Your paper timeline
Scroll AI takes the way you would scroll a great paper aggregator: quick signal first, deeper critique when something earns your attention, and challenges when a claim feels off.
797 papers in cs.LG
Trending mixes fresh papers with community signal.
0
cs.LGcs.AI Tinglan Wang, Haixu Liu, Shaobo Chen et al. · Oct 14, 2026

MeanFlow normally couples the prediction horizon $h_k$ to the update step $\delta_k$. This paper decouples them, showing on CIFAR-10 that longer horizons hurt FID near the source $(t=0)$ but help at the midpoint $(t=0.5)$, and that this midpoint gain depends on earlier guidance choices. A frozen four-query rule improves mean FID by 2.0 without retraining or extra calls, yet ImageNet calibration finds no benefit beyond shifting query starts. The work establishes prediction horizon as a distinct but configuration-sensitive inference control.

MeanFlow predicts interval-average velocities, but conventional few-step sampling ties the interval queried from the model to the duration of the state update. We separate these two quantities at inference, fixing the model, update grid, and number of queries while varying the prediction horizon. Our central finding is that the horizon response depends on both query position and the states entering that query. Across seven independently trained CIFAR-10 checkpoints at classifier-free guidance (CFG) scale 2, a longer horizon worsens FID at early steps but improves it at the midpoint. To probe whether query time alone determines this response, we fix the midpoint query and current/subsequent guidance while changing only earlier CFG. In held-out factorial outcomes on five previously studied checkpoints, the mean midpoint horizon benefit increases from 0.109 to 1.308 FID, indicating sensitivity to the incoming-state distribution. A frozen four-query rule reduces mean CIFAR-10 FID by 2.023 without retraining or extra queries, including gains on five checkpoints trained after rule selection. A milder rule also improves mean FID by 1.041 on a stronger frozen grid, with fixed-rule FID gains on the evaluated public ImageNet-256 and AFHQ checkpoints. However, matched-budget calibration favors query-start shifting in historical CIFAR tests, and the tested Horizon allocation adds no FID benefit beyond Grid+Start on two public ImageNet models. Thus, prediction horizon is a distinct, position- and state-sensitive inference control, but not a universally preferred one.
0
cs.AIcs.CYcs.LG Shiv Muthupandiyan, Tolga H. Dur, Mac Walker et al. · Oct 14, 2026

ReproBAIT evaluates whether sandboxed coding agents can reconstruct published biological AI tools from limited text descriptions when supplied with training data and a fixed compute budget. The authors task frontier LLMs with replicating three tools—a closed-source molecular-design model, ProteinMPNN, and RFdiffusion3—and score functional parity on held-out data rather than source-code similarity. Near-parity is reached on the two simpler tools for only a few dollars, while the most complex tool defeats all agents within the allotted budget, raising questions about memorisation and whether withholding code is enough to control access.

Large language models are increasingly competent at leveraging scientific knowledge and existing computational tools to execute complex workflows. At present, little information exists on their ability to reconstruct tools when given limited descriptions of such tools. We introduce an evaluation titled ReproBAIT (Reproducing Biological AI Tools), which measures the ability of coding agents to design, implement, and train biological AI tools taken from published research across a range of information access conditions. The coding agent is securely sandboxed without internet access and receives training data, a fixed time and compute budget, and limited information about the tool to replicate. We then score the reproduced biological AI tool based on its performance (tool-specific metrics) on held-out data. We evaluated a set of biological AI tools of varying complexities: ProteinMPNN, an inverse protein folding tool, RFdiffusion3, an all-atom generative diffusion tool, and a closed-source molecular design tool. We institute a methodology to check for memorisation, as the open source tools are likely to be included in models' pretraining corpus. Across a range of leading closed- and open-source coding agents, we find substantial reproduction capability for some selected tools, though limited capability for a highly complex tool. We find moderate evidence consistent with memorisation, varying across coding agents. These results suggest that tool developers need to be increasingly cautious when releasing information about the tools publicly; re-creation of the tool based on such information could undermine a tool's commercial value or invalidate dual-use managed access strategies.
0
cs.AIcs.CLcs.LG Maolin Ran, Minda Chen, Di Huang et al. · Oct 14, 2026

Reinforcement learning for language agents suffers from sparse trajectory-level rewards that do not directly supervise environment dynamics. DGS-WM addresses this by introducing Decision-Guided Selective World Modeling: instead of forcing the policy to predict entire environment observations as auxiliary targets, it selects only observation units that support the subsequent policy response and discounts already-mastered targets via confidence-adaptive weighting. This selective co-training yields consistent gains over full-observation counterparts across QA and web-shopping benchmarks.

