Regression: skill tool cannot find valid skills in ~/.agents/skills #4401

Description

The skill tool cannot find or invoke a valid skill installed under ~/.agents/skills, even though the skill directory and SKILL.md are present.

This appears to be a regression or an incomplete fix related to #2230, which is closed.

Environment

• Copilot CLI: 1.0.78
• OS: Windows
• Skill path: C:\Users\omzig\.agents\skills\setup-matt-pocock-skills\SKILL.md

Reproduction

1. Create or install a skill at ~/.agents/skills/setup-matt-pocock-skills/SKILL.md.

2. Ensure its frontmatter includes:

   ---
   name: setup-matt-pocock-skills
   description: Configure this repo for the engineering skills.
   disable-model-invocation: true
   ---

3. Invoke the skill tool with setup-matt-pocock-skills.

Actual result

The tool returns:

Skill not found: setup-matt-pocock-skills

The skill is also absent from the tool's available-skill registry, despite the file being present and having valid frontmatter.

Expected result

Skills in ~/.agents/skills should either be discovered by the CLI automatically or produce a clear configuration/status indication explaining that the directory is unsupported.

Workaround

Copying or linking the skill into a directory that the CLI does discover appears to be required.

Additional validation: minimal test skill

To rule out a problem specific to the original skill, I created a minimal skill with valid frontmatter at:

C:\Users\omzig\.agents\skills\test-skill\SKILL.md

Its contents were:

---
name: test-skill
description: A simple test skill that confirms whether skills installed in ~/.agents/skills are discovered and invoked.
---

# Test Skill

When this skill is invoked, respond with exactly:

`test-skill loaded successfully`

Invoking skill(test-skill) produced the same result:

Skill not found: test-skill

This validates that the failure is with out-of-box discovery of ~/.agents/skills, not with the original skill's complexity or frontmatter.

Follow-up validation: supported path works

I moved the same minimal test-skill directory from:

C:\Users\omzig\.agents\skills\test-skill

to:

C:\Users\omzig\.copilot\skills\test-skill

After moving it, invoking skill(test-skill) succeeded and the skill returned:

test-skill loaded successfully

This confirms that the skill content and frontmatter are valid. The failure is specifically that ~/.agents/skills is not included in the CLI's out-of-box discovery paths, while ~/.copilot/skills is.