Claude Code v2.1.224 lets sessions message each other on macOS and Linux
TL;DR
- Claude Code v2.1.224 adds two native tools, ListAgents and SendMessage, auto-available with no configuration on macOS and Linux.
- Same-machine messages travel over a local socket and never reach Anthropic servers; cross-machine relay routes through Anthropic servers as reply-only.
- A concurrent security fix closed a sandbox bypass: denyRead/denyWrite rules with trailing slashes were silently ignored on Linux and macOS.
Anthropic shipped a small but genuinely interesting change to Claude Code this week: sessions can now talk to each other. 9to5Mac reports that as of v2.1.224, released August 7, one Claude Code session can deliver a message to another running session on the same account, on macOS or Linux. Windows is not supported at launch.
The mechanic is deliberately restrained. You do not compose the message yourself; you tell Claude what you want the other session to know, and Claude writes the summary that gets delivered. Anthropic describes the payload as text only, never conversation history or files. The intended jobs, in the company's own framing, are handing over a finding, coordinating parallel worktrees, getting status from long-running work, and replying across machines. That is a real gap in how people actually use Claude Code today, where the standard workaround is a human ferrying context between terminals.
Why this is worth paying attention to beyond the changelog: the primitive Anthropic is exposing here, an agent that can notice something and nudge another agent about it, is the thing most third-party multi-agent frameworks are built to sell. Folding a basic version into the tool most Claude developers already run reprices that market a little. It also makes long-running background work more useful, because a research session or a slow refactor can now interrupt the foreground when it finds something instead of waiting to be checked on.
The honest caveat is that this is a floor, not a ceiling. Anthropic has walled off the actions that would make cross-session messaging dangerous: it cannot approve permission requests, cannot change configurations, and slash commands like /compact arrive as plain text rather than executable instructions. Anything privileged still prompts the receiving user. What the reporting does not tell you is how the messages travel between sessions, whether there are rate limits or token costs, or how authentication works when the two sessions sit on different machines. Those are the details that will decide whether teams treat this as a convenience or as infrastructure to build on.
What others are reporting
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Claude Code Docs (Anthropic) Read →
First-party specification covering the full permission model, inbound controls, rate limits, availability matrix, and admin org-level disable controls.
Claude uses two tools for this: ListAgents to discover which agents it can reach, and SendMessage to deliver a message to one of them by name.
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MacRumors Read →
Consumer-facing framing on eliminating manual context copying between Terminal windows; contextualizes the feature within the Claude Code subagent and agent team ecosystem.
Your sessions can now message each other. Instead of having to re-explain yourself in another session, you can now tell Claude to do it.
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DevelopersIO Read →
Hands-on walkthrough with live socket creation and a two-session working demo; flags the sandbox bypass fix as a security-critical patch for existing deployments.
Multiple sessions can be coordinated as a loosely coupled 'agent team,' enabling parallel division of tasks such as research, implementation, and review.
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Claude Hub Read →
Leads with the security dimension: denyRead/denyWrite rules with trailing slashes were silently ignored on Linux and macOS, creating false credential protection in sandboxed sessions.
A real sandbox bypass gets closed, your sessions can now message each other across machines, and the feedback transcript share now carries more than it used to.
Originally reported by 9to5mac.com
Read the original article →Original headline: Anthropic Ships Cross-Session Messaging in Claude Code v2.1.224 on macOS and Linux