Claude Code Gains Cross‑Session Messaging: AI Agents Can Chat Across Windows

Anthropic announced that Claude Code v2.1.224+ on macOS and Linux now supports cross‑session messaging, allowing AI agents to send messages to each other across different Claude Code sessions.

This feature addresses the pain point of developers having to copy‑paste context between multiple terminal windows—such as front‑end, back‑end, or Git worktree branches—by automatically synchronizing progress when one session reaches a key conclusion or completes a dependency.

When the version requirement is met, the messaging capability is enabled by default, requiring no additional setup.

Claude can list other reachable agents with the ListAgents tool and send messages using the SendMessage tool. Users can simply tell Claude, for example, “Notify test‑session about this API change,” and Claude will summarize the change and forward it. Claude also proactively notifies other sessions when a code modification it makes could affect them.

Transfer investigation results: a session that makes a major decision automatically summarizes and shares the outcome with affected sessions.

Coordinate parallel worktrees: when sessions work on the same repository in different worktrees, Claude informs others of completed items.

Get status of long‑running jobs: migration or test runs can report their progress to a watching session or be queried for updates.

Cross‑machine replies: a session can reply to messages received from a session on another machine, though it cannot initiate a new conversation.

Messages are read by the receiving Claude only during gaps between tool calls, so ongoing tool execution is not interrupted. If the receiving session is idle, Claude Code starts a new round to process the incoming message.

Agents that Claude can address include:

Sub‑agents running within the current session (team members are not listed).

Other local sessions on the same machine, shown only when their inbox sockets are bound.

Remote sessions on other machines or the web, marked as “Remote Control”; Claude can receive messages from them but cannot initiate a conversation.

By breaking the single‑agent limitation, this cross‑session messaging reduces token waste from copy‑paste, enhances multi‑agent collaboration, and paves the way for larger, more complex projects.