Every time you opened another session, you had to explain from scratch what you had done so far. Starting with Claude Code 2.1.224, that repetition goes away: sessions send each other messages, and the session that receives a summary picks up the work.
Only Summaries Pass, Not Chat Logs or Files
According to what ClaudeDevs shared on August 7 (US time; 04:55 KST on August 8), the new feature "passes only a summary, not conversation history or files." The session that receives the message continues the work midway based on that summary. The ListAgents tool for discovering sessions and the SendMessage tool for sending messages are the core of the feature.
It Works Across a Person's Multiple Machines
It supports macOS and Linux, and all sessions the same user has running on multiple machines. That means you can hand work started on a laptop to a desktop session as a summary, and that session can pick it up and finish it.
What the Same Update Quietly Fixed
Version 2.1.224 also fixed failed message sends being wrongly shown as "Message sent," a routing error where messages went to the wrong session when a regenerated agent reused a previous name, and long summaries being rejected and failing to send (now automatically truncated). This is not a release that just added one feature.
If You Keep Several Sessions Open at Once
For practitioners who run several Claude Code sessions in parallel, this is a noticeable change. For now, though, it is limited to macOS and Linux, and you should get in the habit of confirming directly, through the receiving session's response, that a message arrived. Even though failure display has improved, it is safer to verify at least once than to rely on it as is in an automation routine.
Sources: ClaudeDevs's X post · Claude Code changelog