When modifying imported values, different rules apply to primitive values and objects: 1) Imported bindings are read-only, attempts to reassign them throw a TypeError, 2) However, properties of imported objects can be modified (mutated), 3) In this example, modifying config.debug works because it's mutating an object property, 4) Attempting to reassign API_KEY throws an error because imported bindings are immutable, 5) This behavior enforces module boundary integrity while allowing necessary object mutations, 6) It's similar to how const works - the binding is immutable but object properties remain mutable, 7) This design helps prevent accidental modifications while maintaining practical flexibility.