AI Papers of the Week
Every paper worth reading in AI, hand-picked one week at a time.
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:
Generalizable AI Predicts Immunotherapy Outcomes Across Cancers and Treatments
Introduces COMPASS, a concept bottleneck-based foundation model that predicts patient response to immune checkpoint inhibitors (ICIs) using tumor transcriptomic data. Unlike prior biomarkers (TMB, PD-L1, or fixed gene signatures), COMPASS generalizes across cancer types, ICI regimens, and clinical contexts with strong interpretability and performance. Key contributions:
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:
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.
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:
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.
Reward Modeling as Reasoning
This work proposes a new class of reward models, called ReasRMs, that reformulate reward modeling as a reasoning task. The authors introduce RM-R1, a family of generative reward models that produce interpretable reasoning traces and rubrics during preference judgments. Instead of relying on scalar scores or shallow generation, RM-R1 models leverage structured reasoning and reinforcement learning to improve both interpretability and performance across benchmarks.
Practical Efficiency of Muon for Pretraining
Discusses how Muon, a simple second-order optimizer, outperforms AdamW in large-batch pretraining by expanding the compute-time Pareto frontier and maintaining better data efficiency. Combined with muP scaling and a novel telescoping algorithm for hyperparameter transfer, it enables faster training with minimal tuning overhead up to 4B parameter models.
Phi-4-Mini-Reasoning
Microsoft released Phi-4-Mini-Reasoning to explore small reasoning language models for math. Highlights:
Kimi-Audio
Kimi-Audio is a new open-source audio foundation model built for universal audio understanding, generation, and speech conversation. The model architecture uses a hybrid of discrete semantic audio tokens and continuous Whisper-derived acoustic features. It is initialized from a pre-trained LLM and trained on 13M+ hours of audio, spanning speech, sound, and music. It also supports a streaming detokenizer with chunk-wise decoding and a novel look-ahead mechanism for smoother audio generation. Extensive benchmarking shows that Kimi-Audio outperforms other audio LLMs across multiple modalities and tasks. Key highlights:
MiMo-7B
Xiaomi releases MiMo-7B, a new language model for reasoning tasks. MiMo-7B is explicitly designed for advanced reasoning across math and code. Highlights:
LLM for Engineering
This work finds that when RL is used, a 7B parameter model outperforms both SoTA foundation models and human experts at high-powered rocketry design.
Does RL Incentivize Reasoning in LLMs Beyond the Base Model?
This paper revisits a key assumption in recent LLM development: that Reinforcement Learning with Verifiable Rewards (RLVR) helps models acquire genuinely new reasoning capabilities. By analyzing models across tasks (math, code, vision) using pass@k metrics (with large k), the authors find that RLVR improves sample efficiency but does not expand reasoning capacity beyond the base model.
BitNet b1.58 2B4T
This work introduces BitNet b1.58 2B4T, the first open-source, natively trained 1-bit LLM at the 2B parameter scale, achieving strong performance while being extremely efficient. The model uses a custom ternary quantization scheme (1.58 bits per weight), enabling dramatic reductions in memory (0.4 GB), energy (0.028J/token), and latency (29ms), while still competing with state-of-the-art full-precision models across diverse benchmarks.
Tiny Reasoning Models
Tina is a family of 1.5B parameter reasoning models trained using LoRA-based reinforcement learning (RL) to achieve high reasoning accuracy at very low cost. It outperforms or matches full fine-tuned models on reasoning tasks like AIME and MATH with only ~$9 post-training cost, demonstrating that efficient reasoning can be instilled via minimal updates to a tiny model.
GUI-R1
Researchers from the National University of Singapore and the Chinese Academy of Sciences introduce GUI-R1, a reinforcement learning (RL) framework aimed at improving graphical user interface (GUI) agents through unified action-space modeling. Key insights include:
Scaling Reasoning in Diffusion LLMs via RL
Proposes d1, a two‑stage recipe that equips masked diffusion LLMs with strong step‑by‑step reasoning.
