Ruby 4.0.0 preview3 Released

Posted by naruse on 18 Dec 2025

We are pleased to announce the release of Ruby 4.0.0-preview3. Ruby 4.0 introduces Ruby::BOX and “ZJIT”, and adds many improvements.

Ruby::BOX

A new (experimental) feature to provide separation about definitions. For the detail of “Ruby Box”, see doc/language/box.md. [Feature #21311] [Misc #21385]

Language changes

  • *nil no longer calls nil.to_a, similar to how **nil does not call nil.to_hash. [Feature #21047]

  • Logical binary operators (||, &&, and and or) at the beginning of a line continue the previous line, like fluent dot. The following two code are equal:

      if condition1
     && condition2
    ...
  end

      if condition1 && condition2
    ...
  end

    [Feature #20925]

Core classes updates

Note: We’re only listing outstanding class updates.

  • Kernel

    • Kernel#inspect now checks for the existence of a #instance_variables_to_inspect method, allowing control over which instance variables are displayed in the #inspect string:

        class DatabaseConfig
    def initialize(host, user, password)
      @host = host
      @user = user
      @password = password
    end

    private def instance_variables_to_inspect = [:@host, :@user]
  end

  conf = DatabaseConfig.new("localhost", "root", "hunter2")
  conf.inspect #=> #<DatabaseConfig:0x0000000104def350 @host="localhost", @user="root">

      [Feature #21219]

    • A deprecated behavior, process creation by Kernel#open with a leading |, was removed. [Feature #19630]

  • 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]

  • File

    • File::Stat#birthtime is now available on Linux via the statx system call when supported by the kernel and filesystem. [Feature #21205]

  • IO

    • IO.select accepts Float::INFINITY as a timeout argument. [Feature #20610]

    • A deprecated behavior, process creation by IO class methods with a leading |, was removed. [Feature #19630]

  • Math

  • Method

    • Method#source_location, Proc#source_location, and UnboundMethod#source_location now return extended location information with 5 elements: [path, start_line, start_column, end_line, end_column]. The previous 2-element format [path, line] can still be obtained by calling .take(2) on the result. [Feature #6012]

  • Proc

    • Proc#parameters now shows anonymous optional parameters as [:opt] instead of [:opt, nil], making the output consistent with when the anonymous parameter is required. [Bug #20974]

  • Ractor

    • Ractor::Port class was added for a new synchronization mechanism to communicate between Ractors. [Feature #21262]

        port1 = Ractor::Port.new
  port2 = Ractor::Port.new
  Ractor.new port1, port2 do |port1, port2|
    port1 << 1
    port2 << 11
    port1 << 2
    port2 << 12
  end
  2.times{ p port1.receive } #=> 1, 2
  2.times{ p port2.receive } #=> 11, 12

      Ractor::Port provides the following methods:

      • Ractor::Port#receive
      • Ractor::Port#send (or Ractor::Port#<<)
      • Ractor::Port#close
      • Ractor::Port#closed?

      As result, Ractor.yield and Ractor#take were removed.

    • Ractor#join and Ractor#value were added to wait for the termination of a Ractor. These are similar to Thread#join and Thread#value.

    • Ractor#monitor and Ractor#unmonitor were added as low-level interfaces used internally to implement Ractor#join.

    • Ractor.select now only accepts Ractors and Ports. If Ractors are given, it returns when a Ractor terminates.

    • Ractor#default_port was added. Each Ractor has a default port, which is used by Ractor.send, Ractor.receive.

    • Ractor#close_incoming and Ractor#close_outgoing were removed.

    • Ractor.shareable_proc and Ractor.shareable_lambda is introduced to make shareable Proc or lambda. [Feature #21550], [Feature #21557]

  • Range

    • Range#to_set and Enumerator#to_set now perform size checks to prevent issues with endless ranges. [Bug #21654]

    • Range#overlap? now correctly handles infinite (unbounded) ranges. [Bug #21185]

    • Range#max behavior on beginless integer ranges has been fixed. [Bug #21174] [Bug #21175]

  • Ruby

    • A new toplevel module Ruby has been defined, which contains Ruby-related constants. This module was reserved in Ruby 3.4 and is now officially defined. [Feature #20884]

  • Ruby::Box

  • Set

    • Set is now a core class, instead of an autoloaded stdlib class. [Feature #21216]

    • Set#inspect now returns a string suitable for eval, using the Set[] syntax (e.g., Set[1, 2, 3] instead of #<Set: {1, 2, 3}>). This makes it consistent with other core collection classes like Array and Hash. [Feature #21389]

