What
In remote sessions, tools run in a container, which is an isolated environment on a server. Claude Code now reads a response header, x-ccr-tool-container-restart, whose value is replaced or restarted, and records it for each address. A header is a small label sent with a server's reply. Claude Code already tracked a similar header that says a container's host is shutting down.
Why
A remote session can now tell that its tool container was restarted.