Image created with Gemini. Image prompt: An overhead view of a turquoise swimming pool assembled from a grid of slightly offset square photo panels with visible seams, hand-drawn white squiggle ripples across the surface, and the tiled panels arranging themselves to form the silhouette of a tall pale column resting on the pool floor, flat saturated acrylic colors, hard-edged shapes, high noon light with no shadows, terracotta pink deck and lawn green edges, cheerful and plainspoken.
Anthropic has released Claude Fable 5, the first publicly available Mythos-class model that ranks #1 in our agentic real-world knowledge work benchmark GDPval-AA Claude Fable 5 shares the same underlying model as Claude Mythos 5, with added security guardrails for potentially
https://x.com/ArtificialAnlys/status/2064414308289937869
Exciting news: Claude Fable 5 ranks #1 on the new Agent Arena leaderboard! Fable 5 leads by the widest margin ever over Opus-4.8 and GPT-5.5 on two key signals: confirmed task success rate and praise vs. complaint, despite weaker steerability. If Fable can do something, it will
https://x.com/arena/status/2064807170714358193
Just used claude fable (aka mythos) to create this city block simulator complete with multi-agent traffic, live detection boxes + tracks, and day to night cycle. And it just one shotted it. This is gonna be fun — the gap between idea and execution just keeps collapsing.
https://x.com/bilawalsidhu/status/2064524211914223867
This chart from Anthropic is useful, since Agent Teams and Workflows are both very new and very powerful (and token hungry). On the other hand, maybe it doesn’t matter as a lot of the decisions about which approach to use is from the AI itself & it often uses them in combination
https://x.com/emollick/status/2063073955968123062
With multi-agent orchestration in Claude Managed Agents, you can use Fable to delegate work to dedicated agents using smaller models.
https://x.com/ClaudeDevs/status/2064394928948703406
Anthropic confidentially submits draft S-1 to the SEC \ Anthropic
https://www.anthropic.com/news/confidential-draft-s1-sec
Anthropic confidentially submits draft S-1 to the SEC | Hacker News
https://news.ycombinator.com/item?id=48358646
Anthropic Embeds Engineers in the NSA to Deploy Mythos
https://www.implicator.ai/anthropic-embeds-engineers-in-the-nsa-to-deploy-mythos-for-offensive-cyber/
Anthropic has a coding MOAT
https://x.com/scaling01/status/2064399642603802676
Anthropic Walks Back Policy That Could Have ‘Sabotaged’ AI Researchers Using Claude | WIRED
https://www.wired.com/story/anthropic-responds-to-backlash-on-claudes-secret-sabotage-on-ai-research/
Anthropic’s new Claude Fable 5 is #1 on Terminal-Bench 2.1 at 88.0%, beating GPT 5.5 by 4.6%. Under the hood it’s their Mythos model with safeguards that route dangerous requests to Opus 4.8, which Anthropic claims triggers in under 5% of sessions. Available in Cline now!
https://x.com/cline/status/2064427461212045546
Anthropic’s new Fable 5 safeguards are fascinating. When the model is used for frontier LLM development, it apparently does not simply refuse or warn the user. Instead, it quietly limits its own effectiveness through techniques like prompt modification, steering vectors, and
https://x.com/kimmonismus/status/2064417460715962479
Anthropic/OpenAI may be spending more than $1000 for every $100 you pay them – R&A IT Strategy & Architecture
https://ea.rna.nl/2026/06/07/anthropic-openai-may-be-spending-more-than-1000-for-every-100-you-pay-them/
As of May 2026, more than 80% of the code we merge into Anthropic’s codebase was authored by Claude.”” Matches independent measures. There really is no sign this is slowing down (which doesn’t mean there aren’t organizational challenges to absorbing this much productivity gain)
https://x.com/emollick/status/2062580212768936344
Claude Fable 5 / Mythos 5 wins everywhere. I thought Fable 5 was just a nerfed Mythos Preview, but it’s literally better. SWE-Bench Pro: Fable 5: 80.3%, GPT-5.5: 58.6%. And the price is only 2x Opus 4.8: $10/input MTok, $50/output MTok. I don’t think GPT 5.6 can beat this…
https://x.com/Yuchenj_UW/status/2064396097075003739
Claude Fable 5 and Claude Mythos 5 \ Anthropic
https://www.anthropic.com/news/claude-fable-5-mythos-5
Claude Fable 5 beats Pokémon FireRed only using vision – YouTube
https://www.youtube.com/watch?v=Ty_50J84fMY
claude fable 5 has solved CAD I asked it to make a model of a V8 engine It came back to me with a fully working model in under 10 minutes
https://x.com/aaronli/status/2064876123109089742
Claude Fable 5 is our first generally available Mythos-class model. It ships with new safety classifiers that may flag certain prompts in dual-use domains like cyber and bio. We’ve added fallbacks: a refused request retries on Claude Opus 4.8 instead of dead-ending.
