5. The non-transitory computer-readable medium of claim 1 , wherein the instructions further cause the one or more processors to: compose a second virtual FST using a second language model and based on the sequence of states and arcs, wherein one or more virtual states of the second virtual FST represents the current candidate word; and traverse the one or more virtual states of the second virtual FST, wherein a fourth probability of the candidate word given the one or more history candidate words is determined by traversing the one or more virtual states of the second virtual FST, and wherein the text corresponding to the speech input is determined based on the fourth probability of the candidate word given the one or more history candidate words.
5. The non-transitory computer-readable medium of claim 1 , wherein the instructions further cause the one or more processors to: compose a second virtual FST using a second language model and based on the sequence of states and arcs, wherein one or more virtual states of the second virtual FST represents the current candidate word; and traverse the one or more virtual states of the second virtual FST, wherein a fourth probability of the candidate word given the one or more history candidate words is determined by traversing the one or more virtual states of the second virtual FST, and wherein the text corresponding to the speech input is determined based on the fourth probability of the candidate word given the one or more history candidate words. 6. The non-transitory computer-readable medium of claim 5 , wherein the instructions further cause the one or more processors to: interpolate the second probability of the candidate word given the one or more history candidate words and the fourth probability of the candidate word given the one or more history candidate words, and wherein: a combined probability of the candidate word given the one or more history candidate words is determined by the interpolating; and the text corresponding to the speech input is determined based on the combined probability of the candidate word given the one or more history candidate words.