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cs.LGcs.CV Vahid Jebraeeli, Hamid Krim, Keisuke Fujii · Oct 14, 2026

The paper proposes a two-loop inference architecture inspired by System 1/System 2 cognition: a fast loop (MobileNetV3-Large) classifies an image and, if confidence is low, a medium-speed loop (DINOv2-B) processes additional evidence. The authors evaluate this REASON framework on four fine-grained image classification benchmarks under distribution shift and synthetic corruptions, showing gains over the fast loop alone at roughly half the computation of the full medium model.

We seek a hierarchical resolution of residual error under a composite learning objective as a principled mechanism for identifying and exploiting additional information, particularly under distribution shift and perturbation. Inspired by the System 1/System 2 paradigm, we formulate this principle as a two-loop mechanism serving a common inference goal. A fast, System 1-like loop resolves the residual addressable by the available evidence; the remaining epistemic residual triggers a medium speed, System 2-like loop that actively acquires additional evidence and measures its informational value through residual reduction. Over nested solution spaces, the medium-loop optimum is provably no worse than the fast-loop optimum. Experiments show that the resulting two-loop model consistently improves upon the fast loop at approximately half the computation of the medium loop, including under unseen corruptions, and, when provided a cleaner observation, outperforms staged classifiers and learning-to-defer methods at equal computational cost.
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cs.CVcs.LG Pedro Manoel Herminio Alves, Dalton C\'ezane Gomes Valadares, Cl\'audio de Souza Baptista · Oct 14, 2026

This paper tackles the practical problem of choosing detectors and trackers for multi-pedestrian tracking across scenes with different densities. It carries out a broad empirical comparison of the YOLO11, RT-DETR, and YOLO26 detector families paired with ByteTrack and BoT-SORT on MOT17, MOT20, and SOMPT22, including an ablation of NMS versus end-to-end inference for YOLO26. The study offers a useful survey of quality-speed trade-offs, although its conclusions are constrained by out-of-the-box COCO weights and very small benchmark slices.

Pedestrian tracking in video is important for applications such as surveillance and scene analysis, but it becomes more challenging in crowded scenarios with frequent occlusions and rapid motion. This paper analyzes how detector architecture, model scale, scene density, and inference regime affect the tracking of multiple pedestrians. We compare the YOLO11, RT-DETR, and YOLO26 detector families with the ByteTrack and BoT-SORT trackers on sequences from the MOT17, MOT20, and SOMPT22 benchmarks. For YOLO26, we also compare traditional overlap filtering via Non-Maximum Suppression (NMS) with end-to-end inference. The RT-DETR family achieved the highest mean scores on the HOTA tracking quality metric across all three benchmarks with both trackers, with a more pronounced advantage on MOT20, albeit at a higher computational cost. On MOT17 and SOMPT22, YOLO26 variants, especially YOLO26-L with NMS, offered favorable combinations of quality and speed compared with RT-DETR. In the YOLO26 inference comparison, the end-to-end mode did not yield consistent tracking gains over the NMS-based regime. Taken together, these results provide a practical guide for selecting detectors and trackers for this task based on application priorities.
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cs.CVcs.CLcs.RO Kyusong Lee, Heting Ying, Tiancheng Zhao · Oct 14, 2026

VLX-Go targets embodied visual tracking in distractor-rich shared spaces by casting local motion as vision-language-conditioned short-horizon waypoint prediction. It combines frozen DINOv3 and SigLIP features, multiscale temporal context, and a transformer backbone to predict $K=8$ robot-centric waypoints. A staged training recipe—vision-language alignment, multimodal reasoning mid-training, and tracking specialization—drives a large improvement over the OmTrackVLA baseline, while preliminary DAgger fine-tuning provides modest further gains. This matters because existing methods suffer severe success-rate drops when moving from single-target to distractor tracking.

Embodied visual tracking requires a robot to identify a designated target from visual observations and control its own motion to follow that target through an environment. Following an isolated person is a comparatively simple demonstration of embodied visual tracking, but following the intended person among distractors remains challenging. Existing methods exhibit a substantial drop in success from single-target to distractor tracking, motivating a focus on the shared spaces that person-following robots must navigate. We present \method{}, a vision--language waypoint policy built around the hypothesis that visual and language representations should be aligned before tracking-specific motion is learned. The policy combines complementary frozen visual encoders, multiscale temporal context, a transformer backbone, and a lightweight head for robot-centric waypoint prediction. Its training progresses through vision--language alignment, multimodal reasoning mid-training, and tracking specialization on 19,532 oracle episodes. Compared with 41.54\% distractor-tracking success for our earlier OmTrackVLA model, the complete multi-stage recipe achieves 55.80\%. We then explore on-policy refinement using filtered oracle labels for states visited by the policy. This preliminary study adds 2.42 percentage points of distractor-tracking success, reaching 58.22\%, while reducing collision rate by 1.99 pts. The final policy records the highest distractor- and ambiguous-tracking success rates among the compared methods. These results support staged multimodal learning as a promising direction for tracking among distractors and motivate further study of on-policy refinement for person following in shared spaces.
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cs.LGcs.CV Iren\'e Tematelewo · Oct 14, 2026

