[BUG] a subagent stopped working

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?

In version 2.1.1 and 2.1.2 my formerly frequently used (and working) subagent is not working (claude knows about it but execution fails).

I am getting a new error:

● project-builder(Build trading strategies project)

⎿  Initializing…
⎿  Error: Agent type 'project-builder' not found. Available agents: Bash, general-purpose, statusline-setup, Explore, Plan,
claude-code-guide, file-content-extractor, dotnet-trace-profiler, benchmark-runner, warning-solver,
vsdiagnostics-profiler

The file project-builder.md still exists in the same place (.claude/agents).
THE REAL PROBLEM: The claude knows about the subagent (it tries to execute by it), but the execution fails.
The subagent file is in the attachment.

project-builder.md

What Should Happen?

The subagent shall start working (when called it shall execute as before and not giving an error).

Error Messages/Logs

● project-builder(Build trading strategies project)
  ⎿  Initializing…
  ⎿  Error: Agent type 'project-builder' not found. Available agents: Bash, general-purpose, statusline-setup, Explore, Plan,
     claude-code-guide, file-content-extractor, dotnet-trace-profiler, benchmark-runner, warning-solver,
     vsdiagnostics-profiler

Steps to Reproduce

1. add subagent
2. do something with a build

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.0.76

Claude Code Version

2.1.2 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_