Input Event Cross-Contamination Across Multiple Terminal Sessions

Bug Description
Bug Report: Cross-session input contamination in multi-terminal setup

Environment:

• macOS (Darwin 24.6.0)
• iTerm2
• Multiple Claude Code sessions running simultaneously

Issue Description:
When running multiple Claude Code sessions in separate terminal windows/tabs, input events (specifically Shift+Enter for new lines) are being broadcast to ALL active Claude sessions instead of only the focused terminal.

Steps to Reproduce:

1. Open terminal window A and start claude
2. Open terminal window B and start another claude session
3. In terminal A, type some text and press Shift+Enter to create a new line
4. Expected: New line appears only in terminal A
5. Actual: New line appears in BOTH terminal A and terminal B

Impact:
This creates an annoying user experience when using multiple Claude sessions for different projects/contexts, as Shift+Enter events in one session create unwanted new lines in all other sessions.

Technical Details:

• Multiple Claude processes are running (confirmed via ps aux | grep claude)
• Attempted session isolation using --session-id parameter with unique UUIDs - no effect
• Attempted using separate iTerm2 sessions/profiles - no effect
• Issue persists across terminal application restarts

Workaround:
Multiple sessions can still be used, but users need to press Escape twice when returning to unfocused sessions to clear accumulated new lines.

Expected Behavior:
Each Claude session should be completely isolated from others, with input events only affecting the focused terminal session.

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 1.0.77
• Feedback ID: 423e3a80-c9fb-46c5-8889-9eae33e5bdf0

Errors

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