Pre Tool Use

Pre Tool Use

Configuration for pre-tool-use hooks that run before tools are executed.

All file protection rules are consolidated in this section to prevent Claude from making unintended modifications to protected files, directories, or executing dangerous commands.

Configuration Properties

generatedFileMessage

Custom message when blocking file edits with generation markers.

Available placeholders: - {file_path} - The path to the file being blocked - {marker} - The generation marker that was detected

Example

yaml generatedFileMessage: "Cannot modify {file_path} - it contains '{marker}' marker"

Default: null (uses a generic error message)

Attribute	Value
Type	`string
Default	null

Examples:

generatedFileMessage: "Cannot modify {file_path} - it contains '{marker}' marker"

preventAdditions

Directories where file additions are prevented (in addition to root if preventRootAdditions is enabled).

List of directory paths where new files cannot be created. Useful for protecting build output directories or other generated content.

Attribute	Value
Type	array
Default	[]

Examples:

preventAdditions: - "dist" - "build" - "node_modules"

preventGeneratedFileEdits

Prevent editing of files with generation markers (enabled by default).

When enabled, checks for common markers like “DO NOT EDIT”, “Code generated by”, “@generated”, etc. in file contents before allowing edits.

Default: true

Attribute	Value
Type	boolean
Default	true

preventRootAdditions

Prevent Claude from creating or modifying files at the repository root.

Helps maintain clean project structure by preventing clutter at the root level. This is a security best practice to avoid accidental modification of important configuration files.

Default: true

Attribute	Value
Type	boolean
Default	true

preventUpdateGitIgnored

Block Claude from modifying or creating files that match .gitignore patterns.

When enabled, files matching patterns in .gitignore will be protected. Uses your existing .gitignore as the source of truth for file protection.

Default: false

Attribute	Value
Type	boolean
Default	false

toolUsageValidation

Tool usage validation rules for fine-grained control over tool usage.

Allows controlling which tools can be used on which files or with which command patterns. Rules are evaluated in order.

Attribute	Value
Type	array
Default	[]

Examples:

toolUsageValidation: # Allow writing to JavaScript files - tool: "Write" pattern: "**/*.js" action: "allow"

# Block environment file modifications - tool: "*" pattern: ".env*" action: "block" message: "Environment files cannot be modified"

# Block dangerous git operations - tool: "Bash" commandPattern: "git push --force*" action: "block" message: "Force push is not allowed"

uneditableFiles

Files that Claude cannot edit, using glob patterns.

Supports various glob patterns for flexible file protection. By default, conclaude’s own config files are protected to prevent the AI from modifying guardrail settings - this is a security best practice.

Supports two formats: 1. Simple string patterns: "*.lock" 2. Detailed objects with custom messages: {pattern: "*.lock", message: "..."}

Attribute	Value
Type	array
Default	[]

Examples:

uneditableFiles: - ".conclaude.yml"    # Protect config - ".conclaude.yaml"   # Alternative extension - "*.lock"            # Lock files - pattern: ".env*" message: "Environment files contain secrets. Use .env.example instead."

Nested Types

This section uses the following nested type definitions:

ToolUsageRule Type

Tool usage validation rule for fine-grained control over tool usage based on file patterns.

Allows controlling which tools can be used on which files or with which command patterns. Rules are evaluated in order and the first matching rule determines the action.

Properties:

Property	Type	Default	Description
action	string	-	Action to take when the rule matches: “allow” or “block”
commandPattern	`string	null`	-
matchMode	`string	null`	-
message	`string	null`	-
pattern	string	-	File path pattern to match
tool	string	-	The tool name to match against

UnEditableFileRule Type

Configuration for an uneditable file rule.

Files that Claude cannot edit, using glob patterns. Supports various glob patterns for flexible file protection.

Formats

Two formats are supported for backward compatibility:

1. Simple string patterns: "*.lock" - Just the glob pattern as a string - Uses a generic error message when blocking

2. Detailed objects with custom messages: {pattern: "*.lock", message: "..."} - Allows specifying a custom error message - More descriptive feedback when files are blocked

Variants:

1. object: Detailed format with pattern and optional custom message.

Allows providing a custom error message that will be shown when Claude attempts to edit a file matching this pattern.

Properties:

• message (string | null): Optional custom message to display when blocking edits to matching files
• pattern (string): Glob pattern matching files to protect (e.g., “.lock”, “.env”, “src/**/*.ts”)

2. string: Simple format: just a glob pattern string.

Uses a generic error message when blocking file edits. Backward compatible with existing configurations.

Complete Examples

Here are complete configuration examples for the preToolUse section:

preToolUse: # Prevent root-level file creation preventRootAdditions: true

# Protect specific files with glob patterns uneditableFiles: - ".conclaude.yml" - "*.lock" - pattern: ".env*" message: "Environment files contain secrets"

# Prevent modifications to git-ignored files preventUpdateGitIgnored: false

# Fine-grained tool control toolUsageValidation: - tool: "Bash" commandPattern: "git push --force*" action: "block" message: "Force push is not allowed"

# Block additions to specific directories preventAdditions: - "dist" - "build"

# Protect generated files preventGeneratedFileEdits: true generatedFileMessage: "Cannot modify {file_path} - it contains '{marker}'"

See Also

• Configuration Overview - Complete reference for all configuration options