Integrating Strengths of Different Multi-Agent Workflows via Step-Aware Hybrid Topology Planning

Large language model (LLM)-driven agents are proposed for a wide range of applications. As scenarios become increasingly composite, a graph-structured multi-agent system (MAS) offers a promising solution due to the orchestration of various skills. To architect a reasonable underlying workflow, recent advances mostly investigate two structures: sequential topology and decentralized topology. The former constrains the structure into a directed acyclic graph for multi-step executions but lacks sufficient scalability, while the latter leverages node-wise subgraphs for knowledge aggregation with synchronous parallelization but lacks long-term planning. Therefore, our key insight is that their strengths are mutually complementary. Driven by this motivation, we introduce step-aware hybrid topology for a MAS, where sequential connections support inter-step ordered planning and decentralized connections promote intra-step perspective integration. Concretely, to effectively coordinate different structural components, we clarify the corresponding topological definition and the protocols for step-wise serialization and parallelization. Subsequently, to dynamically refine desired structures, we introduce the parameterized distribution of a hybrid topology, which is initialized by LLM-driven graph planning. Eventually, to further reduce token consumption and time complexity, we supplement the topological density and length normalization for end-to-end learning. Extensive experiments demonstrate that the hybrid topology outperforms single-form topology in 90.4\% of tasks, our agentic initialization improves learning in 88.8\% of scenarios, proposed normalizations reduce token consumption by 20\%$\sim$30\% and time consumption by 7\%$\sim$13\% with a slight utility fluctuation. The code is available at https://anonymous.4open.science/r/HTAS-D107.