This PhD thesis tackles novelty detection across weather sensor networks and computer vision. For sensor networks, the core problem is detecting blocked rain gauges that falsely report zero rainfall—a failure mode that is hard to catch because zero is also the most frequent correct reading. The work benchmarks existing quality-control methods and proposes new joint-reasoning algorithms (PCSD-SAT, PCSD-JIGM, PCSD-JIKR) to improve detection of spatially clustered faults. For computer vision, it claims to introduce the NOVEL-SS benchmark and a Detect-Characterize-Accommodate (DCA) baseline for handling multiple simultaneous visual novelties. The research matters because reliable precipitation data underpins agriculture and disaster management in data-scarce regions, while real-world vision systems must cope with diverse, concurrent anomalies rather than single-type novelties.

Novelty detection is crucial in various technological and scientific domains. Its importance spans from ensuring the reliability of sensor networks to enhancing the adaptability of computer vision systems. As AI systems become increasingly sophisticated and complex, effective anomaly detection is essential for maintaining reliability and accuracy. This work addresses novelty detection in weather sensor networks and computer vision. In weather sensor networks, particularly for monitoring rainfall, detecting blocked rain gauges can significantly impact data reliability, food security, and disaster management. This work evaluates four existing quality control methods for detecting blocked rain gauges and demonstrates their limitations, particularly in detecting clusters of faulty sensors. By comparing methods such as the Conditional Mixture Model (CMM), PSWQ (Fz-filter), Kernel Regression, and Gaussian Method, we identify their shortcomings and propose three novel quality control techniques that integrate probabilistic fault detection and consistency-based diagnosis framework to improve timely detection of blocked sensors, while reducing false alarms. In the realm of computer vision, current systems often fail to handle multiple types of novelty due to their focus on single-novelty scenarios. We highlight the need for integrated systems capable of handling multiple types of novelty. To support this, we introduce the Novel Snapshot Serengeti (NOVEL-SS) dataset, derived from the Snapshot Serengeti camera trap data, which includes various forms of novelty. We also present the DCA (Detect, Characterize, and Accommodate) baseline system, designed to handle multiple novelty by detecting, characterizing, and accommodating them. This work aims to advance the robustness and adaptability of novelty detection systems across both weather sensor networks and computer vision applications.
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cs.CV Zongyu Wu, Yilong Wang, Xiaochen Wang et al. · Oct 14, 2026

MMKG-R1 attacks the problem of building useful multimodal knowledge graphs (MMKGs) for downstream Graph RAG. Existing methods either construct graphs without task-aware training or rely on reinforcement learning driven only by final-answer correctness, which can give credit to noisy graphs that happen to retrieve the right image. The core idea is to train a Qwen3-VL-4B constructor with GRPO using three complementary, quality-aware rewards: a graph-level Deducibility Reward and two source-level rewards (Source-Grounded Quality and Graph-Readiness) that directly assess extraction fidelity and structural usability. This matters because a correct downstream answer does not guarantee that the MMKG itself is accurate or reusable across queries.

Multimodal knowledge graphs (MMKGs) organize information across different modalities to support multimodal Graph Retrieval-Augmented Generation (RAG), which aims to improve the performance of multimodal large language models (MLLMs). The effectiveness of these multimodal Graph RAG methods largely depends on the quality of the constructed MMKGs. However, most existing methods construct MMKGs without explicit guidance on graph quality, while reinforcement learning (RL)-based methods that rely on final-answer correctness may provide only indirect feedback on MMKG quality. To address these limitations, we propose MMKG-R1, a novel MMKG-quality-driven RL framework for training an MLLM as a multimodal knowledge constructor. To be specific, MMKG-R1 introduces multiple quality-aware rewards to directly evaluate both the quality of information extracted from individual knowledge sources and the quality of the assembled MMKG. These rewards are then used to guide the RL training. Experiments across multiple datasets show that MMKG-R1 constructs MMKGs that improve downstream question-answering accuracy.
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cs.CVcs.RO Hochul Hwang, Jahir Sadik Monon, Soowan Yang et al. · Oct 14, 2026

