REVIEW 4 major objections 5 minor 1 cited by
The paper claims that the success of LLM-based multi-agent systems is largely set in the first round of interaction: peak token-level entropy harms correctness across every architecture, and a single agent is the best choice in 43.3% of cas
Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →
T0 review · deepseek-v4-flash
2026-08-03 04:40 UTC pith:IO25R27P
load-bearing objection Solid empirical study of MAS entropy dynamics whose descriptive findings survive scrutiny, but the abstract's causal language overstates what the evidence supports. the 4 major comments →
When Does Multi-Agent Collaboration Help? An Entropy Perspective
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The paper's central claim is that MAS effectiveness is largely determined by early-round uncertainty dynamics, with peak entropy universally harmful across architectures. Across five open-source LLMs and six benchmarks, a single agent achieves the highest accuracy in 43.3% of cases, and in 86.7% of scenarios it matches or exceeds at least one MAS architecture. Three principles emerge: Certainty Preference (low, stable cross-agent entropy correlates with correctness), Base Uncertainty (lower base-model entropy directly benefits MAS performance), and Task Awareness (optimal entropy profiles shift with task difficulty and architecture). The paper further claims that the first round is decisive
What carries the argument
Hierarchical entropy features: 245 features computed from token-level Shannon entropy of every agent's output, aggregated at agent, round, sample, and system levels. These feed an ensemble of gradient-boosted tree classifiers trained to predict per-sample correctness from the entropy trace; feature-attribution analysis then identifies which entropy patterns push predictions toward success or failure. The Entropy Judger is this classifier used for label-free pass@k selection.
Load-bearing premise
The load-bearing premise is that the entropy measured during reasoning causes performance differences—not merely that it happens to correlate with them—so that increasing peak entropy or stabilizing entropy would change outcomes as the paper's SHAP directions suggest.
What would settle it
A reader could split the paper's released data by whether the base model already answered correctly and re-run the correlation between round-1 peak entropy and MAS correctness within each split; if the negative correlation vanishes when base-model correctness is held fixed, the 'peak entropy harms MAS' claim reduces to a proxy for problem difficulty rather than a causal mechanism.
If this is right
- Multi-agent collaboration should not be assumed superior; single-agent baselines are the reference point, and teams only pay off under specific early-uncertainty conditions.
- First-round entropy peaks are a universal warning sign; adding more interaction rounds rarely recovers from initial misalignment and often degrades accuracy.
- The Entropy Judger provides a label-free way to select high-quality outputs from multiple candidates, with consistent accuracy gains across architectures and tasks.
- Base-model entropy is a strong predictor of team performance, so choosing a base model with lower reasoning uncertainty is a direct lever for MAS success.
Where Pith is reading between the lines
- If the entropy signal is this informative, an adaptive router that runs a single agent when first-round entropy is low and only convenes a team when divergence is moderate could get most of the team's benefit at a fraction of the cost; the paper does not test this but its data make it a natural next step.
- The paper's own appendix shows 83.4% of round-1 to round-2 transitions reduce entropy without improving accuracy, which suggests much of the observed convergence may be agents anchoring on each other—so Certainty Preference may be partly about suppressing disagreement rather than about finding the truth.
- The RL-trained base model results imply that entropy's meaning is training-dependent: the same entropy value can signal productive exploration or noise depending on the model, so a single entropy threshold will not transfer across base models and selection rules should be recalibrated per model family.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper studies entropy dynamics in LLM-based multi-agent systems (MAS) built on five open-weight models across six benchmarks and four topologies. It extracts 245 hierarchical entropy features, trains an XGBoost/LightGBM ensemble (the Entropy Judger) to predict per-sample correctness, and uses SHAP analysis to derive three observations: certainty preference, base-model entropy as a limiting factor, and task/architecture-dependent entropy roles. It reports that a single agent achieves the best accuracy in 43.3% of cases, that first-round entropy dynamics dominate prediction, and that entropy-based pass@k selection improves accuracy. The appendices include extensive robustness checks (temperature, model scale, tool-calling tasks, RL-trained base models) and a causal-analysis appendix that explicitly acknowledges unresolved causal identification and reports an 83.4% 'possible anchoring' rate in round 1→2 transitions.
