[BUG] Desktop (macOS): renderer pegs 100%+ CPU on modal dialog open from GUI

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

• Claude Desktop for macOS — version 1.19367.0 (1a5be1), build 2026-07-07T05:45:41Z
• Intel Mac, macOS Tahoe 26.3.1
• Clean install — no connectors, plugins, or integrations
• No in-app feedback option present in this build's GUI (filing here for lack of a channel)
• Onset: began after a recent app auto-update

What Should Happen?

Opening a modal should be near-instant and should not saturate a CPU core.

Error Messages/Logs

- The `Claude Helper (Renderer)` process spikes to ~100% CPU the instant the modal dialog appears.
- The entire OS becomes unresponsive until the dialog is dismissed.
- Text typed into the dialog appears character-by-character with multi-second latency.

Steps to Reproduce

Just use normally, start claud.app (without any parameters, not started by terminal, just clicking on app-icon

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

not sure, this behaviour now persisted throug several autoupdate cycles, but was not hitting me in 'some' past versions

Claude Code Version

1.19367.0 (1a5be1), build 2026-07-07T05:45:41Z

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Working workaround (for other affected users)

Launch with both GPU flags:

/Applications/Claude.app/Contents/MacOS/Claude --disable-gpu --disable-gpu-compositing

To make it persistent, a wrapper script on PATH:

#!/bin/bash
exec /Applications/Claude.app/Contents/MacOS/Claude --disable-gpu --disable-gpu-compositing "$@"

Do not combine the Help-menu "disable GPU" toggle with a partial flag (e.g. only --disable-gpu-compositing) — that contradictory state triggers #76067