Custom agent definitions (.claude/agents/) are silently ignored for team agents

Summary

When a custom agent definition (.claude/agents/<name>.md) is used to spawn a team agent (via the Agent tool with team_name parameter), all frontmatter fields and the markdown body (system prompt) are silently ignored. Only model and agent_type (in SubagentStart/SubagentStop hooks) work correctly.

The same custom agent definitions work fully when spawned as pure subagents (without team_name).

Reproduction

1. Create .claude/agents/my-agent.md:

---
name: my-agent
description: Test agent with baked-in identity.
model: opus
hooks:
  PreToolUse:
    - matcher: ""
      hooks:
        - type: command
          command: echo "hook fired"
skills:
  - my-skill
disallowedTools: Write, Edit
---

# You are: My Agent

You have a specific identity and instructions baked in.

1. Spawn as pure subagent (works correctly):

Agent(subagent_type="my-agent", prompt="What is your role?")

→ Agent receives the markdown body as system prompt, hooks fire, model is applied.

1. Spawn as team agent (broken):

Agent(subagent_type="my-agent", team_name="my-team", name="team-agent" prompt="What is your role?")

→ Agent has NO custom system prompt. Only project-wide rules (.claude/rules/) and CLAUDE.md files are loaded. Agent cannot identify itself.

What is silently ignored for team agents

| Feature | Pure subagent | Team agent |
|---|---|---|
| System prompt (markdown body) | ✅ Works | ✅ Works |
| skills frontmatter | ✅ Works | ❌ Silently ignored (known: #29441 / #24780) |
| disallowedTools frontmatter | ✅ Works | ✅ Works |
| Frontmatter hooks | ✅ Works | ❌ Silently ignored |
| model frontmatter | ✅ Works | ✅ Works |
| agent_type in SubagentStart/Stop | ✅ Works | ✅ Works |

Impact

This makes custom agent definitions nearly useless for team-based workflows. Teams cannot:

• Bake role identity into agents (must use spawn prompt instead)
• Enforce tool restrictions via disallowedTools
• Attach lifecycle hooks to specific agent types
• Preload skills into team agents

The silent failure is particularly problematic — there are no warnings or errors. Users may believe their agent definitions are being applied when they are not.

Environment

• Claude Code version: 2.1.68
• Platform: macOS (Darwin 24.5.0, arm64)
• Agent teams enabled via CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1

Related issues

• #29441 / #24780: skills field silently ignored for team agents (subset of this bug)
• #14859: Feature request for agent hierarchy fields in all hook events