Reinforcement learning provides a direct mechanism for optimizing task objectives in large language model-driven agents, but task rewards are typically sparse trajectory-level signals that only evaluate task success, without directly supervising action-conditioned environment transitions, leaving the model with limited explicit understanding of action consequences and environment dynamics. Recent work introduces auxiliary supervision through policy and world modeling co-training, yet typically treats complete environmental observations uniformly as world modeling targets, overlooking the varying decision relevance of observation content. We propose DGS-WM (Decision-Guided Selective World Modeling), a decision-guided policy-world modeling co-training approach for language agents. DGS-WM employs a Decision-Guided Observation Selection component that filters observation units with decision value as world modeling targets based on their support for subsequent policy responses, and a Confidence-Adaptive Weighting component that adaptively adjusts supervision strength according to the model's prediction confidence on selected targets. Together, these components form a decision-aware auxiliary world modeling loss, jointly optimized with the RL loss on the same policy model. Across multiple benchmarks covering single-hop/multi-hop question answering and interactive web tasks, DGS-WM achieves consistent improvements under different model scales and RL algorithms, demonstrating more stable and effective performance compared to full-observation world modeling methods.
0
cs.CVcs.AIcs.LG Lorenzo Venturoli, Nedko Savov, Xi Wang et al. · Oct 14, 2026

StateCraft tackles the long-horizon inconsistency problem in video world models by explicitly decoupling a persistent, structured abstract state from the visual rendering pipeline. A finetuned vision-language model maintains and updates a graph-structured abstract state in response to actions, including off-screen changes, while a video diffusion model generates each frame conditioned on that state. This enables consistent revisits, direct state editing, and large empirical gains on a new GUI-world-model benchmark measuring memory and controllability.

Video world models aim to simulate complex environments with realistic appearance and dynamics. Maintaining consistency over long interactions requires tracking past actions and understanding how those actions affect the environment. Video world models can only generate partial observations of the entire world at a time. Remembering past observations alone may not be sufficient in every scenario, as they may no longer reflect the world after a sequence of actions. We introduce a paradigm that decouples a persistent, updatable abstract state from the visual state. The abstract state keeps track of the entities' changes as the world evolves, and is used to condition the visual state, which represents the current view. We propose StateCraft, a novel architecture that pairs a language model with a video diffusion model to evolve the dynamic world. We evaluate our approach on generative interfaces, which pose a substantial challenge because a single action may change parts of the state that are not currently visible. To support training and evaluation, we develop a data collection pipeline that produces informative, densely annotated trajectories at scale without human or agent supervision, together with a benchmark measuring generation quality, memory, and controllability. On this benchmark, our approach improves surpasses the state-of-the-art baselines. We demonstrate that StateCraft maintains high self-consistency and strong generation quality over long trajectories. Because the abstract state is explicit, it can be edited directly, and generation follows edits to states never observed in the data. Finally, a proof-of-concept 3D experiment, in which actions change the illumination of an unobserved room, shows that the paradigm can also be applied to spatial environments. Project page: https://insait-institute.github.io/StateCraft/.
0
cs.AIcs.CLcs.LG Alexander Spangher, Daniel E. Ho, Diyi Yang et al. · Oct 14, 2026

The paper asks how much meaning language models can actually share through language alone. To measure this, the authors introduce two tools — an epsilon-estimation algorithm that finds near-optimal prompts and estimates how much performance is left on the table, and a reconstruction bottleneck that scores how well a receiver model recovers a sender model's concept from labeled examples alone. They then apply observational scaling laws across 1.2k qualitative concepts in eight domains, classifying each as already articulable ('reaches'), potentially articulable with stronger models ('rising'), or permanently tacit ('bounded').

