[BUG] Organization Capabilities network egress allowlist not enforced in plain claude.ai chat code execution (403 host_not_allowed)

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?

Our organization (Team plan) added a custom domain (n8n-homolog.yberaclub.com) to the network egress allowlist via Organization settings → Capabilities → Allow network egress → Package managers and specific domains → Additional allowed domains, confirmed present in the UI by our Primary Owner. Despite this, the code execution tool inside a plain claude.ai chat conversation continues to block outbound requests to this domain.

What Should Happen?

Requests to domains explicitly added to the organization's network egress allowlist should be permitted from the code execution sandbox in a plain chat conversation.

Error Messages/Logs

HTTP/2 403
x-deny-reason: host_not_allowed
Host not in allowlist: n8n-homolog.yberaclub.com. Add this host to your network egress settings to allow access.

Steps to Reproduce

1. As an organization Owner, add a custom domain under Organization settings → Capabilities → Allow network egress → Additional allowed domains.
2. Start a new claude.ai chat conversation (rules out stale session config).
3. In the code execution tool, run curl -i https://<your-domain> — tested with GET and POST, same result.
4. Observe 403 host_not_allowed, despite the domain being confirmed present in the allowlist UI. Consistent across multiple days and separate conversations — rules out propagation delay.

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

N/A

Claude Code Version

N/A — not using Claude Code CLI. This occurs in claude.ai web chat.

Platform

Other

Operating System

Windows

Terminal/Shell

Other

Additional Information

This bug report uses the Claude Code issue template because related reports (#23818, #51400, #19087) about the same failure pattern were filed here despite also not being Claude Code CLI issues — they describe Cowork VMs and containers. Several template fields (Version, Platform, Terminal) don't cleanly apply to a plain claude.ai chat scenario; noted above as N/A rather than forced into an inaccurate answer. Happy to move this report if there's a more appropriate venue for claude.ai (non-Code) product bugs.

Organization: Ybera Group