[BUG] Up/Down arrows in input box navigate history instead of moving cursor — regression in 2.1.149+

Summary

Up/Down arrow keys in the chat input box no longer move the cursor within the input. Up immediately jumps to previous prompt history; Down does nothing when cursor is on the last line (used to jump to end-of-input). Confirmed regression via version bisect.

Bisect

• 2.1.148: Up/Down behave correctly — move cursor within input first, history only when cursor at top/bottom edge of a true multi-line input.
• 2.1.153 (latest): Up always jumps to history; Down at end-of-input is a no-op. Behavior also reproduces on 2.1.152.
• Suspect: changelog entry in 2.1.149 — "Fixed editing a recalled prompt-history entry losing the edit when navigating further up/down with arrow keys" likely altered up/down precedence in the input handler.

Environment

• Claude Code 2.1.153 (npm-global install, Node 22.18.0 via nvm4w)
• Windows 11 Home 26200
• PowerShell 5.1 in Windows Terminal
• No custom keybindings (~/.claude/keybindings.json does not exist)

Repro

1. Open claude in PowerShell.
2. Type a multi-line prompt using \ + Enter to insert newlines.
3. With cursor on the bottom line, press Up.
4. Expected: cursor moves to the line above.
5. Actual: input is replaced with the previous history entry.

Related

#62922 describes the same symptom but is mislabeled as enhancement — reporter assumed this never worked. It did, on 2.1.148.