# apply_patch Tool Documentation

## Overview
The `apply_patch` tool enables file changes using a structured patch format with support for multi-file or multi-hunk edits where a single `edit` call would be brittle.

## Core Functionality
This tool processes a single input string containing one or more file operations, structured with `*** Begin Patch` and `*** End Patch` markers.

## Supported Operations
- **Add File**: Introduces new files with `*** Add File: path/to/file.txt`
- **Update File**: Modifies existing files with `*** Update File: src/app.ts`
- **Delete File**: Removes files with `*** Delete File: obsolete.txt`
- **Rename Files**: Uses `*** Move to:` within update hunks

## Key Parameters
The tool requires a single `input` parameter containing the complete patch contents with appropriate delimiters.

## Important Constraints
- Paths resolve relative to workspace root
- Currently experimental and disabled by default
- Requires activation via `tools.exec.applyPatch.enabled`
- OpenAI-exclusive support (including Codex)
- Configuration available under `tools.exec` namespace only

## Special Markers
`*** End of File` designates EOF-only insertions when necessary.