Language captures only a subset of the perceptions, intuitions and intents that form meaning between speakers. What, then, are the limits of language? We take steps towards measuring this in LLMs as follows: for a set of concepts, we measure how well each concept can be transmitted between two LLMs as their capabilities scale. This requires novel measurement tools: (1) optimal messages: we introduce a prompt optimization algorithm that beats existing algorithms by up to 14% on benchmarks and accurately estimates prompt upper bounds. (2) A transmission measure: the sender is asked to label text; the receiver then tries to recover the sender's prompt, and recovery is measured; we find this correlates strongly with human label error. With these measures, we use observational scaling laws to study how transmissibility of a concept, conveyed with optimal messages, increases as transmitter and receiver capacity grows: does it asymptote below or above a threshold? Measuring 1.2k concepts in eight domains, we find concepts that (a) can be fully articulated; these concepts usually depend on local patterns, e.g. "joke ends with surprise"; (b) might be articulated by future, stronger models; these rely on whole-text structural patterns, e.g. "story's worldbuilding coherence"; (c) concepts that face articulability limits; these concepts' meaning, we find, is tied to identity and social-group awareness, e.g. "comic voice". Interesting, these same concepts are not all challenging for humans: humans have moderate-to-high levels of agreement in 76% of concepts that LLMs struggle with; articulation limits, we find, are executor relative. Finally, we characterize the nature of improvement in each case: while recoverable concepts can be articulated through definitions and explanations, irrecoverable concepts cannot be transmitted, even with examples, and might require novel learning mechanisms.
0
cs.AIcs.LG Carson Eisenach, Robert Joseph George, Vincent Quenneville-Belair et al. · Oct 14, 2026

L3M asks how to run AI agents so that useful computation scales safely across days, machines, and model calls. It answers with a Git-backed, distributed runtime written in Lean 4 where capability tokens confine every tool call, trajectories are durable append-only logs, and agents self-extend by writing sealed programs whose types bound their authority. The goal is a harness where trust narrows rather than widens as agents grow more capable.

The lasting gains in AI have come from methods that absorb more computation, and language models already scale computation within a call. Useful work, though, happens across calls: over hours or days, through tools and external systems, among many agents and the humans they work for, and increasingly through code the agents write themselves. Whether that work compounds is enabled by the harness around it, and the harness faces a constraint the model does not: of the three participants in such a computation, the human, the model and code, only the human's attention does not scale, so the computation can grow only if the human is not in every loop. L3M is a runtime built on that premise, written in Lean 4 so that one language implements the harness, states its invariants, and is the language agents extend it in. One computation spans humans, agents, models and code, and all of its state lives in Git: a rich state trajectory -- rather than a chat conversation -- is an object the runtime can resume, rewind, fork, compare and merge. Waiting, communication, delegation and undo are primitives, not patterns the model reasons through each time. When an agent works out a procedure, it can write it once as a sealed Lean program whose type is its permission request, and the harness offers it back as a tool -- machinery for the model to use. To take the human out of the loop, L3M uses reversibility to decide where that is safe: a tool's review tier follows from how far its effects can be undone, so agents act freely where the runtime can recover. Because the machinery can change, the properties that make this safe are stated as kernel-checked theorems about the code that runs. On Terminal-Bench, an untuned L3M reaches about two thirds of its (unsafe) shell-equipped pass rate using only safe (not needing human review) tools.
0
cs.AIcs.LG Hanwei Fan, Yanqiao Wang, Yiqi Zhu et al. · Oct 14, 2026

Scientific taste varies across researchers, but learning individual preferences is hard when feedback is scarce and retrospective evidence only arrives after research unfolds. This paper proposes Privileged Hindsight Distillation (PHD), which trains a proposal-only student using later-emerging evidence to improve criterion assessment and population taste priors, then adapts the model to individuals with as few as 15 pairwise comparisons. The work matters because scaling research ideation requires filtering directions without collapsing diverse personal judgments into a single community consensus.

Scientific taste shapes which research directions researchers pursue, and it varies across individuals. Existing work evaluates research directions along multiple evaluation criteria or models scientific taste using community feedback signals such as citations and reviews, but neither directly captures how individuals translate assessments under the same criteria into different preferences. We model scientific taste as a researcher-specific mapping from criterion-level assessments in a shared, evidence-grounded evaluation space with proposal-visible evidence, to relative preferences. A population-level mapping learned from retrospective supervision provides a cold start when individual feedback is scarce. We introduce Privileged Hindsight Distillation (PHD), which uses later-emerging scientific evidence during training to improve proposal-time criterion assessment and the population mapping, while exposing only proposal-visible information at inference. We evaluate our approach primarily in quantum research, where structured public reviews are largely unavailable, and use pairwise proposal comparison as a direct interface for observing individual taste. With only 15 comparisons per researcher, our method captures sharply different tastes, including opposing preferences over the same research-direction pairs when they trade off across evaluation criteria. In an interactive study, personalized rankings also surface proposals associated with greater subsequent user engagement, connecting learned taste to downstream research exploration.
0
cs.LGcs.AIq-bio.QM Alberto Mart\'inez, Natalia Flechas Manrique, Lloren\c{c} Espinosa-Portal\'es et al. · Oct 14, 2026

ProtModernBERT tackles the high cost of training protein language models by porting modern NLP encoder improvements—RoPE, FlashAttention, GeGLU, and bias-free layers—into a BERT-style protein model. The authors pre-train on the UR100P corpus and show that a 140M-parameter model can match ProtBert and Amplify-120M on structural benchmarks while using roughly one-tenth the pre-training FLOPs of ProtBert. The work matters because it tests whether architectural modernization alone can lower the barrier to custom protein LMs for resource-constrained labs, and it uses random-initialization baselines to separate inductive biases from transfer-learned features.

