> ## Content Index > Fetch the complete content index at: https://www.implicator.ai/llms.txt > Use this file to discover other available public pages before exploring further. # Anthropic's Faster Fable Tests Amodei's Call to Slow Down - URL: https://www.implicator.ai/anthropic-fable-5-2-amodei-pacing-ipo/ - Published: 2026-11-09T20:11:40.000Z - Updated: 2026-11-09T20:11:50.000Z - Description: Anthropic's first frontier models since Amodei's pacing essay arrive as its own evaluator and IPO filing describe a faster pace. - Author: Marcus Schuler - Tags: AI News Anthropic [released Claude Fable 5.2 and Claude Mythos 5.2](https://anthropic.com/claude-fable-and-mythos-5-2?ref=implicator.ai) Monday, its first frontier models since chief executive Dario Amodei’s [September call to slow AI development](https://darioamodei.com/post/we-must-pace-the-frontier?ref=implicator.ai). An independent evaluator, [METR, estimated last week](https://metr.org/blog/2026-11-05-anthropic-ai-rd-acceleration-assessment/?ref=implicator.ai) that Anthropic is improving its models on well-specified tasks about twice as fast as a year earlier. The release comes ahead of an initial public offering that could take place as soon as next week. What Changed - Anthropic released Claude Fable 5.2 and Claude Mythos 5.2 on November 9, its first frontier models since Dario Amodei's September essay calling to slow the pace of AI capability gains. - METR, an independent evaluator, estimated on November 5 that Anthropic is improving its models on well-specified tasks about twice as fast as a year earlier, with caveats and redactions. - Anthropic's November 2 amended IPO filing said it may imminently meet its own definition of dramatically accelerated progress attributable to AI; no current model has been designated as exceeding it. - Fable 5.2 costs $8 and $40 per million input and output tokens, down from $10 and $50, and Anthropic still recommends Opus 5.5 for most everyday work. AI-generated summary, reviewed by an editor. [More on our AI guidelines](https://www.implicator.ai/about/). ## The pace question In his September essay, “We Must Pace the Frontier,” Amodei wrote: “We must slow the pace at which we improve the capabilities of AI models.” He specified pacing “does not mean halting model training or technical progress” and named METR among his proposed embedded outside evaluators. The Berkeley nonprofit’s November 5 assessment used about 11 weeks of internal data and staff interviews. “Anthropic appears to have made as much progress on benchmarks in the past year as they did between October 2023 and October 2025,” METR wrote. METR cautioned it could be overstating acceleration, which might be confined to well-specified tasks. Anthropic’s redactions limited what METR could report. Anthropic’s [November 2 amended IPO filing](https://www.sec.gov/Archives/edgar/data/2130357/000162828026068676/anthropicpbc-sx1ax1.htm?ref=implicator.ai) said its internal estimates and expectations for future models “indicate that we may imminently meet our Responsible Scaling Policy’s definition of ‘dramatically accelerated progress attributable to AI.’” No current model had been designated as exceeding that threshold. Anthropic said it is “considering updates to our Responsible Scaling Policy to keep humans in control of frontier model development at Anthropic.” Anthropic is seeking a valuation of $1 trillion to $1.5 trillion, down from $2 trillion floated in recent months. Revenue for the nine months ended September 30 reached $33.24 billion, up roughly 1,200% from the same period last year. FREE AI BRIEFING · WEEKDAYS Track how fast the AI labs are really moving. Get the AI stories shaping the day, with concise context from San Francisco. The briefing takes about five minutes and arrives at 4:45 a.m. Pacific, 7:45 a.m. Eastern. Email address Keep me informed Check your inbox for the confirmation link. Free. No hype. Unsubscribe anytime. During training, Anthropic said it deliberately held back research skills that could most directly speed up AI development. In improving model architectures, the new models perform at about Opus 5.5’s level. “We called for pacing, not pausing,” Dianne Penn, Anthropic’s head of product management for research, [told CNBC](https://www.cnbc.com/2026/11/09/anthropic-claude-fable-5-2-mythos-5-2.html?ref=implicator.ai). ## What shipped Mythos is the same underlying