[BUG] Deny rules with // prefix for absolute paths incorrectly match substring in any path

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?

Deny rules using the // prefix (documented as absolute path matching) incorrectly match any path containing the specified substring, rather than only matching the absolute path.

For example, adding Edit(//dev/**) to deny edits to /dev/... (the device filesystem) also blocks edits to ~/dev/myproject/... because the path contains /dev/.

What Should Happen?

Edit(//dev/**) should only match absolute paths starting with /dev/, not paths that happen to contain /dev/ as a substring elsewhere in the path.

Error Messages/Logs

None - edits are silently blocked due to deny rule match.

Steps to Reproduce

1. Create a project in a directory containing /dev/ in its path (e.g., ~/dev/myproject/)
2. Add to .claude/settings.json:

{
  "permissions": {
    "deny": [
      "Edit(//dev/**)",
      "Write(//dev/**)"
    ]
  }
}

1. Ask Claude to edit any file in the project
2. Expected: Edit succeeds (project path ~/dev/... is not /dev/...)
3. Actual: Edit is blocked because //dev/** matches the substring /dev/ in ~/dev/myproject/file.ts

Claude Model

Opus 4.5

Is this a regression?

I don't know

Claude Code Version

2.1.25

Platform

Anthropic API

Operating System

macOS (Darwin 25.2.0)

Terminal/Shell

zsh

Additional Information

The // prefix is documented as a way to specify absolute paths in permission patterns. The current behavior appears to perform substring matching rather than anchored path matching.

Affected rules in my config:

• Edit(//dev/**)
• Write(//dev/**)
• Potentially any // prefixed rule where the path segment appears elsewhere

Workaround: Remove the //dev/** deny rules if your working directory contains /dev/ in its path.