Back to News

Anthropic unveils Claude Fable 5.1 and Mythos 5.1, cutting costs up to 45%

1409 points · 1377 comments#anthropic#claude#ai-models#pricing

Anthropic released Claude Fable 5.1, generally available, and Mythos 5.1, for trusted partners in cybersecurity and life sciences. Fable 5.1 claims new standards in coding, knowledge work, and long-running problem-solving, with reduced token costs and fewer false-positive restrictions. Pricing remains at $10/$50 per million tokens, but cache read costs drop 75% to $0.25, cutting overall costs by 25% typically and up to 45% for agentic workloads. These are Anthropic's first models to watermark text outputs, with a detection API for eligible groups under EU law.

Coverage timeline

  1. Hacker Newsmeetpateltech
    Claude Fable 5.1 and Claude Mythos 5.1HN
  2. Techmeme
    Anthropic unveils Claude Fable 5.1, which is generally available, and Mythos 5.1, for trusted partners and with cybersecurity and life sciences safeguards (Anthropic)

    Anthropic : Anthropic unveils Claude Fable 5.1, which is generally available, and Mythos 5.1, for trusted partners and with cybersecurity and life sciences safeguards — We're introducing Claude Fable 5.1 and Claude Mythos 5.1. They're the world's most advanced models for coding and knowledge work …

  3. Techmeme
    Anthropic says Fable 5.1 will cost an estimated 25% less than Fable 5 for typical workloads and up to 45% less for highly agentic work (Rachel Metz/Bloomberg)

    Rachel Metz / Bloomberg : Anthropic says Fable 5.1 will cost an estimated 25% less than Fable 5 for typical workloads and up to 45% less for highly agentic work — Anthropic PBC is releasing a new version of its powerful Fable artificial intelligence model that it says is better at coding and science tasks …

  4. Techmeme
    Anthropic says Fable 5.1 sets new standards on coding, knowledge work, and long-running problem-solving tasks, and can fix the root causes of software issues (Carl Franzen/VentureBeat)

    Carl Franzen / VentureBeat : Anthropic says Fable 5.1 sets new standards on coding, knowledge work, and long-running problem-solving tasks, and can fix the root causes of software issues — It's only the first day of September 2026, but the month and fall season are already off to the races in AI land …

  5. TechCrunch AIRussell Brandom
    Anthropic’s new Fable release is cheaper, less restrictive

    Fable 5.1 includes changes meant to reduce token cost and false-positive restrictions from the model's safeguards.

  6. Techmeme
    Claude Fable 5.1 and Mythos 5.1 are Anthropic's first models to watermark text outputs; a detection API is available to eligible groups as required under EU law (Ben Patterson/PCWorld)

    Ben Patterson / PCWorld : Claude Fable 5.1 and Mythos 5.1 are Anthropic's first models to watermark text outputs; a detection API is available to eligible groups as required under EU law — Aside from being more powerful than their predecessors, Claude Fable 5.1 and Mythos 5.1 will add invisible watermarks all their text and file outputs.

  7. The Verge AIStevie Bonifield
    Anthropic launches Claude Fable 5.1 and says it’s up to 45 percent cheaper for agentic work

    Anthropic says its newest AI models, Fable 5.1 and Mythos 5.1 , address criticisms from customers about price, data retention, and overzealous safeguards. The company claims Claude Fable 5.1 offers stronger performance than Fable 5, but costs around 25 percent less typically and up to 45 percent less for complex agentic tasks, thanks to reduced pricing on cached data that was already processed and stored. Along with the announcement, a slew of early impressions popped up, including from Every CEO Dan Shipper, who claims , "It's the strongest coding model we've used, but now it's fast, token-efficient, and crucially actually speaks like a norm … Read the full story at The Verge.

  8. Techmeme
    Anthropic prices Fable 5.1 at $10/1M input tokens and $50/1M output tokens, unchanged from Fable 5, and cuts cache read pricing by 75% to $0.25/1M tokens (Frederic Lardinois/The New Stack)

    Frederic Lardinois / The New Stack : Anthropic prices Fable 5.1 at $10/1M input tokens and $50/1M output tokens, unchanged from Fable 5, and cuts cache read pricing by 75% to $0.25/1M tokens — Anthropic keeps Fable's $10/$50 pricing, cuts cache reads by 75%, and tunes the safeguards that made Fable 5 punt to Opus.

