Claude Code inside tmux: scroll hits input not scrollback, no rich mode ("waiting for output"), transcript not saved

Observed

Running Claude Code inside tmux produces three broken behaviors:

1. Scroll goes to the input field, not the conversation. Mouse wheel scrolls within the prompt/input box instead of scrolling back through the conversation history. There's no way to scroll up through prior output.
2. Transcript is not saved. No session transcript is persisted for the run.
3. Rich render mode never engages. The UI stays on "waiting for output" and never switches to the normal rich TUI.

Expected

• Mouse wheel should scroll the conversation/scrollback.
• The session transcript should be saved.
• The rich TUI should render normally.

Environment

• Claude Code: 2.1.156
• OS: macOS 15.0.1 (24A348)
• Terminal: tmux 3.6b (TERM=tmux-256color, TERM_PROGRAM=tmux)
• Shell: zsh
• Notably: the claude process was launched detached inside a tmux pane (tmux new-session -d) by a wrapper, with tmux mouse off, then attached to. Symptoms appear specifically in that tmux-hosted context.

Reproduction

1. From a wrapper, create a detached tmux session: tmux new-session -d -s demo, with default mouse off.
2. Launch claude inside that pane and attach.
3. Observe: wheel scroll lands on the input field (not scrollback), no rich mode (stuck on "waiting for output"), and no transcript file is written.

Notes

With tmux mouse off, wheel events pass through to the foreground app rather than entering tmux copy-mode, which seems to explain symptom #1. Symptoms #2 and #3 may be tied to claude being spawned in a detached/non-interactive PTY under TERM=tmux-256color rather than a normal interactive foreground. Filing in case Claude Code can detect the tmux context and either degrade gracefully or document the required tmux setup (set -g mouse on, interactive launch).