Message your other Claude Code sessions changedcross-session-messaging
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6060The receiving Claude reads the message between tool calls during an active turn, so a running tool is never interrupted. When the receiving session is idle, Claude Code starts a new turn with the message.
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62Between two ordinary interactive sessions with default settings, Claude Code delivers the message. Delivery isn't guaranteed in every configuration, though. The receiving session checks each arriving message against its own [inbound controls](#control-inbound-messages), and the check ends in one of three outcomes:
62Between two ordinary interactive sessions with default settings, Claude Code delivers the message. Delivery isn't guaranteed in every configuration, though. Claude Code refuses a message [over the size cap](#limitations) in the sending session, before it leaves. The receiving session checks each arriving message against its own [inbound controls](#control-inbound-messages), and the check ends in one of three outcomes:
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6464* **Delivered**: Claude Code passes the message to the receiving Claude.
6565* **Held**: Claude Code sets the message aside undelivered. A held message reaches Claude only when you approve it or a later mode or settings change allows it.
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261261The limits here are properties of the messaging channel itself and apply wherever the feature runs. For platform and provider gaps, see [Availability](#availability) instead.
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263263* **Plain text only**: Claude sends only plain text across sessions. Structured [agent team](/docs/en/agent-teams) protocol messages stay within a team.
264* **Same-machine message size is capped**: Claude Code refuses a message to a session on this machine once its serialized form passes about a million characters. The refusal [names the exact sizes](/docs/en/errors#message-too-large-for-cross-session-delivery). Nothing reaches the receiving session.
264265* **Message loops are throttled**: Claude Code rate-limits repeated messages per sender, drops identical repeats arriving within a short window, and caps accepted messages waiting for Claude to read them at 50 per session. A message loop between two sessions therefore stops on its own.
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266267## Related resources
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