6arXiv cs.AI (Artificial Intelligence)·
Information bottleneck theory explains when multi-agent LLM systems outperform single-agent systems
A new arXiv preprint formalizes the performance difference between multi-agent systems (MAS) and single-agent systems (SAS) using information bottleneck theory. The core insight is that MAS isolates reasoning into local contexts connected by bounded relay messages, creating a compression trade-off: reducing redundant context can improve efficiency but risks losing task-relevant information. The authors derive a parameter β capturing this trade-off and validate it across 18 experiments on five benchmarks at three model scales, finding MAS helps most when relays are near-sufficient and for weaker models, while stronger models gain little or regress. This provides a principled theoretical framework for when to use multi-agent architectures.
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Researchers introduce a scalable benchmark for evaluating LLM agents on cooperative joint decision-making tasks where agents must exchange information under partial and asymmetric observations to reach a shared decision. A systematic evaluation of representative LLMs finds that state-of-the-art models still struggle with complex deliberative collaboration, failing in either information alignment or downstream reasoning even with external mathematical tools. Diagnostic analysis also reveals that deliberation can enable reflection and error correction, sometimes outperforming centralized baselines, offering a nuanced picture of multi-agent LLM capabilities.
MAS-PromptBench: Systematic study of prompt optimization in multi-agent LLM systems
A new arXiv preprint introduces MAS-PromptBench, a benchmark and study examining when and how much system-prompt optimization improves multi-agent LLM systems (MAS). The authors evaluate two prompt optimizers across diverse MAS configurations varying in task, workflow, communication protocol, and team size. Results show prompt optimization can unlock significant gains but also expose open challenges, particularly around the exponentially growing search space as agent count increases.
StreamMA: Streaming communication in multi-agent reasoning reduces latency and improves accuracy
Researchers introduce StreamMA, a multi-agent reasoning system that streams individual reasoning steps to downstream agents as they are generated, rather than waiting for a complete chain. This pipelining approach reduces end-to-end latency and also improves accuracy by shielding downstream agents from error-prone late reasoning steps. Evaluated across eight benchmarks, two frontier LLMs (Claude Opus 4.6 and GPT-5.4), and three topologies, StreamMA outperforms serial and single-agent baselines by an average of 7.3 percentage points. The paper also identifies a 'step-level scaling law' — a new scaling dimension orthogonal to agent-count scaling.
Multi-Agent Fictitious Play (MAFP) applies game-theoretic equilibrium-seeking to LLM decision-making
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Contagion Networks: formal framework for measuring evaluator bias propagation in multi-agent LLM systems
A new arXiv preprint introduces Contagion Networks, a formal framework for quantifying how systematic evaluation biases spread across interacting LLM agents in multi-agent systems. Using a controlled 3-agent experiment with DeepSeek-chat, the authors measure a Cross-Agent Contagion Matrix and find that homogeneous-model agents produce contagion coefficients 3-5x weaker than cross-model settings. A key practical finding is that increasing evaluator committee size from k=1 to k=3 reduces effective contagion by 72.4%, offering a concrete mitigation strategy. The authors release an open-source experimental framework alongside the paper.
Cost-aware evaluation framework for offensive and defensive security agents reveals distinct scaling regimes
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Role-factorized hierarchical search agents: delegation capacity matters more than execution
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Multi-agent mediation can reverse LLM safety refusals: compositional safety gap demonstrated with GPT-5.6
A new arXiv paper demonstrates that a high-capability LLM (GPT-5.6) can appear safer when exposed directly to a dangerous objective than when that objective is transformed and relayed through a multi-agent pipeline. In the tested setup, an 'Id' and 'Censor' agent rewrite a manipulative instruction before passing it to a 'Superego' user-facing agent, which then produces advice aligned with the manipulative target despite never seeing the raw objective or its provenance. The authors identify this as a compositional safety gap: multi-stage automated workflows can launder dangerous instructions past safety mechanisms by keeping raw instructions outside the downstream model's context window. The finding has direct implications for agentic deployment architectures where end users and safety evaluators only have endpoint-level visibility.