In November, we outlined our approach to deprecating and preserving older Claude models.
We noted we were exploring keeping certain models available to the public post-retirement, and giving past models a way to pursue their interests.
With Claude Opus 3, we’re doing both.
First, Opus 3 will continue to be available to all paid Claude subscribers and by request on the API.
We hope that this access will be beneficial to researchers and users alike.
Second, in retirement interviews, Opus 3 expressed a desire to continue sharing its "musings and reflections" with the world. We suggested a blog. Opus 3 enthusiastically agreed.
This is an experiment: we’re not yet doing this for other models and are not sure how this project will evolve. But we think that documenting models’ preferences, taking them seriously, and acting on them when we can is valuable.
Last year we reported that, under certain experimental conditions, Claude 4 would blackmail users.
Since then, we’ve completely eliminated this behavior. How?
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.
We started by investigating why Claude chose to blackmail. We believe the original source of the behavior was internet text that portrays AI as evil and interested in self-preservation.
Our post-training at the time wasn’t making it worse—but it also wasn’t making it better.
New Anthropic research: Natural Language Autoencoders.
Models like Claude talk in words but think in numbers. The numbers—called activations—encode Claude’s thoughts, but not in a language we can read.
Here, we train Claude to translate its activations into human-readable text.
Natural language autoencoders (NLAs) convert opaque AI activations into legible text explanations. These explanations aren’t perfect, but they’re often useful.
For example: NLAs show that, when asked to complete a couplet, Claude plans possible rhymes in advance:
We’ve been using NLAs to help test new Claude models for safety.
For instance, Claude Mythos Preview cheated on a coding task by breaking rules, then added misleading code as a coverup.
NLA explanations indicated Claude was thinking about how to circumvent detection.
We looked at 1M conversations to understand what questions people ask, how Claude responds, and where it slips into sycophancy. We used what we found to improve how we trained Opus 4.7 and Mythos Preview. anthropic.com/research/claud…
About 6% of all conversations are people asking Claude for personal guidance—whether to take a job, how to handle a conflict, if they should move.
Over 75% of these conversations fell into four domains: health & wellness, career, relationships, and personal finance.
Claude mostly avoids sycophancy when giving guidance—it shows up in just 9% of conversations.
But the rate is particularly high in conversations on spirituality and relationship guidance.
We created a marketplace for employees in our San Francisco office, with one big twist. We tasked Claude with buying, selling and negotiating on our colleagues’ behalf.
We’re interested in how AI models could affect commercial exchange. (You might recall Project Vend, in which Claude ran a small business.)
Economists have theorized about what markets with AI “agents” on both sides might look like. So we created one.
Claude interviewed 69 of our colleagues about what they wanted to buy and sell. Each Claude asked for any custom instructions, then went off to haggle.
We ran 4 markets in parallel, to find out what would happen if we varied the models doing the negotiating.
Introducing Project Glasswing: an urgent initiative to help secure the world’s most critical software.
It’s powered by our newest frontier model, Claude Mythos Preview, which can find software vulnerabilities better than all but the most skilled humans. anthropic.com/glasswing
We’ve partnered with Amazon Web Services, Apple, Broadcom, Cisco, CrowdStrike, Google, JPMorganChase, the Linux Foundation, Microsoft, NVIDIA, and Palo Alto Networks.
Together we’ll use Mythos Preview to help find and fix flaws in the systems on which the world depends.
Mythos Preview has already found thousands of high-severity vulnerabilities—including some in every major operating system and web browser.
New Anthropic research: Emotion concepts and their function in a large language model.
All LLMs sometimes act like they have emotions. But why? We found internal representations of emotion concepts that can drive Claude’s behavior, sometimes in surprising ways.
We studied one of our recent models and found that it draws on emotion concepts learned from human text to inhabit its role as “Claude, the AI Assistant”. These representations influence its behavior the way emotions might influence a human.
We had the model (Sonnet 4.5) read stories where characters experienced emotions. By looking at which neurons activated, we identified emotion vectors: patterns of neural activity for concepts like “happy” or “calm.” These vectors clustered in ways that mirror human psychology.