    • Passing arguments to Set#to_set and Enumerable#to_set is now deprecated. [Feature #21390]

  • Socket

    • Socket.tcp & TCPSocket.new accepts an open_timeout keyword argument to specify the timeout for the initial connection. [Feature #21347]

  • String

    • Update Unicode to Version 17.0.0 and Emoji Version 17.0. [Feature #19908][Feature #20724][Feature #21275] (also applies to Regexp)

    • String#strip, strip!, lstrip, lstrip!, rstrip, and rstrip! are extended to accept *selectors arguments. [[Feature #21552]]

  • Thread

    • Introduce support for Thread#raise(cause:) argument similar to Kernel#raise. [Feature #21360]

  • Fiber

    • Introduce support for Fiber#raise(cause:) argument similar to Kernel#raise. [Feature #21360]

  • Fiber::Scheduler

    • Introduce Fiber::Scheduler#fiber_interrupt to interrupt a fiber with a given exception. The initial use case is to interrupt a fiber that is waiting on a blocking IO operation when the IO operation is closed. [Feature #21166]

  • Pathname

    • Pathname has been promoted from a default gem to a core class of Ruby. [Feature #17473]

Stdlib updates

The following bundled gems are promoted from default gems.

  • ostruct 0.6.3
  • pstore 0.2.0
  • benchmark 0.5.0
  • logger 1.7.0
  • rdoc 6.17.0
  • win32ole 1.9.2
  • irb 1.15.3
  • reline 0.6.3
  • readline 0.0.4
  • fiddle 1.1.8

We only list stdlib changes that are notable feature changes.

Other changes are listed in the following sections. We also listed release history from the previous bundled version that is Ruby 3.3.0 if it has GitHub releases.

The following default gem is added.

  • win32-registry 0.1.2

The following default gems are updated.

  • RubyGems 4.0.1
  • bundler 4.0.1
  • date 3.5.1
  • digest 3.2.1
  • english 0.8.1
  • erb 6.0.0
  • etc 1.4.6
  • fcntl 1.3.0
  • fileutils 1.8.0
  • forwardable 1.4.0
  • io-console 0.8.1
  • io-nonblock 0.3.2
  • io-wait 0.4.0.dev
  • ipaddr 1.2.8
  • json 2.17.1
  • net-http 0.8.0
  • openssl 4.0.0.pre
  • optparse 0.8.1
  • pp 0.6.3
  • prism 1.6.0
  • psych 5.3.0
  • resolv 0.7.0
  • stringio 3.1.9.dev
  • strscan 3.1.6.dev
  • timeout 0.5.0
  • uri 1.1.1
  • weakref 0.1.4
  • zlib 3.2.2

The following bundled gems are updated.

  • minitest 5.26.2
  • power_assert 3.0.1
  • rake 13.3.1
  • test-unit 3.7.3
  • rexml 3.4.4
  • net-ftp 0.3.9
  • net-imap 0.5.12
  • net-smtp 0.5.1
  • matrix 0.4.3
  • prime 0.1.4
  • rbs 3.9.5
  • typeprof 0.31.0
  • debug 1.11.0
  • base64 0.3.0
  • bigdecimal 3.3.1
  • drb 2.2.3
  • syslog 0.3.0
  • csv 3.3.5
  • repl_type_completor 0.1.12

Supported platforms

  • Windows

    • Dropped support for MSVC versions older than 14.0 (_MSC_VER 1900). This means Visual Studio 2015 or later is now required.

Compatibility issues

  • The following methods were removed from Ractor due to the addition of Ractor::Port:

    • Ractor.yield
    • Ractor#take
    • Ractor#close_incoming
    • Ractor#close_outgoging

    [Feature #21262]

  • ObjectSpace._id2ref is deprecated. [Feature #15408]

  • Process::Status#& and Process::Status#>> have been removed. They were deprecated in Ruby 3.3. [Bug #19868]

  • rb_path_check has been removed. This function was used for $SAFE path checking which was removed in Ruby 2.7, and was already deprecated,. [Feature #20971]

Stdlib compatibility issues

  • CGI library is removed from the default gems. Now we only provide cgi/escape for the following methods:

    • CGI.escape and CGI.unescape
    • CGI.escapeHTML and CGI.unescapeHTML
    • CGI.escapeURIComponent and CGI.unescapeURIComponent
    • CGI.escapeElement and CGI.unescapeElement