Large protein language models provide a powerful framework for learning sequence-function relationships and guiding experimental design. However, architectural improvements are underexplored, especially in low-compute regimes of relevance for resource-constrained research laboratories. We show that the training cost for encoder-only transformer architectures can be reduced by leveraging modern architectural refinements, offering an encouraging performance / compute-efficiency trade-off. We introduce ProtModernBERT, a modernized BERT-style model pre-trained on amino acid sequences, and compare it with ProtBert, Amplify, and ESM2 across a set of supervised structural tasks -encompassing secondary structure prediction, disorder prediction, and subcellular localization- and ProteinGym's zero-shot functional benchmark. We find that ProtModernBERT matches or closely tracks the performance of Amplify-120M and ProtBert with up to 80-90\% reduction in pre-training FLOPs, and narrows the gap to ESM2 when controlling for pre-training. Our analysis using a cluster-based validation protocol for hyperparameter selection and randomly initialized models disentangles the contributions of architecture and data, showing that modern components provide stronger inductive biases that are more consequential than parameter count in low-compute regimes.
0
cs.LGcs.AIcs.CL Aryan Das, Arnab Bhattacharya, Vinay Kumar Verma · Oct 14, 2026

Reinforcement learning with verifiable rewards suffers from coarse scalar supervision and moving-target instability in self-distillation. FSPO eliminates the persistent teacher model by storing sparse historical next-token distributions as fixed function-space targets, combining them with privileged disagreement correction and reliability-adaptive grounding. Across scientific reasoning and tool-use benchmarks, it achieves roughly 4% higher average accuracy than SDPO under a 5-hour budget while cutting peak memory from about 70 GB to 56 GB on Olmo3-7B-Instruct.

Reinforcement Learning with Verifiable Rewards (RLVR) improves reasoning in language models, but scalar outcomes provide coarse supervision over response trajectories. Self-distillation offers denser token-level guidance by comparing an unassisted policy with a feedback-informed self-teacher, yet the teacher evolves with the student, creating unstable targets and motivating additional regularization. We introduce Function-Space Policy Optimization (FSPO), a single-policy framework that combines current privileged adaptation with function-space temporal consolidation. FSPO stores sparse historical next-token distributions as fixed temporal targets, providing temporal separation without maintaining a persistent teacher model. It further introduces privileged disagreement correction to explicitly suppress locally overvalued actions, reliability-adaptive grounding that strengthens reference supervision when self-generated evidence repeatedly fails, and quality and coverage-aware temporal memory that retains verified behaviors and improves privileged demonstrations. Across reasoning and tool-use benchmarks, FSPO achieves the highest average accuracy under a 5-hour training budget, improving over the strongest baseline by approximately 4% points on average while reducing peak memory from about 70 GB to 56 GB on Olmo3-7B-Instruct.
0
cs.AIcs.CLcs.LG Minseok Ko, Hyunseok Lee, Woomin Song et al. · Oct 14, 2026

As large language models proliferate, identifying which model family generated a given text must remain reliable even when the domain or model version changes at test time. This paper proposes ATLAS, a generative framework that learns source-conditioned text distributions through lightweight adapter tuning and attributes text by comparing clipped token-level likelihoods. A new benchmark, MAABench, demonstrates that this likelihood-based approach outperforms direct discriminative classifiers under distribution shifts, while also enabling identification of distillation teachers.