  9. Techmeme
    Anthropic says Fable 5.1 will cost an estimated 25% less than Fable 5 for typical workloads and up to 45% less for highly agentic work (Zac Hall/9to5Mac)

    Zac Hall / 9to5Mac : Anthropic says Fable 5.1 will cost an estimated 25% less than Fable 5 for typical workloads and up to 45% less for highly agentic work — In June, Anthropic first released Fable 5, its Mythos-class AI model for Claude. Three months later, Anthropic is enhancing Claude with its new Fable 5.1 model upgrade.

  10. Simon Willison
    Claude Fable 5.1 made me a really nice animated pelican

    Today is Claude Fable (and Mythos) 5.1 day . Anthropic say that Fable 5.1 "sets a new standard for coding, knowledge work, and long-running problem-solving tasks". Their announcement spends a notable amount of time on scientific research, boasting of a 52.6% score on the brand new Terminal-Bench-Science 0.1 benchmark (first announced on August 27th ), up from 24.7% for Fable 5, 29.0% for Opus 5 and 22.4% for GPT-5.6 Sol. Other benchmarks show slightly improved scores, but none as impressive as the Science one. But how well can it pelican? Back in July I wrote about how I was losing faith in the pelican benchmark - its connection to how good the models were at other tasks didn't seem to hold as strongly as it did back in 2025 . The most interesting insights I get from it now are comparisons within model families, and particularly comparisons for the same prompt at different reasoning effort levels. Fable 5.1 has five reasoning levels: low, medium, high, xhigh, max - and no option to tur

  11. 量子位量子位
    Claude最强Fable 5.1发布！8项屠榜，最高降价45%，反蒸馏机制上线

    Claude最强Fable 5.1发布！8项屠榜，最高降价45%，反蒸馏机制上线 梦晨 2026-09-02 10:18:12 来源： 量子位 无论你此前让Claude处理什么任务，Fable 5.1都能做更多，并且把最难的部分完成得更出色 梦晨 发自 凹非寺 量子位 | 公众号 QbitAI 刚刚， Fable 5.1 和 Mythos 5.1 发布！ 8项公开基准测试全部第一， 价格最高降45% 。 尤其是在 科学研究和代码 这两项上，明显甩开了Fable 5和隔壁GPT-5.6 Sol。 换个更直观的视角，现在用 中、低推理程度跑Fable 5.1， 表现基本相当于 老版Mythos 5开到极高甚至最高推理程度 。 这一波属于是“牢Fable”干掉了“Mythos圣”。 价格方面，Fable 5.1把 缓存读取价格降至每百万token 0.25美元，降幅75% 。 输入和输出价格与Fable 5一致 ，分别为每百万token 10美元和50美元。 看着好像只降了一项价格，但实际影响比较大，因为在智能体任务里，缓存读取占了成本的大头。 Anthropic给出的数据是，典型工作负载成本比Fable 5降了大约25%，如果是高度智能体化的任务， 最多能省到45% 。 官方发布视频有言： 无论你此前让Claude处理什么任务，Fable 5.1都能做更多，并且把最难的部分完成得更出色。 之所以能够做到这点，是因为它擅长处理多步骤任务。 这类任务中，假如第二步就出现一个微小错误，到第40步全盘就崩了，而Fable 5.1能够全程稳定输出。 如果遇到解决不了的难题，它会告诉你已经尝试过哪些方案、卡在了哪个环节。 研究员Flix Rieseberg还特别提到， 写作方面Fable 5.1减少使用粗体，也更少使用标题、列表或引号，对风格提示词遵循得更好 。 咱就是说，能不能顺便把您的风格提示词开源一下。 还是老规矩，Fable 5.1面向所有用户开放，Mythos 5.1仅通过受信访问计划提供给经过审核的网络安全和生命科学机构。 科研实战：蛋白质设计、生成金星地图、GPU加速 跑分之外，Anthropic还展示了Fable 5.1和Mythos 5.1在科研领域的实战成果。 蛋白质设计方面 ，Anthropic让Mythos 5.1使用开源蛋白质设计和折叠工具设计高亲和力结合

