Can they offer me a retention bonus and then still let me go anyway?

Unfortunately, yes, unless the retention agreement itself says otherwise — a retention bonus and job security are two separate promises, and one doesn't automatically guarantee the other. A typical retention arrangement promises payment for staying through a defined period or milestone, like the closing of the sale or a transition date after it; it doesn't usually promise your job is protected beyond that point, unless the agreement explicitly says so.

If you're let go after collecting a retention bonus but before any promised protection period ends, or if the termination looks designed specifically to avoid a payment about to come due, that's worth scrutinizing closely. You may still have full termination entitlements, and if the timing looks like it was deliberately arranged to dodge an obligation that was about to trigger, that pattern can matter legally.

Before you sign any retention agreement, read exactly what it promises: is the payment tied only to a date, or does it also address your job security or notice if you're let go early? If you've already been let go shortly after receiving a retention bonus and the timing feels off, get the agreement and the circumstances of your termination reviewed together, not separately.