Update Ruby 3.4.8 → 4.0.0 #1364

depfu · 2026-01-02T00:01:23Z

Here is everything you need to know about this upgrade. Please take a good look at what changed and the test results before merging this pull request.

What changed?

Release Notes

4.0.0

Posted by naruse on 25 Dec 2025

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

Ruby Box

Ruby Box is a new (experimental) feature to provide separation about definitions. Ruby Box is enabled when an environment variable RUBY_BOX=1 is specified. The class is Ruby::Box.

Definitions loaded in a box are isolated in the box. Ruby Box can isolate/separate monkey patches, changes of global/class variables, class/module definitions, and loaded native/ruby libraries from other boxes.

Expected use cases are:

Run test cases in box to protect other tests when the test case uses monkey patches to override something

Run web app boxes in parallel to execute blue-green deployment on an app server in a Ruby process

Run web app boxes in parallel to evaluate dependency updates for a certain period of time by checking response diff using Ruby code

Used as the foundation (low-level) API to implement kind of “package” (high-level) API (it is not designed yet)

For the detail of “Ruby Box”, see Ruby::Box. [Feature #21311] [Misc #21385]

ZJIT

ZJIT is a new just-in-time (JIT) compiler, which is developed as the next generation of YJIT. You need Rust 1.85.0 or newer to build Ruby with ZJIT support, and ZJIT is enabled when --zjit is specified.

We’re building a new compiler for Ruby because we want to both raise the performance ceiling (bigger compilation unit size and SSA IR) and encourage more outside contribution (by becoming a more traditional method compiler). See our blog post for more details.

ZJIT is faster than the interpreter, but not yet as fast as YJIT. We encourage you to experiment with ZJIT, but maybe hold off on deploying it in production for now. Stay tuned for Ruby 4.1 ZJIT.

Ractor Improvements

Ractor, Ruby’s parallel execution mechanism, has received several improvements. A new class, Ractor::Port, was introduced to address issues related to message sending and receiving (see our blog post). Additionally, Ractor.shareable_proc makes it easier to share Proc objects between Ractors.

On the performance side, many internal data structures have been improved to significantly reduce contention on a global lock, unlocking better parallelism. Ractors also now share less internal data, resulting in less CPU cache contention when running in parallel.

Ractor was first introduced in Ruby 3.0 as an experimental feature. We aim to remove its “experimental” status next year.

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 code examples are equal:
<div class="language-ruby highlighter-rouge">
  if condition1
     && condition2
    ...
  end
<p>Previously:</p>

<div class="language-ruby highlighter-rouge">
  if condition1 && condition2
    ...
  end
<div class="language-ruby highlighter-rouge">
  if condition1 &&
     condition2
    ...
  end
<p>[<a href="https://bugs.ruby-lang.org/issues/20925">Feature #20925</a>]</p>
Core classes updates

Note: We’re only listing outstanding class updates.
Array
<ul>
  <li>
Array#rfind has been added as a more efficient alternative to array.reverse_each.find [Feature #21678]
Array#find has been added as a more efficient override of Enumerable#find [Feature #21678]
Binding
<ul>
  <li>
    <p><code class="language-plaintext highlighter-rouge">Binding#local_variables</code> does no longer include numbered parameters.
Also, Binding#local_variable_get, Binding#local_variable_set, and
Binding#local_variable_defined? reject to handle numbered parameters.
[Bug #21049]
Binding#implicit_parameters, Binding#implicit_parameter_get, and
Binding#implicit_parameter_defined? have been added to access
numbered parameters and “it” parameter. [Bug #21049]
Enumerator
<ul>
  <li>
    <p><code class="language-plaintext highlighter-rouge">Enumerator.produce</code> now accepts an optional <code class="language-plaintext highlighter-rouge">size</code> keyword argument
to specify the size of the enumerator. It can be an integer,
Float::INFINITY, a callable object (such as a lambda), or nil to
indicate unknown size. When not specified, the size defaults to
Float::INFINITY.
    <div class="language-ruby highlighter-rouge">
  # Infinite enumerator
  enum = Enumerator.produce(1, size: Float::INFINITY, &:succ)
  enum.size  # => Float::INFINITY
# Finite enumerator with known/computable size

abs_dir = File.expand_path("./baz") # => "/foo/bar/baz"

traverser = Enumerator.produce(abs_dir, size: -> { abs_dir.count("/") + 1 }) {

raise StopIteration if it == "/"

File.dirname(it)