Significance. If the descriptive claims hold, the paper provides a useful, reproducible diagnostic for when MAS collaboration pays off and when it does not, based on openly available models and a large dataset (44,780 samples). Strengths include the favorable sample-to-feature ratio, stratified 5-fold CV, ablation studies, cross-method importance validation, and explicit checks at 14B scale, different temperatures, and a tool-calling agentic benchmark. The authors are also unusually honest in Appendices H and J about the limits of causal inference. However, the headline contributions are framed causally ('peak entropy directly harms', 'base entropy causally drives MAS performance') while the evidence is correlational, and a claimed algorithmic benefit (pass@k selection) is not quantified in the manuscript. The central descriptive findings are defensible, but the causal and universal claims need substantial reframing or additional evidence.
major comments (4)
- [Abstract, §4.3–4.4, Appendix J] The abstract and Section 4.4 state that peak entropy 'directly harms' correctness and that lower base-model entropy 'causally drive[s]' MAS performance. The evidence is SHAP-based correlation from a trained classifier, not causal identification. Appendix J itself says 'strict causal mechanisms... remain inherently challenging' and defers causal identification to future work. Appendix H.4 reports 83.4% of round-1→2 entropy-decrease transitions without accuracy gain ('possible anchoring'). The causal language must be removed or substantiated with within-problem interventions (e.g., same question decoded under high- vs low-entropy traces) or explicit counterfactual manipulations.
- [§5.5, Appendix F.5] The Entropy Judger's central practical contribution is pass@k selection, and the main text claims it 'consistently improves accuracy across all MAS configurations and tasks.' However, no quantitative result for this selection is reported anywhere in the main text or the appendix. Appendix F.5 only describes the protocol (choose argmax predicted correctness) and mentions baselines (Random, Oracle) without giving numbers. The claimed accuracy improvement is therefore unsupported as written. Please add a table/figure reporting pass@k selection accuracy against random and oracle baselines across configurations.
- [§5.2, Figure 4(d)] The claim that 'peak entropy is universally harmful across architectures' is overstated. Figure 4(d) shows an across-architecture reversal: the single-agent architecture has the highest values of round-1 peak/entropy-dispersion features yet the highest accuracy, while sequential (lowest accuracy) has the lowest feature averages. The text acknowledges that the entropy–performance relationship depends on 'architectural capacity to control uncertainty,' which is a conditional rather than universal claim. The headline 'universally harmful' should be replaced with a qualified statement such as 'harmful within each architecture after controlling for architectural capacity', or the figure should be reconciled explicitly with the universal claim.
- [§4.4, Figure 2] The 'Base Uncertainty' observation claims that lower base-model entropy 'directly benefits' MAS performance. The Gbase-H analysis measures base entropy from the same base model trajectory that also produces the base correct/incorrect label; base entropy is likely a proxy for base capability. The authors do include base correctness in Gbase-full, but the causal claim in §4.4 is based on Gbase-H alone. A partial-correlation analysis controlling for base correctness, or an intervention (e.g., temperature/contrastive decoding on the base model), is needed before 'directly benefits' can be defended. Otherwise the claim should be phrased as 'base-model entropy is a strong predictor correlated with MAS accuracy'.
minor comments (5)
- [Abstract vs. §4.4] The abstract uses 'causally drive' while the contribution list in Section 1 says 'strongly correlate with correctness.' This inconsistency should be resolved in favor of the more accurate correlational framing throughout.
- [Figure 1 caption] 'The basedenotes...' is a typo; also the caption does not mention that debate is excluded on HumanEval (Appendix B.1), which affects the interpretation of '30 scenarios' in §4.4.
- [§4.2] The text reports '254 features' and then '245 trainable features' after excluding 9 experimental identifiers. Clarify explicitly which 9 are excluded and why they are not counted among the 245 used in Table 1.
- [Appendix G] Global average ECE is 0.391, with LLaMA models above 0.5. This substantial miscalibration means low entropy does not reliably indicate correctness for these models; this should be mentioned in the main text wherever 'low entropy is beneficial' is claimed, not only in the appendix.
