diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 03227bcd7234fd..3caeee9a3b8796 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -49,9 +49,9 @@ jobs:
 
       - name: Create a release on GitHub
         run: |
-          RELEASE_TAG=$(echo v${{ env.RUBY_VERSION }} | sed 's/\./_/g')
+          RELEASE_TAG=$(ruby tool/ruby-version.rb tag "${{ env.RUBY_VERSION }}")
           echo $RELEASE_TAG
-          PREVIOUS_RELEASE_TAG=$(echo $RELEASE_TAG | awk 'BEGIN {FS="_"; OFS="_"}{ $NF=$NF-1; print }')
+          PREVIOUS_RELEASE_TAG=$(ruby tool/ruby-version.rb previous-tag "${{ env.RUBY_VERSION }}")
           echo $PREVIOUS_RELEASE_TAG
           tool/gen-github-release.rb $PREVIOUS_RELEASE_TAG $RELEASE_TAG --no-dry-run
         env:
diff --git a/include/ruby/win32.h b/include/ruby/win32.h
index 8d9f9ddd80be6b..ae11a61481e74e 100644
--- a/include/ruby/win32.h
+++ b/include/ruby/win32.h
@@ -262,7 +262,6 @@ struct ifaddrs {
 #endif
 
 extern void   rb_w32_sysinit(int *, char ***);
-extern DWORD  rb_w32_osid(void);
 extern int    flock(int fd, int oper);
 extern int    rb_w32_io_cancelable_p(int);
 extern int    rb_w32_is_socket(int);
@@ -306,7 +305,11 @@ extern void   rb_w32_free_environ(char **);
 extern int    rb_w32_map_errno(DWORD);
 extern const char *WSAAPI rb_w32_inet_ntop(int,const void *,char *,size_t);
 extern int WSAAPI rb_w32_inet_pton(int,const char *,void *);
-extern DWORD  rb_w32_osver(void);
+
+RBIMPL_ATTR_DEPRECATED(("as Windows 9x is not supported already"))
+static inline DWORD rb_w32_osid(void) {return VER_PLATFORM_WIN32_NT;}
+RBIMPL_ATTR_DEPRECATED(("by Windows Version Helper APIs"))
+extern DWORD rb_w32_osver(void);
 
 extern int rb_w32_uchown(const char *, int, int);
 extern int rb_w32_ulink(const char *, const char *);
diff --git a/proc.c b/proc.c
index 2df8fbee5e23a9..1a57757d846ceb 100644
--- a/proc.c
+++ b/proc.c
@@ -640,6 +640,10 @@ bind_local_variable_defined_p(VALUE bindval, VALUE sym)
     const rb_env_t *env;
 
     if (!lid) return Qfalse;
+    if (rb_numparam_id_p(lid)) {
+        rb_name_err_raise("numbered parameter '%1$s' is not a local variable",
+                          bindval, ID2SYM(lid));
+    }
 
     GetBindingPtr(bindval, bind);
     env = VM_ENV_ENVVAL_PTR(vm_block_ep(&bind->block));
diff --git a/test/ruby/test_proc.rb b/test/ruby/test_proc.rb
index 2cd97ca32464ab..2eeb7a94ebb706 100644
--- a/test/ruby/test_proc.rb
+++ b/test/ruby/test_proc.rb
@@ -1659,29 +1659,35 @@ def test_numparam_is_not_local_variables
       assert_equal([], binding.local_variables)
       assert_raise(NameError) { binding.local_variable_get(:_9) }
       assert_raise(NameError) { binding.local_variable_set(:_9, 1) }
+      assert_raise(NameError) { binding.local_variable_defined?(:_9) }
       "bar".tap do
         assert_equal([], binding.local_variables)
         assert_raise(NameError) { binding.local_variable_get(:_9) }
         assert_raise(NameError) { binding.local_variable_set(:_9, 1) }
+        assert_raise(NameError) { binding.local_variable_defined?(:_9) }
       end
       assert_equal([], binding.local_variables)
       assert_raise(NameError) { binding.local_variable_get(:_9) }
       assert_raise(NameError) { binding.local_variable_set(:_9, 1) }
+      assert_raise(NameError) { binding.local_variable_defined?(:_9) }
     end
 
