What
Some remote setups run tools inside containers, separate boxed-off environments. Claude Code now reads a new response header, x-ccr-tool-container-stops-soon, but only from hosts that are already winding down. A container that sends it is marked as stopping soon, and one that stops sending it is unmarked. Before, only the winding-down header was tracked.
Why
Claude Code gets advance warning that a tool container is about to stop.