> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ftr10.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Preview and Apply Code Changes with the Diff Viewer

> Review proposed code changes from Hermes Agent as a visual diff before applying them to your files — one command away from accepting or rejecting.

When Hermes Agent proposes a change to a file in your workspace, you don't have to accept it blindly. The diff viewer shows you exactly what would change — original content on the left, proposed content on the right — before anything is written to disk. You stay in control of every edit.

## The diff workflow

The typical flow for reviewing a Hermes-proposed change looks like this:

1. **Hermes proposes a change.** During a chat session, the agent calls the `propose_diff` tool with the file path and new content. The file opens in the editor with inline decorations — red for removed lines, green for added lines — while the original content remains on disk.
2. **The diff viewer opens.** VS Code's native diff panel shows the original file alongside the proposed version, giving you a side-by-side or inline view of every change.
3. **You review the changes.** Scroll through the diff at your own pace. You can make additional edits in the proposed-content pane if needed.
4. **Accept or discard.** Run **Hermes: Apply Hermes Changes** to write the proposed content to disk, or simply close the diff panel to discard without touching the file.

## Commands

Use any of the following commands from the Command Palette (`Ctrl+Shift+P` / `Cmd+Shift+P`) or from the chat interface:

| Command                            | Command ID           | What it does                                                                    |
| ---------------------------------- | -------------------- | ------------------------------------------------------------------------------- |
| **Hermes: Show Diff**              | `hermes.showDiff`    | Opens a visual diff panel comparing the original file with the proposed content |
| **Hermes: Preview Hermes Changes** | `hermes.previewDiff` | Previews the proposed changes in a labeled diff panel (`Hermes: <filename>`)    |
| **Hermes: Apply Hermes Changes**   | `hermes.applyDiff`   | Writes the proposed changes to disk and saves the file immediately              |

All three commands are also accessible from the diff review bar that appears in the chat panel when a `propose_diff` is pending.

<Tip>
  If you are unsure about a change, simply close the diff panel without running Apply — the original file is untouched until you explicitly accept. If you do apply a change and then change your mind, use **Ctrl+Z** (or **Cmd+Z**) in the editor to undo. Note that undoing after a save is reversible only while the file buffer is still open with undo history; once you close the file, the undo stack is lost.
</Tip>