[BUG] Agent teams: active pane border color invisible on tmux < 3.3 (tmux 3.2a, Ubuntu 22.04)

Describe the bug

When using Claude Code agent teams, all tmux pane borders render with the same color — there is no visual distinction between the active and inactive panes. This makes it impossible to tell at a glance which agent pane is currently focused.

Environment

• OS: Ubuntu 22.04.5 LTS
• tmux version: 3.2a
• Claude Code version: 2.1.63

Steps to reproduce

1. Start a tmux session and set pane border colors:

``
tmux set -g pane-active-border-style "fg=blue"
tmux set -g pane-border-style "fg=colour238"
``

1. Start a Claude Code session and prompt it to use agent teams
2. Observe that subagents open split panes — the border colors are overwritten and all pane borders now look identical

Expected behavior

The active pane should have a visually distinct border color compared to inactive panes.

Actual behavior

All pane borders render with the same color. The active pane is indistinguishable from inactive panes.

Workaround

After Claude Code finishes initializing the agent team layout, re-run:

tmux set -g pane-active-border-style "fg=blue"
tmux set -g pane-border-style "fg=colour238"