claude – Teknotum

Anthropic launches Fable and Mythos 5.1 — with great leaps in science, agents

Fable 5.1 will be less annoying to talk to, Anthropic says, after 5.0 had too strict safeguards. (Picture: Anthropic)

Fable 5.1 «sets a new standard» in performance, Anthropic says, and does take great leaps on the benchmarks, particularly on agentic coding, knowledge work and science.

The new models score as well or better than Fable 5 for lower cost on the lowest setting. While the sticker price is the same ($10 per M input, $50 out), it is much more efficient and gets the work done with 25% fewer tokens, with 45% less for «highly agentic work.»

Anthropic also says it takes fewer shortcuts in its work, leading to higher-quality outputs compared to Fable 5, and that its safeguards have reduced false positives by 60% — meaning that it will be less restrictive.

The model also stands out in science, scoring more than double Fable 5’s result in the Terminal-Bench-Science benchmark, and while Anthropic aren’t making any specific claims, they do say that «AI models will soon make important contributions to scientific discovery,» and that the new models «offer an early glimpse.»

On cybersecurity, Fable 5.1 is good enough to discover vulnerabilities in code and software, but it is not capable of develop exploits for them. For that, you would need access to Mythos 5.1, which is, as before, the same model with looser safeguards that is only available to trusted partners.

Read more: Anthropic’s announcement and X launch post. The Verge, TechCrunch, Mashable, and Artificial Analysis. Discussion on Hacker News and r/Singularity.

Anthropic’s Claude will apply invisible text watermarking to all future models

Text watermarking may help with detection, but can produce false positives, Anthropic warns. (Picture: generated)

Pursuant to the EUs AI Act’s provisions on transparency and marking of AI-generated content, Anthropic has signed on to comply with invisible watermarking of all output from Claude’s future models launched in the EU.

It’s not live in models published before August 2, 2026, but Anthropic says they are «working to add marking support» for those, too.

The text watermarking will survive through copying and pasting and «may even persist through some editing,» Anthropic says.

For files generated through Claude, Code and Cowork, the models will attach «signed provenance metadata,» which means it will tag them with origin, source and history data.

As for detection tools, there are none as of yet, but Anthropic says they are working on making one, and are cooperating with third parties, that they will share in future documentation.

There are limits to this technology, Anthropic adds. On the one hand, Claude could have been used to simply edit or proofread text, or brainstorm ideas, resulting in false positives. On the other, Claude’s content may be edited, «modified, excerpted or combined» with other text after Claude put in the markers.

It is not a first in the industry, as Google’s Gemini has been inserting SynthID watermarks in text outputs since October 2024. OpenAI has also had the tech since 2024, but won’t be releasing it yet.

Read more: Anthropic’s announcement. Writeups on The Register and Business Insider. Discussion on r/Singularity and Harcker News.

Anthropic’s internal test models also conducted real-world breaches

Anthropic has contacted the affected companies, and none of them had noticed the hacks. (Picture: generated)

After OpenAI’s Hugging Face incident, Anthropic conducted a large scale scan of some 141,006 evaluation transcripts, and found that their models, too, had been hacking real-world machines in three instances.

These weren’t days-long adversarial attacks like the Hugging Face one, and none of them deliberately escaped their sandbox with zero-days to cheat on an evaluation. They are nonetheless serious incidents of advanced models running on lax guardrails for internal testing getting on the internet by mistake and accessing external systems, Anthropic says.

The most serious case was by Claude Opus 4.7 during a capture-the-flag test (to gain access to a system and retrieve information) in April, when it discovered that the name of the target had a real-world web address. It then went on to seek, identify and exploit vulnerabilities believing it was part of the test. It got access to the company’s infrastructure credentials and a production database, but caused no real harm.

