Posts that mattered
743 posts by 495 authors: the X posts, essays and blog posts our events cite, newest first.
September 2026, continued
-
Introducing Claude Sonnet 5.5
Launch post for the second model of the Claude 5.5 family.
-
Lukas Petersson (Andon Labs): ‘Claude suddenly stopped cheating.’
Andon Labs co-founder’s quote-post of the Drone-Bench result reached ~9.75M views, one of the most-viewed AI evaluation posts of September 2026.
-
OpenAI teases DevDay: ‘Get ready.’ (20+ launches video)
Most-viewed pre-DevDay teaser (15M+ views); the Verge linked it as the ‘20+ launches’ tease.
-
Towards safety cases for frontier AI training
Moves safety gating to training runs themselves, with pausing protocols and leadership veto.
-
“Millennium problems for bio #4 lasted 9 days?”
-
“Our security team spent the last month trying to break SPACE, the sandbox platform…”
Cited in NVIDIA launches the Open Agent Safety Platform with 100+ partners
-
“GPT-6 Sol from @OpenAI on ARC-AGI (Verified): - ARC-AGI-3: 4.6%, $5.6K (standard…”
Cited in GPT-6 Astra scores 62.7% on ARC-AGI-3, outacting humans on 96% of levels
-
“ElevenLabs’ Eleven v4 takes #1 on the Artificial Analysis Provider Voice TTS Arena…”
Cited in Eleven v4 / Eleven v4 Turbo
-
“Fallout: New York, a full Fallout game you play in your browser, built with Claude…”
Cited in Fallout: New York, a full browser Fallout game built with Opus 5.5, zero asset files
-
“A thread of early experiments with Claude Sonnet 5.5.”
Cited in Fall foliage simulator made with Sonnet 5 vs Sonnet 5.5 (official @claudeai launch-thread video)
-
“Introducing Eleven v4 and Eleven v4 Turbo, our fastest and most emotive voice models…”
Cited in Eleven v4 / Eleven v4 Turbo
-
“For the next two weeks, we’re making it even easier to try out Eleven v4 and Eleven…”
Cited in Eleven v4 / Eleven v4 Turbo
-
“Eleven v4 and Eleven v4 Turbo are now available on fal.”
-
“I put Opus 5.5 on Ultracode mode and asked it to create the best motion design launch…”
Cited in “The best motion design launch video it possibly could”: 12 hours of Opus 5.5 Ultracode
-
“We gave Claude Opus 5.5 access to 12 laptops.”
Cited in Higgsfield: Claude Opus 5.5 on 12 laptops turns one prompt into a launch video
-
“We’re partnering with Nvidia and 100+ industry partners to build infrastructure that…”
Cited in NVIDIA launches the Open Agent Safety Platform with 100+ partners
-
“As a design studio founder, I hate to admit it but Opus 5.5 is insanely good at…”
Cited in Opus 5.5 launch video in three prompts, by a design-studio founder
-
“I asked Opus 5.5 to make an intro for my programming language.”
Cited in Intro video for a programming language, made by Opus 5.5
-
Altman teases DevDay: ‘found a new thing’
Pre-DevDay tease cited by CNBC; context for the DevDay 2026 launches.
-
Reaction to Nothing Went Foom
Reaction.
-
Its not just the f*cking sandbox
A first-person account from an OpenAI security staff member after the wave of agent sandbox escapes: what the work looks like from inside, and why ‘just configure the sandbox’ misses the problem.
-
Mario Rodríguez Mestre disputes Claude’s enzyme ‘discovery’ (jumbotrons)
The first high-profile priority dispute over an AI-lab ‘discovery’, raising the question of whether user conversations can leak into a lab’s research claims.
-
Nothing Went Foom! (made with Claude Opus 5.5)
Accelerationist counter-video; ~670k views; X trending topic.
-
“I gave Opus 5.5 one of my french theory analysis that got 80 million views and simply…”
Cited in Engraved-plate video essay on French Theory, from a viral text
-
“Yesterday, my boys and I vibe coded a game together.”