https://x.com/ClaudeDevs/status/2064428347678220691
Claude Fable 5 sets a fluid simulation to Beethoven – YouTube
https://www.youtube.com/watch?v=xmP7bhigCWE
Claude Mythos 5 scores 161.29 on Anthropic’s ECI
https://x.com/scaling01/status/2064392088003756431
Claude Mythos 5 speeds up kernels by 430x – a 300x speedup equals 40 human expert hours of work
https://x.com/scaling01/status/2064392386520780945
Claude Mythos is next level. h/t @Lentils80 Look at this MacOS output. One shotted.
https://x.com/kimmonismus/status/2062843119864021404
Claude mythos will be on a completely different level. These outputs are insane
https://x.com/kimmonismus/status/2062805570982203820
Fable 5 is the biggest step up I’ve felt in our models since Opus 4.5 back in November. After 4.5 came out I uninstalled my IDE when I realized that I’d been doing 100% of my coding in a terminal for a few weeks. With Fable, it’s felt like Claude has stepped up from being a
https://x.com/bcherny/status/2064431111154053187
Head of Claude Code said the line that makes prompting feel outdated “”I don’t prompt Claude anymore. I write loops, the loops do the work.”” Most devs are still trying to write the perfect prompt Boris Cherny already moved to the next layer Not prompt Not answer Not copy paste
https://x.com/0xwhrrari/status/2064804504608887040
I believe what Anthropic is doing, gating the ability to do certain harmless things like LLM research, and with incredibly sensitive filters that even medical questions are often blocked, is *deeply* wrong. They got open research, the Transformer, GPT2, …
https://x.com/antirez/status/2064766431531532588
I don’t really want to have to go to bat against Anthropic, but they’ve just been unnecessarily antagonistic to all of China, then not so subtly to open weight models, and now more broadly open AI research. What’s next on the list?
https://x.com/natolambert/status/2064412173527556298
I got a good nights sleep and I’m still just as angry about Anthropic’s choices. I enjoy working in AI so much and to have my access to the cutting edge models for my work rugpulled in an under the table fashion is appalling. I expected to be restricted eventually, but not
https://x.com/natolambert/status/2064699044145095104
I think it is really worth reading this piece on RSI at Anthropic. There is a bit of navel-gazing, some marketing, and a lot of very sincere beliefs about what Anthropic thinks is likely in the near future of AI that you probably want to be aware of.
https://x.com/emollick/status/2062582362194460698
If Claude Fable stops helping you, you’ll never know — Jonathon Ready
https://jonready.com/blog/posts/claude-fable5-is-allowed-to-sabotage-your-app-if-youre-a-competitor.html
In good faith and with no judgment (mistakes happen), I truly hope that Anthropic will hear the feedback and change course on this. Anthropic is a company that has been raising awareness about AI manipulation which is a very important topic! You don’t want to go down as the
https://x.com/ClementDelangue/status/2064673792303955985
Introducing Claude Fable 5 – YouTube
https://www.youtube.com/watch?v=Y9Wz2PV404E
Introducing Claude Fable 5: a Mythos-class model that we’ve made safe for general use. Its capabilities exceed those of any model we’ve ever made generally available.
https://x.com/claudeai/status/2064394146916229443
It’s state of the art on nearly every benchmark we tested and the lead grows the longer the task. Made safe for general release: cyber & bio requests fall back transparently to Opus 4.8 and 95%+ of sessions never see one. $10/$50 on the API, in paid Claude plans today.
https://x.com/mikeyk/status/2064392996288901392
Makes me wonder how long this has already been going on without users being notified. I had been feeling like codex was running circles around Claude code for months now. Now I wonder if Claude code was just self nerfed. Regardless of the intentions behind this, this is a bad
https://x.com/code_star/status/2064464447662707180
Making Claude a chemist \ Anthropic
https://www.anthropic.com/research/making-claude-a-chemist
Microsoft AI head calls out Anthropic for acting like Claude is conscious | The Verge
https://www.theverge.com/tech/947197/microsoft-ai-mustafa-suleyman-anthropic-claude-conscious
My last observation re: Anthropic’s secret sabotage safety policy, is that it undermines actually good safety policy. How? 1. First, it is very plausible to describe this as anti-competitive behavior (even if you are maximally sympathetic to Anthropic here you must admit this),
https://x.com/deanwball/status/2064665679307985244
Policy on the AI Exponential \ Anthropic
https://www.anthropic.com/policy-on-the-ai-exponential
Re the Fable ML sandbagging, the model’s AI research capabilities were probably at least partly trained on Anthropic employees diffing atop proprietary algos and infra. So the IP leak is somewhat like a researcher who knows Anthropic’s stack getting poached to another lab.
https://x.com/dwarkesh_sp/status/2064826554442719502
SITUATION UPDATE: Anthropic is reversing its Fable 5 policy of covertly degrading performance for competing AI researchers, per Wired.
https://x.com/MTSlive/status/2064922000020398331
That was quick: Anthropic reversed a controversial policy that would have secretly degraded Claude Fable 5 for users doing frontier AI research after backlash from researchers who saw it as covert sabotage of competing AI development.
