A field must act. The PlasticAgency names the capacity of a corpus to intervene in the world: not merely to describe, but to reshape the conditions it analyzes. In the Socioplastics architecture, agency is not a property of individuals. It is a property of the field itself. The field acts through its concepts. When FlowChanneling is applied to a real urban system, it does not merely describe how capital moves. It reveals the channels through which capital moves, and in revealing them, makes them available for intervention. When SystemicLock is applied to a governance regime, it does not merely describe how the regime freezes possibility. It identifies the lock points where pressure can be applied. This is plastic agency: the capacity of a concept to reshape the material conditions it names. The agency is plastic because it is malleable. It does not prescribe a single intervention. It opens a field of possible interventions. Node 2994 places this concept in Core VI — Executive Mode — because agency is the fundamental condition of executive operation. Before a field can govern, deploy, or execute, it must have agency. The PlasticAgency is not about human actors. It is about the field as actor. The corpus is not a passive archive. It is an active instrument. Without this concept, the field is descriptive. With it, the field is operational.