[BUG] Unable to start multiple parallel subagents through custom command or another lead agent.

Environment

• Platform (select one):
• [ ] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [ ] Other: <!-- specify -->
• Claude CLI version: <!-- output of claude --version -->

v1.0.67

• Operating System: <!-- e.g. macOS 14.3, Windows 11, Ubuntu 22.04 -->

macOS

• Terminal: <!-- e.g. iTerm2, Terminal App -->

Bug Description

<!-- A clear and concise description of the bug -->

Unable to start multiple parallel subagents through custom command or another lead agent.
However, the direct prompt given with the instruction to "run multiple parallel subagents to..." has no problem starting multiple subagents at the same time.

Steps to Reproduce

Have either custom command or agent with the following prompt:
Coordinate end-to-end testing workflow for $ARGUMENTS using multiple parallel @agent-e2e-maintainer subagents to implement the test scripts, based on the E2E coordination guidelines below.

Expected Behavior

Multiple subagents should run at the same time to work on the test scripts.

Actual Behavior

Only one subagent is started by custom command.

Thru lead agent, the results is even more unpredictable that sometimes Claude Code even tries invalid bash command or npx to start the relevant subagents instead of the internal Task tool. This makes starting subagents through lead agent even more problematic than the custom command.

Additional Context

n/a