Updates: #API.

[NEW] Claude Fable 5 and Claude Mythos 5 · Anthropic released Claude Fable 5 and Claude Mythos 5 on June 9, 2026. Fable 5 is a Mythos-class model made safe for general use — state-of-the-art on nearly all tested benchmarks, with the `claude-fable-5` model ID. Mythos 5 is identical with cybersecurity safeguards lifted, available in limited release through Project Glasswing. Both support a 1M token context window and up to 128k output tokens by default, priced at $10/$50 per MTok. When a safety classifier declines a request, the Messages API returns stop_reason: "refusal" as an HTTP 200, and the fallbacks parameter (beta) or SDK middleware retries on another Claude model.

[NEW] What's new in Claude Managed Agents — scheduled deployments and environment variables in vaults · Two capabilities land in public beta on the Claude Platform. Scheduled deployments give an agent a cron schedule — each time the schedule fires, the agent starts a new session and completes its task, with no scheduler for you to build or host. Environment variables in vaults store API keys tied to specific approved domains: the agent never sees your key because the sandbox only holds a placeholder, and the real key is attached at the network boundary, only on requests to domains you allow. Supports the Browserbase, KERNEL, Notion, Ramp, and Sentry CLIs plus any CLI using HTTP authentication.

[NEW] Claude in Apple's Foundation Models framework · Anthropic released a Swift package that lets Apple developers use Claude through Apple's Foundation Models framework. The framework gives developers access to tap into models natively from Swift and can return typed Swift values through guided generation in as few as three lines of code. Apps can use on-device models for simple tasks, then hand off to Claude when workflows require multi-step reasoning or code generation, with streaming, tool calls, and structured responses flowing back into your SwiftUI view. Supports iOS 27, iPadOS 27, macOS 27, visionOS 27, and watchOS 27; an Anthropic API key is required.

[NEW] What's new in Claude Managed Agents — Dreaming, Outcomes, Multiagent, Webhooks · A month after the April 8 beta launch, Managed Agents added two new features and promoted three from research preview to public beta. Dreaming (research preview) curates memory between sessions for self-improvement, and outcomes, multiagent orchestration, memory, and webhooks all ship as public beta.

[NEW] Claude Managed Agents · A new API alongside Messages that provides a pre-built agent harness and managed infrastructure — run Claude agents without building your own loop, sandbox, or tool-execution layer.