Enhancing Non-Reasoning Models with Reasoning Models
Researchers explore how to distill reasoning-intensive outputs (answers and explanations) from top-tier LLMs into more lightweight models that don’t explicitly reason step by step. By fine-tuning smaller models on the high-quality final answers (and optionally summarized thinking traces) from advanced reasoning models, they demonstrate consistent performance boosts across multiple benchmarks.
OLMOTrace
Allen Institute for AI & University of Washington present OLMOTRACE, a real-time system that traces LLM-generated text back to its verbatim sources in the original training data, even across multi-trillion-token corpora.
Concise Reasoning via RL
This new paper proposes a new training strategy that promotes concise and accurate reasoning in LLMs using RL. It challenges the belief that long responses improve accuracy; it offers both theoretical and empirical evidence showing that conciseness often correlates with better performance.
Rethinking Reflection in Pre-Training
Reflection — the ability of LLMs to identify and correct their own reasoning — has often been attributed to reinforcement learning or fine-tuning. This paper argues otherwise: reflection emerges during pre-training. The authors introduce adversarial reasoning tasks to show that self-reflection and correction capabilities steadily improve as compute increases, even in the absence of supervised post-training. Key contributions:
Efficient KG Reasoning for Small LLMs
LightPROF is a lightweight framework that enables small-scale language models to perform complex reasoning over knowledge graphs (KGs) using structured prompts. Key highlights:
One-Minute Video Generation with Test-Time Training
One-Minute Video Generation with Test-Time Training introduces TTT layers, a novel sequence modeling component where hidden states are neural networks updated via self-supervised loss at test time. By integrating these into a pre-trained diffusion model, the authors enable single-shot generation of one-minute, multi-scene videos from storyboards, achieving 34 Elo points higher than strong baselines like Mamba 2 and DeltaNet in human evaluations
Command A: An Enterprise-Ready LLM
Cohere announced Command A, a 111B parameter open-weights LLM built for enterprise-grade RAG, agents, code, and multilingual tasks. Key contributions: ● Modular expert merging for domain mastery – Instead of monolithic post-training, Command A uses a decentralized training pipeline. Separate expert models are fine-tuned for specific domains (e.g., math, RAG, multilingual, safety, code), then merged into one model using efficient weighted parameter soup techniques. This preserves most expert performance with just ~1.8% average drop. ● Hybrid architecture for long-context efficiency – Command A interleaves sliding window and full attention layers, achieving 256k context support with drastically lower KV cache memory usage—e.g., only ~33% of LLaMA 3 70B at 128k. It scores 95.0% on RULER, outperforming most long-context peers. ● Superb agentic capabilities – Built for RAG, tool use, and ReAct-style agents, Command A beats GPT-4o and Claude 3.5 on TauBench and BFCL. Tool use is trained via a blend of human-annotated and synthetic data, then aligned with CoPG and SRPO (self-improving preference optimization). ● Best-in-class enterprise evaluations – On real-world generative tasks (e.g., chat summarization, FAQ generation) and RAG use cases (long workplace policy documents), Command A tops the leaderboard with 94.2% pass rate, 4.73 correctness, and 91% unanswerable QA accuracy. ● Multilingual excellence – Command A is trained in 23 global languages with heavy data curation and preference tuning. It scores #1 in dialect alignment (ADI2), 90.3% average LPR (language consistency), and outperforms LLaMA 3.3, GPT-4o, and DeepSeek in manual Arena-style win rates across all languages. ● Polishing for human alignment – Final alignment used a ping-pong loop of offline SRPO and online CoPG with RLHF. This yielded +17pt human win rate gains on code, +10pt on reasoning, and lifted Command A’s win rate over GPT-4o to parity (~50.4%). ● Fast, efficient, and open – Despite its power, Command A runs on just 2×A100s or H100s and generates 156 tokens/sec—faster than GPT-4o and DeepSeek. Model weights are released (CC-BY-NC) on Hugging Face.