[BUG] Fullscreen renderer + CLAUDE_CODE_DISABLE_MOUSE=1: mouse wheel navigates prompt history instead of scrolling the viewport

Description

When the TUI uses the fullscreen renderer and the environment variable CLAUDE_CODE_DISABLE_MOUSE=1 is set, the mouse scroll wheel does not scroll the conversation/viewport. Instead it only navigates the prompt input history (as if pressing Up/Down arrows). The only way to scroll the view is the PgUp/PgDn keys.

Notably, CLAUDE_CODE_DISABLE_MOUSE=1 is often suggested as the supported way to get native scrolling back (e.g. in #66601), but in the fullscreen renderer it does not restore wheel scrolling -- it simply hands the wheel through to the prompt box as history navigation.

Steps to Reproduce

1. Use the fullscreen renderer (/tui fullscreen).
2. Set CLAUDE_CODE_DISABLE_MOUSE=1 and restart Claude Code.
3. Produce enough output to make the conversation scrollable.
4. Hover the cursor over the conversation and scroll the mouse wheel.

Expected Behavior

The mouse wheel scrolls the conversation/viewport up and down -- or there is a documented setting to opt into that behavior.

Actual Behavior

The mouse wheel navigates the prompt input history; the viewport does not scroll. Scrolling the view is only possible with PgUp/PgDn.

Likely Mechanism

The fullscreen renderer uses the terminal's alternate screen buffer, which has no native scrollback. With CLAUDE_CODE_DISABLE_MOUSE=1, Claude releases mouse capture, so the terminal (Windows Terminal here) translates wheel events into up/down arrow keys in alternate-screen mode. Those arrows reach the prompt box and are consumed as history navigation. So unlike the classic renderer -- where releasing the mouse lets the terminal's native scrollback handle the wheel -- in fullscreen there is nothing for the wheel to scroll except via Claude itself.

Request

If this is a bug: in the fullscreen renderer the mouse wheel should scroll Claude's own viewport (since there is no terminal scrollback to fall back on), even with CLAUDE_CODE_DISABLE_MOUSE=1.

If this is intended: please provide a setting/env var to customize it -- e.g. remap the wheel to viewport scroll in fullscreen, or otherwise let users choose between "wheel = history" and "wheel = viewport scroll."

Environment

• Claude Code: 2.1.187
• OS: Windows 11 Pro
• Terminal: Windows Terminal
• Shell: PowerShell
• Renderer: fullscreen (/tui fullscreen)
• CLAUDE_CODE_DISABLE_MOUSE=1

Related Issues

• #66601 -- Scroll wheel intercepted by prompt history navigation, no way to disable (same core symptom; this report is the fullscreen + CLAUDE_CODE_DISABLE_MOUSE=1 facet, where the suggested workaround does not help)
• #62294 -- CLAUDE_CODE_DISABLE_MOUSE=1 + terminal scroll wheel = only full-page scroll
• #65833 -- scroll wheel no longer scrolls conversation, sends arrow keys instead
• #70429 -- Fullscreen renderer: cannot scroll at input prompt