**Claude Code cross-session messaging** lets one 📝Claude Code session send a plain-text message to another of the user's sessions, using the ListAgents tool to find it and SendMessage to deliver it.
📝Anthropic shipped the feature on August 7, 2026 in Claude Code v2.1.224 for macOS and Linux, with native Windows following in v2.1.234; it is on by default once a session meets the requirements. Claude sends a message on its own when a change it made affects another session's work, or on request, and the user can name a target by typing @ and the session's name. Typical uses are warning a session about a breaking change, telling parallel 📝Worktree sessions what landed, getting status from long-running work, and asking another local session for a single notice when it next goes idle.
A message is text one Claude writes for another, never the sender's conversation history or files. Between sessions on the same machine it travels over a per-session socket and never reaches Anthropic's servers; to a session on another machine or in the cloud it travels through Anthropic's servers via Remote Control. An incoming message cannot approve a permission prompt, change configuration, or run a slash command, and the receiving session's own permission rules still apply.
The crossSessionInbound setting decides whether a session accepts, holds, or refuses incoming messages, isolatePeerMachines requires approval before any message leaves the machine, and deny rules on SendMessage and ListAgents stop sending. Loops between sessions are throttled, and delivered messages count toward usage like typed prompts. /list-agents, also /peers, shows which sessions Claude can reach. The feature connects sessions the user runs separately, unlike 📝Claude Code Subagents or agent teams, which Claude spawns itself.
📝How to Message Between Claude Code Sessions walks through first use, and 📝Claude Code Multi-Agent Orchestration places messaging among the other ways to run Claude in parallel.