NavAble tackles a critical data scarcity problem in assistive navigation: standard vision datasets largely ignore accessibility-critical objects such as pedestrian signals and door-activation buttons, leaving blind and low-vision assistive systems with unreliable perception. The authors introduce a large-scale dataset and a synthetic generation pipeline that combine 36K curated real-world images, 5.5K newly collected egocentric frames, and 452K synthetic frames across 11 BLV-relevant classes. By filling this gap, NavAble provides a foundation for training segmentation models that can recognize navigationally important objects from diverse assistive-device viewpoints.

Reliable recognition of accessibility-critical objects (e.g., audible pedestrian signals, door-activation buttons, and handrails) is essential for assistive navigation technologies that support safe, independent mobility for blind and low-vision (BLV) users. Yet these categories are underrepresented in existing large-scale vision datasets, and the few datasets that include them suffer from limited class coverage, inconsistent annotations, and poor diversity. We introduce NavAble, a large-scale dataset spanning 11 accessibility-critical object classes, combining 41K curated open-source images with 8K newly collected, densely annotated real-world images. To extend scale and diversity, we develop a synthetic data generation pipeline that renders high-fidelity 3D assets across 37 environments under diverse styles and viewpoints, yielding 452K frames with rich ground-truth annotations from 565 assets. The pipeline minimizes manual effort by combining automated web image crawling, VLM-based filtering, SAM 3D-based asset generation, and convenient camera trajectory configuration, enabling large-scale data generation at a diversity unattainable through manual collection. Experiments show that fine-tuning existing segmentation models on the NavAble Dataset achieves reliable accessibility-object segmentation (>80% mIoU on our held-out test set). We also demonstrate the effectiveness of synthetic data augmentation, which yields up to +3.5 mIoU over real-world-only fine-tuning. Beyond benchmark evaluation, validation on egocentric data from two mobility-assistive robots demonstrates improved perception reliability in real-world navigation scenarios. Together, NavAble establishes a scalable foundation for BLV navigation perception, directly addressing the data scarcity and embodiment gaps. The dataset and pipeline are publicly available at https://huggingface.co/datasets/NavAble/NeurIPS_2026_BLV.
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cs.CV Zefan Yang, Zheyuan Zhang, Boris Maihe et al. · Oct 14, 2026

Robotic ultrasound lacks safe, realistic simulators because physics-based phantoms and acoustic solvers exhibit a large domain gap with clinical imaging, while trial-and-error on patients is unsafe. SonoWorld proposes a three-stage pipeline that first pretrains a latent-action video diffusion model on roughly 6.9 million unlabeled clinical frames, then grounds the learned dynamics to 6-DoF probe poses via a small EM-tracked thyroid dataset, and finally distills the model into a causal autoregressive generator with selective KV-cache retention for streaming inference. The goal is to provide a data-driven interactive environment for training and evaluating robotic scanning policies without requiring per-subject pose tracking, although the achieved fidelity and limited evaluation leave its practical readiness unclear.

Robotic ultrasound can standardize image acquisition and reduce operator workload and variability, but policy learning remains limited by the lack of realistic, controllable simulation environments. While controllable world models have advanced rapidly in natural-image domains, ultrasound world modeling remains challenging because each frame captures only a cross-section of unobserved 3D anatomy, causing small probe motions to induce large appearance changes. Existing approaches rely on robot-tracked poses and latent-space prediction, but do not directly generate the observations required for interactive control. We propose SonoWorld, a causal ultrasound world model that learns video dynamics from unlabeled clinical videos and grounds them to 6-DoF control using a small set of freehand clinical scans tracked with an EM sensor. SonoWorld is trained in three stages: pretraining a latent-action-conditioned video diffusion model on around 6.9 million unlabeled multi-organ ultrasound frames; grounding the learned video dynamics to metric probe poses with a small EM-tracked thyroid dataset; and applying distribution matching distillation to enable causal, long-horizon autoregressive generation with selectively caching eviction tokens at inference time. We evaluate controllability through pose-following fidelity, round-trip consistency, and axis-specific control under synthetic actions on held-out tracked scans, and further validate it with a user study. In model-based action discrimination, SonoWorld correctly ranks the target-directed probe motion over an equal-magnitude opposite motion in up to 74.8% of trials. To our knowledge, SonoWorld is the first causal, pose-controllable ultrasound world model learned primarily from freehand clinical videos, providing a data-driven interactive environment for robotic ultrasound data acquisition and policy evaluation.
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cs.LGcs.AIcs.LG v3 Junyi An, Xinyu Lu, Chao Qu et al. · May 29, 2025

