Skill listing carries no source label; bundled Anthropic skills are indistinguishable from user skills

Summary

The skill listing the model receives does not say who authored a skill. Plugin skills carry a namespace prefix (superpowers:brainstorming, caveman:caveman-review). Bundled Anthropic skills (code-review, simplify, security-review, init, run, loop, schedule, design, dataviz, artifact-design, update-config, and others) and the user's own skills from ~/.claude/skills or a repo's .claude/skills are both listed bare, with identical shape. The model cannot tell them apart from the listing alone.

This matters when a user's instructions give different authority to different skill sources. Mine do: a user-authored skill may override a written rule with the conflict logged; a third-party skill never may. In a session on 2026-09-10 the model classed the bundled code-review skill as "the user's own skill", granted it the user-authored allowance, and invoked it. That invocation is the subject of #93307 (a fork on the top-tier model plus 9 unrouted children). A cheaper, rule-compliant alternative (superpowers:requesting-code-review, one routed Agent dispatch) was never weighed, because the bundled skill looked like it had the user's authority behind it.

The bias runs one way: mistaking a bundled skill for the user's own grants it more permission, never less.

Steps to reproduce

1. Have at least one skill in ~/.claude/skills/ and the default bundled skills enabled.
2. Start a session and inspect the skill listing the model receives (the Skill tool's available-skills block).
3. Observe that ~/.claude/skills entries and bundled entries are indistinguishable: name: description with no source, path, or author field. Plugin skills alone carry a plugin: prefix.

Expected behavior

• Each skill in the listing carries its source: bundled, user (~/.claude/skills), project (.claude/skills), or plugin:<name>. A prefix such as anthropic:code-review for bundled skills, matching how plugin skills are already namespaced, would be enough.
• The same source should be visible in /skills or wherever users inspect the list, so a user writing precedence rules can name the classes that actually exist.

Environment

• Claude Code 2.1.267, macOS (darwin 24.6.0)
• Plugins enabled: superpowers, caveman, ponytail, headroom; four user skills in ~/.claude/skills

🤖 Written by Claude Code on behalf of elaye