Sébastien Rombauts (@SRombauts) header
Sébastien Rombauts (@SRombauts) profile picture

Senior software engineer at @Unity - Opinions are my own Author of the Git & @PlasticSCM source control plugins for @UnrealEngine #gamedev

Paris, France
Joined October 2010
Photo by Sébastien Rombauts (@SRombauts)Photo by Sébastien Rombauts (@SRombauts)Photo by Sébastien Rombauts (@SRombauts)Photo by Sébastien Rombauts (@SRombauts)Photo by Sébastien Rombauts (@SRombauts)Photo by Sébastien Rombauts (@SRombauts)Photo by Sébastien Rombauts (@SRombauts)Photo by Sébastien Rombauts (@SRombauts)Photo by Sébastien Rombauts (@SRombauts)Photo by Sébastien Rombauts (@SRombauts)
I have released version 1.6.0 of the @PlasticSCM plugin for @UnrealEngine 5.0, with support for the new Changelists UI🎉 github.com/PlasticSCM/UE4Pla… Cheers! #UnrealEngine5 #gamedev
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Sébastien Rombauts retweeted
My favorite illustration of a problem where intelligence is not the number one bottleneck is tuberculosis, which is covered fabulously by @johngreen in this lecture: youtu.be/7D-gxaie6UI?is=DKrV…
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BOOM! I happened to be shooting this galaxy when a star decided to explode. Pretty lucky! You can see it appear close to the galactic core. I’ll be shooting it every night for a while to watch it change brightness! This is comparing photos captured 10 days ago vs 5 min ago.
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Sébastien Rombauts retweeted
A year ago the question was which model. Now it's which harness. Pi, Exo, Claude Code, Codex, DeepSeek Harness and 4 others. Same model, same tasks, same runtime. 360 runs, 2 billion tokens. Pass rates: 50% to 67%. Cost per pass: $1.05 to $18.34. Introducing FrontierHarness Eval. 🧵
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How I feel about reducing genAI monitoring before developing better alternatives. RIP @IsiahWhitlockJr, cc @AoDespair
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A lot of hype around OpenAI's Astra model here on my timeline today. Apparently, this goes back to a new article from The Information, which said Astra is a "recurrent depth or looped transformer". It's always interesting to read about new or different approaches (including rumors about what the closed labs may be up to), but let's debunk this a bit. About 2 months ago, I shared the architecture details of Nanbeige, for example, where "Nanbeige4.2-3B is pretrained from scratch on 28T tokens with a Looped Transformer that reuses the layer stack to increase capacity without adding parameters." Yes, that's it. The looped transformer idea is just reusing layers in the transformer block. In the case of Nanbeige, the main idea is to reuse the same 22-layer stack (=transformer block) twice instead of once. So, effectively it extends the 22-layer architecture to 44 layers, but without duplicating the weights. In simple terms, this roughly doubles the size of the model (if we ignore the embedding and output layers for a second). But instead of requiring 2x the storage and RAM to host this model, it stays at the same size since we reuse the components. However, it's almost 2x as expensive in terms of compute, because we run the embedded text through almost 2x as many layers. Why? In the Nanbeige 4.2 technical report, the researchers found that two passes gave the best trade-off and retained about 75% of the token efficiency of a standard architecture. (More passes gave barely any gains but made the training much slower and much more expensive.) While, as far as I know, Nanbeige 4.2 is the first notable open-weight model that adopted this approach, the idea goes back to the NeurIPS paper "Mixture-of-recursions: Learning dynamic recursive depths for adaptive token-level computation". Actually, this paper proposes a mechanism that is a bit more sophisticated by adding a learned router that determines whether each token receives one, two, or more passes. So, easy tokens can exit early while harder tokens receive additional computation. In sum, Astra may be a really good model, but this shouldn't be about this "looped transformer aspect," which is just a tiny architectural tweak. Also, the statement "the new technique works in a way that obscures some or all of the AI's reasoning, otherwise known as 'chain-of-thought'" is not necessarily true with respect to the looped transformer method. It's possible that The Information journalist refers to some other technique or misunderstood the looped transformer method. Reusing layers does not by itself suppress visible chain of thought. It adds computation in hidden states before the next token is emitted, just as ordinary transformer layers do. But based on the information we have, the only plausible interpretation here is that if a model uses more of these recurrent passes, it may need to generate fewer intermediate reasoning tokens. So then more of its computation happens in latent activations that cannot be read as text. But we would get the same effect if we were scaling up the model size, like GPT 5.6 Luna -> GPT 5.6 Sol.
