1. A method comprising: outputting, by a computing device and for display, a graphical keyboard comprising a plurality of keys; receiving, by the computing device, an indication of a gesture detected at a presence-sensitive input device; determining, by the computing device, based at least in part on the indication of the gesture and at least one characteristic of the gesture, one or more keys from the plurality of keys; determining, by the computing device, based on the one or more keys from the plurality of keys, a character string; and in response to determining that the character string is not included in a lexicon and that a spatial model probability associated with the one or more keys from the plurality of keys exceeds a probability threshold, outputting, by the computing device and for display, the character string.