things you should have fixed in year two.
What matters is that you do something visible with what you hear. If you can change it, change it and say so. If you cannot, say that too. People stop answering the question the first time they see nothing happen.
Let the market set the timetable for pay
Pay reviews on a fixed calendar are among the commonest avoidable causes of exits. The company calendar says March, the market moved in October, and a recruiter found your best engineer in November. You do not have to match every offer, but you should know where your key people sit against the market before someone else tells them.
Make leaving safe, and more people stay
It sounds backwards, but a role that anyone could pick up in a week is a role in which the person holding it is free to take leave, move sideways or be promoted. Handover notes, shared ownership and written process do not make people easy to replace. They make people free to move, and people who are free to move inside your team are less likely to move out of it.