}

traverser.size  # => 4
    <p>[<a href="https://bugs.ruby-lang.org/issues/21701">Feature #21701</a>]</p>
  </li>
</ul>
ErrorHighlight
<ul>
  <li>
    <p>When an ArgumentError is raised, it now displays code snippets for
both the method call (caller) and the method definition (callee).
[Feature #21543]
    <div class="language-plaintext highlighter-rouge">
test.rb:1:in 'Object#add': wrong number of arguments (given 1, expected 2) (ArgumentError)
caller: test.rb:3
| add(1)
  ^^^
callee: test.rb:1
| def add(x, y) = x + y
      ^^^
    from test.rb:3:in '&lt;main&gt;'
Fiber
<ul>
  <li>Introduce support for <code class="language-plaintext highlighter-rouge">Fiber#raise(cause:)</code> argument similar to
Kernel#raise. [Feature #21360]
Fiber::Scheduler
<ul>
  <li>
    <p>Introduce <code class="language-plaintext highlighter-rouge">Fiber::Scheduler#fiber_interrupt</code> 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]
Introduce Fiber::Scheduler#yield to allow the fiber scheduler to
continue processing when signal exceptions are disabled.
[Bug #21633]

Reintroduce the Fiber::Scheduler#io_close hook for asynchronous IO#close.

Invoke Fiber::Scheduler#io_write when flushing the IO write buffer.
[Bug #21789]
File
<ul>
  <li>
File::Stat#birthtime is now available on Linux via the statx
system call when supported by the kernel and filesystem.
[Feature #21205]
IO
<ul>
  <li>
    <p><code class="language-plaintext highlighter-rouge">IO.select</code> accepts <code class="language-plaintext highlighter-rouge">Float::INFINITY</code> as a timeout argument.
[Feature #20610]
A deprecated behavior, process creation by IO class methods
with a leading |, was removed. [Feature #19630]
Kernel
<ul>
  <li>
    <p><code class="language-plaintext highlighter-rouge">Kernel#inspect</code> now checks for the existence of a <code class="language-plaintext highlighter-rouge">#instance_variables_to_inspect</code> method,
allowing control over which instance variables are displayed in the #inspect string:
    <div class="language-ruby highlighter-rouge">
  class DatabaseConfig
    def initialize(host, user, password)
      @host = host
      @user = user
      @password = password
    end
<span class="kp">private</span> <span class="k">def</span> <span class="nf">instance_variables_to_inspect</span> <span class="o">=</span> <span class="p">[</span><span class="ss">:@host</span><span class="p">,</span> <span class="ss">:@user</span><span class="p">]</span>

end
conf = DatabaseConfig.new("localhost", "root", "hunter2")

conf.inspect #=> #<DatabaseConfig:0x0000000104def350 @host="localhost", @user="root">
    <p>[<a href="https://bugs.ruby-lang.org/issues/21219">Feature #21219</a>]</p>
  </li>
  <li>
    <p>A deprecated behavior, process creation by <code class="language-plaintext highlighter-rouge">Kernel#open</code> with a
leading |, was removed. [Feature #19630]
Math
<ul>
  <li>
Math.log1p and Math.expm1 are added. [Feature #21527]
Pathname
<ul>
  <li>Pathname has been promoted from a default gem to a core class of Ruby.
[Feature #17473]
Proc
<ul>
  <li>
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
<ul>
  <li>
    <p><code class="language-plaintext highlighter-rouge">Ractor::Port</code> class was added for a new synchronization mechanism
to communicate between Ractors. [Feature #21262]
    <div class="language-ruby highlighter-rouge">
  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
    <p><code class="language-plaintext highlighter-rouge">Ractor::Port</code> provides the following methods:</p>

    <ul>
      <li><code class="language-plaintext highlighter-rouge">Ractor::Port#receive</code></li>
      <li>
Ractor::Port#send (or Ractor::Port#<<)
Ractor::Port#close

Ractor::Port#closed?
    <p>As a result, <code class="language-plaintext highlighter-rouge">Ractor.yield</code> and <code class="language-plaintext highlighter-rouge">Ractor#take</code> were removed.</p>
  </li>
  <li>
    <p><code class="language-plaintext highlighter-rouge">Ractor#join</code> and <code class="language-plaintext highlighter-rouge">Ractor#value</code> 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 are introduced
to make shareable Proc or lambda.
[Feature #21550], [Feature #21557]
Range
<ul>
  <li>
    <p><code class="language-plaintext highlighter-rouge">Range#to_set</code> now performs 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
<ul>
  <li>A new toplevel module <code class="language-plaintext highlighter-rouge">Ruby</code> 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
<ul>
  <li>A new (experimental) feature to provide separation about definitions.
For the detail of “Ruby Box”, see doc/language/box.md.
[Feature #21311] [Misc #21385]
Set
<ul>
  <li>
    <p><code class="language-plaintext highlighter-rouge">Set</code> is now a core class, instead of an autoloaded stdlib class.
[Feature #21216]
Set#inspect now uses a simpler display, similar to literal arrays.
(e.g., Set[1, 2, 3] instead of #<Set: {1, 2, 3}>). [Feature #21389]

