Users running the latest version of Claude Code on macOS and Linux can now have their sessions message each other to share findings, ask questions, and coordinate work. Anthropic announced the feature for Claude Code v2.1.224, allowing different sessions to communicate with updates, especially useful for multiple sessions working on different parts of the same project.

Instead of re-explaining yourself, you can tell Claude to send a summary (not history or files) to another session. From Anthropic's documentation: cross-session messaging lets Claude deliver a message from one session to another. When a change in one session breaks another, Claude can warn that session. When one session settles a question another is blocked on, Claude can send the answer.

Best use cases include handing over a finding, coordinating parallel worktrees, getting status from long-running work, and replying across machines. Users don't need to compose the message itself; the prompt can include only the content, and Claude writes the message. Importantly, cross-session messaging doesn't work for approving permission requests or changing configurations. Commands like /compact arrive as plain text, and if acting on the message requires permission, the receiving session prompts the user for approval.