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Xiuyu Li
@sheriyuo
Researcher @StepFun_ai | Working on long-horizon tasks | Prev @RUC1937 | Opinions are my own
1.7K Following    12.4K Followers
Same for undergrad, master and industrial job. Productivity decides everything and the coding plan decides productivity. Ever since someone sponsored the API for me I finally got to taste this feeling. Still really grateful for all the support here. Everyone is very kind. So if you need industry positions feel free to reach out. Happy to referral or just chat for help 🤗
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Nowadays, doing a PhD only makes sense if your advisor is happy to support at least one 20x plan (and maybe a 100x one someday). Luckily, that’s actually true in our lab. It’s basically a requirement now lol. Really, really grateful to both @zicokolter and Kaiming for pushing for this ages ago — and especially to Zico for actually footing the bill. ❤️
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Proud to be part of this collaboration! 🎉 Huge thanks to the vLLM team, Ant Group, and FastAFD. Excited to bring AFD to the open-source community.
As part of this launch, biology-related requests that are blocked on Fable 5 will now route to Opus 5 rather than Opus 4.8 👀
Introducing Claude Opus 5. It's a thoughtful and proactive model that comes close to the frontier intelligence of Fable 5 at half the price.
Nice results across diverse tasks with Ling-3.0-Flash 👀 It's a great example of how compact execution models can still be highly capable when given a focused role within a larger agent system. The hybrid reasoning design is also interesting: spending compute only when needed while keeping the default execution path lightweight feels like a practical direction for production agents. Hope to see more Chinese open-source models continue pushing in this direction, optimizing for both efficiency and real-world agent workflows.
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Today, we’re releasing Ling-3.0-flash—a hybrid-reasoning MoE model built for production-scale agents. 124B parameters. Just 5.1B active per token. With 1/8 of the total and 1/12 of the active parameters, it matches or beats our 1T flagship model on most benchmarks shown.
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SOAP, Muon, and Beyond: Pushing LLM Pretraining Scales Paper:
Proximal Policy Optimization (PPO) has been the foundational standard for LLM post-training, yet it quietly suffers from a fatal flaw in long-horizon reasoning: exploration collapse. 🧐 We explore the root cause: PPO suffers from a decade-old Geometric Fallacy! Excited to share our paper published in ICML 2026: "Beyond Euclidean Clipping: Overcoming Exploration Collapse in LLM RL via Riemannian Isometric Policy Optimization" paper: blog: work with: @hello_gensi @ericguoxy @yaqinzhang @haozhou_ai 🚨 PPO’s Geometric Mismatch 🔻 PPO-Clip implicitly adopts a Euclidean metric, resulting in a geometric mismatch with the non-uniform Riemannian policy manifold. 🔻 This mismatch pathologically suffocates trust regions for low-probability tokens while overly expanding high-probability ones, polarizing the policy and triggering exploration collapse! 🚀 Introducing RIPO (Riemannian Isometric Policy Optimization) 🔹 Method: RIPO dynamically aligns isometric trust regions with local geometry, allowing larger updates for low-probability actions while tightening updates for high-probability ones to achieve a balanced exploration-exploitation trade-off. 🔹 Bonus: Geometric isometry mathematically induces statistical homoscedasticity, balancing bias-variance trade-off for fast, stable training! 📌 Key Results 🔹 35% Avg Gain over GRPO: RIPO consistently refresh SOTA across 7 competition-level mathematical reasoning benchmarks. 🔹 5x Token Efficiency: RIPO reaches GRPO's 200-step performance in just 40 steps with highly stable gradient norms. 🔹 Sustained Exploration: RIPO maintains policy entropy at a healthy level throughout late-stage training, preserving policy diversity. 🔹 Unlocks Pass@K Scaling Ceiling: On HMMT25, RIPO outperforms GRPO by a massive 50% of Pass@128, breaking the intrinsic ceiling of base models! 🌟 Summary RIPO is simple, principled, and highly effective. By replacing PPO's heuristic Euclidean clip with a dynamic, geometrically aligned clip, it offers a new foundation for RL scaling in LLM reasoning.