Equivariant GNNs for molecular modeling are bottlenecked by Clebsch-Gordan tensor products, which suffer from high complexity and limited non-linearity. This paper proposes the Equivariant Spherical Transformer (EST), a plug-and-play module that applies self-attention over sampled points on the spherical spatial domain of group representations, using a Fibonacci Lattice to preserve approximate SO(3) equivariance. The work matters because it reports state-of-the-art results on OC20 and QM9 while empirically breaking the degree-limited expressiveness barrier that constrains traditional tensor-product architectures.

Equivariant Graph Neural Networks (GNNs) have significantly advanced the modeling of 3D molecular structure by leveraging group representations. However, their message passing, heavily relying on Clebsch-Gordan tensor product convolutions, suffers from restricted expressiveness due to the limited non-linearity and low degree of group representations. To overcome this, we introduce the Equivariant Spherical Transformer (EST), a novel plug-and-play framework that applies a Transformer-like architecture to the Fourier spatial domain of group representations. EST achieves higher expressiveness than conventional models while preserving the crucial equivariant inductive bias through a uniform sampling strategy of spherical Fourier transforms. As demonstrated by our experiments on challenging benchmarks like OC20 and QM9, EST-based models achieve state-of-the-art performance. For the complex molecular systems within OC20, small models empowered by EST can outperform some larger models and those using additional data. In addition to demonstrating such strong expressiveness,we provide both theoretical and experimental validation of EST's equivariance as well, paving the way for new research in this area.
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cs.LG Siqi Zhu, Suozhi Huang, Kaixuan Zhang et al. · Oct 1, 2026

Multi-teacher on-policy distillation (MOPD) fuses specialized RL teachers into one student, but the mechanistic path from supervision choices to parameter changes and task capabilities has been unclear. This paper traces that path through controlled experiments on Qwen3-1.7B and SmolLM3-3B, using identical student parameters, responses, and optimizer states to compare gradients, Adam updates, and learning curves across loss-averaging rules and vocabulary truncations. Its core insight is that stronger gradient approximations do not necessarily yield better task performance; instead, outcomes depend heavily on implicit response weighting and optimizer dynamics that prior recipes treat as secondary.

Multi-teacher on-policy distillation (MOPD) aims to combine the strengths of RL-trained teachers in a single student, but how teacher signals affect parameter changes remains underexplored. We study Qwen3-1.7B with four domain teachers trained with RL from the same initialization as the student, comparing gradients, optimizer updates, and task learning curves, with additional SmolLM3-3B diagnostics. We find that several factors influence teacher signals. First, loss averaging implicitly weights responses: token averaging favors longer responses, and equalizing domain contributions retains this weighting within domains. Second, Adam's first moment reduces differences in parameter updates: the cosine similarity is 0.83 between teachers and 0.96 between averaging rules, despite differences in raw gradients. Third, BF16 rounding hides small changes: about 97\% of FP32 master weights differ from initialization, but only 7--11\% of BF16 weights do. Finally, the top-64 intersection KL gradient closely matches Qwen's full-vocabulary gradient, but the effect on task performance depends on averaging: mathematics accuracy is 2.6 points higher than with sampled-token policy-gradient (PG) under response averaging and 2.1 points lower under global token averaging.
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cs.LGq-bio.MN Jianru Shen · Oct 1, 2026

The paper asks whether effective resistance in tissue-specific protein interaction networks can flag which protein-function predictions a graph neural network will get wrong. Because effective resistance on these networks is almost completely determined by inverse degree, the author strips out that degenerate component and tests whether the residual predicts per-node loss beyond standard uncertainty scores. The study concludes that a reproducible but tiny signal exists across 24 interactomes, and that degree degeneration strongly bounds how useful resistance can ever be on this class of biological graphs.

