[BUG] Claude Desktop v1.2581.0 - Renderer process pegs CPU at 500%+ immediately on launch, app unusable

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?

On Claude Desktop v1.2581.0 (macOS), the Claude Helper (Renderer) process immediately spikes to 500%+ CPU on every launch, causing the main webview to go black and become unresponsive within minutes. The app is completely unusable.

Steps to reproduce:

1. Launch Claude Desktop v1.2581.0 from /Applications
2. Wait 2-5 minutes
3. App freezes with black screen

What happens:

• main.log shows "Main webview is unresponsive, will kill and reload"
• ps aux shows Claude Helper (Renderer) at 500%+ CPU
• 4 Claude Helper processes enter "stuck" state
• Killing stuck processes does not recover the app
• Clearing session state, caches, and local-agent-mode-sessions does not fix it
• Issue persists across full reinstalls

Root cause appears to be a runaway --resume session being spawned by the Cowork VM on launch (claude-code with --effort max --model claude-opus-4-6 --resume <session-id>)

OS: macOS (Apple Silicon)
Desktop version: 1.2581.0
Claude Code version: 2.1.101

What Should Happen?

Claude Desktop should launch and remain stable. The renderer process should idle at low CPU usage when no active task is running.

Error Messages/Logs

From main.log:
2026-04-14 18:10:11 [info] Main webview is unresponsive, will kill and reload
2026-04-14 18:10:12 [error] Sentry caught: Main webview became unresponsive

From ps aux:
davantealexander 4621 100.9 8.4 ... Claude Helper (Renderer) --type=renderer ... --effort max --model claude-opus-4-6 --resume 14313d47-3aa5-4c06-9eb5-d628c71f3163

Steps to Reproduce

1. Install Claude Desktop v1.2581.0 on macOS
2. Launch the app from /Applications
3. Wait 2-5 minutes
4. Observe black screen / frozen UI
5. Run: ps aux | grep -i claude | grep -v grep | awk '{print $3, $11}' | sort -rn | head -5
6. Observe Claude Helper (Renderer) at 500%+ CPU

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Unknown - issue present since installing 1.2581.0

Claude Code Version

2.1.101

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

• Clearing ~/Library/Application Support/Claude/local-agent-mode-sessions does not fix it
• Clearing caches does not fix it
• Full reinstall does not fix it
• The renderer spawns a claude-code process with --resume flag pointing to a previous session, which appears to be the trigger for the CPU spike
• Two DMGs were mounted simultaneously (Claude and Claude 1) suggesting a mid-session auto-update may have triggered the issue