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Let's all listen to the teachings of Saint Liang Here comes the extended audio of the investor meeting excerpt that was all over everyone's timeline yesterday.
Liang Wenfeng: Continual learning is the next step, embodied intelligence is the endgame. Too much to learn from Liang's argument ...
SLAI T-Rex raises full-parameter DeepSeek-V4-Pro post-training on Ascend from 11.67% to 34.22% MFU, then demonstrates a solver-grounded CPT and SFT pipeline on the Flash model. SLAI T-Rex: Full-Parameter Post-training of the DeepSeek-V4 Family on Ascend SuperPOD Paper:
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Criteria-based GRPO + β·OPSD, where the RL objective regularizes self-distillation, avoiding the collapse observed under pure self-distillation 👀
Improving exploration for rubric RL using OPSD to generate guidance for underexplored or penalized criteria. As combining criteria to construct rewards is common maybe it could be useful beyond rubric RL.
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Also feels like a similar angle to Apollo's recent reward-seeking work. Paper:
Interesting pattern that's worth studying more systematically 👀 This is exactly why we need much more analysis of long-horizon tasks.
Maybe we're seeing a closer academic approach toward the Meta-RL endpoint.
(1/n) Introduce LLM-as-a-Coach for non-verifiable tasks. Scalar rewards discard rich feedback. LLM-as-a-Coach guides policy with context, leveraging high bandwidth to provide rich experiential knowledge that preserves fine-grained preference on non-verifiable tasks.
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Interesting pattern that's worth studying more systematically 👀 This is exactly why we need much more analysis of long-horizon tasks.
OPSD will likely become an auxiliary objective for dense credit assignment 🧐
𝗢𝗻-𝗽𝗼𝗹𝗶𝗰𝘆 𝗱𝗶𝘀𝘁𝗶𝗹𝗹𝗮𝘁𝗶𝗼𝗻 𝗶𝘀𝗻'𝘁 𝗮 𝗳𝗿𝗲𝗲-𝗹𝘂𝗻𝗰𝗵 On-policy distillation has become a default post-training tool in many open-source frontier model training recipes. Recent releases lean on it heavily: DeepSeek v4, MiMO, and Nemotron-Cascade-2 use MOPD, and GLM 5.x uses on-policy cross-stage self-distillation. It provides RL's on-policy nature reducing exposure bias, while providing token level supervision like SFT. But OPD and OPSD have their own failure modes. In this post I discuss a few of them: 1. 𝗘𝗮𝗿𝗹𝘆 𝗺𝗶𝘀𝘁𝗮𝗸𝗲𝘀 𝗮𝗿𝗲 𝘀𝘁𝗿𝘂𝗰𝘁𝘂𝗿𝗮𝗹𝗹𝘆 𝘂𝗻𝗰𝗼𝗿𝗿𝗲𝗰𝘁𝗮𝗯𝗹𝗲. When the student samples a rollout and takes an early wrong turn, the per-token KL computed along that frozen rollout cannot pull it back onto a correct path. TRD proves that this failure is built into the objective rather than being a matter of noisy gradients. Even with a perfect teacher, the gradient obtained from token-level KL on the student's own rollout agrees with the ideal corrective gradient at exactly one point, the token where the student first diverged, and disagrees everywhere after it. Every later supervision target is therefore anchored to a context that the student should never have entered. Because reweighting or clipping only rescales the magnitude of each token's gradient, and here the terms point in the wrong direction, no per-token adjustment can recover the correct update. TRD's proposed fix is to distill along a teacher-refined trajectory rather than the raw student rollout, which restores a target the student can actually follow. 