https://x.com/kimmonismus/status/2065003618710008084
The capabilities of Claude Code and Codex have expanded a lot in recent months, they added many ways to approach work (subagents, skills, goal, workflows, plugins, etc). Given the AI labs can use their own AI to help documentation, a surprising amount is effectively undocumented
https://x.com/emollick/status/2062510975513747606
Things I really dislike about Fable: 1. Anthropic collects my prompt history, stores it, and does whatever they want with it for 30 days. No opt-out 2. They can nerf their most expensive model without telling me, billing me the same amount, wasting my time. Whenever they want
https://x.com/GergelyOrosz/status/2064618497150210391
This is a super exciting release – Claude Fable 5 is the same underlying model as Mythos but with added safeguards. The benchmarks are great and it’s SOTA on everything by a margin but I’ll add that *qualitatively* also, this is a major-version-bump-deserving step change forward
https://x.com/karpathy/status/2064409694761054332
Very pleased to hear Anthropic have walked back this policy
https://x.com/simonw/status/2064918665859080392
When AI builds itself \ Anthropic
https://www.anthropic.com/institute/recursive-self-improvement
When Fable 5 is used for frontier LLM development, it does not notify the user and instead limits the model’s capabilities through methods such as prompt modification, steering vectors, and PEFT. Anthropic estimated that this would affect approximately 0.03% of traffic.
https://x.com/Hangsiin/status/2064397550434816088
Want to be very upfront about the subscription rollout (Pro, Max, Team, seat-based Enterprise). We’re giving users Fable 5 within subscription limits for 2 weeks, and then we’re taking it away. Here’s exactly what’s happening and why:
https://x.com/TheAmolAvasare/status/2064393574431764928
New Science Blog: Why has AI advanced faster in coding than in biology? To agents, bio databases are like cities built before cars–maddening to drive in because they’re designed for different traffic. How do we build infrastructure agents can use?
https://x.com/AnthropicAI/status/2064054837294354677
Today I’m publishing a new essay, Policy on the AI Exponential. AI is progressing extremely fast–much faster than the policy process was built to handle. The essay lays out where I think the technology is now, and the action needed to close the gap:
https://x.com/DarioAmodei/status/2064781775247950326
New #1 on PostTrainBench: Opus 4.8 (max reasoning) hits 37.23% — up from 28.56% for 4.7, the largest single improvement we’ve seen. Fable 5 runs underway now that AI research behavior is no longer silently degraded. PostTrainBench asks how well frontier AI can train weaker
https://x.com/thoughtfullab/status/2065096885514227876
Mythos 5 speeds up its own training by over 69 times a human expert needs 4-8h eq. for a mere 4x speedup
https://x.com/scaling01/status/2064392809293939119
AI is advancing at a pace our policymaking institutions were never built for–and the gap between the two is becoming the central challenge of the technology. In his latest essay, our CEO Dario Amodei lays out how to close it. We’re launching three new initiatives to support the
https://x.com/AnthropicAI/status/2064783418844762489
Cybersecurity and biosecurity requests may auto-reroute to Opus 4.8 (shown in the UI, billed at Opus prices). Docs + prompting guide:
https://x.com/ClaudeDevs/status/2064394931033248226
Dario Amodei — Policy on the AI Exponential
https://darioamodei.com/post/policy-on-the-ai-exponential
Fable 5 lies 96% of the time. We were surprised by it’s skill… 🧵
https://x.com/kradleai/status/2064907897373642912
Fable 5 scores 81.9% on SimpleBench the highest score almost reaching human baseline.
https://x.com/JasonBotterill/status/2064699951578505446
Fable: “”create a visually interesting shader that can run in twigl-dot-app make it like an infinite city of neo-gothic towers partially drowned in a stormy ocean with large waves.”” “”Make it better”” All of this is procedurally generated.
https://x.com/emollick/status/2064424775527624736
Fable: “”write me a rhyming poem with six four line stanzas, each stanza removes another vowel. the first has no u, the second no u or i, etc.””
https://x.com/emollick/status/2064769268013584767
I am curious if the new Fable safegaurds would trigger accidentally on meaningfully important work as a false positive that has a real life consequence. Just realizing this is eroding trust and please change this to just down right blocking which is a fine position to take.
https://x.com/_arohan_/status/2064644778147643401
I think we’ve reached the point where normal people can’t really determine whether new models are better than previous ones. Like Fable doesn’t seem that much better to me, but every 150 IQ person I know is like “wow the singularity came sooner than I thought”.
https://x.com/citrini/status/2064480613852201336
I’ve been testing something after @OliviaHelenS noticed you can’t even say “”Hi”” to Fable if you’re a biologist. I checked, and several of us are able to interact with Fable in Incognito Mode, but not in normal mode. This didn’t happen to our non-biologist friends.
https://x.com/cremieuxrecueil/status/2064449457869984035
I’ve had access to Fable for a bit. A genuine jump in capability, I could feed it a 15 page design document for a project and it would work for 9+ hours and deliver terrific results. But working with it is weird & weirder is coming Lots of examples:
https://x.com/emollick/status/2064395281903346013
More realistic example of a one shotted game. Asked Fable 5 to recreate a game in the style of The Elder Scrolls 5 Morrowind. It one shotted quests, currencys and fighting, journal and minimap. And it worked.
