Under the hoodTier: how much it should matter to you
2Useful: my rating, 1 to 5
3Signal: worth watching, 1 to 5
AgentsArea: what it touches
Internal ChangesKind: in v2.1.224,
Internal ChangesSection of the release
What
The tool that sends messages between agents now reports a delivery outcome to telemetry instead of failing silently, using not_reachable when the recipient is not in the roster or cannot be resolved and mailbox_write_failed when the write itself fails.
Evidence
mailbox_write_failed
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 agreeAdded cross-session SendMessage: Claude Code sessions can now message each other, on any of your machines, with ListAgents to discover them…