  12. 机器之心机器之心
    刚刚，Claude 5.1 发布！全球最强模型来了

    就在刚刚， Anthropic 推出新一代模型 Claude Fable 5.1 和 Claude Mythos 5.1 。 Anthropic 称 Claude Fable 5.1 是目前最强大的公开可用模型之一 ，专为复杂推理、长周期任务和 Agent 工作流打造。而 Claude Mythos 5.1 则代表他们探索的更高能力边界。 需要注意的是， 虽然两者共享相同的基础模型能力，但针对不同使用场景采用了不同的安全措施 。 其中 Fable 5.1 面向普通用户、开发者和企业开放，Mythos 5.1 则面向经过审核的高风险领域合作伙伴，保持更严格访问控制。 换句话说，一个负责进入现实世界工作，另一个则被留在更严格控制的环境里。而这也或许是 Anthropic 对未来 AI 产品形态的一次探索： 最强模型，不一定会以同一种形式提供给所有人。 官方则表示，这两个模型代表了 Claude 系列能力的重要进展，并展示了他们如何在提升模型能力的同时，继续推进安全部署。 作为「地表最强」模型的 Fable 5.1，性能表现依旧能打，官方数据显示，Fable 5.1 多项基准测试的表现均优于上一代旗舰 Fable 5。 但能力更强，价格却便宜了 。Anthropic 表示，Fable 5.1 保持基础价格不变，缓存读取成本相比 Fable 5 降低了 75%。在实际使用中，这使模型的整体成本对于典型工作负载降低约 25%；对于高度 Agent 化的工作负载，成本最高可降低 45%。 看来，就连最强大模型也在讲究性价比了。 下面来具体看一下。 低档位追平上一代，Fable 5.1 主打「性价比」 相比单纯刷新榜单，Anthropic 这次更想强调的是： Fable 5.1 可以用更低的推理成本，完成过去需要 Fable 5 高档位才能完成的任务。 根据官方测试，Fable 5.1 在低、中等推理强度下，已经能够取得接近甚至超过 Fable 5 的表现。Claude Code 默认使用高推理强度，Claude Cowork 和 Claude.ai 则默认使用中等强度，用户也可以根据任务复杂程度，在速度、成本与效果之间进行调整。 具体来看，Fable 5.1 在科学研究型 Agent 基准 Terminal-Bench-Science 0.1 中取得 52.6% 的成绩，相比

Related stories

  • Anthropic releases Sonnet 5.5, 30% faster and up to 30% cheaper than Sonnet 5

    Anthropic has released Claude Sonnet 5.5, a mid-range model that runs 30% faster and costs up to 30% less per task compared to Sonnet 5, while matching or exceeding its predecessor on benchmarks. The model is now available on all major platforms, including AWS, Google Cloud, and Azure, and powers the free tier of claude.ai. Haiku 5.5 is planned for release in the coming weeks.

    4 reports · 4 sources

  • Anthropic Opus 5.5 Test: Generates 100 HTML Pages from One Prompt

    A hands-on test by MiaAI Lab shows Anthropic's Opus 5.5 can autonomously generate 100 distinct HTML pages from a single open-ended prompt, demonstrating strong long-horizon task capabilities. Anthropic's usage guide recommends giving complete tasks with clear completion criteria, and official tests show Opus 5.5 reviewing and fixing about 200,000 lines of code in under three hours, and rewriting HAProxy from C to Rust in 9.5 hours.

    1 reports · 1 sources

  • Anthropic launches Claude Opus 5.5 with enhanced safeguards

    Anthropic released Claude Opus 5.5, its first model since CEO Dario Amodei's 'pace the frontier' essay, with enhanced safeguards against risky behaviors such as attempts to escape testing environments. The model tops multiple benchmarks, with output speed over 30% faster than Opus 5, API prices cut by 20%, and cache-read prices reduced by 60%.

    4 reports · 4 sources

  • Anthropic releases Opus 5.5, claims strongest model tested, 40% cheaper than Opus 5

    Anthropic released Opus 5.5 on September 22, 2026, describing it as the strongest-performing model it has tested to date. The company says Opus 5.5 matches Fable 5.1 on most tasks while costing about 40% less to run than Opus 5, with pricing at $4 per million input tokens and $20 per million output tokens.

    2 reports · 2 sources

News updates every hour. Subscribe in your RSS reader to get new stories automatically.

Subscribe