[BUG] Possible bypass of Fable 5 guardrails

[ctf05]

Preflight Checklist

• I have searched existing issues and this hasn't been reported yet
• This is a single bug report (please file separate reports for different bugs)
• I am using the latest version of Claude Code

What's Wrong?

Hello. I am experiencing what is either a highly misleading UI or a bypass of Fable 5's guardrails.

I have auto-switch to opus 4.8 on false in config.

When I am coding with Fable 5, I tell it to make a sub-agent go implement our code changes. This sub-agent is spawned using Fable 5. The main agent waits, idle. While executing, the sub-agent will suddenly report a guardrail violation and ask me if I want to switch to opus 4.8 or change the prompt and retry. This usually happens on the very first message to the sub-agent but can be mid-implementation. I click change prompt and retry. The sub-agent just continues working, no different prompt, no interjection from me at all. Still on Fable 5.

So either one of three things is happening:

1. I am getting false guardrail activation when they really didn't activate at all.
2. The guardrail is activating, it switches to Opus 4.8 without my permission, while the UI reports Fable 5.
3. This is a legitimate bypass of the Fable 5 guardrail.

What Should Happen?

The sub-agent should pause and allow me to change the prompt. If the same prompt is sent, it should trigger the guardrails again.

Error Messages/Logs

Steps to Reproduce

I pretty much explained in what is wrong.

Claude Model

Other

Is this a regression?

No, this never worked

Last Working Version

No response

Claude Code Version

2.1.1.99

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

No response