The Distributed Algorithmic Boundary: When the System No Longer Coincides with the Machine

For much of the history of computing, the material boundary of a computational system could be represented with relative simplicity: processors, memory, storage, and software execution were located within machines whose participation in the system was architecturally specified in advance. Distributed computing complicated this picture without necessarily dissolving it. Recent developments in distributed inference, edge computing, external memory, agentic tool use, and dynamically allocated computational resources introduce a stronger problem: the components causally participating in an algorithmic trajectory may change during execution itself. This paper proposes that, for a class of contemporary algorithmic systems, functional boundary and physical machine boundary should no longer be assumed to coincide. A computational resource initially belonging to the environment may temporarily become causally constitutive of an ongoing process; external memory may preserve state; tools may participate in operational trajectories; sensors and actuators may close loops between computation and environment; and execution may migrate across materially distinct substrates while preserving functional continuity. The argument does not claim that these mechanisms require a new technological ontology. The ontological question arises at another level: what should count as the system when its effective causal organization is not coextensive with any single machine or with its initial material configuration? A provisional answer is advanced: in dynamically distributed algorithmic systems, system boundaries may be better reconstructed from the components that become causally constitutive of an operational trajectory than from the physical enclosure of the substrate on which that trajectory began.