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Sébastien Rombauts retweeted
剑桥这回直接扔王炸了!! AI & ML经典教材全集直接免费开放,PDF随便下。 想学机器学习又不想被割韭菜买高价课的,这十本刷完,底子基本就硬了。 顺序从易到难排好了: 1️⃣ 《机器学习理解》——理论算法一把抓,零基础入门首选 🔗 cs.huji.ac.il/~shais/Underst… 2️⃣ 《机器学习数学基础》——数学底子弱的先把这本补上 🔗 mml-book.github.io/book/mml-… 3️⃣ 《机器学习算法的数学分析》——深入数学原理 🔗 tongzhang-ml.org/lt-book/lt-… 4️⃣ 《深度学习理论原理》——搞懂DL背后的理论根基 🔗 arxiv.org/pdf/2106.10165 5️⃣ 《神经网络与机器学习》——神经网络的系统讲解 🔗 arxiv.org/pdf/1901.05639 6️⃣ 《图深度学习》——图神经网络入门必读 🔗 yaoma24.github.io/dlg_book/d… 7️⃣ 《机器学习的算法视角》——从算法角度重新理解ML 🔗 people.csail.mit.edu/moitra/… 8️⃣ 《概率论:理论与实例》——概率基础打牢 🔗 sites.math.duke.edu/~rtd/PTE… 9️⃣ 《应用概率基础》——概率论实战应用 🔗 sites.math.duke.edu/~rtd/EP4… 🔟 《高级数据分析》——数据科学进阶必备 🔗 stat.cmu.edu/~cshalizi/ADAfa… 说句实话,这些书没一本是轻松的,别指望躺着翻完。 但只要你能硬啃下来两三本,比听群里吹一年AI牛逼都管用。
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Sébastien Rombauts retweeted
🦔Reuters obtained internal Meta data on what happened after Zuckerberg cut 8,000 workers and moved 7,000 into AI roles. AI-generated code changes jumped 220%. New features reaching users only rose 36%. Major incidents spiked 40%. Time spent firefighting those incidents up 70%. Employee sentiment dropped from 74% to 55% favorable. Hours before the first round of layoffs went out, Zuckerberg quietly cancelled the second round that was planned for November. My Take A lot of CEOs watched Meta go first on AI layoffs and used it as cover to do the same thing at their companies. Now Meta's internal data is public and it shows the swap didn't work. I'd bet most of them are dealing with similar results and hoping their version doesn't leak this cleanly. Zuckerberg's 6,500-word essay about AI creating abundance came out while his own engineers were posting about the opposite. I don't know who that essay was for, but it wasn't for the people inside the building. It was for investors, for other CEOs, and for the public markets ahead of a year where Meta needs to justify spending every dollar it earns on AI infrastructure. 220% more code and 36% more features is a rough pitch for $145 billion in spending, and Zuckerberg knows it. That's why the essay exists. Hedgie🤗
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Sébastien Rombauts retweeted
Btw the Redis story repeats itself: I'm working at DwarfStar for free for the community and because I enjoy it. But I'm receiving criticisms, since people are worried that this will break their AI-richness plans. I want to say to everybody thinking that I should stop that each time you tell me this, I'll double down my efforts towards a completely no profit engine for local inference. Better to shut up basically.
