Codex macOS app becomes slow, unstable and crashed with high CPU when using inline browser on large React apps

What version of the Codex App are you using (From “About Codex” dialog)?

Version 26.519.41501 (3044)

What subscription do you have?

Pro

What platform is your computer?

Darwin 25.3.0 arm64 arm

What issue are you seeing?

Codex app appears to become unstable/unresponsive and crashed.

<img width="557" height="226" alt="Image" src="https://github.com/user-attachments/assets/db3f5481-ab45-4ca1-aad0-7070538b6209" />

macOS recorded repeated resource diagnostic reports:

App: /Applications/Codex.app/Contents/MacOS/Codex
Identifier: com.openai.codex
Version: 26.519.41501 (3044)
macOS: 26.3 (Build 25D125)
Architecture: arm64
Event: cpu usage
Action taken: none

Latest incident:
CPU: 90 seconds cpu time over 135 seconds (67% cpu average), exceeding limit of 50% cpu over 180 seconds
CPU limit: 90s
Limit duration: 180s
CPU used: 90s
CPU duration: 135s

What steps can reproduce the bug?

Uploaded performance trace: b0ba7f24-a447-446f-9105-f436be8f0439

I do not have a minimal standalone reproduction yet. The issue happens while using Codex on a large proprietary React/Vite frontend application, mainly when using multiple inline browsers.

Environment / app stack:

• Codex.app version: 26.519.41501 (3044)
• macOS: 26.3 arm64
• Frontend stack: React 19, Vite, TypeScript
• State/data libraries include Redux Toolkit, Jotai, Zustand, TanStack Query
• UI/runtime includes Three.js, PlayCanvas, Mapbox/MapLibre/deck.gl, Playwright tests, Storybook

Observed reproduction pattern:

1. Open Codex app on macOS.
2. Work in a large proprietary React/Vite frontend workspace.
3. Start 3-4 Codex inline browser sessions.
4. After some time, Codex becomes unstable/unresponsive or appears to crash.
5. macOS does not generate a hard crash .ips / .crash file. Instead, it records resource diagnostics.

What is the expected behavior?

Codex should remain responsive during long sessions and should not repeatedly exceed macOS resource diagnostic thresholds for CPU

Additional information

I used the same Codex app version on two different machines and experienced the same issue on both. My colleagues also reported similar slowdowns.

Also the time to first token feels noticeably slower than the CLI version.