sbt: found version conflict(s) in library dependencies
Two dependencies need different versions of the same library, sbt picked the newer one, and the version scheme that library declares says the two are not binary compatible. Since sbt 1.5 that is an error rather than a warning, because it tends to end in a NoSuchMethodError at runtime. It typically appears when one library has moved to a new major version of something like cats-effect or scala-xml and another has not.
Quick fix
Read the commands before running them. Anything that restarts a service, deletes data or changes permissions should be tried on a non-production system first.
# Which modules pull in which version?
sbt evicted
# Full tree: add addDependencyTreePlugin to project/plugins.sbt, then
sbt dependencyTree
# Best fix: upgrade the library that still wants the old version
# If you have checked the versions really are compatible, declare it
ThisBuild / libraryDependencySchemes +=
"org.scala-lang.modules" %% "scala-xml" % VersionScheme.Always
# Blunt: downgrade the check to a warning for the whole build
ThisBuild / evictionErrorLevel := Level.WarnHow to diagnose Scala errors
Scala's most distinctive error class is binary incompatibility: libraries are published per Scala major version, and mixing artifacts built for different versions produces confusing "not a member of" or NoSuchMethodError failures. The %% operator in sbt exists precisely to append the right suffix, and most unresolved-dependency errors are a % where %% was needed.
If the quick fix above does not resolve it, work through these steps. They apply to this whole class of error, not just to this one message, which is usually what saves the time.
- Check the Scala version suffix on every dependency. Use
%%for Scala libraries and plain%only for Java ones. - Run
sbt evictedto list dependencies that were evicted by version conflict. A frequent source of runtime NoSuchMethodError. - Use
sbt dependencyTreeto see the resolved graph and locate the transitive dependency pulling in an old version. - For inference failures, add explicit type annotations at the boundary rather than at the error site; inference failures usually propagate from further up.
- Clear stale state with
sbt cleanand remove~/.ivy2/cacheor~/.cache/coursierentries only for the specific failing artifact.
Tools worth reaching for
sbt evictedsbt dependencyTreecoursier resolvescalac -explainMiMa (binary compat checks)
Authoritative references
Primary documentation for this error, worth reading before applying any fix in production.
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Something missing or wrong?
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