Passing arguments to Set#to_set and Enumerable#to_set is now deprecated.
[Feature #21390]
Socket
<ul>
  <li>
Socket.tcp & TCPSocket.new accepts an open_timeout keyword argument to specify
the timeout for the initial connection. [Feature #21347]
When a user-specified timeout occurred in TCPSocket.new, either Errno::ETIMEDOUT
or IO::TimeoutError could previously be raised depending on the situation.
This behavior has been unified so that IO::TimeoutError is now consistently raised.
(Please note that, in Socket.tcp, there are still cases where Errno::ETIMEDOUT
may be raised in similar situations, and that in both cases Errno::ETIMEDOUT may be
raised when the timeout occurs at the OS level.)
String
<ul>
  <li>
    <p>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
<ul>
  <li>Introduce support for <code class="language-plaintext highlighter-rouge">Thread#raise(cause:)</code> argument similar to
Kernel#raise. [Feature #21360]
Stdlib updates

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 3.4.0 if it has GitHub releases.

The following bundled gems are promoted from default gems.

ostruct 0.6.3

0.6.1 to v0.6.2, v0.6.3

pstore 0.2.0

0.1.4 to v0.2.0

benchmark 0.5.0

0.4.0 to v0.4.1, v0.5.0

logger 1.7.0

1.6.4 to v1.6.5, v1.6.6, v1.7.0

rdoc 7.0.2

6.14.0 to v6.14.1, v6.14.2, v6.15.0, v6.15.1, v6.16.0, v6.16.1, v6.17.0, v7.0.0, v7.0.1, v7.0.2, v7.0.3

win32ole 1.9.2

1.9.1 to v1.9.2

irb 1.16.0

1.14.3 to v1.15.0, v1.15.1, v1.15.2, v1.15.3, v1.16.0

reline 0.6.3

0.6.0 to v0.6.1, v0.6.2, v0.6.3

readline 0.0.4

fiddle 1.1.8

1.1.6 to v1.1.7, v1.1.8

The following default gem is added.

win32-registry 0.1.2

The following default gems are updated.

RubyGems 4.0.3

bundler 4.0.3

date 3.5.1

3.4.1 to v3.5.0, v3.5.1

delegate 0.6.1

0.4.0 to v0.5.0, v0.6.0, v0.6.1

digest 3.2.1

3.2.0 to v3.2.1

english 0.8.1

0.8.0 to v0.8.1

erb 6.0.1

4.0.4 to v5.1.2, v5.1.3, v6.0.0, v6.0.1

error_highlight 0.7.1

etc 1.4.6

fcntl 1.3.0

1.2.0 to v1.3.0

fileutils 1.8.0

1.7.3 to v1.8.0

forwardable 1.4.0

1.3.3 to v1.4.0

io-console 0.8.2

0.8.1 to v0.8.2

io-nonblock 0.3.2

io-wait 0.4.0

0.3.2 to v0.3.3, v0.3.5.test1, v0.3.5, v0.3.6, v0.4.0

ipaddr 1.2.8

json 2.18.0

2.9.1 to v2.10.0, v2.10.1, v2.10.2, v2.11.0, v2.11.1, v2.11.2, v2.11.3, v2.12.0, v2.12.1, v2.12.2, v2.13.0, v2.13.1, v2.13.2, v2.14.0, v2.14.1, v2.15.0, v2.15.1, v2.15.2, v2.16.0, v2.17.0, v2.17.1, v2.18.0

