Reaching other sessions

Claude Code sessions can message each other by name with SendMessage, which is Claude Code’s own tool. Threads use it, and so can any tab: Claude in one tab can send a message to another tab’s session, or to a session you have open in a terminal. This page covers how a session is named, how you point Claude at one, and how a message from another session shows up. The sessions and their messaging are Claude Code’s; see its tools reference.

A session’s name

A tab’s session goes by the tab’s name in Claude Code, as long as Settings → Claude Code → Name each tab’s session in Claude Code after the tab is on (Names, marks and pins explains it). Without it, Claude Code names a session after its folder with two characters added, like claudette-3f, so every tab in a folder looks alike to the others’ Claude.

The name a session is reached by can differ from the tab’s. Claude Code adds a word to a name another session already has, such as Art page-joyful-stearns. The tab’s info card shows what it really is:

• Session is the session’s ID, which claude --resume takes.
• Reached as is the name other sessions message it by.

Each has Copy in the card (The tab info card). The tab’s menu has Copy session ID once the tab has a session.

Naming a session in a message

Type @ in the composer and the list starts with the sessions Claude can message, up to eight, under the header Sessions and files. Each is marked with what it is:

• Sub-thread: one of a thread’s sub-threads, by the name its thread knows it by.
• Tab: the session in another of Claudette’s tabs, by the tab’s name.
• Session · C:\work\api: another Claude Code session on this computer, a terminal’s or another app’s, by its own name and with its folder. Claudette reads Claude Code’s list of running sessions each time you start a mention.
• Subagent · Explore: one of this tab’s subagents, newest first, by its task. SendMessage reaches a subagent by its ID.

Type some of a name to narrow the list. Picking one puts @name in the message, or @"a name" when the name has spaces. Names that clash get (2). Files and folders come after in the same list (Slash commands and mentions).

When you send, Claude gets the message without the @, which Claude Code would take for a file, and a note after it saying who each one is and what to send to: “Art page” in this message is another Claude Code session on this machine, open in another of Claudette’s tabs. To message it, call SendMessage with to: “Art page”. Your message’s card keeps what you typed, with Told Claude how to reach Art page under it and the note as its tip. A message that starts with a slash command gets no note.

By session ID

A session’s ID, pasted into a message as a word of its own, names it too: a tab’s (from Copy session ID), a sub-thread’s or another session’s on this computer. SendMessage takes a name, not an ID, so the ID stays in the message and the note gives the name. A tab’s own ID names nobody.

Messages from other sessions

When another session sends a tab a message, the tab shows it as a card labeled From the session ‹name› (From another session when the sender has no name), and the tab’s Claude reads it.

See also

• What threads are: the case where a tab’s Claude hands work to sub-threads on its own.
• Slash commands and mentions: the @ list in full.