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When agent types change mid-conversation (e.g., from plugin/MCP server updates), Claude now receives explicit notifications: "New agent types are now available for the Agent tool" and "The following agent types are no longer available" — helping it stay aware of available capabilities.
Evidence
Agent notifications (search for "New agent types are now available", "The following agent types are no longer available")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.