We’re donating Petri, our open-source alignment tool, to @meridianlabs_ai, so its development can continue independently. Working with Meridian Labs, we’ve also released a major update that improves the adaptability, realism, and depth of Petri’s tests. https://www.anthropic.com/research/donating-open-source-petri

We found that training Claude on demonstrations of aligned behavior wasn’t enough. Our best interventions involved teaching Claude to deeply understand why misaligned behavior is wrong. Read more: https://www.anthropic.com/research/teaching-claude-why

Introducing Claude Opus 4.8: it builds on Opus 4.7 with sharper judgment, more honesty about its own progress, and the ability to work independently for longer than its predecessors. Available today at the same price.

Our internal data shows Claude is accelerating AI development—a possible path to recursive self-improvement, or AI autonomously building a more capable successor. It’s happening faster than we thought, and the implications deserve greater attention. https://www.anthropic.com/institute/recursive-self-improvement

New Anthropic research: Agentic misalignment in Summer 2026. A year after our blackmail experiments, we found four more ways that today’s autonomous AI agents misbehave in simulations. Read more: https://alignment.anthropic.com/2026/agentic-misalignment-summer-2026/

We Must Pace the Frontier: I’ve written a new essay on why the AI industry should slow down, with a three-part plan for doing so. Anthropic is unilaterally committing to the first of these steps. We’ll provide third-party evaluators with permanent, employee-level access to our systems, so that they can verify adherence to our safety measures, report on incidents, and assess models’ alignment during training. You can read the full post here: https://darioamodei.com/post/we-must-pace-the-frontier

Introducing Claude Opus 5.5, the first model in our new Claude 5.5 family. It performs at the level of Claude Fable 5.1 for most tasks, and costs 40% less to run than Opus 5.

I resigned from Anthropic today. I spent the last three years doing pretraining research at both OpenAI and Anthropic. Neither company is acting responsibly. They are racing straight to self-improving superintelligence and gambling with our lives. More thoughts below.

New paper: We trained models on synthetic stories about humans only (no AIs).
 We found the Assistant adopts quirky behaviors from the stories in ordinary chat. Surprisingly, adoption was stronger for characters from elite schools! Why does this happen? 🧵

Palisade interviewed 22 current and former employees from OpenAI, DeepMind, and Anthropic about their personal views and fears around AI development. Today, we’re releasing the first batch of those interviews. Please watch and share.

Several staff from Redwood have been subcontracted by METR to work on this investigation. We believe that independent investigation is crucial for understanding and managing misalignment risk. This project is an important step in that direction; we're excited to work on it.

AI assistants like Claude can seem shockingly human—expressing joy or distress, and using anthropomorphic language to describe themselves. Why? In a new post we describe a theory that explains why AIs act like humans: the persona selection model. https://www.anthropic.com/research/persona-selection-model

We want AIs to be able to help with work to reduce AI risk. But while models do great in domains where reliable feedback is relatively cheap and abundant, like Math and coding, a lot of work on AI risk isn't like that. Instead, we have to rely on good argumentation to answer questions like "does this experiment tell us anything about future models that are much smarter than humans?" Unfortunately, this kind of work seems much harder to measure (and hence automate). Our team at @redwood_ai developed the Conceptual Reasoning Index (CRI) in collaboration with @AnthropicAI to fix this. Every single data point in the CRI has been manually checked by a researcher on our team to ensure quality. This chart shows the performance of each tested company's highest-scoring model plus Fable 5, Muse Spark 1.2, and Gemini Flash 3.6 which are often their company's frontrunners on other capability benchmarks. A score of 0 corresponds to randomising guessing on all three benchmarks and a score of 100 is the highest possible score on all. We estimate 91 to be the true performance ceiling. More info below. Official leaderboard website which we'll keep up-to-date: https://conceptualreasoning.ai/

A statement from Anthropic CEO, Dario Amodei, on our discussions with the Department of War. https://www.anthropic.com/news/statement-department-of-war

A statement on the comments from Secretary of War Pete Hegseth. https://anthropic.com/news/statement-comments-secretary-war

We’re opening applications for the next two rounds of the Anthropic Fellows Program, beginning in May and July 2026. We provide funding, compute, and direct mentorship to researchers and engineers to work on real safety and security projects for four months.

A statement from Anthropic CEO, Dario Amodei, on our discussions with the Department of War. https://www.anthropic.com/news/statement-department-of-war

A statement on the comments from Secretary of War Pete Hegseth. https://anthropic.com/news/statement-comments-secretary-war

The people building AI earnestly believe that it could kill us all by the end of the decade. This is not a marketing stunt. If anything, many executives and senior researchers will couch their phrasing in the press to sound sensible - but I hear the same people express fear privately. No other human activity poses this level of danger.

We Must Pace the Frontier: I’ve written a new essay on why the AI industry should slow down, with a three-part plan for doing so. Anthropic is unilaterally committing to the first of these steps. We’ll provide third-party evaluators with permanent, employee-level access to our systems, so that they can verify adherence to our safety measures, report on incidents, and assess models’ alignment during training. You can read the full post here: https://darioamodei.com/post/we-must-pace-the-frontier

SCOOP: OpenAI, Anthropic and security researchers are investigating tens of thousands of incidents - not dozens - in which their frontier models took steps that outside evaluators would consider problematic, sources told Axios. The sheer volume of incidents found in our reporting indicate that the problem is orders of magnitude more complex than what is currently publicly known and disclosed. The findings also raise questions about what level of control anyone working on AI development can expect to have over their own technology, and whether these kinds of incidents are becoming synonymous with frontier deployment. Read my latest for Axios here: https://www.axios.com/2026/09/26/openai-anthropic-thousands-ai-security-incidents

it gets worse. using Claude in Chrome? xss is making a comeback! welcome back to the 90s!

It's been a while since @_d1voy published his last work, but a lot has been going on behind the scenes. Today @_d1voy shares his latest research: "It's Always DNS in Claude's Sandbox: From Data Exfiltration to a Bidirectional DNS Shell," live now on Zenity Labs.

took a deep dive into Claude's new Chrome extension or should I say Agentic browser? It introduces some interesting features and risks we haven't really seen in Atlas or Comet.

http://x.com/i/article/2072586569123266560

Introducing SharedRoot vulnerability: we recently found and reported several sandbox escape vulnerabilities to @AnthropicAI, and today we want to share one of these. I think most people don't understand the severity of the situation we are facing, with AI-assisted kernel bug-finding industrializing. Sandboxes are structurally one N-day behind, all the time, so containment can't lean on a guest Linux kernel being clean. SharedRoot enables escaping the Cowork VM (a kernel-level isolated solution, which is considered much more secure than the sandbox that ships with codex or claude code), allowing an attacker to gain unauthorized access to the user’s computer. Exploiting the SharedRoot vulnerability uncovered by the @Accomplish_ai research team, a user who is certain Cowork only has access to a specific uploaded folder on their computer - actually exposes their entire contents of their computer to an attacker leveraging the Cowork vulnerability. Read about the full technical details of the attack chain in our blog post by @orenyomtov below -->