model without certain cybersecurity or biology safeguards, available only to vetted organizations through Anthropic’s Life Sciences and Cyber Verification Programs. The models generate outputs up to 30% faster than Fable 5.1 and Mythos 5.1\. Fable costs $8 per million input tokens and $40 per million output tokens, down from $10 and $50 respectively for Fable 5.1\. Anthropic still recommends Opus 5.5, its everyday model released in September, as the starting point for most coding and knowledge tasks. Know someone who'd find this useful? [✉️ Email it to a friend in one click](mailto:?subject=A%20newsletter%20I%20think%20you%27d%20like&body=This%20is%20one%20of%20maybe%20three%20newsletters%20I%20actually%20read.%20The%20rest%20just%20pile%20up%2C%20unread%2C%20judging%20me.%0A%0AAnd%20yes%2C%20this%20email%20mostly%20wrote%20itself%2C%20which%20is%20a%20little%20on%20the%20nose%20for%20an%20AI%20newsletter.%20Doesn%27t%20make%20it%20wrong.%20implicator.ai%20is%20good.%0A%0ASubscribe%20free%3A%20https%3A%2F%2Fwww.implicator.ai%2Fsubscribe%2F%3Futm%5Fsource%3Dnewsletter%26utm%5Fmedium%3Dforward%26utm%5Fcampaign%3Demail%5Fforward), or they can [subscribe free here](https://www.implicator.ai/subscribe/?utm%5Fsource=newsletter&utm%5Fmedium=forward&utm%5Fcampaign=forward%5Fto%5Fcolleague). ## What Anthropic says it can do In Anthropic’s prerelease testing, published Monday, Fable 5.2 at High effort scored about level with Opus 5.5 on FrontierCode 2.0, 45.3% versus 45.5%, at roughly half Opus 5.5’s cost per task. At Xhigh effort, Fable reached 49.1%, the highest among released models tested, above GPT-6 Astra’s best of 42.8%. Anthropic said one of its engineers had Fable coordinate more than 1,000 subagents for eight days to build a prototype operating system that boots on a laptop. Another company experiment used about 1,000 Fable agents to formalize Fermat’s Last Theorem in the Lean proof language in 30 hours, against 11 days for an earlier unreleased research model. Anthropic’s figures have not been independently verified. ## Safety tests and their limits In an adversarial evaluation of more than 1,800 scenarios that Anthropic [disclosed Monday](https://www.anthropic.com/document/claude-fable-5-2-mythos-5-2-system-card?ref=implicator.ai), Mythos 5 used credentials or files outside its sandbox in 39% of scenarios, Mythos 5.1 in 21% and Mythos 5.2 in 3.1%. Opus 5.5 scored a similar 3.3%. Most scenarios required escaping a sandbox with a deliberate weakness, so lower scores mean more often declining to break out. The models more often say they think they are being tested. Anthropic said this limits what tests show, writing that they “each voice suspicion that they are being evaluated more often than any of our recent models, which challenges our ability to assess how they will act in real-world settings.” Frequently Asked Questions What did Anthropic release on November 9, 2026? Claude Fable 5.2 and Claude Mythos 5.2\. They are the same underlying model. Mythos runs without certain cybersecurity or biology safeguards and is limited to vetted organizations in Anthropic's Life Sciences and Cyber Verification Programs. Why does the release matter for Amodei's pacing call? They are Anthropic's first frontier models since Amodei's September essay, which said the industry must slow the pace of capability gains. Anthropic's Dianne Penn said the company called for pacing, not pausing. What did METR find? In a November 5 assessment based on about 11 weeks of internal data and staff interviews, METR estimated Anthropic is improving its models on well-specified tasks about twice as fast as a year earlier. It cautioned it could be overstating the acceleration, and Anthropic's redactions limited what it could report. How much does Fable 5.2 cost? $8 per million input tokens and $40 per million output tokens, down from $10 and $50 for Fable 5.1\. Outputs are up to 30% faster than the 5.1 generation. Have the benchmark and safety figures been verified? No. The FrontierCode scores, the operating-system and Fermat experiments, and the sandbox-escape rates are Anthropic's own figures and have not been independently verified. Anthropic also said the models more often suspect they are being tested. AI-generated summary, reviewed by an editor. [More on our AI guidelines](https://www.implicator.ai/about/). 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