Terminal scrollback jumps to top when scrolling up during output

Description

When scrolling up in the Claude Code terminal to read previous output, the viewport frequently jumps back to the top of the buffer. This makes it very difficult to review long outputs or find specific information in earlier tool results.

Steps to reproduce

1. Run Claude Code in a terminal (Konsole/KDE, Wayland, Fedora 43 Atomic)
2. Let Claude produce several screens of output (e.g. a multi-file edit session)
3. Scroll up to read earlier output
4. The viewport jumps to the top of the buffer
5. Scroll down to find where you were — the viewport may jump again when you stop scrolling

Expected behaviour

Scrollback position should remain stable while the user is scrolled up, only auto-scrolling to bottom when new output arrives AND the user was already at the bottom.

Actual behaviour

• Scrolling up frequently causes a jump to the very top of the buffer
• Finding the desired content and trying to read it results in another jump away from that position
• The viewport does NOT jump to the bottom (which would at least be predictable) — it jumps to the TOP
• This makes reviewing long outputs nearly impossible

Environment

• Claude Code version: 2.1.81
• Terminal: Konsole (KDE Plasma 6)
• OS: Fedora 43 Atomic (Wayland)
• Model: claude-opus-4-6 (1M context)

Impact

High — this significantly impairs the ability to review Claude's work during long sessions, especially when multiple files are edited or many tool results are produced. Users must resort to re-reading via Read tool calls instead of scrolling, wasting context and time.