net-http 0.9.1

0.6.0 to v0.7.0, v0.8.0, v0.9.0, v0.9.1

openssl 4.0.0

3.3.1 to v3.3.2, v4.0.0

optparse 0.8.1

0.6.0 to v0.7.0, v0.8.0, v0.8.1

pp 0.6.3

0.6.2 to v0.6.3

prism 1.7.0

1.5.2 to v1.6.0, v1.7.0

psych 5.3.1

5.2.2 to v5.2.3, v5.2.4, v5.2.5, v5.2.6, v5.3.0, v5.3.1

resolv 0.7.0

0.6.2 to v0.6.3, v0.7.0

stringio 3.2.0

3.1.2 to v3.1.3, v3.1.4, v3.1.5, v3.1.6, v3.1.7, v3.1.8, v3.1.9, v3.2.0

strscan 3.1.6

3.1.2 to v3.1.3, v3.1.4, v3.1.5, v3.1.6

time 0.4.2

0.4.1 to v0.4.2

timeout 0.6.0

0.4.3 to v0.4.4, v0.5.0, v0.6.0

uri 1.1.1

1.0.4 to v1.1.0, v1.1.1

weakref 0.1.4

0.1.3 to v0.1.4

zlib 3.2.2

3.2.1 to v3.2.2

The following bundled gems are updated.

minitest 6.0.0

power_assert 3.0.1

2.0.5 to v3.0.0, v3.0.1

rake 13.3.1

13.2.1 to v13.3.0, v13.3.1

test-unit 3.7.3

3.6.7 to 3.6.8, 3.6.9, 3.7.0, 3.7.1, 3.7.2, 3.7.3, 3.7.4, 3.7.5

rexml 3.4.4

rss 0.3.2

0.3.1 to 0.3.2

net-ftp 0.3.9

0.3.8 to v0.3.9

net-imap 0.6.2

0.5.8 to v0.5.9, v0.5.10, v0.5.11, v0.5.12, v0.5.13, v0.6.0, v0.6.1, v0.6.2

net-smtp 0.5.1

0.5.0 to v0.5.1

matrix 0.4.3

0.4.2 to v0.4.3

prime 0.1.4

0.1.3 to v0.1.4

rbs 3.10.0

3.8.0 to v3.8.1, v3.9.0.dev.1, v3.9.0.pre.1, v3.9.0.pre.2, v3.9.0, v3.9.1, v3.9.2, v3.9.3, v3.9.4, v3.9.5, v3.10.0.pre.1, v3.10.0.pre.2, v3.10.0

typeprof 0.31.1

debug 1.11.1

1.11.0 to v1.11.1

base64 0.3.0

0.2.0 to v0.3.0

bigdecimal 4.0.1

3.1.8 to v3.2.0, v3.2.1, v3.2.2, v3.2.3, v3.3.0, v3.3.1, v4.0.0, v4.0.1

drb 2.2.3

2.2.1 to v2.2.3

syslog 0.3.0

0.2.0 to v0.3.0

csv 3.3.5

3.3.2 to v3.3.3, v3.3.4, v3.3.5

repl_type_completor 0.1.12

RubyGems and Bundler

Ruby 4.0 bundled RubyGems and Bundler version 4. see the following links for details.

Upgrading to RubyGems/Bundler 4 - RubyGems Blog

4.0.0 Released - RubyGems Blog

4.0.1 Released - RubyGems Blog

4.0.2 Released - RubyGems Blog

4.0.3 Released - RubyGems Blog

Supported platforms
Windows
<ul>
  <li>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:
<ul>
  <li><code class="language-plaintext highlighter-rouge">Ractor.yield</code></li>
  <li><code class="language-plaintext highlighter-rouge">Ractor#take</code></li>
  <li><code class="language-plaintext highlighter-rouge">Ractor#close_incoming</code></li>
  <li><code class="language-plaintext highlighter-rouge">Ractor#close_outgoing</code></li>
</ul>

<p>[<a href="https://bugs.ruby-lang.org/issues/21262">Feature #21262</a>]</p>
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]

A backtrace for ArgumentError of “wrong number of arguments” now include the receiver’s class or module name (e.g., in Foo#bar instead of in bar). [Bug #21698]
Backtraces no longer display internal frames. These methods now appear as if it is in the Ruby source file, consistent with other C-implemented methods. [Bug #20968]
<p>Before:</p>
<div class="language-plaintext highlighter-rouge">
ruby -e '[1].fetch_values(42)'
<internal:array>:211:in 'Array#fetch': index 42 outside of array bounds: -1...1 (IndexError)
        from <internal:array>:211:in 'block in Array#fetch_values'
        from <internal:array>:211:in 'Array#map!'
        from <internal:array>:211:in 'Array#fetch_values'
        from -e:1:in '<main>'
<p>After:</p>
<div class="language-plaintext highlighter-rouge">
$ ruby -e '[1].fetch_values(42)'
-e:1:in 'Array#fetch_values': index 42 outside of array bounds: -1...1 (IndexError)
        from -e:1:in '<main>'
Stdlib compatibility issues
CGI library is removed from the default gems. Now we only provide cgi/escape for the following methods:
<ul>
  <li>
CGI.escape and CGI.unescape
CGI.escapeHTML and CGI.unescapeHTML

