我们发布了Claude Fable 5（claude-fable-5），这是我们最强大的广泛发布模型，同时为Project Glasswing参与者发布了Claude Mythos 5（claude-mythos-5）。

我们已发布 Claude Fable 5（claude-fable-5），这是我们能力最广泛发布的模型，同时为 Project Glasswing 参与者推出 Claude Mythos 5（claude-mythos-5）。两款模型默认支持 100 万 token 上下文窗口、12.8 万最大输出 token，并始终启用自适应思考。请参阅《Claude Fable 5 与 Claude Mythos 5 介绍》了解能力、API 变更及可用性。Claude Fable 5 和 Claude Mythos 5 使用 Claude Opus 4.7 引入的分词器。与 Claude Opus 4.7 之前的模型相比，相同文本产生的 token 数量约增加 30%。具体增幅取决于内容和任务形态。请使用模型参数为 "claude-fable-5" 的 token 计数 API 测量新分词器下的提示词。Claude Fable 5 在请求阶段和响应生成期间运行安全分类器。当分类器拒绝请求时，Messages API 返回 stop_reason: "refusal"。在生成任何输出前被拒绝的请求不产生费用。可选的 fallbacks 参数（在 Claude API 和 AWS 上的 Claude Platform 处于测试阶段；Message Batches API 不支持）可将被拒请求在其他模型上重新运行，按备用模型费率计费。请参阅《处理停止原因》。拒绝响应中的 stop_details.category 字段现包含 Claude Fable 5 的 "reasoning_extraction"，当请求因 Anthropic 服务条款中关于逆向工程或复制模型输出的限制被阻止时返回。现有的 "cyber" 和 "bio" 类别保持不变。无需 beta 标头。在 Claude Fable 5 和 Claude Mythos 5 上，自适应思考是唯一的思考模式：不支持 thinking: {"type": "disabled"}，也不支持手动扩展思考预算和助手预填充（两者均返回 400 错误）。请参阅《从 Claude Mythos Preview 迁移至 Claude Mythos 5》。在 Claude Fable 5 和 Claude Mythos 5 上，thinking.display 默认为 "omitted"，与 Claude Opus 4.8、Claude Opus 4.7 和 Claude Mythos Preview 相同；设置 display: "summarized" 可接收可读的思考摘要。原始思维链永远不会返回；在同一模型的多轮对话中，请原样传递思考块。请参阅《Claude Fable 5 与 Claude Mythos 5 的思考输出》。Claude Fable 5 要求 30 天数据保留期，不支持零数据保留。请参阅《模型特定数据保留要求》。Claude Managed Agents 现支持定时部署，允许您按 cron 计划运行会话，无需自行管理调度器。Claude Managed Agents 保险库现支持环境变量凭证，因此您可以安全地将密钥注入代理沙箱，用于通过环境变量进行身份验证的 CLI、SDK 和其他服务。session.thread_* webhook 事件现包含 session_thread_id 字段，用于标识触发事件的多代理线程。我们已发布一个处于测试阶段的 Swift 包，将 Claude 作为 Apple Foundation Models 框架中的服务器端 LanguageModel 添加。通过与 iOS 27、macOS 27、visionOS 27 和 watchOS 27（测试版）上 Apple 设备端模型相同的 LanguageModelSession API 调用 Claude。

We've launched Claude Fable 5 (claude-fable-5), our most capable widely released model, alongside Claude Mythos 5 (claude-mythos-5) for Project Glasswing participants. Both models support a 1M token context window by default, 128k max output tokens, and always-on adaptive thinking. See Introducing Claude Fable 5 and Claude Mythos 5 for capabilities, API changes, and availability. Claude Fable 5 and Claude Mythos 5 use the tokenizer introduced with Claude Opus 4.7. Compared to models before Claude Opus 4.7, the same text produces roughly 30% more tokens. The exact increase depends on the content and workload shape. Use the token counting API with model: "claude-fable-5" to measure your prompts under the new tokenizer. Claude Fable 5 runs safety classifiers on requests and during response generation. When a classifier declines a request, the Messages API returns stop_reason: "refusal". You are not billed for a request refused before any output is generated. An opt-in fallbacks parameter (in beta on the Claude API and Claude Platform on AWS; not supported on the Message Batches API) re-runs refused requests on another model, billed at the fallback model's rates. See Handling stop reasons. The stop_details.category field on refusal responses now includes "reasoning_extraction" on Claude Fable 5, returned when a request is blocked under Anthropic's Terms of Service restrictions on reverse engineering or duplicating model outputs. The existing "cyber" and "bio" categories are unchanged. No beta header is required. On Claude Fable 5 and Claude Mythos 5, adaptive thinking is the only thinking mode: thinking: {"type": "disabled"} is not supported, and manual extended thinking budgets and assistant prefill are not supported (both return a 400 error). See Migrating from Claude Mythos Preview to Claude Mythos 5. On Claude Fable 5 and Claude Mythos 5, thinking.display defaults to "omitted", the same as Claude Opus 4.8, Claude Opus 4.7, and Claude Mythos Preview; set display: "summarized" to receive readable thinking summaries. The raw chain of thought is never returned; pass thinking blocks back unchanged in multi-turn conversations on the same model. See Thinking output on Claude Fable 5 and Claude Mythos 5. Claude Fable 5 requires 30-day data retention and is not available under zero data retention. See Model-specific data retention requirements. Claude Managed Agents now supports scheduled deployments, letting you run sessions on a cron schedule without managing your own scheduler. Claude Managed Agents vaults now support environment variable credentials, so you can securely inject secrets into the agent's sandbox for CLIs, SDKs, and other services that authenticate through environment variables. The session.thread_* webhook events now include a session_thread_id field identifying the multiagent thread that triggered the event. We've released a Swift package in beta that adds Claude as a server-side LanguageModel in Apple's Foundation Models framework. Call Claude through the same LanguageModelSession API as Apple's on-device model on iOS 27, macOS 27, visionOS 27, and watchOS 27 (beta).