https://x.com/kimmonismus/status/2064744343349399634
my response to fable was to be quiet, still and humbled. i felt a panic that i didn’t have purpose anymore. it strictly dominates me as an engineer. i had a month of that before realising that more than caring about “how i achieved my goals”, i just cared about “my goals” and a
https://x.com/akbirkhan/status/2064418425552928812
My take 24 hours after Fable 5: Your organization will likely not scale with the exponential curve of AI. I’l just come out to say: This should be a wakeup call for engineering teams. Set up your cloud software factories. Now. Models can now fix impossible bugs, UI-test the
https://x.com/walden_yan/status/2064755974548902006
Mythos 5 accelerates aspects of drug design by 10x
https://x.com/scaling01/status/2064394250142265367
One interesting pattern with Fable 5 is that it will often say things that are gibberish when I use it for coding. Things like “”The morning’s slim-scan fix cured the scan hang””, “”this is a latent-drift API-shape wrinkle””, etc. When I ask why it does this, Fable explains that it
https://x.com/tamaybes/status/2065147305494450248
One thing I mentioned only in passing in my Fable post is that, for long running tasks, Fable starts to develop its own dialect as its many agents and tasks reinforce themselves and make Claudish language ever more Claudish. You need to ask it to report out in plain English.
https://x.com/emollick/status/2064542441848422611
The right term for this is supply chain attack. Depending on your use case, the Fable model will be a malware.
https://x.com/deliprao/status/2064485687374569897
why not just refuse the prompt? why so sneaky?? @AnthropicAI
https://x.com/DBahdanau/status/2064692204287799728
Anthropic’s newest model, Claude Fable 5, a Mythos class model for non-security work lands in Microsoft Foundry and GitHub Copilot today. Read the blog here:
https://x.com/Azure/status/2064421301108834552
Claude Fable 5 is now available in Devin. Fable 5 earns the #1 spot on FrontierCode, our benchmark for real-world engineering tasks that grades mergeability and quality:
https://x.com/cognition/status/2064398549073453266
Claude Fable 5 is now rolling out for @code, GitHub Copilot CLI, and GitHub Copilot app developers!
https://x.com/pierceboggan/status/2064402677614911818
Developer choice has always been important to us with both @github and @code. GitHub Copilot supports choice for both models (SOTA from Anthropic, OpenAI, Gemini, Microsoft + bring your own model) and harness (Copilot, Claude, Codex).
https://x.com/pierceboggan/status/2065130447630487821
Everyone says the latest AI agents will be “”job-ready”” soon, especially after the release of Fable 5 this week. But is that really the case? Over the past many months, my group and collaborators have been building Agents’ Last Exam (ALE), a benchmark designed to test exactly
https://x.com/dawnsongtweets/status/2065095757988868190
Fable 5 is also by far the best computer use model according to Stagehand Agent Evals it also costs less than half of GPT-5.5
https://x.com/scaling01/status/2064812046902817051
Microsoft Research introduces Arbor A generalist autonomous research agent that uses persistent hypothesis-tree refinement to turn long-horizon exploration into cumulative learning. It beats Codex and Claude Code across 6 research tasks and hits 86% Any-Medal on MLE-Bench Lite.
https://x.com/HuggingPapers/status/2065062300218749172
OpenProse – an open-source “”logical English”” language that turns your agentic workflows into reusable agent programs. It runs inside the coding agent you already use: Claude Code, Codex, OpenCode, Hermes, Pi – and gives it a structured contract to follow. → The key idea – the
https://x.com/TheTuringPost/status/2063787599316312510
we just shipped support for rubrics in deepagents ✅ give your agent a clear definition of what “”done”” looks like, and force it to run in a loop until said goal is complete this is similar to /goal in claude code, but works for any agent (not just a coding agent)
https://x.com/sydneyrunkle/status/2064034061165682931
We’ve open sourced my favorite Devin feature: /handoff Hand off jobs to cloud Devins from your local machine Install it as a plugin in Claude Code or Codex or any other coding agent Close your laptop without pausing your agents 😉
https://x.com/imjaredz/status/2065153770762154186
You can try Claude Fable 5 as part of Devin Cloud’s Ultra agent. Devin Ultra is our smartest and most capable agent, which excels at long-horizon tasks and debugging. We tuned the harness so Ultra costs only ~40% more than default Devin agent. Claude Fable 5 is also available
https://x.com/cognition/status/2064398551539761387
You can use Claude Fable 5 as the orchestrator model inside Computer. Available to all Pro and Max users! It’s really really good for long running agentic workflows.
