Is there an application that guesses what language you are typing in and switches the keyboard layout automatically? The idea is that you may start typing in, say, German in any text editor, the application guesses that what you are typing makes more sense in, say, English, so it switches the keyboard layout to English and corrects what you had mistyped.

That's good for lazy typing but more importantly it helps with those annoying moments where you realise that 3–4 words you've just typed are in the wrong language, so you have to delete them, switch layout and start again.

Keyboard Switcher supports only three languages and Key Switcher disappeared.

Sounds like a business opportunity for you.

That sounds very interesting and very complex, but I guess you might only need to target the languages that use similar character sets to English. I don't know enough about Asian languages to comment on them.

I don't have this issue due to my second language having a very different character set and dialect.

I speak in the sense of making it yourself, maybe best would be a small LM that is just a vocabulary list that tries to match language and maybe have setting to set percentage of how sure the language model is before switching your keyboard

Happy to give the idea away.

I quite often switch between multiple European languages, and can basically type any character in any of them using a US-international layout, with dead keys.

I can make all French and Italian accents, German Umlauts, and put a Tilda on the n for the Spaniards. Both uppercase and lowercase letters.

Yeah just learn the EURKEY layout and you won't ever have to switch it.

No no, you first, I insist!

I found keyboard layout switching to be too much friction.

I am programming in English and writing in English and German. What I use now is the UK international layout with dead keys. Plus compose key bindings for less frequently used symbols like € or °. This allows me to keep the same layout everywhere, which makes my life easier - and typing faster.

That's true with Latin based alphabets and in certain scenarios. It's probably not a coincidence that the application I mentioned supports only 3 layouts: English, Russian, Hebrew. And I would imagine typing a lot of text in German would be more efficient with the German layout.