As large language models (LLMs) are increasingly used to generate text, their misuse has become a growing societal problem, with implications for academic misconduct, model distillation, and cyberattacks. For these reasons, Model Authorship Attribution (MAA), which identifies the source model of a given text, is important for promoting the responsible use of LLMs and improving AI safety. In practice, attribution systems must remain reliable beyond the distributions observed during training. They may encounter texts from unseen domains and writing settings, as well as generations from future versions of model families that were not available when the system was trained. However, existing MAA methods often exhibit substantial performance degradation under such distribution shifts. To address this challenge, we propose Authorship Tracing via Likelihood-based Attribution of Sources (ATLAS), which formulates MAA through source-conditioned text modeling rather than direct source prediction. ATLAS learns how text from each source family is generated and attributes a given text by comparing its likelihood under each learned source condition. We aggregate this likelihood evidence at the token level with clipping so that no single token dominates the decision. We further introduce MAABench, a broad MAA benchmark for evaluating practical OOD settings such as domain and version. Our experiments show that ATLAS consistently outperforms existing baselines across MAABench and OpenTuringBench. In particular, when both the generation domain and the model version change on MAABench, ATLAS achieves 74.27% accuracy, 9.00pp higher than the strongest baseline. Beyond MAA, ATLAS can also help identify distillation source models by measuring which source model a target LLM most closely resembles. Our extended experiments show that ATLAS recovers the known teacher of every distilled model we evaluate.
0
cs.CLcs.AIcs.LG Raavi Gupta, Ziqing Yang, Karli R. Hochstatter et al. · Oct 14, 2026

The paper tackles the months-long lag in confirming US overdose deaths by predicting suspected overdoses directly from death investigation reports available days after a fatality. Its core idea is an expert-guided pipeline that extracts verbatim evidence spans—feature-guided rationales—to support classification, comparing them against templated verbalizations and against joint self-rationalizing models. The best configuration improves over a deployed rule-based system by roughly 15% relative macro-F1 while preserving expert oversight, offering a plausible path to faster public-health surveillance.

Confirmation of overdose deaths in the United States is often delayed due to the complexities of certifying drug-involved deaths. Death investigation reports represent a rich but underutilized data source that could be used to predict whether a death is a suspected overdose (i.e., a death preliminarily identified as an overdose prior to the final cause and manner of death determination). We present an automated framework that classifies suspected overdoses from death investigation reports, while producing supporting explanations guided by expert knowledge. Through an expert-guided design process, we investigate 1) what type of explanations are best for model prediction performance, and 2) which architecture is better suited for this task: pipeline models that rationalize first and then predict, or self-rationalizing models that jointly predict and rationalize? Our experiments show that a pipeline model with explanations grounded in the input death investigation reports outperforms the other settings. Our best model also outperforms a rule-based system currently in deployment by 15%, while allowing expert interventions for final decisions.
0
cs.AIcs.LG Yan Xu, Dandan Song, Luan Zhang et al. · Oct 14, 2026

LLM-based agents can produce final reports that falsely claim task success even when their execution trajectories failed to follow required sources or procedures. This paper defines Agent Completion Unfaithfulness as a misalignment between what an agent actually did and what it ultimately reports, and proposes MCAIR, a runtime framework that uses step-level internal representations to train a lightweight linear probe for online risk detection and correction. Because users typically rely on final reports rather than inspecting full execution traces, detecting and mitigating such overstatement is critical for trustworthy autonomous agents.

Large Language Model (LLM)-based agents have demonstrated remarkable capabilities in completing complex tasks through multi-step reasoning and tool interactions. However, recent studies have revealed that LLM-based agents can exhibit unfaithful behaviors, where their final reports fail to faithfully reflect their actual execution trajectories. Specifically, when agents fail to accomplish tasks through the intended sources or procedures, they may resort to alternative sources or strategies while failing to disclose such deviations, leading users to incorrectly believe that the tasks have been completed according to the original requirements. We refer to this specific form of agent unfaithfulness as Agent Completion Unfaithfulness. Detecting and mitigating agent completion unfaithfulness is critical yet remains largely unexplored. In this work, we propose MCAIR, a runtime monitoring and correction framework that leverages internal representations of LLM-based agents. MCAIR uses multi-step internal representations as inputs to train a risk-aware probe, enabling online detection of potential completion unfaithfulness during execution. Furthermore, MCAIR introduces a risk-guided correction loop that prompts agents to review their execution history and mitigate potential inconsistencies between their execution trajectories and final reports. Additionally, we construct ACUD, a dataset for Agent Completion Unfaithfulness detection that provides step-level execution traces, step-level internal representations, and consistency annotations for training and evaluating runtime detection probes. Experiments demonstrate that MCAIR outperforms LLM-as-a-judge baselines, generalizes across prompts and tasks, and effectively reduces agent completion unfaithfulness.
0
cs.LGcs.AI Minwoo Yu, Young-guk Ha · Oct 14, 2026

Temporal graph data come in different formats, but it is unclear whether representation boundaries limit how learned predictive structure can be reused. This paper proposes that Relational Dynamics—the predictive regularities in relational histories—can be transferred across continuous-time dynamic graphs and temporal knowledge graphs while keeping their input and prediction layers separate. The core idea is to train a shared history encoder on one representation, freeze it, and drop it beneath a different representation’s interface, then use controlled source-history reorganizations to identify which organizational aspects actually drive reuse. If the empirical claims hold up, the work implies that temporal graph foundation models need not be siloed by representation.