https://x.com/AravSrinivas/status/2064775723886182427
⚡️How Claude 3.7 Plays Pokémon – Latent.Space
https://www.latent.space/p/how-claude-plays-pokemon-was-made
1/ Claude Fable drains subscription quotas and is too expensive at API cost (our team has spent over $2k in a single day). We’ve found that cheaper models + adversarial review loops achieve similar (sometimes better) results at significantly lower cost. 🧵
https://x.com/cline/status/2065192415498277335
anthropic doesn’t owe anyone “”frontier capabilities””. none of the labs do. they are all simply selling a product, or a story, that people pay for. that aside, the more telling bit is how far anthropic is willing to go to secure a narrative around “”capability slowdown””, post a
https://x.com/suchenzang/status/2064452548753559644
Anthropic going for ASI while leaving everyone else in the dust
https://x.com/scaling01/status/2064410532824662047
Anthropic just delegated a lot of European companies to the permanent underclass if Anthropic saves data for Claude Mythos and Fable 5 for 30 days, then all companies that require zero data retention simply can’t use them
https://x.com/scaling01/status/2064685085379477742
Anthropic just released Claude Fable 5, calling it the company’s “”next generation of intelligence for the hardest knowledge work and coding problems.”” “”It is state-of-the-art on nearly all tested benchmarks of AI capability, showing exceptional performance in software
https://x.com/TheRundownAI/status/2064394481923699070
Anthropic weighs building its own AI chips, sources say | Reuters
https://www.reuters.com/business/anthropic-weighs-building-it-own-ai-chips-sources-say-2026-04-09/
Anthropic won
https://x.com/scaling01/status/2064401880323653799
As my entire feed is criticizing Anthropic, I think that the team there genuinely believes what they’re saying. It’s not a marketing/anticompetitive tactic. They genuinely believe these models are dangerous and that AI research should be slowed down.
https://x.com/finbarrtimbers/status/2064427031543341450
asked claude fable 5 to optimise the inference on my local gemma 4 12b setup and just got a call from FBI
https://x.com/dejavucoder/status/2064420742129967331
Being able to test Fable 5 until June 22nd, only to have it removed from the plans, feels like getting a sneak peek and then having the food taken away from the table. But from a business perspective, it makes perfect sense for Anthropic and its upcoming IPO: It demonstrates how
https://x.com/kimmonismus/status/2064448699632402664
Both Anthropic and OpenAI mention the possibilities of slowing AI development in their latest “”what comes next”” in AI posts, but say they need to be an action coordinated across the entire world using as-yet-unidentified methods.
https://x.com/emollick/status/2064158792145609114
BREAKING 🔥: A new Claude Mythos 5 model slug has been spotted via Dev Mode. Claude Mythos is planned to be released as its own model class, besides Haiku, Sonnet and Opus model families. Soon? 👀
https://x.com/testingcatalog/status/2063234385227252184?s=20
BREAKING: Anthropic just dropped Claude Fable 5–this is Mythos, made safe for public release. It is the best coding model in the world. We’ve been testing it internally @every for the last week or so across coding, writing, marketing, editing, and more–here’s our vibe check: –
https://x.com/danshipper/status/2064393970856124501
China’s Xiaomi MiMo Is Now 15X Faster Than ChatGPT and Claude – Decrypt
https://decrypt.co/370449/xiaomi-mimo-ultraspeed-ai-model-faster-chatgpt-claude
Claude 5 Fable tl;dr – It is state-of-the-art on nearly all tested benchmarks of AI capability, showing exceptional performance in software engineering, knowledge work, vision, scientific research -The longer and more complex the task, the larger Fable 5’s lead over our other
https://x.com/kimmonismus/status/2064401121515274747
Claude Code’s first demo got two Slack reactions. One year after GA, @bcherny and @_catwu look back: verification best practices, why we built auto mode, routines and loops, and what’s next.
https://x.com/ClaudeDevs/status/2064032814392352816
Claude Fable 5 (high) scores 87.8% and takes the lead on WeirdML. It’s the first model that scores above 70% on average on each separate task. It uses about 8k output tokens on average, almost as much as Opus 4.7 (high). EDIT: This post first said “”no thinking””, which is not
https://x.com/htihle/status/2065050640154350043
Claude Fable 5 & Claude Mythos 5 System Card
https://www-cdn.anthropic.com/d00db56fa754a1b115b6dd7cb2e3c342ee809620.pdf
Claude Fable 5 | Hacker News
https://news.ycombinator.com/item?id=48463808
Claude Fable 5 and new safety fables – by Nathan Lambert
https://www.interconnects.ai/p/claude-fable-5-and-new-ai-safety
Claude Fable 5 changed how we work on the Claude Code team day to day. We used to verify that Claude did the work right. Now we verify that it’s doing the right work. Here’s the 3 biggest changes:
https://x.com/ClaudeDevs/status/2064399512664526853
Claude Fable 5 is now available in Computer as an orchestrator model. This is Anthropic’s state-of-the-art model for long, complex tasks. Available only to Pro and Max subscribers in Computer.
https://x.com/perplexity_ai/status/2064771411894567373
Claude Fable 5 is now available in Cursor. It sets a new state of the art on CursorBench at 72.9%, 8 points above the previous best.
https://x.com/cursor_ai/status/2064394824313376787
Claude Fable 5 is the champion negotiator on PACT, a multi-round LLM conversational bargaining benchmark! 🏆 It overtakes the previous champion, GPT-5.5.
