Terminal resize extremely slow in v2.1.15 (regression from 2.1.12)

Description

After upgrading from Claude Code CLI 2.1.12 to 2.1.15, terminal resize operations become extremely slow (6-7 seconds delay) when running Claude Code inside an embedded terminal environment.

Environment

• Claude Code version: 2.1.15 (issue), 2.1.12 (works fine)
• OS: Debian (Docker container based on python:3.11-slim)
• Terminal: xterm.js frontend connected via WebSocket to tmux session running Claude Code
• Node.js: 20.x

Steps to Reproduce

1. Run Claude Code inside a tmux session in a Docker container
2. Connect to the tmux session via WebSocket and render output in xterm.js
3. Resize the browser window/terminal panel
4. Observe significant delay (6-7 seconds) before the terminal updates

Expected Behavior

Terminal should resize almost instantly (as it does with v2.1.12).

Actual Behavior

With v2.1.15, there's a 6-7 second delay between resizing the window and the terminal content updating. The backend processes the resize command quickly (confirmed via logs), but Claude Code itself seems to delay the re-rendering.

Suspected Cause

Based on the changelog, v2.1.15 introduced "Improved UI rendering performance with React Compiler". This change may have altered how Claude Code handles terminal resize signals (SIGWINCH) or re-renders its UI.

Workaround

Downgrade to v2.1.12:

RUN npm install -g @anthropic-ai/claude-code@2.1.12

Additional Context

• The tmux session correctly propagates SIGWINCH to Claude Code
• Backend resize operations complete in milliseconds (verified via logs)
• The delay is specifically in Claude Code's response to the resize, not in the infrastructure
• v2.1.14 was not tested but may also work since it doesn't include the React Compiler change