AI Papers of the Week
Every paper worth reading in AI, hand-picked one week at a time.
RewardBench 2
RewardBench 2 is a new multi-skill benchmark for evaluating reward models with more challenging human prompts and stronger correlation to downstream performance. It highlights gaps in the current reward model's effectiveness and aims to support more rigorous evaluation, showing existing models score ~20 points lower than their predecessor.
New Lens on RAG Systems
Introduces a new conceptual and empirical framework for analyzing RAG systems through the lens of sufficient context, whether the retrieved content alone enables answering a query. This notion helps decouple retrieval failures from generation errors in LLMs, providing clarity on model behavior under different contextual adequacy. Key findings:
Open-Ended Evolution of Self-Improving Agents
This work presents the Darwin Gödel Machine (DGM), a system that advances the vision of self-improving AI by combining self-referential code modification with open-ended evolutionary search. Unlike the original Gödel machine, which requires provable benefits for code changes (a practically intractable constraint), the DGM adopts an empirical approach: it modifies its own codebase and evaluates improvements on coding benchmarks. Key contributions and findings:
Learn to Reason via Mixture-of-Thought
While most prior approaches train with a single modality and only ensemble during inference, this work introduces Mixture-of-Thought (MoT) to jointly train and infer across modalities, resulting in notable gains in logical reasoning performance. Key findings:
QwenLong-L1
A new reinforcement learning framework that scales large reasoning models (LRMs) from short to long contexts using progressive context scaling and hybrid rewards. It achieves top performance on seven long-context benchmarks, surpassing models like OpenAI-o3-mini and Qwen3-235B-A22B, and matching Claude-3.7-Sonnet-Thinking, demonstrating strong reasoning with up to 120K token inputs.
End-to-End Policy Optimization for GUI Agents
ARPO introduces an end-to-end reinforcement learning method for training GUI agents using Group Relative Policy Optimization (GRPO) with experience replay. It significantly improves in-domain performance on the OSWorld benchmark, outperforming baselines by up to 6.7%, while offering modest gains on out-of-domain tasks and enabling self-corrective behaviors through structured reward feedback.
Generalist Agent Enabling Scalable Agentic Reasoning
Proposes Alita, a generalist agent framework that enables scalable agentic reasoning through minimal predefinition and maximal self-evolution. Unlike traditional agents reliant on handcrafted tools, Alita autonomously constructs reusable MCPs (Model Context Protocols) using web search and code synthesis, outperforming more complex systems like OpenAI DeepResearch and OctoTools on GAIA, MathVista, and PathVQA benchmarks.
EfficientLLM
Introduces the first large-scale, empirical benchmark for evaluating efficiency trade-offs in LLMs across architecture, fine-tuning, and inference. Conducted on a high-performance cluster (48×GH200, 8×H200 GPUs), the study evaluates over 100 model–technique pairs spanning 0.5B–72B parameters, using six metrics: memory utilization, compute utilization, latency, throughput, energy consumption, and compression rate. Key insights include:
J1
Introduces a novel training approach for LLMs to act as evaluators (LLM-as-a-Judge) by explicitly incentivizing thoughtful reasoning during judgment. Instead of relying solely on prompting or preference fine-tuning, J1 employs online reinforcement learning with verifiable rewards to teach models to think through evaluations systematically. Key insights:
The Pitfalls of Reasoning for Instruction- Following in LLMs
Explores an unexpected flaw in reasoning-augmented large language models (RLLMs): while chain-of-thought (CoT) prompting often boosts performance on complex reasoning tasks, it can degrade instruction-following accuracy. The authors evaluate 15 models (e.g., GPT, Claude, LLaMA, DeepSeek) on two instruction-following benchmarks and find that CoT prompting consistently reduces performance across nearly all models and datasets. Key findings:
Towards a Deeper Understanding of Reasoning in LLMs
This paper investigates whether LLMs can adapt and reason in dynamic environments, moving beyond static benchmarks. Using the SmartPlay benchmark—a suite of four interactive games that require diverse cognitive skills—the authors evaluate three prompting strategies: self-reflection, heuristic mutation (via an Oracle), and planning. They test these methods across models of varying size (Llama3-8B to Llama3.3-70B) and draw several conclusions on how model scale and prompting interact with task complexity. Key findings:
MedBrowseComp
MedBrowseComp is a new benchmark designed to evaluate LLM agents’ ability to perform complex, multi-hop medical fact-finding by browsing real-world, domain-specific web resources. Testing over 1,000 clinically grounded questions, the benchmark reveals major capability gaps in current models, with top systems achieving only 50% accuracy and GUI-based agents performing even worse.
