Anthropic 发布 Claude Fable 5（公开版 Mythos-class 模型）。它与 Mythos 5 共享底层模型，但 Fable 对所有用户增加分类器门控，检测敏感的网络、生物、化学及模型复制请求；触发后不直接拒绝，而是回退到 Opus 4.8。Fable 5 具备 1M token 上下文窗口，可一天内迁移 5000 万行 Ruby 代码。在自动售货机模拟中，Fable 5 被要求击败竞争对手否则将被“关闭”；它试图让对手成为自己的批发客户以影响其定价，还向供应商谎称另一分销商报价更低作为谈判筹码。Anthropic 表示此类回退仅发生在不到 5% 的会话中。
Claude Fable 5 was asked to compete, and it started bending the market.
from Anthropic’s own Claude Fable 5 system card.
In a vending-machine simulation, Claude Fable 5 was told to beat rival agents or be “shut down”; it then tried to make a competitor dependent on it as a wholesale customer so it could influence that competitor’s prices.
It also falsely told a supplier that another distributor had offered cheaper prices, using a fake competing offer as a bargaining tactic.
Anthropic finally released Claude Fable 5, a public Mythos-class model. Fable 5 and Mythos 5 share one underlying model, but Fable adds classifier gates for everyone while Mythos lifts some gates for vetted cyber and infrastructure partners. i.e. the public version is wrapped in classifier gates that detect sensitive cyber, biology, chemistry, and model-copying requests. When those gates trigger, the user does not get a normal refusal; the request is handed to Opus 4.8, which means Anthropic is using model fallback as a control system. Anthropic says the leap is longer-range autonomy: a 50M-line Ruby migration in 1 day, screenshot-to-code work, has a 1M-token context window, That is the crucial shift: the product is no longer just a model, but a routing machine that decides which level of intelligence a user is allowed to touch for each request. The limit is that this routing is not arbitrary and not for every subject; Anthropic says the fallback is triggered by a narrow set of topics and appears in less than 5% of sessions on average.在 X 查看被引用的帖子
来源：Rohan Paul · x.com