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 first gesture detected at a presence-sensitive input device, the first gesture to select a first sequence of one or more keys from the plurality of keys; determining, by the computing device, a set of candidate strings based at least in part on the first sequence of one or more keys; outputting, by the computing device and for display, at least one of the set of candidate strings; receiving, by the computing device, an indication of a second gesture detected at the presence-sensitive input device, the second gesture to select a second sequence of one or more keys from the plurality of keys; determining, by the computing device, that characters associated with the second sequence of one or more keys are included in either: a first candidate word of a lexicon, the first candidate word being based at least in part on the set of candidate strings, or a second candidate word of the lexicon, the second candidate word not being based on the first sequence of one or more keys; modifying, by the computing device, the set of candidate strings based at least in part on the determination; and outputting, by the computing device and for display, at least one of the modified set of candidate strings.