tmux send-keys stops working after interrupting multi-line input with Esc,Esc

Summary

After interrupting a multi-line input with Esc, Esc in Claude Code running inside tmux, tmux send-keys -l stops working for that pane. tmux paste-buffer -p still works.

Reproduction steps

1. Run Claude Code in a tmux pane
2. Paste multi-line text (via bracketed paste) and submit
3. While Claude is processing, press Esc, Esc to interrupt
4. Try tmux send-keys -t <pane> -l "test" → no input appears
5. Try tmux paste-buffer -p → works normally

Key observations

• Single-line input interrupted with Esc,Esc does NOT cause this issue
• Only multi-line (bracketed paste) input triggers it
• /clear resets the state and send-keys works again
• Terminal settings (stty -a) are identical between affected and unaffected panes
• tmux pane flags (pane_mode, pane_input_off, pane_dead) are all normal
• The same pattern with cat + Ctrl+C does not reproduce → tmux is not the cause

Environment

• Claude Code: 2.1.71
• tmux: 3.6a
• OS: Linux (Manjaro)