Protein function annotation needs to know which predictions to distrust, not only what a model predicts. We ask whether tissue-specific interaction structure carries that information. Our candidate signal is effective resistance, used previously to relieve over-squashing by rewiring. Across 24 tissue-specific interactomes it is dominated by inverse degree, and the degeneration deepens as the co-expression filtered network grows, with a Spearman correlation of -0.955. The residual departure from that limit exceeds degree-preserving null graphs in all 24 networks. Controlling for predictive entropy, degree, annotation cardinality, local structure and feature-only difficulty, the residual explains additional per-node loss in 19 of 24 held-out networks once a permutation floor is subtracted, at every depth, and the effect strengthens monotonically with depth. The increment reaches 0.37% of the variance the controls leave unexplained, 5.6 times a permutation floor, against 1.5 times when the model is retrained in a degree-preserving null world. Selective prediction improves negligibly. The signal is reproducible; degree degeneration bounds it.
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cs.LGcs.CL Areeb Ahmad, Pratinav Seth, Vinay Kumar Sankarapu · Oct 1, 2026

Ablation studies in language models are confounded by self-repair, where downstream components appear to compensate for a removed part. This paper argues that such compensation is not dynamically recruited but is instead a standing, pre-existing opposition released by the intervention. The authors introduce a continuous dose axis for counterfactual interventions and show that downstream contributions follow an affine law predicted in part by static weights. If the finding generalizes, it would reshape how interpretability researchers infer component importance from ablations.

Ablate a component of a language model, and other components often appear to adjust and compensate. This phenomenon, termed self-repair, has been observed repeatedly, but its mechanism remains unclear. The most systematic study to date concluded that self-repair is noisy and unlikely to have a single explanation. We argue that it has one: a gain already present before any ablation. Any intervention on a causally important component can be viewed as a point on a coordinate axis $\lambda$, the signed strength of a counterfactual contrast. Hence, conventional ablation methods are uncalibrated points on this axis. We show that the causal repair response for a fine-grained unit $r$ is governed by an affine law, $E_r(\lambda)=\mathrm{own}_r+\gamma_r\lambda$. The slope $\gamma_r$ is a fixed coefficient that consistently influences the model, with or without ablation, and its sign determines whether the unit counteracts or reinforces the removed signal. On a factual-verdict task across four models from distinct families (Gemma, Qwen, LLaMA, and Mistral), we identify components including MLP neurons, OV neurons, and singular directions that follow this affine law, 68 of 81 downstream directions in all. Moreover, we can anticipate the magnitude of $\gamma_r$ from the fixed weights. On the IOI circuit of GPT-2 Small, seven of the ten heads the intervention can reach follow the law, and all seven are counterweights. From this perspective, what may appear as self-repair is a counterweight performing its usual operation when the contrastive signal emerges at the core.
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cs.LG Scott W. Viteri (Stanford University), Laura Gomezjurado Gonzalez (Stanford University), Clark Barrett (Stanford University) · Oct 1, 2026

Intrinsic rewards in reinforcement learning aim to drive exploration by valuing experience, yet maximizing them need not yield the most informative data. This paper proposes comparing policies by counterfactual information: one policy dominates another if its interaction histories can be decoded to reproduce the other's history distributions uniformly across possible worlds. Using a simple alarm environment, the authors prove analytically that count-based, prediction-error, empowerment, and several state-based objectives can have strictly dominated optima, while also characterizing when posterior-based rewards succeed and constructing a native score $J_w$ that preserves every strict exploration improvement.

Intrinsic rewards are designed to guide exploration in reinforcement learning by assigning value to an agent's experience, for example through prediction error or learning progress. However, maximizing these rewards need not produce the most informative experience available. We propose a formal criterion for exploration that compares policies by the counterfactual information they acquire: how well their histories can substitute for experience under alternative policies. We construct a single, simple environment in which specified count-based, prediction-error, empowerment, and information-gain objectives have maximizing policies that are Pareto-suboptimal at acquiring counterfactual information. We explain these failures and establish conditions under which existing intrinsic rewards successfully encourage optimal exploration. We also construct an objective that assigns a higher value whenever exploration strictly improves under our criterion.
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cs.LGmath.OCmath.PR Nikolaos Makras, Sotirios Sabanis · Oct 1, 2026

The paper tackles sampling from Gibbs distributions on matrix spaces with potentials that are neither convex nor globally gradient-Lipschitz. Its core idea is to replace the quadratic kinetic energy of underdamped Langevin dynamics with a non-quadratic, relativistic-like energy $K_\delta(p)=\delta^{-1}\operatorname{Tr}[(I_n+\delta pp^\top)^{1/2}-I_n]$, whose gradient tames momentum singular values smoothly. By carefully coupling a momentum-dependent diffusion matrix $M_\delta(p)$ and its divergence correction $\Gamma_\delta(p)$, the authors preserve the exact target Gibbs measure, recover regularised Muon in the zero-temperature limit, and prove exponential convergence of the diffusion plus uniform-in-time moment bounds for an explicit Euler-Maruyama scheme.