    [Feature #21258]

  • With the move of Set from stdlib to core class, set/sorted_set.rb has been removed, and SortedSet is no longer an autoloaded constant. Please install the sorted_set gem and require 'sorted_set' to use SortedSet. [Feature #21287]

C API updates

  • IO

    • rb_thread_fd_close is deprecated and now a no-op. If you need to expose file descriptors from C extensions to Ruby code, create an IO instance using RUBY_IO_MODE_EXTERNAL and use rb_io_close(io) to close it (this also interrupts and waits for all pending operations on the IO instance). Directly closing file descriptors does not interrupt pending operations, and may lead to undefined behaviour. In other words, if two IO objects share the same file descriptor, closing one does not affect the other. [Feature #18455]

  • GVL

    • rb_thread_call_with_gvl now works with or without the GVL. This allows gems to avoid checking ruby_thread_has_gvl_p. Please still be diligent about the GVL. [Feature #20750]

  • Set

    • A C API for Set has been added. The following methods are supported: [Feature #21459]

      • rb_set_foreach
      • rb_set_new
      • rb_set_new_capa
      • rb_set_lookup
      • rb_set_add
      • rb_set_clear
      • rb_set_delete
      • rb_set_size

Implementation improvements

Ractor

A lot of work has gone into making Ractors more stable, performant, and usable. These improvements bring Ractors implementation closer to leaving experimental status.

  • Performance improvements
    • Frozen strings and the symbol table internally use a lock-free hash set
    • Method cache lookups avoid locking in most cases
    • Class (and geniv) instance variable access is faster and avoids locking
    • Cache contention is avoided during object allocation
    • object_id avoids locking in most cases
  • Bug fixes and stability
    • Fixed possible deadlocks when combining Ractors and Threads
    • Fixed issues with require and autoload in a Ractor
    • Fixed encoding/transcoding issues across Ractors
    • Fixed race conditions in GC operations and method invalidation
    • Fixed issues with processes forking after starting a Ractor

JIT

  • ZJIT
    • Introduce an experimental method-based JIT compiler. To enable --zjit support, build Ruby with Rust 1.85.0 or later.
    • As of Ruby 4.0.0, ZJIT is faster than the interpreter, but not yet as fast as YJIT. We encourage experimentation with ZJIT, but advise against deploying it in production for now.
    • Our goal is to make ZJIT faster than YJIT and production-ready in Ruby 4.1.
  • YJIT
    • RubyVM::YJIT.runtime_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.
  • 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, 3776 files changed, 222800 insertions(+), 293617 deletions(-) since Ruby 3.4.0!

Download

  • https://cache.ruby-lang.org/pub/ruby/4.0/ruby-4.0.0-preview3.tar.gz

    SIZE: 23865890
SHA1: a348f196e0314d8863ae5d5f0a588a37c52aa89c
SHA256: 43d0926e776fbd5599adcc7bccb4ccc804e109f402a2068607a2a86562c2cdc0
SHA512: 1c7f10405832646eceacb278ea7cc3445dc0e1778e9a9331062f2fb0164d45ba5af0b4244dc6ae46e36730d6cafb4c4196fbd4f4fb74029afde5ecf4fd433a6b

  • https://cache.ruby-lang.org/pub/ruby/4.0/ruby-4.0.0-preview3.tar.xz

    SIZE: 17915004
SHA1: b7b99831558b9cd6cf8fb148f07cd4e8e59d9e99
SHA256: 8d7a503b2c4abcfacf0fa54ac56d37f7dd6d643a3a717661729cabbe947610a6
SHA512: b046c015a58daafb1640d8db62a36ebf64c7f83fbfb033fa327458afab6e9c31b1c2b194b347fd63f16e413e732d3e6ac20076282b433ef16923343c9ed84aa1

  • https://cache.ruby-lang.org/pub/ruby/4.0/ruby-4.0.0-preview3.zip

    SIZE: 29403010
SHA1: 689cb6c497afb96d26745708e772b63afca52e1a
SHA256: c29147727a8eacf01b942012e3d6fa26010f98f43f6ab249c391f47c744f44cf
SHA512: c07d6069b391e38ec99725201d021998ccfb913423636f729eccd0cff17cb9ab7e8565f46d68eea96cf7f546cee647892ca3f37b720a202e8e5496cd10dd168b

What is Ruby

Ruby was first developed by Matz (Yukihiro Matsumoto) in 1993, and is now developed as Open Source. It runs on multiple platforms and is used all over the world especially for web development.