Ruby 4.0.0 Preview2 Released

Summary

Posted by naruse on 17 Nov 2025 We are pleased to announce the release of Ruby 4.0.0-preview2. Ruby 4.0 updates its Unicode version to 17,0.0, and so on. Language changes *nil no longer calls nil.to_a, similar to how **nil does not call nil.to_hash. [[Feature #21047]] Core classes updates Note: We’re only listing notable updates of Core class. Binding Binding#local_variables does no longer include numbered parameters. Also, Binding#local_variable_get and Binding#local_variable_set reject to handle numbered parameters. [[Bug #21049]] IO IO.select accepts +Float::INFINITY+ as a timeout argument. [[Feature #20610]] String Update Unicode to Version 17.0.0 and Emoji Version 17.0. [[Feature #19908]][[Feature #20724]][[Feature #21275]] (also applies to Regexp) Standard Library updates Note: We’re only listing notable updates of Standard librarires. ostruct 0.6.1 pstore 0.2.0 benchmark 0.4.0 logger 1.7.0 rdoc 6.13.1 win32ole 1.9.2 irb 1.15.2 reline 0.6.1 readline 0.0.4 fiddle 1.1.6 Compatibility issues Note: Excluding feature bug fixes. Standard library compatibility issues C API updates JIT YJIT YJIT stats ratio_in_yjit no longer works in the default build. Use --enable-yjit=stats on configure to enable it on --yjit-stats. Add invalidate_everything to default stats, which is incremented when every code is invalidated by TracePoint. Add mem_size: and call_threshold: options to RubyVM::YJIT.enable. ZJIT Add an experimental method-based JIT compiler. Use --enable-zjit on configure to enable the --zjit support. As of Ruby 4.0.0-preview2, ZJIT is not yet ready for speeding up most benchmarks. Please refrain from evaluating ZJIT just yet. Stay tuned for the Ruby 4.0 release. RJIT --rjit is removed. We will move the implementation of the third-party JIT API to the ruby/rjit repository. Miscellaneous changes See NEWS or commit logs for more details. With those changes, 3607 files changed, 197451 insertions(+), 285607 deletions(-) since Ruby 3.4.0! Download https://cache.ruby-lang....