Nothing to try yetTier: how much it should matter to you
2Useful: my rating, 1 to 5
4Signal: worth watching, 1 to 5
Cross-Session MessagingArea: what it touches
In DevelopmentKind: in v2.1.236,
What probably matters to youSection of the release
The notify_when_idle parameter is only added to the message tool's schema when cross-session messaging is enabled.
What
The tool Claude uses to message another session on the same machine gained a notify_when_idle input that subscribes to a single notice when that session next goes idle or exits; sent without a message body it is a pure subscription. The parameter is only added to the tool schema when cross-session messaging is on, so with the gate off the model never sees it.
Refusal reasons each get their own sentence: no-inbox, self-target, peer-unsupported, unreachable-namespace, cap, peer-gone.
Subscriptions live in a table with a maximum size, eviction and expiry.
Sub-agents and teammates are refused, recorded as subscribe_refused_principal, under cross_session_notify_idle telemetry.
Evidence
Ask a session ON THIS MACHINE to send you ONE notice when it next goes idle
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
Read from
Names in the bundlenotify_when_idle
Feature flag
tengu_harbor_kiteOff by default, switched on for this account
The shipped code defaults this off, and the flag server returned on for the one account this site reads on this version. That is the reading that makes the entry above worth a second look, and it still says nothing about your account.
This account: on · anonymous baseline: on · compiled default in v2.1.236: off
tengu_harbor_kite_winOff in both readings
The flag server returned off for the account this site reads and for the anonymous baseline. A reading of off cannot rule out a rollout these two readings sit outside of.
This account: off · anonymous baseline: off · compiled default in v2.1.236: off
Flag reading movedThe flag server now returns on for tengu_harbor_kite, read as this account.A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
Flag reading movedThe flag server now returns off for tengu_harbor_kite, read as this account.A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
Flag reading movedThe flag server now returns on for tengu_harbor_kite, read as this account.A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
Flag reading movedThe flag server now returns nothing at all, having stopped carrying it for tengu_harbor_kite, read as this account.A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
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…
