[BUG] Cowork desktop app: white screen on launch, RPC "message too large" error

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?

Description

Claude Cowork desktop app on Windows shows a white/blank screen on launch and never loads the UI. Task Manager shows 8 Claude processes running in the background, but the app is unusable.

Environment

• OS: Windows (ARM64)
• App version: Claude 1.9255.2.0 (latest, after multiple reinstalls)
• Issue duration: ongoing since ~May 14, 2026

Root cause (found in cowork-service.log)

Recurring critical error:

What Should Happen?

Cowork should launch as usual in working order

Error Messages/Logs

2026/05/26 16:31:27.862708 [Server] Persistent RPC: connection ended: message too large: 2065853797 bytes
2026/05/26 16:31:27.862708 [Server] Session Jasna:...LocalCache\Roaming\Claude has no active connections, idle timeout starts
2026/05/26 16:31:27.916810 [Server] Client connected
2026/05/26 16:31:28.415540 [Server] Client signature verified: ...claude.exe (subject: Anthropic, PBC)
2026/05/26 16:31:28.420797 [Server] Client connected: user=Jasna exe=claude.exe isDev=false
2026/05/26 16:31:28.420797 [Server] Persistent RPC: entering loop

Steps to Reproduce

1. Open the Claude desktop app on Windows (ARM64)
2. Navigate to Cowork
3. Wait for the app to connect to the CoworkVMService
4. App shows white/blank screen instead of loading the UI
5. Check C:\ProgramData\Claude\Logs\cowork-service.log — shows repeated "message too large: 2065853797 bytes" errors on each connection attempt

This happens on every launch, consistently, since May 14, 2026. Not intermittent.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

N/A — using Claude Cowork (desktop app), not Claude Code CLI. Desktop app version: Claude_1.9255.2.0 (from log)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_