[BUG] Cowork SDK install loop on every spawn, all projects fail with exit code 1

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?

Cowork fails on every project with UI error Claude Code process exited with code 1. Logs show the VM boots cleanly and the network layer is healthy (API reachability: REACHABLE), but [postConnect] Installing SDK ... version=2.1.121 fires repeatedly — multiple times within seconds of each other — and Spawn confirmed never appears for any spawn on the failing day. It looks like the SDK install completion isn't being signaled back, so the next spawn attempt re-triggers install instead of running claude code, and the actual process invocation exits 1.
Confirmed not project-specific: reproduces across multiple projects.
Confirmed not local state: persists after full reset (deleted claude-code-vm/ and vm_bundles/, fresh app rebuild from scratch).

Environment

Claude Desktop: 1.5354.0
Platform: macOS, Apple Silicon
SDK version (per logs): 2.1.121
Subscription: [your plan]

What Should Happen?

Claude cohort should work

Error Messages/Logs

Logs — repeated install on a freshly-reset Cowork

2026-04-30 20:54:55 [info] [postConnect] Installing SDK: subpath=Users/taka/Library/Application Support/Claude/claude-code-vm, version=2.1.121
2026-04-30 20:55:18 [info] [postConnect] Installing SDK: subpath=Users/taka/Library/Application Support/Claude/claude-code-vm, version=2.1.121
2026-04-30 20:55:18 [info] [postConnect] Installing SDK: subpath=Users/taka/Library/Application Support/Claude/claude-code-vm, version=2.1.121

Earlier same day, same pattern across hours, never followed by a Spawn confirmed:
2026-04-30 20:14:04, 20:14:23, 20:14:27, 20:14:32, 20:14:44, 20:14:55, 20:14:55
2026-04-30 20:27:19, 20:28:27, 20:28:32

For comparison, healthy spawn from April 20 (same machine):
2026-04-20 19:27:44 [info] [Spawn:vm] id=... OAuth token approved with MITM proxy
2026-04-20 19:27:44 [info] [Process:...] Spawn confirmed, flushing 2 buffered stdin chunks
2026-04-20 19:27:44 [info] [Spawn:vm] id=... Spawn succeeded in 74ms
Network/VM layer is fine — [VM] API reachability: REACHABLE, MITM proxy started, IPv4 route up, user recovery complete: recovered=19 skipped=1 failed=0.

Steps to Reproduce

Update to Claude Desktop 1.5354.0
Open any project in Cowork
Send any message
UI: Something went wrong — Claude Code process exited with code 1
Logs: SDK install loop, no Spawn confirmed

Already Tried

Restart Claude Desktop ✓
Restart Mac ✓
Different projects (multiple) ✓
Full reset: deleted ~/Library/Application Support/Claude/claude-code-vm/ and vm_bundles/, rebuilt from scratch ✓
All fail identically.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.123

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

<img width="812" height="379" alt="Image" src="https://github.com/user-attachments/assets/8d27479d-7c0b-4daf-b8a4-221820706c0f" />

<img width="849" height="405" alt="Image" src="https://github.com/user-attachments/assets/b02dcbc0-3113-421d-af3d-d0f6984765ba" />