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kotlinlang

Screenshot 2025-04-25 at 11.33.17.png

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trying to add Arrow 2.1.0 to one of our repos and getting this error (more in screenshots)

```some kotlin runtime libraries have an unsupported binary format```
```some kotlin runtime libraries and 6 other jars have an unsupported binary format```
my understanding is this repo has kotlin 1.9 so what's the dealio?

indeed, updating to Kotlin 2.1.0 should fix this

<https://github.com/arrow-kt/arrow/blob/main/gradle/libs.versions.toml#L8>
Arrow 2.1.0 is built with Kotlin 2.1.20

The binary format however only makes an attempt to be <https://kotlinlang.org/docs/kotlin-evolution-principles.html#evolving-the-binary-format:~:text=Preferably%20(but%20we%20can%27t%20guarantee%20it)%2C%20the%20binary%20format%20is%20mostly%20forwards%20compatible%20with%20the%20next%20language%20release%2C%20but%20not%20later%20ones%20(in%20the%20cases%20when%20new%20features%20are%20not%20used%2C%20for%20example%2C%201.9%20can%20understand%20most%20binaries%20from%202.0%2C%20but%20not%202.1).|forward compatible> with the next language release, but not later ones (so 1.9 can mostly read 2.0 binaries but won't read 2.1)

the new 2.1.1 version makes only 2.0 required, not 2.1