2. 𝗔 𝘀𝘁𝗿𝗼𝗻𝗴𝗲𝗿 𝘁𝗲𝗮𝗰𝗵𝗲𝗿 𝗰𝗮𝗻 𝗯𝗲 𝗮 𝘄𝗼𝗿𝘀𝗲 𝘁𝗲𝗮𝗰𝗵𝗲𝗿. On-policy distillation can only teach the student at states the student itself visits, and the usable signal at each of those states lives in the overlap between the student's and teacher's next-token distributions. Rethinking OPD shows that a bigger, higher-scoring teacher can fail to move a student while a weaker one succeeds, because if the teacher's token distribution places its mass on tokens the student rarely produces, the overlap is small and almost nothing transfers, no matter how capable the teacher is in absolute terms. What actually predicts success is early top-k thinking-pattern overlap. In runs that work, the shared top-k tokens carry 97 to 99% of the probability mass and the overlap ratio climbs steadily during training, whereas a run that starts with low overlap never recovers it. A teacher trained on the same recipe as the student also converges toward the student's own distribution, so its higher benchmark score does not correspond to any new knowledge it can transfer. The practical rule is to pick teachers by distributional closeness to the student, not by leaderboard rank. 3. 𝗣𝗿𝗶𝘃𝗶𝗹𝗲𝗴𝗲𝗱-𝗶𝗻𝗳𝗼𝗿𝗺𝗮𝘁𝗶𝗼𝗻-𝗰𝗼𝗻𝗱𝗶𝘁𝗶𝗼𝗻𝗲𝗱 𝗢𝗣𝗦𝗗 𝗰𝗮𝗻 𝗳𝗮𝗶𝗹 𝘁𝗼 𝘁𝗿𝗮𝗻𝘀𝗳𝗲𝗿. In OPSD you distill a teacher that was conditioned on privileged information, such as the gold answer, into a student that will never have it. The Many Faces of OPD shows what goes wrong when that information is instance-specific. The student cannot recover the teacher's per-instance reasoning, since it never sees the answer, so it instead learns a single answer-free policy that effectively averages the teacher's behavior across all problems, and that averaged policy is too generic to solve any particular one. The signature is initial gains followed by collapse: rollouts grow long, fill with hedging tokens, and accuracy craters toward zero. The approach works only when the privileged information is a shared rule that applies across all instances, such as a system prompt or an alignment preference, and not when it is a per-problem answer. 4. 𝗧𝗵𝗶𝗻𝗸𝗶𝗻𝗴 𝗰𝗼𝗹𝗹𝗮𝗽𝘀𝗲: 𝗱𝗲𝗻𝘀𝗲 𝘀𝘂𝗽𝗲𝗿𝘃𝗶𝘀𝗶𝗼𝗻 𝘀𝘂𝗽𝗽𝗿𝗲𝘀𝘀𝗲𝘀 𝘁𝗵𝗲 𝗺𝗼𝗱𝗲𝗹'𝘀 𝗼𝘄𝗻 𝗱𝗲𝗹𝗶𝗯𝗲𝗿𝗮𝘁𝗶𝗼𝗻. A teacher conditioned on the answer has no reason to hesitate, backtrack, or explore, so its per-token targets quietly push down the student's deliberation tokens. Diagnosing and Mitigating Thinking Collapse names this phenomenon thinking collapse: over training, the student's native reasoning behavior erodes as the exploratory tokens that carry it, words like wait, maybe, and alternatively, become progressively less frequent. The mechanism is local rather than global. The damage concentrates at high-entropy decision forks, the branch points where the student is genuinely uncertain and would normally deliberate. Exactly there, the student's top-1 token is often an exploratory marker while the answer-conditioned teacher's top-1 token is not, so the mismatch produces a strong gradient that suppresses the very tokens that make reasoning work. The result is a model whose native reasoning behavior is measurably suppressed, and downstream reasoning accuracy falls in step with it.
