The agent resume mechanism has been updated. Instead of passing a resume parameter with an agent ID, agents are now continued by sending a SendMessage with the agent's ID or name as the to field. The agent resumes with its full context preserved.
Evidence
New text (search for "with the agent's ID or name as the \to\ field") replacing old resume parameter documentation
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
How sure we are
One source agreesOne thing we can check says the same as this entry.
Anthropic's release notes agreeSendMessage now auto-resumes stopped agents in the background instead of returning an error
