[FEATURE] Sticky input bar at bottom of TUI while scrolling conversation history

Summary

Keep the input prompt pinned to the bottom of the terminal so it stays visible (and editable) while the user scrolls up through earlier messages in the same session.

Use case

While Claude is mid-stream or has just finished a long response, I often want to read the message above and start typing my next question at the same time. Today the input box scrolls off-screen along with the rest of the terminal buffer, so I have to choose between reading history and composing the next prompt.

Two interactions would be enough:

1. While reading scrollback, the input bar stays visible at the bottom.
2. Keystrokes go to the input bar (not the scroll buffer) unless an explicit scroll-mode keybinding is active.

Prior demand

This has been requested repeatedly and every prior issue has been closed without an implementation:

• #13591 — 45 👍, 17 comments (closed)
• #17875 — 34 👍, 7 comments (closed)
• #26101 — closed, locked as resolved
• #41025 — closed as duplicate, locked

Reopening here because the underlying problem is still present in 2.1.x. The related open issue #28077 ("Allow scrolling back to view full conversation history in CLI TUI") is a prerequisite — sticky input only makes sense once scrollback within the TUI exists — but the two are different features and shouldn't be merged.

Workarounds today

• "autoScrollEnabled": false reduces auto-snap-to-bottom but doesn't pin the input.
• tmux copy-mode lets you scroll the terminal buffer but the input still scrolls with it.

Environment

• Platform: darwin (Darwin 25.5.0)
• Terminal: zsh
• Claude Code version: 2.x (current as of 2026-05-20)