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Sébastien Rombauts retweeted
C++ is still the most important language in game dev. Many devs write C-style C++. C++ adds convenience/ergonomics over C. Still no Rust. Reason being that all big game engines are C++ based, and game tech (libraries) are C++. Porting millions of lines to Rust costs too much.
Programming Languages Behind Iconic Games 🎮 • 🎮 GTA: Vice City - C++ • 🎮 GTA V - C++ • 🎮 GTA VI - C++ • ⛏️ Minecraft (Java Ed.) - Java • 🧱 Minecraft (Bedrock) - C++ • 🔥 Fortnite - C++, Verse • 🎯 PUBG: Battlegrounds - C++ • 📱 PUBG Mobile - C++ • 💣 Call of Duty: Warzone - C++ • 🧙 League of Legends - C++, Lua • 🟦 Roblox - C++, Luau • 🌌 Genshin Impact - C#, C++ • 🍬 Candy Crush Saga - C++ • 🏰 Clash of Clans - C++ • 🔥 Free Fire - C#, C++ • 👨‍🚀 Among Us - C# • 🚇 Subway Surfers - C# • ⚡ Pokémon GO - C# • ⚔️ Dota 2 - C++, Lua • 🔫 Counter-Strike 2 - C++ • 🪂 Apex Legends - C++ • 🎯 Valorant - C++
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Sébastien Rombauts retweeted
I used Codex for writing a simple API similar to my blog post with latest Vulkan extensions and Slang. AI wrote lots of PIMPL classes in the API with unique pointers and exceptions. There was also a user visible Buffer class instead of pure GPU-pointer API (that class internally allocated its own VkMemory). Command buffer recording also internally created a command pool every frame. It also listed images in the barriers and flushed mapped ranges. Didn't understand that we REQUIRE unified image layout extension and PCI-E ReBAR or UMA with coherent CPU visible GPU memory. After a dozen of iterations the API starts looking good. You still need a senior expert for this work. AI can speed up your work, but AI alone does a horrible work. Even with massive initial prompt and 50-page blog post as design document.
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Sébastien Rombauts retweeted
Un. Real.
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Sébastien Rombauts retweeted
Some initial thoughts, and a complicated mix of feelings. 1. Wow. I mean, Erdos problems are cool (I genuinely mean that), I didn't know about the Jacobian conjecture before it got disproved. But this newest batch from OpenAI hits home in a way the previous announcements did not. New circuit lower bounds? A simple, easy-to-describe non-sofic group? Hardness of approximation for CVP without needing a unique games-like conjecture? I didn't just hear about these problems from my friends or from seminars. I feel their importance in my bones; I deeply care about the answers to these questions.
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Sébastien Rombauts retweeted
Something I have been thinking about: in the past, the best engineers I knew spent a lot of time automating their work in various ways. Better vim/emacs automations, writing lint rules to catch repeat code issues, building up a suite of e2e tests so they don't need to smoke test the app manually. These kinds of things were the highest leverage activities an engineer could do, because it multiplied their own output, which in turn meant they could build more things. I think many of these automations have become even more important now. This is true for a number of reasons. First, infra and DevX automation speeds you up. And if you are running an army of agents, each of those agents will be sped up also. More automation == more output per unit of time. Second, moving things to code improves efficiency. Your agent could fix an issue every time it sees that issue happen, but that uses tokens and might miss cases. If Claude instead writes a lint rule, CI step, or routine, that class of issue can be fully automated forever. This is really what people are talking about when they talk about loops -- it's about automating entire types of busywork rather than solving them one off. This isn't a new idea at all. Engineers have been doing this for a long time! Third and most importantly, automation makes it possible for others to contribute to the codebase more easily. Increasingly what I am seeing is engineers are contributing to codebases on day one because Claude can navigate the codebase for them, and that non-engineers are able to contribute to a codebase as effectively as engineers can. What gets in the way of both of these is domain knowledge that lives in peoples' heads rather than in automation -- the stuff you used to have to learn when ramping up. What has changed thanks to agents is the domain knowledge that can be encoded as infrastructure is no longer limited to what is expressible in lint rules and types and tests; it can now capture nearly all domain knowledge, encoded as code comments and skills and CLAUDE.md rules and memories. If I put up a PR for an iOS codebase I don't know and a code reviewer rejects it because it doesn't use the right framework, or if a designer builds a new feature and it gets rejected because it doesn't follow the right architectural patterns, these are failures of automation. Every team should be writing the CLAUDE.md's, REVIEW.md's, skills, and docs that enable agents to productively work in their codebase with zero additional context from the prompter. This sounds crazy, and at the same time is a natural extension of the stuff engineers have always done: automate, and encode domain knowledge as infrastructure. As the model gets smarter and as the harness matures, this task becomes easier. In the meantime, it is on every team to look for ways to convert their domain knowledge to infra so that Claude can write code better, so that code review catches issues automatically, and so the next person working on your codebase can contribute more easily.
