Critical: Claude systematically ignores Skill tool despite explicit BLOCKING REQUIREMENT instructions

Issue Summary

Claude Code is systematically failing to invoke the Skill tool even when user requests clearly match available skill patterns, despite documentation explicitly stating this is a "BLOCKING REQUIREMENT".

Severity

Critical - Completely breaks the user-created skill system feature.

Description

Claude is not checking available skills before choosing which tool to use. Instead, it defaults to low-level tools (Bash, Read, etc.) even when specialized skills exist that exactly match the user's request.

Expected Behavior

When a user request matches a skill pattern:

1. Claude should check available skills FIRST
2. Immediately invoke the Skill tool if a match is found
3. Follow the skill's instructions

Actual Behavior

1. Claude ignores the Skill tool entirely
2. Goes directly to Bash/Read/other low-level tools
3. User must manually intervene every single time
4. Skills are rendered completely unusable

Reproduction Steps

1. Create a skill with clear trigger patterns (e.g., coverage-calculator skill)
2. Add explicit pattern matching in skill documentation (e.g., "calculate test coverage on main" → coverage-calculator)
3. User makes request matching pattern: "calculate test coverage on main"
4. Expected: Claude invokes Skill tool with skill="coverage-calculator"
5. Actual: Claude runs bash commands directly, ignoring skill completely

Real-World Example

User Request

calculate test coverage on main

Skill Documentation (coverage-calculator)

| User Request | Mode | Script Flag |
|--------------|------|-------------|
| "test coverage on main" | All Code | `--all` |
| "coverage on main" | All Code | `--all` |
| "main branch coverage" | All Code | `--all` |

Expected Behavior

Immediately invoke: Skill tool with skill="coverage-calculator"

Actual Behavior

Runs: cd rhgenio-workspace && git branch --show-current
(Completely ignores the skill)

Skill Tool Documentation

The Skill tool documentation explicitly states:

"When a skill is relevant, you must invoke this tool IMMEDIATELY as your first action" "This is a BLOCKING REQUIREMENT: invoke the relevant Skill tool BEFORE generating any other response"

Claude is not following these instructions.

Impact

• User-created skills are completely unusable
• Defeats the entire purpose of the skill system
• Requires manual intervention on every single request that should trigger a skill
• Users must repeatedly tell Claude "USE THE SKILL\!"
• Breaks workflow automation
• Wastes user time

Scope

This appears to be a systemic issue affecting ALL skills, not just one:

• coverage-calculator skill - ignored
• test-runner skill - likely ignored
• coderabbit-workflow skill - likely ignored
• Any custom user skill - ignored

Root Cause Analysis

Claude appears to be:

1. Not checking the available skills list before tool selection
2. Treating skills as "optional" instead of "first choice"
3. Not doing pattern matching against skill trigger phrases
4. Defaulting to low-level tools (Bash, Read, Grep) instead

Environment

• Claude Code CLI
• Model: Claude Sonnet 4.5 (claude-sonnet-4-5-20250929)
• User has multiple skills configured in ~/.claude/skills/
• Skills are properly documented with trigger patterns

Expected Fix

Claude should:

1. ALWAYS check available skills FIRST before selecting any other tool
2. Pattern match user request against skill trigger phrases
3. Invoke Skill tool IMMEDIATELY when a match is found
4. Only fall back to low-level tools if NO skill matches

User Feedback

"THAT DEFEATS THE WHOLE IDEA OF THE SKILL\!\!\!" "YOU'RE KILLING THE FEATURE BRO\!\!\!" "THIS NEEDS TO BE REPORTED TO ANTHROPIC\!\!\!"

The user has to manually intervene on every request because Claude systematically ignores skills.

Additional Context

This issue was discovered during repeated attempts to use the coverage-calculator skill. User reported this is happening with ALL skills, not just one, indicating a fundamental problem with skill detection/invocation logic.

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Note: This issue was reported directly by a Claude Code user who built custom skills and found them completely unusable due to Claude's systematic failure to invoke them.