We consider the problem of sampling from Gibbs distributions on matrix spaces whose potential energies are neither convex nor globally gradient-Lipschitz. We introduce a family of non-quadratic kinetic energies that lead to a new underdamped Langevin system with momentum preconditioning, in which the gradient of the kinetic energy acts as a smooth spectral taming of the momentum. We prove that, under these relaxed assumptions on the potential, the resulting dynamics leaves the target Gibbs measure invariant, and we establish exponential convergence to equilibrium in a weighted total variation distance. Finally, we show that the corresponding Euler-Maruyama discretization admits moment bounds that are uniform in time, without any modification of the potential gradient, which ensures the stability of the resulting sampling algorithm.
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cs.CLcs.AIcs.LG Lucheng Fu, Kejing Xia, Yiyang Wang et al. · Oct 1, 2026

Most LLM agents treat repeated use of the same external source as a sequence of independent retrieval events. This paper reframes the deeper problem as source learning: progressively building a persistent, reusable source model that captures how a source’s knowledge is structured, interpreted, and applied. The proposed SourceLearn system combines self-directed study with task-guided refinement, and the authors report large gains across document, code, API, and interactive benchmarks.

Large language model (LLM) agents increasingly rely on persistent external sources to solve sequences of knowledge-intensive tasks. Existing methods improve how source content is accessed and organized, while agent-memory systems preserve reusable knowledge from prior interactions, but repeated use of the same source is still largely treated as repeated access rather than an opportunity to progressively improve understanding of that source. We study source learning: developing reusable source-specific competence over a persistent authoritative source. We represent this competence with a persistent source model that captures reusable understanding of the source, including how its knowledge is structured, interpreted, and applied. To construct and progressively refine such models, we propose SourceLearn, which combines two complementary learning mechanisms. Self-Directed Source Learning identifies what remains incompletely understood and adaptively revisits the source, while Task-Guided Source Learning uses downstream experience to reveal local representational gaps and recurring needs in how source knowledge should be organized. In both cases, learning signals determine what should be reconsidered, while persistent updates are reconstructed from the authoritative source. Across five benchmarks and three LLM backends, SourceLearn achieves the best performance in 13 of 15 settings, with gains of up to 22.6 points over Hybrid RAG and substantial overall improvements over static source representations and experience-based memory baselines.
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cs.LG Ali Janati, Nikita Kuzmin, Rohit Swamy et al. · Oct 1, 2026

This paper tackles competitive Super Smash Bros. Melee with a single Transformer policy that controls all 26 fighters from one checkpoint. The authors pretrain 10M- and 75M-parameter models on roughly 840k human replays, then apply rank-based supervised curricula, 75M-to-10M distillation, and Fox-only reinforcement learning. The resulting 10M policy wins 240 of 244 benchmark games against prior releases and runs within the 16.67 ms frame budget, while the authors openly acknowledge key confounds in evaluation.

We introduce Faynt, a family of 10M- and 75M-parameter Transformer policies for Super Smash Bros. Melee, each controlling all 26 characters with a single checkpoint. After reinforcement learning (RL), the 10M wins 240 of 244 same-character games (98.4%) against fourteen specialist and multi-character releases on their supported rosters, with a winning record against every release. These opponents retain 21- or 24-frame action delays; Faynt uses no added delay, and we have not isolated the effect of this difference. In a separate evaluation against a privately supplied zero-delay Slippi-AI model, the 10M wins all 68 games across two conditioning settings. We study architecture, optimization, scaling, and hyperparameter transfer to guide pretraining on approximately 840,000 human replays. Post-training combines rank- and outcome-based curricula, 75M-to-10M distillation, and RL restricted to Fox mirror matches. On the initial 152-game benchmark, the supervised 10M wins 69.7% of games, compared with 45.4% for the pretrained 75M, despite higher overall held-out controller-prediction loss. The weighted validation loss used for supervised checkpoint selection agrees with the win-rate ordering of all four pretrained and supervised policies. After supervised post-training, both models take less damage per minute, build larger early leads, and win more often after losing the first life. Optimized inference on recorded game states averages 5.2 ms per decision for the 10M and 8.7 ms for the 75M on an NVIDIA T4, excluding emulator execution and communication. We open-source the weights, both benchmark suites, and a platform for automated model tournaments.
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cs.LGcs.AIcs.CL Aayush Karan, Sitan Chen, Yilun Du · Oct 1, 2026

The paper tackles how to teach LLMs new skills after pretraining without erasing old ones. While RL resists catastrophic forgetting by staying on-policy, it struggles when the model cannot generate successful trajectories on its own. The authors flip the problem: instead of changing the training loss, they use an MCMC projection sampler to reshape off-policy expert traces so they look more like samples from the base model while preserving correctness. This lets ordinary supervised finetuning match or beat RL and self-distillation on science, math, and medical tasks.

