Is cereal a soup?

The case for yes is purely geometric: solids in liquid, in a bowl, eaten with a spoon. If that were the whole definition, the yes side would win, and so would a glass of ice water qualifying as soup, which is the first sign the definition is broken.

Dictionaries rescue us: soup is characteristically a cooked dish, typically made by simmering ingredients in stock or water until the liquid and solids become one unified food. Cereal fails every element. Nothing is cooked at service, the milk and flakes meet seconds before eating and remain strangers, the milk is a complement you could omit, dry cereal is still cereal, and the dish is served cold by design rather than as leftovers. Structurally, cereal is closer to a salad dressed at the table: prepared solids plus a poured liquid accent.

Ruling: cereal is not soup. Gazpacho survives as soup on the cooking-and-blending intent standard, before anyone tries the cold counterexample. The spoon proves nothing; the spoon also eats pudding.