scatter-gather plus saga pattern

A Methodology for Selecting and Composing Runtime Architecture Patterns for Production LLM Agents

This paper introduces the stochastic-deterministic boundary (SDB) as a foundational architectural primitive for production LLM agent runtimes, defining it as a four-part contract (proposer, verifier, commit step, reject signal) governing how LLM outputs become system actions. The authors organize agent runtime design around Coordination, State, and Control concerns, presenting a catalog of six runtime patterns applicable to conversational, autonomous, and long-horizon agents. A five-step pattern-selection methodology and diagnostic procedure mapping production failures to pattern weaknesses are contributed, along with a newly named failure mode—replay divergence—where LLM consumers of deterministic event logs produce inconsistent outputs across model versions or prompt changes. The paper argues that as model variance decreases, architectural pattern choice and SDB strength become the dominant reliability levers.