- [§5.2] The phrase 'single agents channel higher entropy into genuine exploration' is a mechanistic interpretation not directly supported by the data; suggest softening to 'single agents can tolerate higher entropy without accuracy loss' or provide direct evidence.
Circularity Check
No significant circularity: the entropy-based findings come from a fitted classifier with cross-validated evaluation, and the paper's own caveats concern causal validity, not definitional circularity.
full rationale
The paper's central pipeline is an empirical supervised-learning analysis: it extracts 245 entropy/computational features, fits XGBoost/LightGBM to per-sample correctness labels, and reports cross-validated accuracy (Table 1) plus SHAP-based feature correlations (Sections 4.3-4.4). These relations are learned from data rather than assumed into the conclusions; the sign/direction of the SHAP correlations could in principle have come out differently, so the findings are not equivalent to the input by construction. The Entropy Judger's pass@k selection is a practical use of the fitted predictor and is supported by held-out evaluation and generalization checks (Appendices D.7-D.8). The only load-bearing assumption is causal: the paper says peak entropy 'directly harms' correctness, while Appendix J concedes 'strict causal mechanisms... remain inherently challenging' and future work, and Appendix H.4 reports 83.4% possible anchoring. That is a validity/overclaim concern about the entropy-to-accuracy direction, not circularity: no equation defines the conclusion into the input, and there is no self-citation chain used to force the result. The one possible self-citation (Ye et al. 2025, if 'Chen, S.' is the current author) appears only in a limitations paragraph about heterogeneous MAS and is not load-bearing.
Axiom & Free-Parameter Ledger
free parameters (3)
- XGBoost/LightGBM trained model parameters (Entropy Judger)
- XGBoost/LightGBM hyperparameters (max_depth=6, lr=0.1, n_estimators=100, reg_lambda=1.0, num_leaves=31, etc.)
- Class-balance weight scale_pos_weight = N_neg/N_pos
axioms (4)
- standard math Token-level Shannon entropy H(s) = -Σ_v p(v|s) log p(v|s) is computed from the full softmax and is a meaningful uncertainty signal for reasoning correctness.
- domain assumption All agents in a MAS share the same base model (homogeneous agents), and small open-source LLaMA/Qwen results generalize to larger or proprietary systems.
- domain assumption SHAP-value/feature correlation indicates directional influence of entropy on MAS correctness.
- domain assumption Benchmark ground truth via Math-Verify, exact string matching, and code execution is reliable.
read the original abstract
Multi-agent systems (MAS) have emerged as a prominent paradigm for leveraging large language models (LLMs) to tackle complex tasks. However, the mechanisms governing the effectiveness of MAS built upon publicly available LLMs, specifically the underlying rationales for their success or failure, remain largely unexplored. In this paper, we revisit MAS through the perspective of \textit{entropy}, considering both intra- and inter-agent dynamics by investigating entropy transitions during problem-solving across various topologies, six reasoning benchmarks, and two agentic tasks. By analyzing 245 features spanning token-, agent-, and round-level entropy, we counterintuitively find that a single agent outperforms MAS in approximately 43.3\% of cases, and that entropy dynamics are largely determined during the first round of interaction. Furthermore, we provide three key observations: 1) \textit{Certainty Preference}: peak entropy directly harms and stable entropy directly benefits MAS correctness; 2) \textit{Base Entropy}: base models with lower entropy during problem-solving causally drive MAS performance; and 3) \textit{Task Awareness}: entropy dynamics of MAS play varying roles across different tasks. Building on these insights, we introduce a simple yet effective algorithm, the \textit{Entropy Judger}, to select solutions from MAS's pass@$k$ results, leading to consistent accuracy improvements across all MAS configurations and tasks. Our source code is available at \href{https://github.com/AgenticFinLab/multiagent-entropy}{this https URL}.
Figures
Forward citations
Cited by 1 Pith paper
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Oracle Gap and Signal Fidelity: A Fixed-Pool Diagnostic for Test-Time Collaboration
Training-free LLM collaboration gains are bounded by the fixed pool's oracle gap and then by signal coverage, fidelity, and harm, measurable with a small labeled audit.