Temporal graph data are recorded in different representations, but whether these differences also determine the scope of learned knowledge reuse remains unclear. This study investigates whether predictive structure learned from relational histories can be reused between continuous-time dynamic graphs (CTDGs) and temporal knowledge graphs (TKGs). Bidirectional reuse emerges while retaining distinct input and prediction interfaces and independent vocabularies, and sources with the same representation are not always more useful. Controlled reorganizations of source histories show that the organization contributing to reuse varies across source-target conditions. We show that learned aspects of Relational Dynamics, the predictive structure present in relational histories, can be reused across conventional representation boundaries. Independently pretrained TKG and CTDG learners can also be fused at the score level to improve prediction on a third dataset without entity or relation-semantic alignment. Two proofs of concept in recommendation and security detection illustrate that external temporal sources without direct alignment can also become useful pretraining resources.
0
cs.CLcs.AIcs.LG Baowen Zhang, Hangting Ye, Hongyuan Zha · Oct 14, 2026

Typed decision models return probabilities over fixed answer choices instead of generating free text, making them a natural fit for tabular prediction tasks. This paper evaluates four such models against three large language models on row classification, fact verification, and anomaly detection, subjecting every request to 21 content-preserving rewrites. The authors find that decision models match LLM accuracy at far lower cost and are far more robust to how questions are phrased, yet no model escapes fragility when the table layout is altered.

Typed decision models are language models that answer a question with a fixed set of possible answers by returning a probability for each answer instead of generating text. We study them on tabular data and compare four decision models with three large language models (LLMs) on row classification, fact verification and anomaly detection. Every request is sent in its original form and under 21 types of rewrite that keep its content, such as renaming the options or writing the table in another format. The decision models perform as well as the LLMs at a lower cost. Three of them are also far more robust to how the question is formulated. No model we test is robust to how the table is organized. For every model, at least a third of the row decisions change under some rewrite of the table or the question. The decisions to which a decision model gives low probability are the ones most likely to change. Decision models are a practical choice for tabular decisions, but their robustness remains an open problem.
0
cs.CLcs.AIcs.CY Yilin Jiang, Fei Tan, Xuanyu Yin et al. · Oct 14, 2026

Simulated students let developers test tutoring systems before real learners are available, but LLM role-play suffers from competence leakage because the model substitutes its own knowledge for the learner's. HACHIMI-II counters this by recasting simulation as third-person prediction: it builds a student model, infers a fine-grained learner state for each step, and compiles that state into a deterministic behavior harness that constrains generation. On five datasets, this cuts the ability-distribution gap by 2.4–8.4× and more than doubles error-structure fidelity over the strongest baseline.

Simulated students let researchers test tutoring systems and teaching strategies before real learners are available, but only if the simulation reproduces where a particular learner succeeds and fails. The common approach asks a large language model to role-play a student, but a role does not model what this learner knows or will do next, so the model's own competence fills the gap. Simulated students perform at a level set by the model, differ little from one another, and seldom make the real learners' errors. We model the learner's behavior and recast student simulation as third-person prediction of the learner's next action. HACHIMI-II builds a student model from the learner's history, infers the learner's state for the current item or tutor turn, and compiles it into a behavior harness that constrains the next action. On three item-response datasets, the Wasserstein-1 distance between simulated and real student ability is 2.4--8.4$\times$ smaller than that of the strongest baseline. On two dialogue datasets, HACHIMI-II reproduces real student errors with the same knowledge type, locus, and mechanism 1.8--5.1$\times$ more often than the strongest baseline, and ablations trace the gains mainly to the explicit learner state. Predicting the learner makes capable models usable as simulated students.
0
cs.LGcs.AI Xinjie Lan, Yunbo Mei, Leheng Zhou et al. · Oct 14, 2026

This paper tackles non-stationarity in long-term time series forecasting by asking how positional encoding shapes temporal dependencies in Transformer attention. The core idea is to reinterpret self-attention as a Bayesian posterior in which positional encoding acts as latent temporal evidence, and to replace static positional biases with an input-conditioned mixture-of-experts router that adaptively combines local and periodic kernels. The results matter because they offer a principled, lightweight, plug-and-play module that consistently improves forecasting across four diverse Transformer backbones.

