Fault-tolerant systems and methods to process and correct input errors are disclosed. Original inputs can be received, each original input being defined as mapping to multiple characters in a language, each original input having one or more associated proximity measurements. Original inputs that have proximity measurements with one or more non-zero probabilities for respective intended inputs are identified as potentially incorrect original inputs. Each of the potentially incorrect original inputs is expanded to the respective intended inputs, and each of the original inputs and each of the respective intended inputs are converted to characters in the language, each of the conversions being a combination of the converted original inputs and/or the respective intended inputs. Likelihoods of conversions of the original inputs and the respective intended inputs to the characters based in part on the proximity measurements are determined, and most likely conversions are identified for presentation.