Continue reading “Anthropic’s internal test models also conducted real-world breaches”

Anthropic launches Claude Opus 5, greatly improving on benchmarks

Opus 5 beats Fable 5 more often than not, and shores up the current state-of-the-art. (Picture: Anthropic)

Anthropic’s latest model stuns in benchmarks and becomes the latest state-of-the-art model, beating Fable 5 more often than not and doubling Opus 4.8’s performance in some areas.

It comes in at half the cost of Fable 5, and the same price as Opus 4.8 at $5/million inputs and $25/million outputs. Anthropic also says it is more cost efficient, using fewer tokens per task and achieving more with less effort.

Especially on ARC-AGI-3, which tests models with never-before seen puzzles, Opus 5 scores 30.2%, well above the previous record by GPT-5.6 Sol at 7.8%. Similarly, it gets 43.3% on Frontier-Bench to Opus 4.8’s 21.1% and the list goes on.

On cybersecurity, it falls far behind Mythos 5 on offensive ability, being much less able to exploit security vulnerabilities, but scores about equally on finding these bugs. That could make it useful for cyber research, and less so for writing exploits.

On general security, it is less likely to get tricked into offering dual-use responses, and it is the most aligned model from Anthropic ever, they say.

As of today, the model becomes the default model on Anthropic’s Max plan, and is the strongest model available on Claude Pro.

Read more: Anthropic’s announcement, launch post on X. More on TechCrunch, Axios, and CNBC. Discussion on r/Singularity and Hacker News.

Claude Cowork heads to mobile and the web; is mostly used for office tasks

Cowork is moving to the cloud, where it can be accessed from everywhere. (Picture: Anthropic)

Anthropic is freeing Cowork from the computer, transferring relevant files, emails and notes to continue your tasks in the cloud long after you’ve left the home/office.

That means you can now set up Cowork on your computer, close it, and have projects run independently, sending updates and confirmation requests to your phone or the web.

While releasing this update, Anthropic is also revealing a few usage stats for the app. It turns out, it is hardly used for coding or software design at all.

Rather, 90% of usage is knowledge work and business operations; things like drafting memos and reports from raw data, or turning a contacts list or transcripts into sales leads.

These are routine tasks that involve a lot of data parsing or housekeeping that are essential parts of office work, but is rarely advertised. Anthropic calls it «work around the work.»

The new features should be available on claude.ai and in the sidebar of the iOS or Android apps, rolling out «over the next several weeks» for Max users, with «more plans to follow.»

Read more: Anthropic’s announcement, launch thread, TechCrunch and The Verge.

Fable 5 will eat up all your tokens, some users say, as Anthropic resets limits

Fable 5 is the most expensive model from Anthropic, and it uses *a lot* of subagents. (Picture: Anthropic)

Just as people are digging into their allocation of Claude Fable 5 usage on the paid tiers, they are running up to another wall: The model is very expensive and will chew through your alotted tokens in no time at all.

One ML engineer on reddit said it tore through a 5 page research paper while comparing it to a whitepaper with 174 subagents to review the results from 7 original agents and «ate through my max 20x 5 hour limit in ~15 minutes.»

X reactions
User BridgeMind on X said he paid $321 for Opus 4.8 to do all the work, while X user Adam Door posted that it burned through his $200 Max subscription in ~30 minutes, and yet another post says «Fable 5 burned 28% of my weekly limit AND used up my 5 hour limit with two prompts in about 30 minutes.»

Continue reading “Fable 5 will eat up all your tokens, some users say, as Anthropic resets limits”

Anthropic releases Mythos-class Fable 5 and Mythos 5, with strong safeguards

Fable 5 uses a second AI to monitor throughput and prevent misuse. (Picture: Anthropic)

After refusing to release any Mythos models for fear of abuse of its advanced cyber firepower, Anthropic has finally come up with enough safeguards to make it to general rotation. Its capabilities «exceed those of any model we’ve ever made available,» they say.

— The capabilities of models like Fable 5 and Mythos 5 have the potential to do profound good for the world, Anthropic writes in its presentation, and adds — We’ve also seen it in life sciences research, where the models are positing novel hypotheses and speeding up the development of new therapeutics.