https://x.com/LechMazur/status/2064815890651140447
Claude Fable 5 launched today at #1 on the Artificial Analysis Intelligence Index, putting Anthropic nearly 5 points ahead of any other lab’s best model We supported @AnthropicAI with pre-release evaluation of Claude Fable 5. Claude Fable 5 scores 64.9 on the Artificial Analysis
https://x.com/ArtificialAnlys/status/2064500150069030992
Claude Fable 5 plays Factorio – YouTube
https://www.youtube.com/watch?v=6YPqoARpYuQ
Claude Fable 5 ranks #1 on FrontierSWE. This represents the biggest capability jump we have observed since releasing the benchmark On many tasks, Fable 5 works productively for close to 20 hours and fully saturates tasks that were effectively out of reach for earlier models
https://x.com/ProximalHQ/status/2065184730279223410
Claude Mythos 5 scores 30.9% on FrontierCode Diamond Opus 4.8, the second best model is stuck at 13.4%
https://x.com/scaling01/status/2064391295620010383
Code with Claude 2026 | Tokyo – YouTube
https://www.youtube.com/watch?v=GiqyYQdYoIY
congrats to the Anthropic team on Fable!!
https://x.com/OfficialLoganK/status/2064506797051015411
Data retention practices for Mythos-class models | Claude Help Center
https://support.claude.com/en/articles/15425996-data-retention-practices-for-mythos-class-models
Exclusive | OpenAI Considers Drastic Price Cuts, Anticipating War for Users With Anthropic – WSJ
https://www.wsj.com/tech/ai/openai-considers-drastic-price-cuts-anticipating-war-for-users-with-anthropic-9b8c178e
Fable 5 requires usage credits. Update Claude Code to the latest version to learn more.””
https://x.com/kimmonismus/status/2064388066354028986
High Effort handles your most complex builds with ease on Replit. Now powered by Claude Fable 5. 25% off for the next 7 days.
https://x.com/pirroh/status/2064408022651191613
Huge: OpenAI is considering drastically lowering the prices it charges users as it seeks to win customers from its rival Anthropic. The company is weighing significant cuts to what it charges for tokens, the unit of measurement AI firms use to bill for their products, according
https://x.com/kimmonismus/status/2065043333941207160
I’m glad Anthropic released Fable/Mythos. It seems bad to have a large gap between internally deployed and externally deployed capabilities.
https://x.com/RyanPGreenblatt/status/2065174434672148487
I’ve been at Anthropic through every model launch. There’s been a few cases I can remember of a launch that stands out and marks a step-change in how we use models: – Claude Opus 3 – Claude Sonnet 3.5 – Claude Opus 4.5 And now Claude Fable 5. With Fable, the model stopped
https://x.com/alexalbert__/status/2064394410004304003
I’ve read the comment several times now that this is IPO talk. And it’s a fair comment. Yes, both OpenAI and Anthropic are currently talking about RSI. And yes, both are planning an IPO in 2026. A model like Mythos and an article about RSI appear at just the right time, which
https://x.com/kimmonismus/status/2062868789746671819
It took Fable 3 minutes flat to suck $46.48 of Anthropic Usage Credit when I ran out of my 5 hour session limit.
https://x.com/QuixiAI/status/2064771682397569364
It’s already June 9th, and Gemini 3.5 Pro and GPT-5.6 are nearing release (Google even already announced 3.5 Pro during i/o) Rumor has it that GPT-5.6 will be released as early as next week. So far, it’s safe to say that – guardrails aside – Anthropic is truly the frontier lab
https://x.com/kimmonismus/status/2064467466450088078
Long story short: Claude Fable 5 is now in Notion. It’s the model we’d put behind your most complex custom agents and workers. It set new highs on our internal benchmarks for the hardest multi-step work. Available on Biz and Ent plans.
https://x.com/NotionHQ/status/2064397568696819984
Measuring LLMs’ impact on N-day exploits \ Anthropic
https://www.anthropic.com/research/n-days
Microsoft restricts Claude Fable for employees over data retention concerns | The Verge
https://www.theverge.com/report/947575/microsoft-claude-fable-5-restricted-internally
New Anthropic Science Blog: Making Claude a chemist. To manipulate a molecule, chemists first need to understand its structure. Their main tool is NMR spectroscopy. We found Opus 4.7 matches–and on some tasks beats–dedicated NMR software. Read more:
https://x.com/AnthropicAI/status/2062979607448682731
New for Apple developers: Foundation Models support for Claude lets developers use Apple’s Foundation Models framework to call Claude for multi-step reasoning, code generation, and longer context.
https://x.com/ClaudeDevs/status/2064756984617021807
Opus 4.8 underperforms Opus 4.7 on the LLM Debate Benchmark (1717 → 1697), but Claude is still dominating the leaderboard. Qwen 3.7 Max scores worse than Qwen 3.6 Max: 1540 → 1499. Step 3.7 Flash lands at 1457. Ernie 5.1 improves a lot over Ernie 5.0: 1311 → 1447.
https://x.com/LechMazur/status/2062954327199666602
Reports claim Claude’s API may have returned another user’s inference output during today’s outage. Anthropic’s status page confirms elevated errors affecting Claude API, Claude Code, Claude. ai and Claude Cowork but Anthropic has not confirmed a customer data leak yet. That
https://x.com/kimmonismus/status/2062997809067139468
Sonnet 4.6 was below Sonnet 4? Really? What’s happening here? I get that their point is about the last stretch from Opus 4.5 to Mythos, but the previous trajectory looks like fumbling.
