What
When Claude Code starts a teammate (another agent working alongside the main one) in its own tmux session, it now controls which environment variables that session gets. tmux is a program that runs terminal sessions in the background, and environment variables are named values that programs read when they start.
The session now receives the variables as they were before Claude Code applied the ones from your settings, limited to those still set. It no longer inherits the full current set. Before this change, only the working folder was passed on.
Why
If you set environment variables through Claude Code's settings and expected them to appear inside a teammate's tmux session, they no longer arrive there this way.