     "foo".tap do
       assert_equal([], binding.local_variables)
       assert_raise(NameError) { binding.local_variable_get(:_9) }
       assert_raise(NameError) { binding.local_variable_set(:_9, 1) }
+      assert_raise(NameError) { binding.local_variable_defined?(:_9) }
       "bar".tap do
         _9 and flunk
         assert_equal([], binding.local_variables)
         assert_raise(NameError) { binding.local_variable_get(:_9) }
         assert_raise(NameError) { binding.local_variable_set(:_9, 1) }
+        assert_raise(NameError) { binding.local_variable_defined?(:_9) }
       end
       assert_equal([], binding.local_variables)
       assert_raise(NameError) { binding.local_variable_get(:_9) }
       assert_raise(NameError) { binding.local_variable_set(:_9, 1) }
+      assert_raise(NameError) { binding.local_variable_defined?(:_9) }
     end
   end
 
@@ -1690,31 +1696,39 @@ def test_it_is_not_local_variable
       it
       assert_equal([], binding.local_variables)
       assert_raise(NameError) { binding.local_variable_get(:it) }
+      assert_equal(false, binding.local_variable_defined?(:it))
       "bar".tap do
         assert_equal([], binding.local_variables)
         assert_raise(NameError) { binding.local_variable_get(:it) }
+        assert_equal(false, binding.local_variable_defined?(:it))
       end
       assert_equal([], binding.local_variables)
       assert_raise(NameError) { binding.local_variable_get(:it) }
+      assert_equal(false, binding.local_variable_defined?(:it))
       "bar".tap do
         it
         assert_equal([], binding.local_variables)
         assert_raise(NameError) { binding.local_variable_get(:it) }
+        assert_equal(false, binding.local_variable_defined?(:it))
       end
       assert_equal([], binding.local_variables)
       assert_raise(NameError) { binding.local_variable_get(:it) }
+      assert_equal(false, binding.local_variable_defined?(:it))
     end
 
     "foo".tap do
       assert_equal([], binding.local_variables)
       assert_raise(NameError) { binding.local_variable_get(:it) }
+      assert_equal(false, binding.local_variable_defined?(:it))
       "bar".tap do
         it
         assert_equal([], binding.local_variables)
         assert_raise(NameError) { binding.local_variable_get(:it) }
+        assert_equal(false, binding.local_variable_defined?(:it))
       end
       assert_equal([], binding.local_variables)
       assert_raise(NameError) { binding.local_variable_get(:it) }
+      assert_equal(false, binding.local_variable_defined?(:it))
     end
   end
 
diff --git a/test/ruby/test_zjit.rb b/test/ruby/test_zjit.rb
index 49b3616425ecd3..232c46079f5b38 100644
--- a/test/ruby/test_zjit.rb
+++ b/test/ruby/test_zjit.rb
@@ -626,6 +626,15 @@ def entry = test(e: :e, d: :d, c: :c, a: :a, b: :b)
     }, call_threshold: 2
   end
 
+  def test_send_kwsplat
+    assert_compiles '3', %q{
+      def test(a:) = a
+      def entry = test(**{a: 3})
+      entry
+      entry
+    }, call_threshold: 2
+  end
+
   def test_send_kwrest
     assert_compiles '{a: 3}', %q{
       def test(**kwargs) = kwargs
diff --git a/thread_pthread_mn.c b/thread_pthread_mn.c
index 2211d4d1067c39..ad4d0915e790b2 100644
--- a/thread_pthread_mn.c
+++ b/thread_pthread_mn.c
@@ -1078,12 +1078,12 @@ timer_thread_polling(rb_vm_t *vm)
 
     switch (r) {
       case 0: // timeout
-        rb_native_mutex_lock(&vm->ractor.sched.lock);
+        ractor_sched_lock(vm, NULL);
         {
             // (1-1) timeslice
             timer_thread_check_timeslice(vm);
         }
-        rb_native_mutex_unlock(&vm->ractor.sched.lock);
+        ractor_sched_unlock(vm, NULL);
         break;
 
       case -1: // error
diff --git a/tool/format-release b/tool/format-release
index b38263f9f4fb05..8bb61542433fb2 100755
--- a/tool/format-release
+++ b/tool/format-release
@@ -9,6 +9,7 @@ end
 
 require "open-uri"
 require "yaml"
+require_relative "./ruby-version"
 
 Diffy::Diff.default_options.merge!(
   include_diff_info: true,
@@ -54,30 +55,10 @@ eom
     unless /\A(\d+)\.(\d+)\.(\d+)(?:-(?:preview|rc)\d+)?\z/ =~ version
       raise "unexpected version string '#{version}'"
     end
-    x = $1.to_i
-    y = $2.to_i
-    z = $3.to_i
-    # previous tag for git diff --shortstat
-    # It's only for x.y.0 release
-    if z != 0
-      prev_tag = nil
-    elsif y != 0
-      prev_ver = "#{x}.#{y-1}.0"
-      prev_tag = version_tag(prev_ver)
-    else # y == 0 && z == 0
-      case x
-      when 3
-        prev_ver = "2.7.0"
-      when 4
-        prev_ver = "3.4.0"
-      else
-        raise "it doesn't know what is the previous version of '#{version}'"
-      end
-      prev_tag = version_tag(prev_ver)
-    end
+    teeny = Integer($3)
 
     uri = "https://cache.ruby-lang.org/pub/tmp/ruby-info-#{version}-draft.yml"
-    info = YAML.load(URI(uri).read)
+    info = YAML.unsafe_load(URI(uri).read)
     if info.size != 1
       raise "unexpected info.yml '#{uri}'"
     end
@@ -92,9 +73,10 @@ eom
       tarballs << tarball
     end
 
