Under the hoodTier: how much it should matter to you
1Useful: 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
An idle subscription can accompany a plain-text message or stand alone with an empty message, but not a structured one. Bridge targets, did-scheme targets and messaging yourself are each refused with their own message.
Details
Outcomes are recorded under a new telemetry name.
Unconditional inside the tool; which refusal you get depends on the target's address scheme.
Evidence
notify_when_idle cannot ride a structured message \u2014 send plain text, or omit the message for a pure subscription
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…
