[BUG] TUI: Copy and paste not working in tmux [Claude Code, Opencode, Github Copilot] [Dev, Production]

[flora131]

Description

Copy and paste functionality does not work when the TUI is running inside a tmux session. Users are unable to copy text from the TUI output or paste text into the TUI input while inside tmux.

Affected Agents

• Claude Code
• Opencode
• Github Copilot

Environment

• Dev (bun run / local development)
• Production (binary build)

Reproduction Steps

1. Start a tmux session (tmux new-session)
2. Launch the TUI inside the tmux session
3. Attempt to select and copy text from the TUI output (using system clipboard shortcuts or tmux copy mode)
4. Attempt to paste text into the TUI input field
5. Observe that copy and/or paste operations fail or produce no result

Expected Behavior

Copy and paste should work seamlessly within the TUI when running inside tmux, consistent with standard terminal application behavior. Users should be able to copy output text and paste input text using standard clipboard mechanisms.

Actual Behavior

Copy and paste operations do not work. Text cannot be copied from the TUI output or pasted into the TUI input when running inside a tmux session.

Additional Context

• OS: macOS
• Terminal: Unknown (running inside tmux)
• Shell: zsh
• Version/Commit: Unknown
• tmux is commonly used to manage TUI sessions, so this is a high-impact usability issue

Investigation Notes

IMPORTANT: Do NOT assume or speculate on the root cause in the initial filing. The purpose of this section is to capture raw observations only. Root cause analysis happens during investigation.

• The issue is specific to running inside tmux — copy/paste may work outside of tmux.
• Further investigation needed to determine if this is a tmux clipboard integration issue, a TUI input handling issue, or a terminal escape sequence issue.