ARC-AGI-2
ARC-AGI-2 is a new benchmark designed to push the boundaries of AI reasoning beyond the original ARC-AGI. It introduces harder, more unique tasks emphasizing compositional generalization and human-like fluid intelligence, with baseline AI models performing below 5% accuracy despite strong ARC-AGI-1 results.
AlphaEvolve
AlphaEvolve is a coding agent developed by Google DeepMind that uses LLM-guided evolution to discover new algorithms and optimize computational systems. It orchestrates a pipeline where LLMs generate code changes, evaluators provide feedback, and an evolutionary loop iteratively improves solutions. AlphaEvolve shows that LLMs can go beyond conventional code generation and assist in scientific and algorithmic discovery. Key highlights:
LLMs Get Lost in Multi-Turn Conversation
Investigates how top LLMs degrade in performance during underspecified, multi-turn interactions, common in real-world usage but rarely evaluated. The authors introduce a novel "sharded simulation" framework that breaks down fully-specified instructions into gradual conversation shards, simulating how users naturally provide information over time. Key findings:
RL for Reasoning in LLMs with One Training Example
This paper shows that Reinforcement Learning with Verifiable Rewards (RLVR) can significantly improve mathematical reasoning in LLMs even when trained with just a single example. On the Qwen2.5-Math-1.5B model, one-shot RLVR improves accuracy on the MATH500 benchmark from 36.0% to 73.6%, nearly matching performance achieved with over 1,200 examples. Two-shot RLVR (with two examples) even slightly surpasses that, matching results from full 7.5k example training.
AM-Thinking-v1
Introduces a dense, open-source 32B language model that achieves state-of-the-art performance in reasoning tasks, rivaling significantly larger Mixture-of-Experts (MoE) models. Built upon Qwen2.5-32B, the model is trained entirely with public data and showcases how a meticulously crafted post-training pipeline can unlock competitive performance at mid-scale sizes. Key points:
HealthBench
HealthBench is a benchmark of 5,000 multi-turn health conversations graded against 48,562 rubric criteria written by 262 physicians across 60 countries. Unlike prior multiple-choice evaluations, HealthBench supports open-ended, realistic assessments of LLM responses across diverse health themes (e.g., global health, emergency care, context-seeking) and behavioral axes (accuracy, completeness, communication, context awareness, instruction following).
Nemotron-Research-Tool-N1
Introduces Tool-N1, a family of tool-using LLMs trained using a rule-based reinforcement learning (R1-style RL) approach, without reliance on supervised reasoning trajectories. The key idea is to enable models to learn to invoke external tools correctly through binary feedback based on functional correctness and format adherence, rather than step-by-step imitation.
CellVerse
Introduces a benchmark to evaluate LLMs on single-cell biology tasks by converting multi-omics data into natural language. While generalist LLMs like DeepSeek and GPT-4 families show some reasoning ability, none significantly outperform random guessing on key tasks like drug response prediction, exposing major gaps in biological understanding by current LLMs.
The Leaderboard Illusion
The Leaderboard Illusion investigates systemic distortions in how the Chatbot Arena leaderboard evaluates LLMs, arguing that current practices undermine fair model comparison and scientific progress. Through extensive data analysis covering 2M Arena battles, the authors identify four key issues distorting rankings:
Llama-Nemotron
NVIDIA introduces the Llama-Nemotron model series, LN-Nano (8B), LN-Super (49B), and LN-Ultra (253B), a family of open, efficient, and high-performing reasoning models. These models rival or outperform DeepSeek-R1 on various benchmarks while offering significantly better inference throughput and memory efficiency. LN-Ultra is noted as the most "intelligent" open model by Artificial Analysis. A key innovation is a dynamic reasoning toggle ("detailed thinking on/off") that allows users to control reasoning behavior at inference time. Highlights:
Discuss-RAG
This paper introduces Discuss-RAG, a plug-and-play agent-based framework that enhances retrieval-augmented generation (RAG) for medical question answering by mimicking human-like clinical reasoning. Standard RAG systems rely on embedding-based retrieval and lack mechanisms to verify relevance or logical coherence, often leading to hallucinations or outdated answers. Discuss-RAG addresses these gaps via a modular agent setup that simulates multi-turn medical discussions and performs post-retrieval verification. Key ideas:
The Value of RL in Fine-Tuning
This work shows that, in theory, every popular preference-fine-tuning objective collapses to maximum-likelihood estimation (MLE), yet experiments show a consistent RL advantage on real tasks. They reconcile this gap with a generation-verification complexity hypothesis.