Under the hoodTier: how much it should matter to you
2Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
Cross-Session MessagingArea: what it touches
In DevelopmentKind: in v2.1.236,
In DevelopmentSection of the release
What
A subscription to another session's idle state results in a single [Cross-session idle notice] message, or a notice that the subscription expired. Peers running an older version are reported as unsupported and nothing is subscribed.
Details
The local socket channel gained request and notice frame types, correlated back to the original message id.
Self-targets and out-of-reach namespaces are vetted and refused.
Analytics under cross_session_notify_idle cover own_inbox_unbound, unvettable_reply_target, self_target_frame, malformed_frame and malformed_notice.
Session records advertise their supported peer features so version mismatches are detected before subscribing.
The parameter is only present in the cross-session-messaging build of the tool.
Evidence
notify_when_idle: that session runs a version without idle notices \u2014 nothing was subscribed.
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 notify_when_idle to cross-session SendMessage: ask another Claude Code session on this machine to send one notice when it next goes…
