- **Real-time Preview**: Diagrams appear and update in your browser as Claude creates them. The preview is the web app's canvas: a change Claude makes to the page on screen is outlined, and one Ctrl+Z takes it back
- **Selection**: Select shapes in the preview and say "move these"; Claude reads what you selected with `get_selection`
- **Draw from Your Files**: ask Claude to draw from a document, image or web page; it reads the source with its own tools and draws. Existing .drawio files open with load_diagram
- **Version History**: The last 20 versions appear as cards next to the canvas, with thumbnails; restore one, undo the latest, or compare a version with the canvas
- **Custom Instructions**: keep your own drawing rules in `~/.next-ai-drawio/instructions.md` (for example "Always draw in minimal style"); they are appended to the drawing guide on every call
| `start_session` | Opens browser with real-time diagram preview; the result includes the drawing rules. Pass `session_id` to continue a saved diagram |
| `list_saved_diagrams` | List the auto-saved diagrams of earlier sessions, newest first, with their pages |
| `DRAWIO_BASE_URL` | unset (the bundled draw.io) | An external draw.io, such as a self-hosted instance. With it Claude's changes are not outlined on the canvas, Ctrl+Z does not take them back and `get_selection` cannot read the selection |
| `DRAWIO_DATA_DIR` | `~/.next-ai-drawio` | Folder for auto-saved diagrams and your `instructions.md`; `off` turns auto-save off (`instructions.md` is then read from the default folder) |
| `DRAWIO_LANG` | unset | Language of the draw.io editor, such as `en`, `zh`, `zh-tw`, `ja` or `de`. Unset, draw.io chooses (the browser language on `embed.diagrams.net`, English on a self-hosted draw.io) and the user can change it under **Extras > Language** |
| `DRAWIO_UI` | unset | draw.io theme: `kennedy`, `atlas`, `dark`, `min`, `sketch` or `simple`. Unset, the user picks one under **Extras > Theme** |
| `DRAWIO_DARK` | `auto` | Dark mode of the preview and the editor until the user switches it with the button at the top right: `auto` follows the system, `1` starts dark, `0` starts light |
| `DRAWIO_PREVIEW_UI` | `shell` | The preview page; `classic` opens the previous preview page for one more release |
| `DRAWIO_AUTO_SCREENSHOT` | unset | Set to `true` to attach a screenshot to every `create_new_diagram` and `edit_diagram` result (costs 2 to 10 s per call) |