[BUG] Skill tool fails on markdown files containing backticks or single quotes

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 built-in Skill tool fails when loading skill files (.md) that contain backticks (`) or single quotes ('). The error indicates the file content is being processed through a shell command that interprets these characters.

Steps to Reproduce

1. Create a skill file at ~/.claude/skills/test-skill/SKILL.md with content:

# Test Skill

Use as const for literal types.
Don't forget to check you've handled all cases.

1. In Claude Code, run:

Skill(test-skill)

1. Observe the error

Expected Behavior

The skill file should be read and its content displayed without error.

Actual Behavior

Error: Bash command failed for pattern "!` when you've verified externally
...
[stderr]
(eval):17: unmatched '

The content is being processed through zsh eval, which interprets:

• Backticks (`) as command substitution
• Single quotes (') as string delimiters

Environment

• OS: macOS (Darwin 25.1.0)
• Shell: zsh
• Claude Code version: (current)

What Should Happen?

Expected Behavior

The skill file should be read and its content displayed without error.

Actual Behavior

Error: Bash command failed for pattern "!` when you've verified externally
...
[stderr]
(eval):17: unmatched '

The content is being processed through zsh eval, which interprets:

• Backticks (`) as command substitution
• Single quotes (') as string delimiters

Error Messages/Logs

Steps to Reproduce

1. Create a skill file at ~/.claude/skills/test-skill/SKILL.md with content:

# Test Skill

Use as const for literal types.
Don't forget to check you've handled all cases.

1. In Claude Code, run:

Skill(test-skill)

1. Observe the error

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.69

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_