Sessions, input & checkpoints
Use undo batches, autosave, and Git milestones.
batch_design previews content edits in order while the call runs, then commits them as one named undo step. A batch containing only select or set_viewport operations changes the current view without a content preview or undo step. If an operation fails or the call is interrupted, content edits in the batch roll back; selection and viewport changes are not transactional. The result identifies a failing operation. Use a descriptive label for a single component or coherent section; a whole screen in one batch is harder to follow and review.
Canvas edits autosave to .fnx after editing stops. Review the source diff and use Git commits for durable milestones. A dirty Code workspace FNX or JSON buffer locks canvas editing until its draft is saved or discarded. Source Save validates and reloads the project; Discard draft reloads the selected buffer from disk. Finish a source edit and its reload before returning to canvas edits on the same nodes.
An undoable canvas batch and a persisted source change are separate checkpoints. When a structural edit would discard an authored FNX attribute or comment, the source writer can refuse the save even after the change appeared on canvas. Read the save error and diff; Undo the canvas edit or make an intentional, validated FNX change before retrying.
The external MCP server does not expose pointer-event replay, checkpoints, or try_edit tools. Use the editor for manual interaction and the MCP tools for state, node queries, transactional edits, screenshots, source reading, comments, and agent activity.