v2.1.175: bottom input box / status line renders corrupted (stale duplicated lines, detached prompt, border drawn through typed text) — iTerm2, macOS

Environment

• Claude Code: v2.1.175 (upgraded from the stable channel; the previous stable version rendered correctly)
• Terminal: iTerm2 3.6.11, TERM=xterm-256color
• OS: macOS 26.5.1 (build 25F80), Apple Silicon

Description

After upgrading to v2.1.175, the bottom interactive region (input box + status lines) no longer redraws cleanly. The scrollback content above it — markdown tables, prose, lists — renders fine; the corruption is confined to the input/status area.

Visible artifacts (screenshot below):

1. The ❯ prompt sits alone on its own line; the typed input text is pushed to the line below it instead of following the prompt.
2. The input box border is mostly missing — and on redraw the horizontal border line is drawn through the typed text on the same row (e.g. typed file github issue renders as —file—github—issue), with a detached cursor/highlight block.
3. The keyboard-hint fragment · ← for agents is intermittently drawn twice: once at the end of the -- INSERT -- ▶▶ auto mode on (shift+tab to cycle) line, and again as a stale orphan line below it that is never cleared.
4. The directory/branch status line (lab5.ca main ⇡3 ✓) renders in between the typed text and the INSERT mode line rather than in its usual position.

This looks like the differential renderer failing to clear previous frames of the bottom UI, leaving stale fragments behind and compositing the box border over the text row as the input area updates. The corruption reproduces continuously during normal typing (vim INSERT mode, auto mode on).

Steps to reproduce

1. On macOS with iTerm2, upgrade Claude Code from stable to v2.1.175.
2. Start an interactive session and let a long response fill the scrollback.
3. Type into the input box (vim INSERT mode active, auto mode on).
4. Observe the bottom UI: duplicated hint lines, detached prompt, border line drawn through the typed text.

Expected behavior

A single cleanly bordered input box with the prompt and typed text on one line, followed by exactly one status line and one mode line, with no stale fragments from prior frames.

Screenshot

_(attaching screenshot in a follow-up comment)_