[BUG] Agent skills: frontmatter field does not inject skill content at startup

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?

The skills: field in agent YAML frontmatter is documented to preload skill content into the subagent's context at startup ("The
full skill content is injected, not just the description"), but in practice the content is never injected. The agent starts
without the skill knowledge and must manually invoke the Skill tool to load it.

What Should Happen?

From https://code.claude.com/docs/en/sub-agents#preload-skills-into-subagents:

The full content of each listed skill is injected into the subagent’s context at startup.

Error Messages/Logs

Steps to Reproduce

 Reproduction

  1. Create an agent file with valid skills declared in frontmatter:
  ---
  name: dev
  skills:
    - skill1
    - skill2
  ---
  You are an agent. The skills above are preloaded.

  2. Start a session with this agent (e.g., --agent dev)
  3. Ask the agent: "What's in your context? Were the skills pre-loaded?"


  Actual behavior

  - The agent receives only the body text of the agent file (the prose after the frontmatter)
  - The skill names appear in the "available skills" system-reminder list (same as any session)
  - The skill content is not injected
  - Manually invoking the Skill tool works fine and loads the full content

Claude Model

Opus 4.8

Is this a regression?

Unknown

Last Working Version

_No response_

Claude Code Version

2.1.170.370

Platform

AWS Bedrock

Operating System

Other Linux

Terminal/Shell

Other

Additional Information

_No response_