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GEAR turns long-context grounding into a reward-shaping problem, by rewarding n-gram overlap with annotated evidence while penalizing overlap with distractors, reducing both copying and reasoning length. The method still depends on automatically generated evidence annotations and overlap proxies, but it gives long-context RL a concrete selectivity objective instead of another generic accuracy bonus. Copy Less, Ground More: Overcoming Repetitive Copying in Long-Context Reasoning via Evidence-Aware Reinforcement Learning Paper:
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So it really just means that V4 did not perform well during training from the start 🧐
There are two hypotheses for the DeepSeek-V4's strange performance (as in, V4-Flash is about as good as we expected, but V4-Pro is disappointing given its scale): 1) failed pretrain 2) big difference in the RL/MOPD stage Flash probably got multiple such iterations
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⚙ LongCat-2.0 is really a story about adapting frontier LLMs to domestic compute Zhihu contributor Robin shared a technical take on Meituan’s open-source trillion-parameter model LongCat-2.0, from the perspective of both an early LongCat-2.0-Preview user and a former Ascend 910 user. The key point is not just “Meituan released a huge model.” It is that LongCat-2.0 shows how much work is needed to make a frontier-scale MoE model actually train on domestic accelerators: precision alignment, kernel optimization, memory pressure, parallelism, reliability, and training stability all have to move together. 🧩 LongCat-Next was the proof of concept Robin frames LongCat-Next as a PoC for LongCat-2.0. Even at that stage, you could already see the hard engineering around Ascend 910: BF16 precision alignment, kernel optimization, ScMoE with chunking on expert parallelism, and reliability work. LongCat-Flash-Lite’s N-gram Embedding is also inherited, while the newer architectural addition is LongCat Sparse Attention, which will likely get more technical analysis from the community. 🔥 The real new content is large-scale training According to Robin, the most important new part of the LongCat-2.0 tech blog is not inference, but large-scale training. Scaling from LongCat-Next to a SOTA-sized model is already hard. Doing it on Ascend 910 makes it harder because of VRAM pressure and ecosystem constraints. Compared with LongCat-Next, LongCat-2.0 switched to Muon, which Robin sees as another endorsement of the optimizer. On the memory side, Zero-1, recomputation, and offloading are now almost standard tools; Meituan’s more distinctive piece is the use of zero-computation experts. The broader system also points to a deeper hardware-software fit: supernodes and 6D parallelism are close to the design logic behind Huawei’s 384-card supernode idea. 🇨🇳 Domestic compute is not a drop-in replacement This is the part worth highlighting. LongCat-2.0 suggests that domestic compute for large models is not simply about swapping NVIDIA cards for Chinese accelerators. The model, training stack, precision path, parallel strategy, communication layer, and reliability system all have to be adapted together. Robin points to several key lessons from Ascend 910 training work: Correctness alignment comes first. Router TP and NormHead fixes under MindSpeed matter. Training stability needs long, careful treatment. Cost calculation is not a side note; it affects whether this path is practical. The bigger message: domestic AI chips become useful for frontier LLMs only when the model architecture and the training system are co-designed around their constraints. 🧱 What Ascend 910 proved, and what it cost Robin is cautiously respectful but not blindly optimistic. With enough Ascend 910 cards, certain frontier-scale paths now look possible. Models around the DeepSeek V4-Flash or DeepSeek-V3.2 scale may be trainable. At the 1.6T LongCat-2.0 scale, the ceiling may be high enough to approach very strong models if teams and compute are organized well. But the cost was high. The 910 product line caused real engineering pain across its lifecycle. From release to actually carrying serious training workloads, the path was long and expensive. Robin’s question is what happens to deployed 910 clusters next: do they shift mostly to inference, or do teams continue integrating and squeezing out their remaining training potential? The hope is that experience accumulated on 910 does not get reset when Ascend 950 arrives. A100 and even V100 still create value today; 910 should not be treated as disposable if the software and architecture lessons can carry forward. 