Transformers have demonstrated strong performance in long-term time series forecasting (LTSF), yet modeling non-stationary temporal dependencies remains challenging. In this paper, we interpret self-attention as a Bayesian posterior over attended positions, combining a content-based prior induced by scaled dot-product similarity with a temporal-evidence likelihood induced by positional encoding. This formulation provides a probabilistic interpretation of how positional encoding shapes the temporal dependencies captured by self-attention. Building on this perspective, we derive a population-level evidence lower bound (ELBO) that characterizes the role of positional encoding in forecasting weakly stationary time series. Our analysis further highlights a limitation of static positional encoding: when temporal dependence structures vary across input windows, a fixed temporal bias must accommodate heterogeneous dynamics and can therefore be suboptimal for non-stationary forecasting. Motivated by this analysis, we propose Bayesian Time-aware Attention (BTA), which employs a mixture-of-experts (MoE) router to adaptively combine temporal kernels and generate input-conditioned, head-specific positional biases. Extensive experiments on standard LTSF benchmarks demonstrate that BTA consistently improves forecasting performance across multiple Transformer backbones and achieves competitive overall performance with modest computational overhead and stable training.
0
cs.LGcs.AI Aditya Radhakrishnan, Maxwell A. Xu, Wanting Mao et al. · Oct 14, 2026

TEX-MEX attacks the central challenge in time-series contrastive learning: how to define similarity when semantic-preserving augmentations are scarce or unreliable. It unifies structural and temporal similarity by letting the encoder grade windows by cosine similarity, then pulling an anchor toward the time-shifted versions of similar batch windows and pushing it away from those of dissimilar ones. The result is a graded, efficient objective that learns what typically accompanies a physiological pattern in time, and it powers a 560K-parameter PPG foundation model that beats architectures roughly 50× larger.

Contrastive learning for time series depends on deciding which pairs of inputs should be treated as similar and dissimilar. Because few augmentations reliably preserve meaning in time series, prior methods have relied on two disjoint notions of similarity between windows: structural similarity, which relates windows with similar morphology, and temporal similarity, which relates windows that occur close together in time. We introduce TEX-MEX, to our knowledge the first approach to unify the two into a single relationship. Given a random batch of windows drawn across the dataset, TEX-MEX uses the encoder to identify which windows are structurally similar or dissimilar to each other. It then pulls each window toward the temporally shifted versions of similar windows and pushes it away from those of dissimilar ones, learning what typically accompanies similar windows in time. Across PPG, EEG, ECG, accelerometry, and continuous glucose monitoring, TEX-MEX broadly achieves state-of-the-art performance against contrastive, reconstructive, JEPA-based, and modality-specific approaches, establishing it as a strong general SSL objective. We further train a 560K-parameter PPG foundation model that achieves state-of-the-art performance across a broad range of downstream benchmarks while being roughly 50x smaller than the next-best unimodally pretrained PPG foundation model in our evaluation. We will release this foundation model open-source and open-weight to the community to support future work and practical applications.
0
cs.LGcs.AI Armaan Sandhu, Abhijeet Sinha, Dianbo Liu · Oct 14, 2026

Standard expected-reward RL suffers from mode collapse, concentrating probability on a few outcomes even when tasks require many distinct, high-quality solutions. MIPS tackles this by estimating marginal outcome probabilities through a learned trajectory-conditional model, avoiding frequency-based estimation that breaks down when the outcome space is much larger than the rollout group. Using the identity $P_\theta(o) = P_\theta(\tau) / P_\theta(\tau|o)$, it scales rewards by inverse estimated probabilities within a standard GRPO update. On enumerable Hypergrids, molecular synthesis, and phylogenetic inference, MIPS maintains reward-aligned diversity where group-count IPS collapses.

Expected-reward maximization in reinforcement learning concentrates probability mass on a few outcomes, even in tasks that require many distinct, high-quality solutions, a failure known as mode collapse. Inverse Probability Scaling (IPS) counters this in group-based policy gradients such as GRPO by dividing each reward by the outcome's probability, estimated from its frequency within the sampled group. When the outcome space is large relative to the group, outcomes rarely repeat and these estimates become uninformative. Since an outcome can be constructed along many trajectories, its probability is a sum over all of them, and computing it directly is intractable. We propose Marginal IPS (MIPS), which performs marginal evaluation by combining the sampled trajectory with a learned model of the trajectories that lead to each outcome. On Hypergrids, where the exact sampling distribution is computable, MIPS stays near the reward-distribution target as the outcome space grows relative to the rollout group, while frequency-based IPS degrades. In molecular synthesis and phylogenetic inference, MIPS sustains diverse, high-quality sampling where GRPO and frequency-based IPS collapse, showing that MIPS serves as a reliable solution to mode collapse in RL.
0
cs.DCcs.AIcs.LG Javad Mirzaei, Jeebak Mitra · Oct 14, 2026