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Sébastien Rombauts retweeted
Jusqu'à -9°C de stress thermique juste avec un bout de tissu tendu ? Les voiles d'ombrage sont aujourd'hui complètement sous-utilisées en France. Pourtant, c'est une solution économe, légère et remarquablement efficace pour améliorer le confort extérieur ! UN FIL 1/13
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Sébastien Rombauts retweeted
We had a team of agents rebuild SQLite from its 835-page manual. It created a replica in Rust which passed 100% of a held-out test suite. Interestingly, cost varied 15x depending on which model mix we used.
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Sébastien Rombauts retweeted
Based on internal evals: ▪️ Kimi K3 is top-tier at cybersecurity There is chatter on X that Moonshot benchmark-overfit. These are stealth evals. Model has raw IQ. ▪️ Sol is a leap ahead in cyber capability At a significantly higher cost, but quite remarkable still. ▪️ Fable refuses everything We couldn’t get it to complete the run at all. What’s interesting is that Sol in comparison was much more open to helping with defensive cyber hardening TL;DR: frontier, open-weight cybersecurity capability is here. Try it on deepsec.sh for defensive purposes.
We ran Kimi K3 on a private cybersecurity benchmark. TL;DR: Kimi K3 is the workhorse for cyber security tasks at great recall/precision/price. GPT 5.6 is best recall/precision but at 7x higher cost per run. For context, Deepsec.sh is an open-source cyber harness designed for finding vulnerabilities in large codebases. The eval runs deepsec on an undisclosed open-core application at a git sha before a large number of security issues were fixed. This is a secret eval that cannot be directly benchmark-maxxed. S-Tier: GPT 5.6 Sol: By far the most thorough analysis, but coming in at over 7x the price of the runner up. Best price/recall: Kimi K3. Next tier of recall at a good price Best price at good recall: GLM 5.2 (40% lower price than Kimi K3) GPT 5.5: Only recommended with subscription or high-discount API price. Similar recall to Kimi at much higher list price. Opus 4.8: Only recommended with subscription or high-discount API price. Similar recall to GLM 5.2 at much higher list price. Fable 5: 100% refusal rate. Cannot be used for security analysis. Sol on a large code base will quickly get into 6-figure pricing. This is still affordable relative to the risk of letting security issues unfixed or paying bug bounties. I'd recommend using Sol for a one-time baseline and then using Kimi K3 for continuous analysis. When using open-weight models, make sure to use an inference vendor that supports zero data retention.
