[BUG] Advisor blocks Fable 5 usage

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?

Setup:
Claude Code Desktop App: Claude 1.11847.5 (9692f0) 2026-06-09T17:34:27.000Z
Macbook Air M3
macOS Tahoe 26.4.1

I launch a Claude Code session on Fable 5, Ultracode (or Max)
My prompts were on reviewing my code generally to find bugs

I get this message
API Error: 400 tools.17.model: 'claude-opus-4-8' cannot be used as an advisor
when the request model is 'claude-fable-5'.

Tried to start the prompt with: "Without advisor", but still failed.

What Should Happen?

Claude Code session should resume normally.

Error Messages/Logs

API Error: 400 tools.17.model: 'claude-opus-4-8' cannot be used as an advisor when the request model is 'claude-fable-5'.

Steps to Reproduce

Open a Claude Code session on the Claude Desktop App
Select Fable 5 1M
Select Effort Max or Ultracode

Ask it to review a code repo

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude 1.11847.5 (9692f0) 2026-06-09T17:34:27.000Z

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

Not in a terminal but on the Claude Code App directly