Reference graph
Works this paper leans on
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[1]
Architecture dominance: Architecture is the top predictor on both FinanceAgent Benchmark (ρ≈0.83 ) and the main benchmarks (Section 5), confirming that structural choices outweigh individual feature-level entropy in determining system performance
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[2]
Initial uncertainty as failure signal: step 0 mean entropy on FinanceAgent Benchmark (ρ≈ −0.75) parallels the dominance of round-1 entropy features on mathematical tasks (Appendix D.5), extending the ”first-round decisive” principle to sub-round granularity
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[3]
Base model correctness supremacy: The near-perfect correlation of base model is finally correct (ρ≈ 0.96) on FinanceAgent Benchmark matches the pattern observed across all six primary benchmarks (Appendix D.1)
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[4]
This consistency suggests that the entropy signal captured by our framework reflects ageneralproperty of LLM uncertainty rather than task-specific patterns
Entropy variance as failure predictor: Inter-agent entropy dispersion metrics maintain negative correlations on FinanceAgent Benchmark, consistent with the MAS failure analysis in Appendix D.2. This consistency suggests that the entropy signal captured by our framework reflects ageneralproperty of LLM uncertainty rather than task-specific patterns. Whethe...
2025
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[5]
Convert the base-b numbers17 b and97 b to decimal form, resulting in1·b+ 7and9·b+ 7, respectively
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[6]
Establish the divisibility condition:9b+ 7must be divisible byb+ 7, i.e., 9b+7 b+7 is an integer
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[7]
Perform algebraic manipulation to simplify the divisibility condition, leading to the conclusion that b+ 7 divides −56 (equivalently,b+ 7divides56)
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[8]
Identify all positive divisors of56that satisfyb+ 7>16(sinceb >9)
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[9]
For each valid divisord=b+ 7, computeb=d−7and ensureb >9
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[10]
Sum all valid integer values ofbobtained from step 5
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[11]
only output the final answer without words, labels, and steps
Computeb= 21,49; sum = 70 Analysis:Qwen performs deep reasoningwithinthe <think> block, independently deriving the complete solution before outputting a structured plan. Solver Agent. System Prompt You are the solver agent. Solve strictly according to the provided plans. Execute each step precisely and produce the final result. Output the final result int...
2024
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[12]
sample_mean_answer_token_entropy × sample_median_answer_token_entropy r = +0.991
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[13]
base_model_min_answer_token_entropy × base_model_median_answer_token_entropy r = +0.989
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[14]
sample_round_1_max_agent_std_entropy × sample_round_1_max_agent_variance_entropy r = +0.961
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[15]
architecture × exp_infer_average_entropy r = -0.723
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[16]
architecture × sample_total_entropy r = -0.683
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[17]
architecture × sample_entropy_reduction_vs_base_total r = +0.678
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[18]
architecture × sample_round_1_all_agents_total_entropy r = -0.677
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[19]
architecture × round_1_total_token r = -0.652
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[20]
base_model_min_answer_token_entropy × answer_token_entropy_change_direction r = +0.651
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[21]
base_model_min_answer_token_entropy × base_model_vs_sample_final_answer_entropy_diffr = +0.651
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[22]
base_model_min_answer_token_entropy × answer_token_entropy_change r = +0.645
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[23]
architecture × sample_entropy_range r = -0.614
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[24]
architecture × sample_max_entropy r = -0.614
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[25]
architecture × sample_num_agents r = -0.612
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[26]
architecture × exp_total_entropy r = -0.608
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[27]
architecture × exp_total_token r = -0.588
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[28]
base_model_is_finally_correct × is_finally_correct r = +0.554
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[29]
exp_infer_average_entropy × sample_round_2_all_agents_total_entropy r = +0.536
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[30]
architecture × sample_round_1_mean_agent_max_entropy r = -0.529
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[31]
The lower triangle shows pairwise Pearson correlations; the upper-right inset lists the top 20 most strongly correlated feature pairs
base_model_format_compliance × base_model_format_compliance_rate r = +0.521 0.75 0.50 0.25 0.00 0.25 0.50 0.75 1.00 Correlation Coefficient Figure 32.Feature correlation heatmap for GMAS on LLaMA models. The lower triangle shows pairwise Pearson correlations; the upper-right inset lists the top 20 most strongly correlated feature pairs. 53
discussion (0)
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