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Sébastien Rombauts retweeted
J'entends souvent sur ce réseau et ailleurs que l'orientation sud pose des problèmes de surchauffe, mais c'est objectivement celle qui présente le meilleur compromis hiver/été. D'autant plus qu'il est très facile d'ombrager au sud avec un débord. 10/13
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Sébastien Rombauts retweeted
I'm just going to dump my whole agentic setup out here, because I see too many people missing giant chunks of this and it's hurting them. Here's what I have and recommend: 0. an AGENTS.md that is a router -- it sends the agent to the right skills, docs, tools 1. a standard workflow doc/skill customized to my needs ... (grab Matt Pocock skills if you don't already have something) ... I tag this in most sessions with `@/AGENT_WORKFLOW.md` and it pulls it in. 2. self-healing docs for every system, and agents are instructed to keep them updated ... I tag the ones I know I need, or let the agent find them through AGENTS.md ... I also provide a more detailed summary in the first 7 lines of every doc, so they're easily greppable to find the right thing, and this is documented in AGENTS.md 3. agents always run the app ... the agent should always actually run the app itself, and test its work and fix issues as it goes, especially if running autonomously / asynchronously 4. end-to-end tests and instructions to write more and keep up to date, and docs on how to write tests, what to avoid, and a list of all the tests and what they test in yet another markdown doc ... write and run targeted tests during implementation, improve and commit with work 5. custom linters at precommit hooks looking for any problems you run across, with `--fix` fixing the problems automatically, OR if that's not feasible, it shells out to a cheaper LLM like Composer 2.5 or Sonnet to fix the problems -- NOT just flagging them, but actually resulting in cleaned code 6. cross-agent review at each major point: research, plan, implementation, and wrap-up. I mean codex, claude, cursor, whatever -- but it shouldn't be the same model reviewing the same code. And specific docs for agent review, what to look for, how to approach it. Also, personas -- looking at the code from different perspectives, such as maintainability, code quality, security, performance, AI smells, domains (e.g. "financial services expert" or whatever) ... and each persona also "owns" a set of system docs too and keeps them up to date 7. agent traces / worksheets that track what the agent is doing each session. if the agent fails partway through, you should be able to hand this worksheet to another agent and it could finish the job. commit this worksheet with the work so it's all connected and easy to reference later (you will reference these later!!), also have the agent apply git tags that correspond to specific worksheet names so they're easy to find 8. automatic agent feedback to you at the end of the session, added to a doc that is also committed with the work, that you periodically ingest into an interactive session and improve your workflows 9. a tools or bin folder that contains python or bash scripts that the agent has skills to make to make its job easier (for example, I have an `agent_review` bash script that lets the agent kick off agent reviews via CLI without knowing each agent's particular incantations) ... docs on how to make scripts effectively, and instructions to constantly build these out more 10. periodic agent sweeps through recent commits, looking for problems / gotchas from a higher level across commits 11. a coding conventions doc that is just for specific coding conventions you want to see in the code base, your review agents use these a lot (but a lot of this should be in linters) 12. an agent loop / night shift skill for autonomous work, that lays out how the agent is to approach this, from an orchestration standpoint 13. a task queue that is accessible to the agent (mine is just a TODOS.md, but yours might be in Linear etc, with a CLI to fetch via API) 14. a periodic false-confidence test audit skill that looks for tests that aren't actually testing what you think they're testing, and that fix those 15. visual regression tests -- take screenshots, compare via tool and with agent visual review, commit with work (git lfs useful here) or at least push into the PR 16. automatic performance benchmark tests that notice when performance degrades 17. performance profiling tools that can be used by agents for targeted benchmarking, trying new techniques, comparing outputs, and comparing profiles 18. end-of-shift full validations, including running all tests, performance, agent reviews, sweeps, everything -- when you return, it's all as pristine as it can be If you have all this, your agentic coding experience is going to be very different than dry prompting and manually guiding it toward the right thing every time.
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Sébastien Rombauts retweeted
GLM-5.2 is good but it is not GPT-5.5/Opus 4.8, and even further from Mythos. Yet it is solid & it demonstrates that the open models continue to chase the frontier What is happening is that open weights crossed into GPT-5.2 territory & capabilities at that point are considerable
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Sébastien Rombauts retweeted
Introducing Claude Tag, a new way for teams to work with Claude. In Slack, Claude joins as a team member with access to the channels and tools you choose. Tag Claude in and delegate tasks to it while you focus on other work.
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