JRuby 10.0.4.0 Released Wednesday, March 04 2026 The JRuby community is pleased to announce the release of JRuby 10.0.4.0. - Homepage: https://www.jruby.org/ - Download: https://www.jruby.org/download JRuby 10.0.4.x targets Ruby 3.4 compatibility. Thank you to our contributors this release, you help keep JRuby moving forward! @evaniainbrooks, @katafrakt, @mrnoname1000 Standard Library - The syslog library moves to bundled gems. (#9198) - The unicode_normalize library is now thread-safely loaded as an internal library (#9231, #9232) 43 Issues and PRs resolved for 10.0.4.0 #8697 Tracing :call doesn't work if the traced code is running on a different thread #8876 import_methods doesn't allow calling another refined method #9120 File.path doesn't raise Encoding::CompatibilityError for ASCII-incompatible string #9195 Refactor keyword arguments logic #9198 Move syslog to bundled gems #9206 Fix exception message when calling import_methods without a Module #9208 Inconsistency with block parameter default value #9211 Fix block argument destructuring with optional parameters #9212 Fix method owner when using import_methods #9213 Make refine method of Module private #9214 Data.define single-attribute class rejects positional arguments #9215 Ignore empty kwrest in Data subtypes' constructors #9217 Add an error for running jruby.sh from a broken JRUBY_HOME #9218 JavaFX AnimationTimer + Mutex.synchronize triggers "deadlock; lock already owned by another fiber belonging to the same thread" on JRuby 10.0.3.0 #9222 String interpolation of BasicObject object raises NameError instead of NoMethodError #9224 ClassCastException handling kwargs in Struct #9225 Expand Data initialize empty kwargs fix to Struct #9226 Narrow deadlock check for sibling fibers locking mutex #9227 Version output may not accurately represent JIT mode #9228 Fix version output to reflect current runtime #9230 Use normal call type error for missing dynamic string to_s #9231 Thread safety of require and implications on stdlib string.normalize() #9232 Internalize and threadsafetify String#unicode_normalize #9237 Fix for import_methods does not allow calling another refined method #9240 Fix for File.path doesn't raise Encoding::CompatibilityError for ASCII incompatible string #9241 Data#to_h and Data#deconstruct return values in wrong order when module overrides initialize in a subclassed Data class #9242 Spurious Struct#initialize keyword argument warning (and crash) with ... forwarding through super #9243 Data#==/Data#eql? and Struct#eql? return false when instances are extended in initialize #9244 Fix for ClassCastException inside Struct#initialize when delegating … from a prepended module #9247 Fix Array#slice raises a RangeError when the start index is out of range of Fixnum #9248 Additional fixes for import_methods with JIT #9252 Use prepared accessors to retrieve Data fields #9254 Compare "real" classes for Data#== and eql? #9258 Kernel#respond_to? fails if #respond_to_missing? is not defined #9259 Only set locking thread once successful #9260 Restore Cleaner API use for embedding cleanup #9272 Avoid passing bogus -classpath when empty #9280 Check if respond_to_missing? exists before respond_to? #9281 unexpected ArgumentError: wrong number of arguments #9283 Only localize TracePoint to thread if specified #9285 Clear callInfo so it does not taint other calls #9289 Include gem extension stubs in stdlib artifacts #9290 Improve dist verification -- blog: http://blog.enebo.com twitter: tom_enebo mail: tom.enebo@gmail.com