External diff tools

If you have a diff tool you prefer, Claudette can open a changed file’s diff in it instead of the built-in diff view.

Choosing a tool

Open Settings → Files and diffs, or choose Diff tool settings… on a changed file’s right-click menu.
Pick one from the Diff tool list:
- Built-in diff view, the default.
- A preset, listed with where Claudette found it.
- Custom command…

Claudette finds presets by looking in each tool’s usual install places and on your PATH (on macOS and Linux, your login shell’s, as claude gets), and a preset is listed only if its tool is found. The presets are Beyond Compare, VS Code, WinMerge (on Windows), Kaleidoscope (on macOS), Meld, P4Merge and Your git difftool, which uses your git configuration.

A preset fills in the tool’s arguments, including a title for each side (auth.cs (before) and auth.cs (now)), and opens the left side read-only where the tool supports it.

A custom command

Choose Custom command… and write a program and its arguments in Command. These placeholders are filled in:

{left}: the file before Claude’s changes, a read-only copy;
{right}: the file now;
{leftTitle} and {rightTitle}: a title for each side.

For example, Beyond Compare on Windows:

"C:\Program Files\Beyond Compare 5\BCompare.exe" "{left}" "{right}" /title1="{leftTitle}" /title2="{rightTitle}"

If the command isn’t valid, the page says why.

Testing it

Click Test to open a sample diff in the tool. The page says Opened a sample diff. If nothing appeared, check the command., or why it couldn’t open.

What changes once a tool is set

Every changed file gets Open in diff tool, in its menu in Changed files and in the diff view. A turn’s changes, opened from its Modified files card, get it too (Changes per turn).
Settings → Files and diffs → Open in the diff window can have the diff view’s Open button open the tool too (The diff view).
A double-click on a file in Changed files opens the tool, and a single click only selects it. The built-in view stays in the file’s menu as Open diff.
A file whose earlier contents aren’t known always opens in the built-in view.

What the tool gets

The “before” side is a temporary read-only file in a folder of its own, with the file’s name and extension (auth (before).cs), so the tool picks the right language.
The “now” side is the real file in your folder, so edits you make in the tool are saved to it.
The temporary files are deleted when the tab closes.

On Windows, a .cmd or .bat tool (VS Code’s code.cmd, say) runs through cmd.exe, where a file name could run commands. Claudette refuses arguments that cmd.exe would read as commands, such as % or ", and says so. A file name that trips this, such as Q&A.md in a path without spaces, can still be opened in the built-in view.

Settings

Setting	Default	Where
Diff tool	Built-in diff view	Settings → Files and diffs
Command	none	Settings → Files and diffs, with Custom command…

Reset to defaults in the Diff tool section goes back to the built-in view.