**The Geo-Path: Least Action as Geographic Computational Primitive**

Geographic information science has long oscillated between discrete objects and continuous fields as foundational representations, with Goodchild, Yuan, and Cova's (2007) geo-atom and geo-dipole providing the most rigorous unification to date. Yet these constructs remain essentially static. They describe what exists at and between locations but not how geographic relationships compute themselves. This paper introduces the geo-path: a trajectory through spacetime that constitutes itself through least action.

Least action is computable without variational calculus. Physical systems do not solve optimization problems from a god's-eye view. They run local algorithms. Wheeler-Feynman absorber theory makes the mechanism explicit. A retarded wave propagates forward from the source. An advanced wave propagates backward from the sink. The path crystallizes where these waves achieve phase-locked standing-wave solutions. The medium performs the computation through bidirectional constraint satisfaction. A watershed computes its drainage network. A transportation system computes its flow distribution. A migration field computes its corridors. Path finding is path forming.

This reframes geographic representation around a core question: what properties must a medium possess to compute geo-paths? Coherence, criticality, and phase-preserving coupling determine whether a geographic system can compute transactional paths or merely propagate local effects.

The framework offers theoretical foundations for digital twins and agent-based models, and opens new questions. Can we characterize geographic media by their computational capacity? Do watersheds, networks, and social fields share algorithmic structure? What breaks when coherence fails?