CGI.escapeURIComponent and CGI.unescapeURIComponent

CGI.escapeElement and CGI.unescapeElement
<p>[<a href="https://bugs.ruby-lang.org/issues/21258">Feature #21258</a>]</p>
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]
Net::HTTP
<ul>
  <li>The default behavior of automatically setting the <code class="language-plaintext highlighter-rouge">Content-Type</code> header
to application/x-www-form-urlencoded for requests with a body
(e.g., POST, PUT) when the header was not explicitly set has been
removed. If your application relied on this automatic default, your
requests will now be sent without a Content-Type header, potentially
breaking compatibility with certain servers.
[GH-net-http #205]
C API updates
IO
<ul>
  <li>
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
<ul>
  <li>
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
<ul>
  <li>
    <p>A C API for <code class="language-plaintext highlighter-rouge">Set</code> has been added. The following methods are supported:
[Feature #21459]
    <ul>
      <li><code class="language-plaintext highlighter-rouge">rb_set_foreach</code></li>
      <li><code class="language-plaintext highlighter-rouge">rb_set_new</code></li>
      <li><code class="language-plaintext highlighter-rouge">rb_set_new_capa</code></li>
      <li><code class="language-plaintext highlighter-rouge">rb_set_lookup</code></li>
      <li><code class="language-plaintext highlighter-rouge">rb_set_add</code></li>
      <li><code class="language-plaintext highlighter-rouge">rb_set_clear</code></li>
      <li><code class="language-plaintext highlighter-rouge">rb_set_delete</code></li>
      <li><code class="language-plaintext highlighter-rouge">rb_set_size</code></li>
    </ul>
  </li>
</ul>
Implementation improvements

Class#new (ex. Object.new) is faster in all cases, but especially when passing keyword arguments. This has also been integrated into YJIT and ZJIT. [Feature #21254]

GC heaps of different size pools now grow independently, reducing memory usage when only some pools contain long-lived objects

GC sweeping is faster on pages of large objects

“Generic ivar” objects (String, Array, TypedData, etc.) now use a new internal “fields” object for faster instance variable access

The GC avoids maintaining an internal id2ref table until it is first used, making object_id allocation and GC sweeping faster

object_id and hash are faster on Class and Module objects

Larger bignum Integers can remain embedded using variable width allocation

Random, Enumerator::Product, Enumerator::Chain, Addrinfo, StringScanner, and some internal objects are now write-barrier protected, which reduces GC overhead.

Ractor

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

Performance improvements

Frozen strings and the symbol table internally use a lock-free hash set [Feature #21268]

Method cache lookups avoid locking in most cases

Class (and generic ivar) instance variable access is faster and avoids locking

CPU cache contention is avoided in object allocation by using a per-ractor counter

CPU cache contention is avoided in xmalloc/xfree by using a thread-local counter

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

GC allocation counts are now accurate under Ractors

Fixed TracePoints not working after GC [Bug #19112]

JIT

ZJIT

Introduce an experimental method-based JIT compiler. Where available, ZJIT can be enabled at runtime with the --zjit option or by calling RubyVM::ZJIT.enable. When building Ruby, Rust 1.85.0 or later is required to include ZJIT support.

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.

See NEWS or commit logs for more details.

With those changes, 3889 files changed, 230769 insertions(+), 297003 deletions(-) since Ruby 3.4.0!

Merry Christmas, a Happy New Year, and Happy Hacking with Ruby 4.0!

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Update Ruby to version 4.0.0

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depfu bot added the depfu label Jan 2, 2026

depfu bot assigned mockdeep Jan 2, 2026

depfu bot requested a review from mockdeep January 2, 2026 00:01

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Update Ruby 3.4.8 → 4.0.0 #1364

Update Ruby 3.4.8 → 4.0.0 #1364

depfu bot commented Jan 2, 2026

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Update Ruby 3.4.8 → 4.0.0 #1364

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Update Ruby 3.4.8 → 4.0.0 #1364

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depfu bot commented Jan 2, 2026

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4.0.0

Ruby Box

ZJIT

Ractor Improvements

Language changes

Core classes updates

Stdlib updates

RubyGems and Bundler

Supported platforms

Compatibility issues

Stdlib compatibility issues

C API updates

Implementation improvements

Ractor

JIT

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