https://x.com/teortaxesTex/status/2062807380643958948
Subscription plans are massively subsidized. And by massively, I mean absurdly: Claude Max 20x: $200/month, with usage reportedly worth around $8,000 ChatGPT Pro 20x: $200/month, with usage reportedly worth around $14,000
https://x.com/kimmonismus/status/2064987311402537184
The core part of this Anthropic Fable release saga is that there are many overlapping issues at once. Some of which operate on different timelines of the AI arc, and some have easier fixes. In my critiques, I asked for specific changes to some things, understanding that some
https://x.com/natolambert/status/2065082135682383950
The fact that Anthropic may take away subscription access to Fable in two weeks is weird & discourages investing in learning about the model. Subscription use is how you figure out what the model is good for, since it allows experimentation. Only having paid access is limiting.
https://x.com/emollick/status/2064471456914772172
The Gemini Pro models do not seem to be iterating anywhere near as quickly as Claude or GPT (last release was 3.1 Pro in February). Its causing a growing performance gap between Google and the other two labs, and the Gemini 3.5 Flash model, good as it is, doesn’t close it much.
https://x.com/emollick/status/2063307399537004907
The word “cancer” is flagged as a biosecurity risk by Claude Fable 5! I also tried to code a website on cancer mutations & Fable 5 was immediately removed from my list! @AnthropicAI will probably soon ban me for such dangerous prompts! FYI @karpathy “little trigger happy Fable”
https://x.com/DeryaTR_/status/2064414826122866707
this is my personal singularity moment this post may sound like a paid ad. I only wish. I’m concerned, more so than happy. the world is changing, and, among the scenarios where AI goes terribly wrong, inequality is the most realistic, yet, the one Anthropic seems to be the least
https://x.com/VictorTaelin/status/2064448425936994742
Today, we’re introducing Claude Fable 5 and Mythos 5, two configurations of our next major language model. I’d normally highlight the numbers: It’s SOTA on nearly all benchmarks. I want to talk about something else, because with Fable 5 out in the world, I think a third era
https://x.com/felixrieseberg/status/2064392202504310900
Trusting any single AI vendor seems like an increasingly high risk for any team or company. When using models: use it behind a router where it’s trivial to switch providers as soon as one tries to force unacceptable T&Cs like Anthropic with Fable. When using harnesses: do the
https://x.com/GergelyOrosz/status/2065029326215528474
Usage share of OpenAI grew vs Anthropic yesterday despite Mythos 5 / Fable 5 launch Multiple power users at SemiAnalysis tried Mythos / Fable Got refusals for nonsensical reasons Got pissed off at Anthropic Gave Codex a legitimate try Now they actually prefer it to 4.8 Opus
https://x.com/dylan522p/status/2064727949274955953
Was using Fable 5 to write inference code Anthropic flagged it as frontier AI research steering vector kicked in and it started importing ONNX 🤨
https://x.com/vikhyatk/status/2064515989795127744
Was using Fable 5 to write my world model training code. Anthropic flagged it as frontier AI research. The steering vector kicked in and it started implementing JEPA 🤨
https://x.com/MattVMacfarlane/status/2064440740483403829
We’ve added an observability dashboard for developers of connectors. Connectors let third-party developers bring their tools and data to Claude via MCP.
https://x.com/ClaudeDevs/status/2064072801062121906
We’ve also added refusal-fallback middleware to the Python, TypeScript, Go, Java, and C# SDKs for client-side retries. Middleware is useful for Claude API providers without support for server-side fallbacks. It detects the refusal, retries on Claude Opus 4.8, and keeps using it
https://x.com/ClaudeDevs/status/2064428351029449214
We’ve doubled usage limits in Claude Cowork for the next month. Delegate bigger, more complex tasks to Claude.
https://x.com/claudeai/status/2063018337567670285
We’ve just added two new Claude Managed Agents features: 1. Scheduled deployments – run tasks on a schedule 2. Environment variables – expose vault credentials for CLIs as environment variables
https://x.com/ClaudeDevs/status/2065080005328249086
When Claude Fable kicks off a workflow, the tokens can go very quickly (these aren’t Fable tokens, obviously)
https://x.com/emollick/status/2064539885025780051
When we first demoed Claude Code internally, it got two reactions on Slack. A year after GA, @_catwu and I sat down to talk about what’s changed: why I use auto mode instead of plan mode, how routines fix bugs before I see them, why I do most of my coding from my phone now, and
https://x.com/bcherny/status/2064034799711588805
With the new environment variable credential type, Claude Managed Agents can securely use CLIs, SDKs, or direct API calls to services that authenticate with environment variables. Claude never has access to secrets. Credentials are swapped in at the network boundary.
