Contagion Tensor Measures LLM Output Coupling in Multi-Agent Systems.

Zewen Liu· June 30, 2026 View original

Summary

This paper introduces the Contagion Tensor, a framework to quantify how LLM output distributions couple across modalities, agents, and time. It derives the Coupling Amplification Factor (CAF) metric, enabling quantitative auditing of claims about multi-agent system interactions, revealing significant image-condition super-linear effects in GPT-4o-mini.

As Large Language Model (LLM) systems become more complex, especially in multi-agent and multi-modal configurations, understanding how their outputs influence each other is crucial. This research introduces the Contagion Tensor, a novel measurement framework designed to quantify the coupling of LLM output distributions across different modalities, interacting agents, and sequential time steps. From this tensor, the authors derive the Coupling Amplification Factor (CAF), a family of ratio-based metrics. CAF provides a unitless, baseline-referenced measurement, complete with bootstrap confidence intervals, allowing for rigorous quantitative analysis. The framework was tested through a comprehensive simulation design, revealing that an apparent super-linear effect under image conditions (CAF = 1.40) collapsed to sub-linear (CAF = 0.87) when the image perturbation module was disabled, indicating a design artifact rather than genuine coupling. Further validation involved real-API experiments with models like DeepSeek-Chat and GPT-4o-mini. These experiments showed that text-only communication generally resulted in a CAF near 1.0, while diverse personas could drive convergence (CAF = 0.88). Crucially, GPT-4o-mini demonstrated a significant super-linear effect (CAF = 1.72) under real vision conditions compared to text-only, validating the simulation's prediction. This framework provides a robust instrument for falsifying claims about output-distribution coupling and offers a transferable ablation protocol for auditing modular multi-agent simulators.

Why it matters

For professionals designing, deploying, or auditing multi-agent LLM systems, the Contagion Tensor provides a critical tool to quantitatively understand and measure how different components and modalities interact. This enables more robust system design, better debugging, and verifiable claims about system behavior, especially in complex multi-modal scenarios.

How to implement this in your domain

  1. 1Adopt the Contagion Tensor framework to analyze interaction dynamics in your multi-agent LLM applications.
  2. 2Utilize the Coupling Amplification Factor (CAF) to quantitatively measure output-distribution coupling.
  3. 3Implement the transferable ablation protocol to distinguish genuine coupling from system design artifacts.
  4. 4Integrate these measurement tools into your LLM system development and testing pipelines.
  5. 5Use the insights gained to refine agent interaction strategies and improve multi-modal integration.

Who benefits

AI/ML PlatformsSoftware DevelopmentRoboticsGamingContent Creation

Key takeaways

  • The Contagion Tensor quantifies LLM output coupling in multi-agent systems.
  • CAF metrics provide unitless, baseline-referenced measurements of coupling.
  • Ablation protocols help distinguish genuine coupling from design artifacts.
  • GPT-4o-mini shows significant super-linear coupling with real vision input.

Original post by Zewen Liu

"arXiv:2606.28839v1 Announce Type: new Abstract: We introduce the Contagion Tensor, a measurement framework for quantifying how large language model (LLM) output distributions couple across modalities, agents, and time steps. From the tensor we derive the Coupling Amplification Fa…"

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