🚀 What this means for Ascend 950 Robin expects the 910 experience to transfer directly to 950 training. The most valuable lessons are around scale-up, precision alignment, loss spikes, reliability, and the messy parts of keeping a large cluster alive. Bigger VRAM will help. But even with 950, memory will still be tight for the largest models. FP8 support is another major shift, but the larger point is continuity: the most expensive hardware is not hardware with too many specs, but hardware whose architecture and software stack cannot inherit past work. That is why the LongCat-2.0 story matters for domestic compute. It creates reusable knowledge for training large models on Chinese accelerators, instead of treating each generation as a one-off fight. ⚠️ Bigger clusters matter, but fragmentation is dangerous Robin also warns against the “small blast furnace” trap: trying to build frontier models with scattered, undersized clusters. For large model training, cluster size is a hard constraint. A large cluster can always use only part of its capacity. A small cluster runs into limits that cannot be wished away. So the industry impact is not just technical. It is organizational: serious frontier training may require concentrating domestic compute, not spreading it too thinly. 🧠 Model capability is not yet the whole win Robin is more reserved about LongCat-2.0’s model quality. After testing the preview tokens, the model felt undertrained in pretraining and somewhat unstable in post-training. Reasoning seemed weak under constrained thinking budgets, and longer thinking sometimes led to overthinking instead of better answers. Agentic behavior also had rough edges, such as writing scripts into the home directory too freely. So the conclusion is nuanced: LongCat-2.0 may not prove that Meituan already has SOTA control over a model at this size. But it does show something else very clearly: Meituan’s AI infrastructure capability is close to the frontier. ✅ The real impact LongCat-2.0’s impact is not just that another trillion-parameter model exists. Its real significance is that it pushes forward the adaptation loop between domestic accelerators and large-model training: hardware constraints force model and system changes model scale exposes gaps in precision, memory, kernels, and reliability training pain creates reusable infrastructure experience that experience can carry into the next generation of domestic compute In other words, LongCat-2.0 is less a simple model release and more an engineering checkpoint. It shows that China’s AI stack is moving from “can domestic compute run inference?” toward a harder question: can domestic compute support the full lifecycle of frontier-scale LLM training and deployment? 🔗 Full analysis: #LongCat# #Meituan# #AIInfra# #LLM# #ChinaAI# #Ascend# #MoE# #OpenSourceAI#
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SWE-Pro, DeepSWE, SWE-Multilingual, SWE-Interact, … , SWE-World 👀
From Long-horizon Tasks to Endless Frontier Tasks. The next frontier for LLM agents may not be merely completing longer and more complex workflows, but continuously improving open-ended objectives with no fixed endpoint. These tasks require agents to autonomously conduct broad research, propose hypotheses, design and run experiments, judge their own results, identify failure modes, refine strategies, and repeat this loop again and again. The goal is not to finish a task, but to keep pushing the frontier. Examples include exploring mathematical theories, discovering scientific hypotheses, finding market alpha, improving model training recipes, optimizing codebases, designing better products, running autonomous security research, and even improving agent systems themselves. Long-horizon tasks test whether agents can complete a difficult workflow. Endless Frontier Tasks test whether agents can sustain discovery, optimization, and self-improvement over time.
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HIPPO targets a quiet contaminant in RL for reasoning: pre-RL data overlap. When the RL dataset overlaps with pretraining or SFT corpora, the model can exploit the shortcut of recalling a memorized answer and then fabricating post-hoc reasoning to match, so the reward goes up while genuine reasoning does not. The framework injects hints and uses a pairwise objective designed to break that shortcut, forcing the model to reason toward the answer rather than reverse-engineer a justification for one it already memorized. To Reason or to Fabricate: Reasoning Without Shortcuts via Hint-Anchored Pairwise Optimization Paper:
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Keep cooking 🙌
Step 3.7 Flash is currently top 10 on @OpenRouter this month, with 4.29T tokens routed. Builders are pushing it through real agent runs, coding tasks, and long-context workflows. Keep sending the hard stuff.
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The industry's first trillion-parameter model to complete end-to-end training and inference on a 50,000-GPU Chinese computing cluster 👀
Introducing LongCat-2.0 🐱 1.6T parameters · MoE with ~48B active · 1M context The full model behind Owl Alpha on @OpenRouter — now available. Built for agentic coding from the ground up: ◆ LongCat Sparse Attention (LSA) — scales efficiently for 1M-context tokens ◆ Zero-Compute Experts — dynamic activation 33B–56B per token, zero wasted compute ◆ MOPD — three specialized expert groups (Agent / Reasoning / Interaction), gate-routed per task How it stacks up: → Terminal-Bench 2.1: 70.8 → SWE-bench Pro: 59.5 (GPT-5.5: 58.6) → SWE-bench Multilingual: 77.3 → FORTE: 73.2 · RWSearch: 78.8 · BrowseComp: 79.9 📖 Tech Blog: Try it across different scenarios 🧵👇
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