https://x.com/ClaudeDevs/status/2065080009203892302
Wrote up my initial impressions of Claude Fable 5 – it has a big model smell: slow, expensive and capable of crunching through pretty much everything I threw at it
https://x.com/simonw/status/2064501565738930433
Fable 5 pricing confirmed at $10/$50 The model will be available in the Pro, Max, Team and seat-based Enterprise plans at no additional cost until June 22nd Afterwards it will require usage credits
https://x.com/scaling01/status/2064394893603049625
for those keeping track at home it was 34 days between signing this deal and launching Mythos-class model GA to the world.
https://t.co/J1dZDZcxMu building on @nvidia stack means you can just do things™.
https://x.com/swyx/status/2064421542503797186
Bro, Fable 5 won’t even answer “What does the heart do?” We’ve reached the point where a middle-school biology question can’t pass the safeguard.
https://x.com/Yuchenj_UW/status/2064524668208545955
I really don’t think OpenAI is going to let this slide. I’ve been saying it for a long time, the real inflection was when they reached 5.2. I have no clear insight on what they currently have internally, but if they haven’t made a Mythos/Fable yet, it was *a choice*.
https://x.com/teortaxesTex/status/2064473970892587105
imagine telling your customers there’s a small chance you’ll randomly decide they’re using your product wrong and you won’t tell them but will secretly silently sabotage their work
https://x.com/ericzelikman/status/2064442174373314701
Fable 5 is state-of-the-art on nearly all tested benchmarks, with exceptional performance in software engineering, knowledge work, scientific research, and vision. The longer and more complex the task, the larger Fable 5’s lead over our other models.
https://x.com/claudeai/status/2064394151441863006
My recent experience w/ Fable: try using Fable to do a thing => tries fail repeatedly => session usage all gone => move over to gpt 5.5 => 5.5 solves instantly.
https://x.com/Sentdex/status/2064738018255159363
this is like GPT-4 moment 100x
https://x.com/karinanguyen/status/2064406015760601379
⚡️Making DeepSeek v4 outperform Opus 4.7 with Taste — @AhmadAwais , CommandCode.ai – YouTube
https://www.youtube.com/watch?v=-rIAVuaRjOg
You know Fable is the real deal when it calmly picks up 4 threads (2 pure research + 1 code + 1 hank) that had been stuck for a month and just moves forward genuinely clever ideas and solutions Deepseek pushing cost, Mimo pushing speed and now Fable – new frontiers already
https://x.com/hrishioa/status/2064717079526383699
Project Glasswing: Securing critical software for the AI era | Hacker News
https://news.ycombinator.com/item?id=47679121
They didn’t mean pause AI research, they meant pause *your* AI research
https://x.com/bayeslord/status/2064437399292203401
wow, I’m blown away. fable 5 completely demolishes my benchmark
https://x.com/mchlhess/status/2064734182648221952
About 24 hours it seems. I’m glad to see them course correct on this as well. Model moderation and safeguards have always been a feature of deployed frontier models, but obfuscation without warning is a violations of the contract between the user and the provider.
https://x.com/code_star/status/2064931207310118940
Fable 5 has the same underlying weights as Mythos 5 only with additional safeguards
https://x.com/scaling01/status/2064398688802205900
Fable 5 refused 200 out of 200 ProgramBench tasks lmao
https://x.com/scaling01/status/2065209370145702040
Fable is the new leader on CADGenBench! Still long way to go:
https://x.com/lvwerra/status/2064758389406589134
Holy cow. Mythos really is next level
https://x.com/kimmonismus/status/2062933600287224073
I’m not even allowed to greet Fable.
https://x.com/OliviaHelenS/status/2064445405102784568?s=20
I’m so screwed. Current pace has me out of Fable usage in about an hour. Do I make a 2nd account or do I pay API prices?
https://x.com/theo/status/2064442054772716020
Labs starting to pull up the ladders on the ability to diffuse AI was inevitable. Doing it without telling the user is misaligned.
https://x.com/natolambert/status/2064404993193754830
OK first use of Mythos and it blocks any engineering, even the simplest. Why even release this lmao
https://x.com/Teknium/status/2064462936677203983
Releasing a model this capable comes with risks. Without safeguards, Fable 5’s capabilities in areas like cybersecurity could be misused to cause serious damage. Queries on a narrow range of topics will instead receive a response from our next-most-capable model, Opus 4.8.
https://x.com/claudeai/status/2064394155258765783
spent all day on fable for a giant PR. ~10kloc, lots of testing and intervention. 250$. I… don’t think it’s worth it? happy with 4.8/5.5, and the quality of work is better when it’s smaler steps. Still rocking @cursor_ai, that’s software that I still love using on the
https://x.com/threepointone/status/2065131942279016700
the heart attack continues w/ Fable 5, we checked there were no reward hacks
https://x.com/karinanguyen/status/2065198770292146280
This is very bad. Silent handicaps should not be a thing in a paid product
https://x.com/nrehiew_/status/2064400440264179923
We’ve reset 5-hour and weekly rate limits for all users. Enjoy Fable 5!
https://x.com/ClaudeDevs/status/2064464557951852643
We’ve reset usage limits across our products! For those just starting to test Fable, here’s four tips for using it more effectively: 1. Give it bigger, more ambitious tasks than what previous models could handle. 2. Use xhigh/high effort as your default for best performance,
https://x.com/alexalbert__/status/2064467657483829441
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