[BUG] Web session stalls indefinitely at "Start Claude Code" step after successful setup

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?

Claude Code on the web (claude.ai/code) consistently hangs at the final "Start Claude Code" step of container initialization. This happens on brand-new sessions, not just resumed ones.

Progress steps observed, in order:

1. Starting your cloud container — completes
2. Cloning your repository — completes
3. Run setup script — completes
4. Start Claude Code — hangs indefinitely, no error, no timeout

Reproduces: 100% across multiple fresh attempts (not resumed sessions)
Platform: Claude Code on the web
Browser/OS: macOS
Status page: status.claude.com shows all systems operational at time of report, so this doesn't appear to be a broad flagged outage.

Additional context: Tried starting completely new sessions from scratch (not resuming) — same stall occurs every time at the same step.

What Should Happen?

Claude Code should start and become interactive after setup completes.

Error Messages/Logs

API Error occurred

Steps to Reproduce

1. Start a new Claude Code on the web session connected to a GitHub repo
2. Watch the four initialization steps
3. First three steps complete normally
4. Session stalls permanently on "Start Claude Code" with no error message

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.123 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_