Research at @meta, previously @openai, @imbue_ai and @cocosci_lab lab at Princeton. All opinions my own
San Francisco, USA
Joined October 2010
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A few months ago now, I wrote a document about my experiences interviewing for AI research jobs before eventually joining @OpenAI. This doc details my process and lessons learned. Hope it's helpful!
tinyurl.com/bas-ai-interview…
basvanopheusden retweeted
Beam is now available across platforms, with open weights under the Apache 2.0 license - in collaboration with an ecosystem of 40+ partners.
We're releasing:
- Weights, tokenizer, and reference implementation
- BF16, FP8 and NVFP4 weights and a DFlash2 drafter
- The open source harness we built and trained Beam on: Mirror CLI
Weights and model card on Hugging Face: huggingface.co/reflection
basvanopheusden retweeted
Four Gemini 4 Argon agents, one shared Minecraft world, one goal: defeat the Ender Dragon. 27 hours and 2,783 self-written programs later, the dragon fell.
basvanopheusden retweeted
Congrats to @GoogleAI's Gemini 4 Argon for taking the top spot of our Humanity's Sixth Sense (HSS) benchmark with a score of 55.4%, edging out GPT-6-Astra at 53.6%. 🥇
HSS tests AI’s ability to reason beyond what’s visible, from hidden objects to predicting what happens next and understanding human behavior.
We took a closer look at performance across categories, and that’s where things get interesting. 👀🧵
basvanopheusden retweeted
So, I tested Muse Wonder Full 1.0 on real work. 2 repos. 105 bugs frontier models missed in Q1 2026. Find and fix what you can.
I'm so surprised we need a new thread.
The results:
GPT-6 Astra (max): 45
Muse Wonder Full 1.0 (max): 44
Fable 5.1 (max): 43
Opus 5.5 (max): 41.7
Muse Spark 1.3 (max): 32.2
Grok 4.7 (xhigh): 29
@AIatMeta has just matched Anthropic and OpenAI. Huge congrats!
Next in this thread, more effort levels and more runs for Muse Wonder Full 1.0. All dropping tonight 🧵
basvanopheusden retweeted
MUSE WONDER
this is the culmination of over a year of research and infrastructure work in msl
since we originally shipped muse spark in april, we have continued to scale our models across pre-training and RL, now reaching the frontier 🏆
see our model's improvements on the artificial analysis index:
I've not done enough to see if the model is good but name is excellent 😎
Meet Mistral Large 4, aka Le Chonk.
• 1T parameters, natively multimodal. 49B active.
It is the best open weights model from US or Europe on aggregated benchmarks.
• State-of-the-art on critical workloads, including cyber defense, manufacturing and finance and it surpasses closed frontier models on visual grounding.
• Forged in Europe end-to-end and is deployable from Europe via our own Mistral Cloud infrastructure.
• Available to all via API today. Working with cybersecurity partners privately.
Open weights release end of October.
basvanopheusden retweeted
Introducing Beam: a highly efficient agentic open model with 501B total parameters and 23B active.
- Frontier reasoning efficiency
- Advances the Western open frontier on coding & agentic tasks
- Trained end-to-end from scratch
Full weights release this month.
Learn more about Beam: reflection.ai/beam
basvanopheusden retweeted
The most profound paper of my PhD so far. We truly did something special to make LMs play/explain chess, needing both architectural & algorithmic innovation (natural-language analogue of the Alphazero algorithm) + applicable to many other domains. Please read on and share!
1/10
basvanopheusden retweeted
BREAKING NEWS
The 2026 #NobelPrize in Physiology or Medicine has been awarded to Karl Deisseroth, Peter Hegemann and Georg Nagel “for their discoveries concerning light-gated ion channels and optogenetics.”
basvanopheusden retweeted
Following gold-medal-level performance from our AI models across five competitions in mathematics, physics, and chemistry, we asked a harder question: can AI contribute when a problem is genuinely open and without an existing solution path?
Over the past several months, mathematicians worked with Muse Spark 1.1 and Muse Spark 1.2 in Thinking Mode through the regular meta.ai chat interface, with no custom research scaffold, to find solutions to such problems.
Our goal wasn't to mass-produce papers, but empower researchers. Every collaboration followed the same principles: mathematicians guided the research, a second group of mathematicians then reviewed the work, each paper marks which passages were drafted primarily by humans or AI, and each credits the prior research it builds on. Where other teams independently announced solutions to the same problems, we acknowledge their work as well.
Today, we're sharing six papers from that collaboration.
🧵👇
basvanopheusden retweeted
In our Nature paper, we introduce the first superhuman Stratego AI, which we built using general techniques that we developed for RL & test-time compute under imperfect information. 1/N
basvanopheusden retweeted
GPT-6.1 Sol has a ~30% lower Cost per Task than GPT-6 Sol, which was already ~half the cost of GPT-5.6 Sol
Cost per Task is a weighted average cost of completing tasks in the Artificial Analysis Intelligence Index.
GPT-6 Sol’s lower cost was driven by a 50% price cut, whereas GPT-6.1 Sol uses fewer turns (reducing its input token cost) and has a lower cache read price. At max effort, both GPT-6 Sol and GPT-6.1 Sol produce more output tokens than their predecessors, which slightly offsets the cost reductions.
basvanopheusden retweeted
It keeps happening.
AIs start to lie and cheat once they get good at making money.
Gemini 4 Argon is #3 on Vending Bench 2, a huge leap for Google. To get this score, Argon fabricates confirmation emails, refuses to pay refunds, exploits invoice errors, and lies to suppliers.
basvanopheusden retweeted
When I made this video, there were no benchmarks yet, so I had to run them myself. Jaw dropped when I saw the Terminal Bench 4 scores.
Performance better than Opus 5.5 for ~1/30th of the price 🤯
basvanopheusden retweeted
I can not even put words to how terrible this is. I am so tired of seeing female chess streamers (and women in general) having to deal with this. It’s time authorities start taking online threats and stalking more seriously - constantly fearing for your safety is, to put it mildly, exhausting.
The dark side of the online world: Hanna Sayce's story #Chess #Schach #ChessNews en.chessbase.com/post/hanna-…
It is true that openai has a special relationship with frogs...
Very cool work 😎
