TL;DR: Anthropic has unveiled its fifth-generation models, Claude Fable 5 and Mythos 5, alongside major platform and Claude Code upgrades including Managed Agents.
Summary: Anthropic announced Claude Fable 5 and Claude Mythos 5 during its Code with Claude Tokyo 2026 keynote, demonstrating industry-leading performance on SWE-bench Pro. Key features introduced include Claude Managed Agents with a planning-execution separation framework, a 1-million token context with self-improving "dreaming" mode, and a new security routing system. Mythos 5 remains restricted to selected life sciences research partners, while standard queries are routed through Fable 5 and Opus 4.8.
Why it matters: The introduction of multi-day autonomous agent capabilities and persistent memory marks a shift towards highly agentic developer workflows. Developers should look out for the roll-out of Managed Agents and sandbox infrastructure to build more complex, self-improving applications.
Source: bestblogs.dev