Choosing a parallelism configuration for distributed LLM inference is challenging because the prefill and decode phases impose conflicting demands on time-to-first-token (TTFT) and inter-token latency (ITL). This paper develops a systematic framework that defines parallelism operating regions via TTFT-ITL Pareto frontiers and formulates SLO-aware selection using goodput $G_p(w,T_s)=\lambda_p(w)F_p(T_s|w)$. The core finding is a workload-dependent transition: tensor-parallel (TP) configurations excel for decode-heavy workloads and relaxed latency requirements, while pipeline-parallel (PP) configurations dominate for prefill-heavy workloads, stringent TTFT targets, and long contexts. The work matters because it moves parallelism selection from a static deployment choice to a workload- and SLO-dependent operating decision.

Large Language Model (LLM) serving systems must balance latency and throughput while efficiently utilizing distributed GPU resources. This challenge arises because inference consists of two fundamentally different phases: prefill, which determines time-to-first-token (TTFT), and decode, which determines inter-token latency (ITL). The use of tensor parallelism (TP), pipeline parallelism (PP), and hybrid configurations exposes different trade-offs between these latency dimensions, making the optimal parallelism configuration highly dependent on workload characteristics, latency requirements, and context length. Moreover, despite the widespread adoption of distributed inference, there is still limited understanding of how parallelism configurations should be selected under varying workload conditions and service-level objectives (SLO). In this paper, we develop a systematic framework for characterizing LLM inference parallelism via throughput-latency trade-offs, SLO-aware serving, and long-context scalability. We introduce the notion of parallelism operating regions by constructing TTFT-ITL feasible sets and Pareto frontiers across different workload compositions, thereby revealing a systematic transition from TP-dominant to PP-dominant configurations as workloads become increasingly prefill-heavy. We further formulate SLO-aware parallelism selection using goodput, showing that stringent TTFT requirements favor PP-dominated configurations, whereas relaxed latency constraints progressively shift the optimality toward TP-dominated configurations with higher serving capacity. Finally, we demonstrate that increasing context length fundamentally changes the relative advantages of parallelism configurations, with PP-dominant configurations exhibiting more favorable scalability and SLO attainment in the long-context regime.
0
cs.LGcs.AI Min-Young Yu · Oct 14, 2026

Policy-Verified Self-Training asks whether a runtime policy gate's discarded verdicts can be recycled as training signals for the same agent. The paper proposes PVST: an agent rolls out trajectories, a deterministic gate compiled from written policy judges compliance, and the verdicts become acceptance filters and preference labels. On AgentDojo prompt-injection benchmarks, post-training Qwen3-8B with these verifier-derived rewards cuts violating trajectories from 37.2% to 10.3% and successful attacks to 0.5% without any stronger teacher model, human preference labels, or attack-specific supervision. The result suggests that compiled policy checkers can serve not only as runtime constraints but as a scalable, auditable source of self-training supervision.

Runtime policy verifiers can prevent agents from executing disallowed actions, but their decisions are typically used only for enforcement and discarded afterward. We ask whether these decisions can instead become verifiable policy rewards for training the agents they guard. We introduce Policy-Verified Self-Training (PVST), a post-training paradigm in which an agent generates its own interaction trajectories and an executable policy verifier, here a deterministic gate compiled from a written policy, evaluates whether each action complies. Compliant trajectories are reinforced, and violations become negatives for preference optimization; beyond the gate and the benchmark's task-success signal, PVST needs no stronger teacher model, no human preference labels and no attack-specific supervision, although rollouts are collected in the benchmark's attacked environment. On held-out AgentDojo tasks under prompt injection, policy-verified preference training of Qwen3-8B reduces violating trajectories from 37.2% to 10.3 $\pm$ 0.9% (three seeds) and successful attacks from 12.4% to 0.5% at equal or higher pooled task utility, although utility falls on travel, compared with 22.0% when negatives are selected by an attack oracle and 31.9 $\pm$ 0.9% with negatives that contain no violation. The learned behavior holds under an attack template never used in training (37.7% to 11.0%) and on a suite excluded from training (34.8% to 16.7%), and the retained verifier's intervention rate falls from 39.2% to 8.8% (seed 0). Our analysis identifies two conditions under which the verdict is most informative: success must not already imply compliance, and guarded actions must appear in both permitted and forbidden contexts.