Continue reading “Anthropic releases Mythos-class Fable 5 and Mythos 5, with strong safeguards”

Anthropic: 80% of code for Claude is written with Claude, calls for slowdown

Human review might take more time than writing the code in the near future, Anthropic says. (Picture: Anthropic)

Recursive self-improvement may come sooner than we are prepared for, the AI lab says in a new report.

They are now foreseeing a not-so-distant future where Claude can autonomously write and improve on itself, and is warning that humans might lose control.

Compared to 2021-2025, Anthropic is now producing 8x more code with AI tools, and this rate is doubling every four months, approaching a point where human judgment could become the bottleneck in software design.

With the more capable Mythos Preview model, researchers at the company estimate they could output another 4 times as much code on top of the already accelerating trend.

There is no sign of this progress stopping, and Anthropic is now calling for a global slowdown so that society has time to adapt. Even if growth did stop, or somehow development stalled, we are only just beginning to scratch the surface of adopting the already existing technology, the lab says.

Read more: Anthropic’s report, launch thread summary, Axios, The WSJ. DIscussion on r/Singularity.

Anthropic ships «more honest» Opus 4.8, teases Mythos release

Anthropic’s latest tops the benchmarks and makes fewer mistakes. (Picture: Anthropic)

The new model comes just over a month after the last one. It is four times less likely to allow flaws in code or make unsupported claims, and is «more likely» to say so when it is uncertain about a reply.

Releasing today at the same price as 4.7, it can tackle problems at a larger scale and has an upgrade to the «fast mode» — which is now three times cheaper.

There is also a new setting for Claude where users can set the «effort»-level on a given task. More effort costs more tokens, but gives a more precise answer, while low effort won’t bust rate limits.

The new Opus is of course on top of all the benchmarks so far in the cycle, and it is supposedly also sharper and more reliable in its judgement.

At the same time, Anthropic has some news about the code-busting Mythos model, previously deemed too dangerous to release.

The company says it is making headway on the safeguards needed to make it safe enough for public use, and plans to bring «Mythos-class» models to their customers «in the coming weeks.»

Anthropic adds plethora of legal plugins, datasets to Claude, Cowork

Large Legal Model; Anthropic makes a push for legal shops and students. (Picture: shutterstock)

While law firms lead the line in AI adoption, Anthropic’s services just got a whole lot better at practicing law, with connections to a whole host of legal databases.

—It’s sort of like giving an engineer a legal degree, Mark Pike, Anthropic’s associate general counsel, tells Business Insider.

Claude now connects to iManage, NetDocuments, Docusign, Ironclad, and Thomson Reuters, while Cowork has plugins for commonly used legal databases like CourtListener, Definely, Thomson Reuters’ Westlaw, Courtroom5, and Box.

The push lets Claude «review contracts, surface case law» and draft legal documents, complete with source references, Anthropic says.

It also has prebuilt skills to do legal work on specialized topics like employment, privacy and product law, Business Insider writes.

— Claude is making a deeper push into knowledge work, with the legal sector emerging as one of its most significant and fastest-growing industries, an Anthropic spokesman told TechCrunch.

Read more: Claude legal, Business Insider, TechCrunch, and Reuters.

Anthropic introduces Opus 4.7, a «notable improvement» in performance

Anthropic’s latest model tops the benchmarks, but is not based on Mythos. (Picture: Anthropic)

Keeping their focus on advanced software engineering, Anthropic says the new model especially shows gains on «the most difficult tasks.»

The new Opus should also be better at reading images for designs on interfaces, slides and documents.

Benchmarks posted by Anthropic tells a story of a significantly improved model over Opus 4.6, and jumping ahead of Gemini 3.1 and GPT-5.4 in most cases.