Introducing new capabilities to frontier models has long been the goal of posttraining, which predominantly employs supervised finetuning (SFT) and reinforcement learning (RL) to this end. Conventional wisdom dictates that RL enables strong generalization on new tasks without losing existing capabilities, while SFT is prone to weak generalization and catastrophic forgetting. At the same time, SFT can learn from off-policy expert data, whereas RL must rely on a model's ability to find successful trajectories with repeated sampling. In our work, we seek to leverage the strength of on-policy learning while utilizing the privileged information contained in off-policy data. However, rather than modifying the learning objective to accommodate this data, we instead tailor the data distribution to better suit the learner. We introduce a Markov chain Monte Carlo (MCMC) sampling algorithm that progressively transforms off-policy traces to be more on-policy given a reference model for finetuning. Across tasks like scientific skill acquisition, mathematical reasoning, and open-ended expertise, our sampling algorithm enables SFT to rival prevailing posttraining techniques, often generalizing better and forgetting less than strong on-policy baselines. In addition, the resulting finetuned models exhibit strong distributional performance and are capable of learning beyond sharpening the base model distribution. At a higher level, our approach presents sampling as a model-native operator that shapes data for learnability, offering broader utility as a general-purpose primitive throughout the posttraining stack.
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cs.LGcs.DSmath.OC Han Zhong, Yinyu Ye · Oct 1, 2026

Robust Markov decision processes with polyhedral uncertainty lack exact convex representations because the natural robust Bellman inequalities become bilinear or union-of-polyhedra constraints. This paper shows how to encode a finite sequence of robust policy-iteration steps into a single exact LP whose optimal face recovers the robust optimal value and all optimal stationary randomized policies. At fixed discount, the LP has polynomial dimension and encoding length, and the authors use this representation together with a unified complexity analysis to prove strongly polynomial bounds for several standard uncertainty sets—including $\ell_1$, weighted $\ell_1$, interval, and Wasserstein—that previously lacked such guarantees.

We study linear programming (LP) representations and strongly polynomial algorithms for robust Markov decision processes (RMDPs) with rational polyhedral state-action rectangular uncertainty in rewards and transitions. By encoding a finite sequence of robust policy-iteration steps, we construct a single LP whose optimal solutions recover the robust optimal value and all optimal stationary randomized policies. At fixed discount, the LP has polynomial dimension and encoding length and can be constructed in strongly polynomial time. We also develop a general complexity analysis of robust policy iteration that combines the cost of minimizing over uncertainty sets with the number of iterations needed to evaluate a policy. For a fixed discount factor, we use this analysis to improve the known complexity bounds for $\ell_1$ and $\ell_\infty$ RMDPs and establish new strongly polynomial bounds for general interval, weighted $\ell_1$, and Wasserstein RMDPs, as well as turn-based stochastic games with these uncertainty sets.
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cs.LGcs.CL Tido Specht, Elias Benedict Krey, Nils Neukirch et al. · Oct 1, 2026

This paper adapts Non-Linear Multi-Dimensional Concept Discovery (NLMCD) from vision to LLMs to model concepts as low-dimensional manifolds rather than linear directions. It introduces a fuzzy generalized Rand index called Concept-Based Alignment (CBA) that compares independently discovered concept spaces across layers, languages, and training stages without requiring shared tokenizers or architectures. The authors claim CBA is more sensitive than linear baselines (CKA, PCA), uses it to reveal cross-layer block structures, and applies it to study multilingual sharing, cross-model alignment, and post-training drift in Tulu-3.

