Under the hood
Cross-session message tool now warns that a successful send doesn't mean the message was read
What
The description for the tool that sends messages between Claude Code sessions (such as to a background agent) has been rewritten to warn that a successful send only confirms the message reached the target session's queue, not that it was read. It also explains:
- Sessions in a different permission mode may hold the message for approval, let it expire, or refuse it outright
- For Remote Control, cloud, and Desktop sessions, nothing reports back on what happened to the message
Why
This sets clearer expectations that sending a message across sessions is a fire-and-forget action whose delivery can silently stall or fail depending on the receiving session's settings, so a successful send call shouldn't be read as confirmation of a reply or action.