Arena lens
An arena is a world made actionable.
An arena is the situated, task-relevant portion of a larger world: entities, roles, rules, resources, risks, constraints, histories, and consequences disclosed to one or more agents.
What does this situation make possible, costly, visible, or consequential?
Not as the first event in time, and not as a claim that agents or environments are unreal. Relationship is structurally prior in this model because agent, arena, relevance, affordance, and agency become intelligible through mutual constraint.
Observation remains operationally first: it is the first deliberate move available inside an already-active relationship.
Agent ↔ relationship ↔ arena
What repeats across episodes.
What matters enough that losing or advancing it changes the agent.
Arena
What world is actionable from here?
The task-relevant and consequential portion of a larger world as encountered by one or more agents from a particular standpoint.
Agent-arena and ecological cognition lineage