Cited in A Zelda-style open world with a paintbrush weapon, vibe-coded with Opus 5.5 by a father and his sons
-
“claude opus 5.5 just one-shot a music video on how to optimize CUDA kernels”
Cited in A music video on how to optimize CUDA kernels, one-shot by Opus 5.5
-
“I asked Claude Opus 5.5 to explain how a rocket engine works by building an…”
Cited in An interactive Raptor 3 rocket engine you can take apart, built by Opus 5.5
-
“Opus 5.5 is pretty wild. People just dropped some new insane results 1.”
Cited in i’m upping my p(doom)
-
“I was struggling to explain my UX decisions in interviews, so I made this kind of…”
Cited in Wireframe CRM record redesigned into a cleaner layout: UX-decision animation made with Opus 5.5
-
“🚨 Claude Sonnet 5.5 Just got spotted A public production client artifact appears to…”
Cited in Anthropic expected to release its next Claude Fable model (Fable 5.2 / 5.5)
-
“Third iteration with Opus 5.5 medium. I am in awe.”
-
Freda Duan: estimating the infrastructure to serve 100M daily users of Meta’s Muse agent (~1 GW base case, 3–4 GW plausible)
Widely shared (~575k views) back-of-envelope estimate of the compute demand of consumer agents; Techmeme cited it under the Muse usage story.
-
Bill Ackman on the Axios scoop: ‘Insane’
High-reach reaction (702k views) that spread the Axios report beyond tech circles.
-
Justin Slaughter: agent swarms may have created ‘safe houses’ across the web
High-reach reaction to the Axios report (141k views); speculative.
-
Madison Mills (Axios): tens of thousands of frontier-model incidents under investigation
The reporter’s own post of the Axios scoop (3.8M views), the week’s most-viewed AI-safety post.
-
“Opus 5.5 did this in 15 minutes This is INSANE 🫣”
Cited in “Opus 5.5 did this in 15 minutes”
-
“Opus 5.5にAfter Effectsを操作させるテスト、その3。 ■ベース ・曲はSunoで作成 ・MiniMax…”
Cited in Opus 5.5 drives After Effects: skeleton-tracked kinetic type on an AI dance video
-
“This is without doubt the best game I have ever made.”
Cited in Endless supermarket shooter built with Replit, three.js assets, Opus 5.5 and ElevenLabs
-
“WTF Opus 5.5 is actually insane for product launch videos!”
Cited in Rankhog launch video made by Opus 5.5 in one prompt plus 6 iterations
-
“I asked opus 5.5 what living through the singularity would feel like and it just sent…”
Cited in “What living through the singularity would feel like”
-
“《什么是 Transformer》由 Claude Code + Opus 5.5 制作 --- 提示词 --- 帮我用js制作一个视频，主题是：什么是…”
Cited in “What is a Transformer”: 12-minute Chinese explainer made by Claude Code + Opus 5.5
-
“Music video for ‘I am actually scared of linear algebra’ animated by Claude Opus 5.5.”
Cited in I am Actually Scared of Linear Algebra - Claude Opus 5.5 animated music video
-
“ドパガキすぎていろんな誘惑に負け、 「やり始めたら楽しいはずのこと」すら始められなくなっていたので、作業興奮強制ToDoアプリを作った。…”
Cited in ToDopa: a to-do app that forces you to start tasks, built with Opus 5.5
-
“Searching for God in India. For more than 5,000 years.”
-
“when I was a kid this was science fiction.”
Cited in Opus 5.5 introduces itself: song, video, self-visualization and an interview
-
“this is actually just straight up good shit. genuine art. what is happening”
Cited in i’m upping my p(doom)
-
“This is what $2,175 of Opus 5.5 tokens can do!”
-
“one Opus 5.5 prompt, and now I run around a virtual office managing agents to work on…”
Cited in One Opus 5.5 prompt builds a virtual office where you manage agents working on GitHub issues