Regression: TUI alternate-screen breaks tmux scroll-back; cannot review conversation above top of screen (accessibility regression)

Claude Code version: 2.1.172
Platform: macOS 15.6.1 (arm64)
Terminal: tmux 3.5a (TERM=screen-256color), history-limit 1000000

Summary

The latest version appears to have broken the ability to review terminal scroll-back. I depend critically on scrolling back through prior output because I cannot always keep up with reading output in real time. There now appears to be no facility for reviewing the conversation beyond the top of the current screen. This is profoundly disabling.

What changed

Previously, normal terminal scroll-back worked: I could scroll up (including via tmux copy-mode) to re-read earlier output and earlier parts of the conversation that had scrolled off the top of the screen. In 2.1.172, scroll-back no longer lets me review content above the top of the visible screen.

Expected behavior

Output that has scrolled off the top of the screen remains reviewable via the terminal's / tmux's native scroll-back buffer (copy-mode), exactly as it did in the prior version.

Actual behavior

Scroll-back above the top of the screen is broken / unavailable. There is no facility within the TUI to review the conversation back beyond the top of the screen.

Why the obvious workaround is inadequate

Saving the conversation and reviewing it externally completely undermines the close interactive integration that worked so well before. The value was being able to glance back at recent output without leaving the live session.

Impact

• Accessibility regression: users who cannot keep pace with live output rely on scroll-back. Removing it is disabling, not merely inconvenient.
• Relative to the previous version, this is a large step backward in the UI.

Likely mechanism (after inspecting local tmux config)

This appears to be caused by the TUI now rendering on the terminal's alternate screen buffer (the same mode vim/less/htop use). While an app is on the alternate screen, tmux copy-mode / native scroll-back has nothing to show, because the app repaints a fixed-size screen instead of emitting scrolling lines into the normal buffer — which precisely matches the symptom.

The local tmux config is not the cause:

• history-limit 1000000 (large scroll-back buffer)
• alternate-screen at tmux default (on)
• the smcup@/rmcup@ override that would disable alt-screen is commented out

Setting alternate-screen off is at best a partial workaround and does not reliably restore scroll-back for a continuously-redrawing TUI.

Request

Please provide a setting/flag to run the TUI in the normal screen buffer (line-by-line, scrolling output) so native terminal/tmux scroll-back works again as it did before — or otherwise restore the previous scroll-back-friendly rendering.

Suggestion

If the goal is a richer interactive environment, consider supporting running the TUI from within an editor such as vim, where text-folding could provide the same "hide text" behavior without sacrificing the ability to scroll back and review the full transcript.