Ice cream may hold its shape after the ice starts melting. What else must fail?

Answer: Fat-stabilized foam

Syrup-thickened body — Not quite. The concentrated syrup phase is part of ice cream's body, so this is a plausible guess. But syrup thickness is not the main scaffold that lets a scoop keep its shape after some ice melts. The hidden support is the air-and-fat foam network, which must collapse before the scoop fully slumps.

Fat-stabilized foam ✓ — Right. Melting has two linked events: ice crystals turn to water, and the fat-stabilized foam structure collapses. A scoop can look surprisingly intact after some ice has melted because the air-and-fat scaffold is still standing. Emulsifiers can even improve shape retention by promoting the right amount of fat destabilization, which sounds backwards because 'destabilization' helps stabilize the foam.

Package insulation — Not quite. Packaging matters during storage and transport, but a scoop sitting on a plate is no longer being held up by its carton. The structure comes from inside: air cells, fat globules, ice crystals, and concentrated syrup. Once the internal foam collapses, the scoop slumps even if the room temperature has not changed.