Keystrokes work only sporadically in the scala REPL (a key works sometimes, other times not). Windows 11. Scala 3.4.2. Java Version 8 update 411. I am new to scala.
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Welcome to the Scala community.
Is your keyboard working OK? Can you try a different keyboard?
Is your command line working OK? Can you try a different Terminal? Powershell maybe? (I don’t know much about Windows)
You should update your Java version to at least 11.
Are you launching via Scala-cli? Or Scala directly?
I would recommend trying scala-cli… Scala-cli will shortly become the Scala command …
scala-cli works! Problem solved.
Many sincere thanks for your quick and helpful reply 
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It might be because Scala-cli uses a newer JVM. I think it requires 17, and downloads it if it’s not present.
If you start running into other issues outside the REPL, then try newer JVM versions.
Thanks!
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For the record, Scala 3.4.2 has JLine 3.25.1 since this commit and Scala 2.13.14 since this commit.
“I don’t have a Windows 11 box to test on,” but I see there is a current ticket that is Windows-specific and says “missing keystrokes” in the title. There is no diagnosis or precise reproduction, but maybe some combination of factors causes a problem.
Since the solution here was to use scala-cli, I guess this problem used scala at a command line prompt and not from the sbt prompt. In any case, the other item to verify is that the correct jline.jar and related jna.jar are getting used.
There was a previous issue with JDK 8 support in JLine that is not relevant here, but just goes to show that you can’t take anything for granted. Probably “don’t use JDK 8 any more” is good advice for those just starting out. I don’t know if there is any reason not to “use JDK 21 by default”.
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I had the same issue using Windows 11. The problem was related to the JDK version because I installed the latest one available now (version 22), now I downgraded it to the version 21 and it worked fine.
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