[markpapadakis]

Could you please tell me what you entered?

As for prefixes and typos, in our case, the FST is used for both matching a prefix and spelling correction of the prefix.

The first character is treated specially; the chance of getting the first character wrong is very low(according to our findings) so only completions/corrections that score very high get to be matched.

[ssubu]

Sure. cmputer gets corrected, not omputer.

Just to provide some additional information, our library Keyvi(https://github.com/KeyviDev/Keyvi) has a very fast implementation of an FST based spell correct.

[markpapadakis]

Got it. This is by design - though I suspect we need to dial down the cost for misspelled first character in prefixes.

We built our own FST, which is somewhat similar to the design of the Rust fst crate ( https://blog.burntsushi.net/transducers/#fst-construction ).