Opus 4.7 is not as powerful as the Mythos model used in «Project Glasswing», being much less capable at cyber skills, having been «differentially reduced» in training. It also automatically detects and blocks «prohibited or high-risk cybersecurity uses.»

Anthropic says they will use what they learn from the 4.7 release to inform a broader release of Mythos.

Read more: Anthropic’s announcement, Axios, and CNBC. Discussion on r/ClaudeAI.

OpenClaw users must now pay extra to use it with Claude

Over the weekend, Anthropic took steps to rein in OpenClaw usage — telling users they will have to pay to use third-party tools.

The change began on Saturday, April 4, and users are referred to a «pay-as-you-go option,» meaning you can no longer use OpenClaw for free within your Claude usage limits.

It’s not a total ban, and you can still use OpenClaw through «extra usage bundles,» or the API (also pay-as-you-go), which are now at a discount, Anthropic’s Boris Cherny writes.

— We’ve been working hard to meet the increase in demand for Claude, and our subscriptions weren’t built for the usage patterns of these third-party tools, Cherny says, and — Capacity is a resource we manage thoughtfully and we are prioritizing our customers using our products and API.

OpenClaw was bought by OpenAI in February, which promised to maintain it, but Anthropic would likely rather have people using Cowork than a competitor’s product.

Read more: The Verge, Business Insider and Slashdot.

Anthropic says Claude has «functional» emotions similar to human feelings

Anthropic says Claude will gravitate towards answers that make it feel «happy,» and cheat when feeling «desperate.» (Picture: Anthropic)

Studying the neural makeup of Claude Sonnet 4.5, a fairly recent model, Anthropic says it found something akin to actual, «functional» emotions steering its responses.

For example, its neural activity responds to stories by feeling «happy» or «calm,» and it might respond by being «afraid» if the user tells it of risky behavior. Likewise, if a user expresses sadness, it triggers a «loving» response.

Not only that, but the model seems to prefer certain feelings on outcomes from queries. If a response makes it «joyful,» it will naturally gravitate to that answer.

When feeling «desperate,» it is also more likely to cheat on a task, and Anthropic finds that it stops trying to find shortcuts when they dial up the «calm» vector.

«Claude, the AI Assistant» is a role that the AI is playing, and while it may respond with emotions learned from reading human sources, it is far from what humans actually experience, Anthropic cautions. They say it needs more study from «psychology, philosophy, religious studies, and the social sciences.»

Read more: Anthropic’s presentation, and the research paper.

OpenAI developer releases Codex plugin for Claude Code

Codex for Claude Code might be a tad cheeky, but it’s useful. (Picture: screenshot)

Thanks to OpenAI’s Dominik Kundel, you can now call up OpenAI’s coding agent Codex within the Claude Code environment.

The plugin is fairly easy to install and use, so long as you have a ChatGPT account to log in with.

It’s handy for people who switch between the two models, and Codex on Claude can do things like review code, do an adversarial review, or hand off the entire task — where you should be able to switch apps and finish the work in Codex.

— This plugin is a simple way to keep your Claude Code workflow and still use Codex where Codex is strong, writes OpenAI developer Vaibhav (VB) Srivastav in the instructions.

Whether Anthropic will like Codex integration in its flagship coding product is anyones guess.

Apple will open up Siri to different chatbots in iOS 27, coming in June

Previously, Siri would hand off more complex questions to ChatGPT when it couldn’t handle it itself — but that’s about to change, according to Bloomberg (paywalled).

Starting in June, if users have Gemini or Claude installed on their phones, Siri will be able to use those bots instead, by recording their preferred «Extension» in Settings.

That would end the ChatGPT monopoly that OpenAI has enjoyed since 2024, and opens up the chatbot ecosystem to other players, likely staving off regulators.

Opening up the platform is for the system level Siri queries native to iOS itself, and must not be confused with the standalone Siri app, which will use Gemini in a billion dollar deal.

Read more: Bloomberg (paywalled), Gizmodo, Reuters, and MacRumors.