[BUG] Fable 5 repeatedly spawns verify subagents in `/effort ultracode` workflow mode and exhausts session limit

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?

Summary

When using Claude Code with Fable 5 in /effort ultracode mode, starting a workflow can trigger runaway subagent spawning. In my case, the workflow created around 96 verification agents, many of which failed immediately, and the session limit was exhausted before the task could complete.

This appears to happen specifically when Fable 5 is running a workflow under /effort ultracode.

Environment

• Product: Claude Code
• Model: Fable 5
• Mode: /effort ultracode
• Workflow enabled: Yes

What Should Happen?

When a workflow is started in /effort ultracode mode, Claude Code should create a reasonable and bounded number of subagents. It should avoid repeatedly spawning duplicate verification agents for the same or very similar subtasks.
If the workflow is becoming too large or circular, Claude Code should stop, deduplicate the tasks, or ask for confirmation before continuing.

Error Messages/Logs

Steps to Reproduce

Fable 5 repeatedly spawned verification subagents during the workflow. The left panel showed approximately 96 agents, mostly under verify:* tasks. Many of them failed, and the session ended with the following message:

Claude Model

Other

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.170

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_