[BUG] Cowork sessions fail with "Failed to create bridge sockets after 5 attempts" on desktop app 1.3036.0

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?

Every Cowork session in the Claude desktop app (v1.3036.0) fails immediately on message send. The VM boots successfully, but the claude binary inside (SDK 2.1.111) exits with code 1 within ~1 second with the error "Failed to create bridge sockets after 5 attempts". Affects both brand-new sessions AND resumed sessions.

Local (non-Cowork) sessions work fine, so it's specifically the Cowork sandbox that's broken. This started happening immediately after the app auto-updated to 1.3036.0.

What Should Happen?

Cowork session should start and accept messages normally, as it did before the 1.3036.0 update.

Error Messages/Logs

From ~/Library/Logs/Claude/cowork_vm_node.log:

[VM:start] Startup complete, total time: 256407ms
[Spawn:config] Creating spawn function for process=bold-fervent-pascal, isResume=false, mounts=9 (outputs, .claude, .claude/skills, .remote-plugins, .cowork-lib, .cowork-perm-req, .cowork-perm-resp, uploads)
[Spawn:vm] Spawn succeeded in 64ms
[vm-stderr] Error: Failed to create bridge sockets after 5 attempts
[Process] Exited, code=1, signal=null, duration=1081ms, oom=false

Steps to Reproduce

1. Open Claude desktop app (version 1.3036.0)
2. Start a new Cowork session
3. Send any message (e.g., "hello")
4. Session exits immediately with code 1

Already tried:

• Fully quitting and relaunching the app — no change
• Deleting ~/Library/Application Support/Claude/vm_bundles so the VM is re-downloaded fresh — app downloads pristine VM, same error
• Both new and resumed sessions fail identically

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

The app version immediately prior to 1.3036.0. Don't know the exact number — Cowork broke right after the auto-update on 2026-04-16.

Claude Code Version

Desktop app: 1.3036.0 Bundled SDK (broken in Cowork): 2.1.111 CLI via Homebrew (works fine, unrelated): 2.1.92 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Additional evidence the bug is in SDK 2.1.111 specifically:

1. Local (non-Cowork) sessions in the same desktop app work fine — so OAuth, network, and general app state are healthy.

1. The standalone CLI installer from https://claude.ai/install.sh (which also installs 2.1.111) crashes on this machine with a Bun bus error:

"panic: Bus error at address 0x10664EB80 — Bun v1.3.13, macOS 15.6.1"
Crash reported via bun.report.

1. Homebrew's cask (claude-code 2.1.92) installs and runs fine on the same machine. claude doctor reports: Search OK, no version locks, no config problems.

This suggests SDK 2.1.111 has regressions in both:

• The macOS native binary (installer crash)
• The Linux binary running inside the Cowork VM (bridge socket creation)

Reset steps attempted before filing:

• killall / relaunch — no effect
• rm -rf ~/Library/Application Support/Claude/vm_bundles — VM re-downloaded fresh — no effect