This feature was discussed in #6123, but it doesn't look like anything was ever incorporated into the IPython Notebook. Here's a brief overview of the changes: - Display of messages from other clients can be toggled on and off from within a notebook, either using the ``<M-m>e`` keyboard shortcut in the web UI, or through the option in the "Kernel" menu. - notebook.js controls whether messages are displayed through a callback that is invoked from kernel.js when no callbacks are available for a message. - The UI displays ``execute_input`` messages originating from an other clients in new cells at the end of the notebook. Output messages (``execute_result`` et al.) will only be displayed if a cell exists with a matching message ID. Pending design questions: - Should each ``execute_input`` message cause a new cell to be created? - Should new cells be placed at the end of the notebook, or elsewhere? If the latter, what criteria should be followed?