From Standalone LLMs to Integrated Intelligence: A Survey of Compound Al Systems

TL;DR

This survey reviews the integration of large language models with external modules in Compound AI Systems, analyzing paradigms, design trade-offs, and future challenges for more capable AI.

Contribution

It defines CAIS, proposes a multi-dimensional taxonomy, and analyzes four foundational paradigms, providing a comprehensive framework for future research and development.

Findings

Analyzed four key CAIS paradigms: RAG, LLM Agents, MLLMs, and Orchestration.

Compared design trade-offs and evaluation methodologies across paradigms.

Identified key challenges like scalability, interoperability, and benchmarking.

Abstract

Compound AI Systems (CAIS) are an emerging paradigm that integrates large language models (LLMs) with external components, including retrievers, agents, tools, and orchestrators, to overcome the limitations of standalone models in tasks requiring memory, reasoning, real-time grounding, and multimodal understanding. These systems enable more capable and context-aware behaviors by composing multiple specialized modules into cohesive workflows. Despite growing adoption in both academia and industry, the CAIS landscape remains fragmented and lacks a unified framework for analysis, taxonomy, and evaluation. In this survey, we define the concept of CAIS, propose a multi-dimensional taxonomy based on component roles and orchestration strategies, and analyze four foundational paradigms: Retrieval-Augmented Generation (RAG), LLM Agents, Multimodal LLMs (MLLMs), and Orchestration. We review representative systems, compare design trade-offs, and summarize evaluation methodologies across these paradigms. Finally, we identify key challenges - including scalability, interoperability, benchmarking, and coordination - and outline promising directions for future research. This survey aims to provide researchers and practitioners with a comprehensive foundation for understanding, developing, and advancing the next generation of system-level artificial intelligence.