Plugin agent skills: frontmatter silently fails to inject skill content

Summary

The skills: field in agent frontmatter works correctly for project-level agents referencing project-level skills, but silently fails when plugin-deployed agents reference plugin skills. No error is thrown — the agent simply starts with an empty skill context.

Reproduction

1. Create a plugin with an agent that references plugin skills via skills: frontmatter:

# plugin/agents/my-agent.md
---
name: my-agent
skills:
  - my-skill
---

1. Create the corresponding skill in the plugin:

plugin/skills/my-skill/SKILL.md

1. Install the plugin and spawn the agent. The agent will not have the skill content in its context.

Tested variations (all fail)

| Agent location | Skill reference | Result |
|---|---|---|
| Plugin agent | Plugin skill by name (my-skill) | NOT INJECTED |
| Project-level agent | Plugin skill by name (my-skill) | NOT INJECTED |
| Project-level agent | Plugin skill namespaced (plugin-name:my-skill) | NOT INJECTED |

Tested across 17 different plugin agents — 0/17 had skills injected.

Working case

| Agent location | Skill reference | Result |
|---|---|---|
| Project-level agent | Project-level skill (test-injection-skill) | WORKS — confirmed with unique test string |

Verification method

Created a project-level skill containing a unique string ("BANANA HELICOPTER 42") and a project-level agent referencing it. The agent could retrieve the string from context without reading any files — confirming skill injection works for project-level skills.

Repeated the same test with plugin skills — agent reported content was not in its context.

Expected behavior

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

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

This should work regardless of whether the skill is project-level or plugin-level.

Actual behavior

Skill content is silently not injected for any plugin-related skill reference. No error, no warning — the agent starts without its skills.

Impact

All plugin-deployed agents run without their skill knowledge, requiring manual file reads as a workaround. This defeats the purpose of the skills: frontmatter field for any plugin-based agent framework.

Environment

• Claude Code CLI (latest as of Feb 2026)
• macOS
• Plugin installed via marketplace