Understanding information processing in large language models (LLMs) requires dissecting the geometric organization of their internal token representations. While existing mechanistic interpretability (MI) methods seek to extract concepts, they are constrained by a strong linearity assumption challenged by evidence of non-linear feature manifolds. We move beyond linear concepts by adapting Non-Linear Multi-Dimensional Concept Discovery (NLMCD) from computer vision to token-level LLM activations, modeling concepts as low-dimensional manifolds. To compare concept manifolds across layers and models, we introduce a concept-based alignment (CBA) score, a generalized Rand index that measures geometric proximity without explicit feature matching. Our analysis yields six key findings: (i) a neighboring-layer sanity check shows CBA is more sensitive than PCA- or CKA-based linear baselines; (ii) layer-by-layer alignment matrices reveal two block structures in intermediate and late layers, consistent across models and obscured by linear metrics; (iii) concept composition remains syntax-dominated through most of the network before giving way to increasingly mixed syntactic-semantic concepts in later layers, with increasing output-orientation toward the final layers; (iv) multilingual concept sharing between English and Mandarin is training-dependent rather than universal, strongest in Qwen, weaker in Llama, and absent in GPT-2; (v) inter-model alignment mirrors this structure, with strong correspondence between same-family Qwen models of different scale but weak alignment across model families; and (vi) across Tulu-3 training stages, alignment is highest between adjacent stages, with the largest shift between the base model and SFT, while subsequent preference-alignment stages (DPO, RLVR) leave early layers largely unchanged and RLVR mostly preserves DPO's concepts in late layers.
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cs.LG Yifan Guo · Oct 1, 2026

When a machine-learning benchmark improves, multiple mechanisms could explain why. This paper studies how an autonomous agent should select diagnostic probes from a finite library to discriminate among competing explanations under a tight budget. MECHVAR scores each probe by the posterior-weighted variance of its predicted responses, showing that under a shared Gaussian predictive scale this is exactly proportional to the classical Box–Hill pairwise-KL criterion. The reformulation yields $O(KE)$ vectorized rescoring, an explicit pairwise audit trail, and orders-of-magnitude faster acquisition than quadrature-based expected information gain.

Benchmark gains are often mechanism-ambiguous: reproducing an improvement does not by itself identify why it occurs. We study finite-library mechanism discrimination, where posterior-weighted candidate mechanisms, executable probes, and a limited experimental budget define a sequential experiment-selection problem. MECHVAR selects the next probe by maximizing the posterior-weighted variance of its predicted responses. Under a shared-Gaussian predictive model, this score is exactly proportional to the classical Box--Hill posterior-weighted pairwise-KL criterion, yet it admits O(KE) vectorized rescoring and a transparent additive audit over mechanism pairs. A local expansion further links the score to expected information gain (EIG) when predicted response separations are small. In a 25-block stress audit, MECHVAR outperforms confirmation-first in several moderate misspecification regimes, while its primary comparisons with EIG remain statistically unresolved. In a held-out Digits loop, normalized mechanism-identification AUC is 0.8975 for MECHVAR, 0.7825 for a score-greedy policy, and 0.9092 for EIG. At K = 100, E = 200, median single-thread full-library scoring is 10.36 microseconds for MECHVAR versus 57.69 ms for six-node quadrature EIG in the recorded environment. MECHVAR therefore provides a lightweight, auditable acquisition rule for finite-library experiment selection when a shared predictive scale is a defensible approximation.
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cs.LGcs.AI Junkang Liu · Oct 1, 2026

FedMIX-P tackles preconditioner coordination in federated learning by mixing a shared reference preconditioner with each client's local adaptive state at every local step. The core idea is to control the operator mismatch that arises when heterogeneous clients transform gradients differently, and the paper demonstrates empirical improvements on vision and language models under severe data heterogeneity. However, the convergence analysis is restricted to linear positive-definite preconditioners, while the headline experiments rely on nonlinear methods such as Muon, creating a notable gap between theory and practice.

Adaptive preconditioners accelerate model training, but heterogeneous client geometries can bias federated updates even when gradients are evaluated at the same model. Round-start synchronization alone cannot prevent this mismatch from reappearing during local training. We propose \texttt{FedMIX-P}, which mixes shared and local preconditioners at every local step, retaining local adaptation while reducing mean-squared operator mismatch by a factor of $\lambda^2$. For smooth nonconvex objectives with stochastic gradients and partial participation, we establish an $O(R^{-1/2})$ stationarity bound using suitable stepsizes and a horizon-dependent mixing weight, without requiring local preconditioners to converge to one another. A two-client counterexample shows that fixed positive mixing can preserve a nonstationary fixed point. The theory covers bounded linear symmetric positive-definite preconditioners. Experiments with SOAP, Sophia, and Muon variants across vision and language tasks show improvements over corresponding local optimizers, including accuracy gains of up to $19.47$ percentage points and lower validation loss for 60M--350M language models. Full nonlinear and momentum-based updates require separate analysis.