-    if prev_tag
+    if teeny == 0
       # show diff shortstat
-      tag = version_tag(version)
+      tag = RubyVersion.tag(version)
+      prev_tag = RubyVersion.tag(RubyVersion.previous(version))
       stat = `git -C #{rubydir} diff -l0 --shortstat #{prev_tag}..#{tag}`
       files_changed, insertions, deletions = stat.scan(/\d+/)
     end
@@ -188,7 +170,7 @@ eom
     if /\.0(?:-\w+)?\z/ =~ ver
       # preview, rc, or first release
       entry <<= <<eom
-  tag: #{version_tag(ver)}
+  tag: #{RubyVersion.tag(ver)}
   stats:
     files_changed: #{files_changed}
     insertions: #{insertions}
@@ -247,15 +229,6 @@ eom
       puts line
     end
   end
-
-  def self.version_tag(version)
-    major_version = Integer(version.split('.', 2)[0])
-    if major_version >= 4
-      "v#{version}"
-    else
-      "v#{version.tr('.-', '_')}"
-    end
-  end
 end
 
 def main
diff --git a/tool/make-snapshot b/tool/make-snapshot
index 041b1a0f2aba6d..4af6a855ebb793 100755
--- a/tool/make-snapshot
+++ b/tool/make-snapshot
@@ -272,10 +272,18 @@ def package(vcs, rev, destdir, tmp = nil)
   when /\A(\d+)\.(\d+)\.(\d+)-(preview|rc)(\d+)/
     prerelease = true
     tag = "#{$4}#{$5}"
-    url = vcs.tag("v#{$1}_#{$2}_#{$3}_#{$4}#{$5}")
+    if Integer($1) >= 4
+      url = vcs.tag("v#{rev}")
+    else
+      url = vcs.tag("v#{$1}_#{$2}_#{$3}_#{$4}#{$5}")
+    end
   when /\A(\d+)\.(\d+)\.(\d+)\z/
     tag = ""
-    url = vcs.tag("v#{$1}_#{$2}_#{$3}")
+    if Integer($1) >= 4
+      url = vcs.tag("v#{rev}")
+    else
+      url = vcs.tag("v#{$1}_#{$2}_#{$3}")
+    end
   when /\A(\d+)\.(\d+)\z/
     url = vcs.branch("ruby_#{rev.tr('.', '_')}")
   else
diff --git a/tool/releng/update-www-meta.rb b/tool/releng/update-www-meta.rb
index 100f0bee181806..0dd5b2563122e7 100755
--- a/tool/releng/update-www-meta.rb
+++ b/tool/releng/update-www-meta.rb
@@ -1,6 +1,7 @@
 #!/usr/bin/env ruby
 require "open-uri"
 require "yaml"
+require_relative "../ruby-version"
 
 class Tarball
   attr_reader :version, :size, :sha1, :sha256, :sha512
@@ -41,27 +42,7 @@ def self.parse(wwwdir, version)
     unless /\A(\d+)\.(\d+)\.(\d+)(?:-(?:preview|rc)\d+)?\z/ =~ version
       raise "unexpected version string '#{version}'"
     end
-    x = $1.to_i
-    y = $2.to_i
-    z = $3.to_i
-    # previous tag for git diff --shortstat
-    # It's only for x.y.0 release
-    if z != 0
-      prev_tag = nil
-    elsif y != 0
-      prev_ver = "#{x}.#{y-1}.0"
-      prev_tag = version_tag(prev_ver)
-    else # y == 0 && z == 0
-      case x
-      when 3
-        prev_ver = "2.7.0"
-      when 4
-        prev_ver = "3.4.0"
-      else
-        raise "it doesn't know what is the previous version of '#{version}'"
-      end
-      prev_tag = version_tag(prev_ver)
-    end
+    teeny = Integer($3)
 
     uri = "https://cache.ruby-lang.org/pub/tmp/ruby-info-#{version}-draft.yml"
     info = YAML.load(URI(uri).read)
@@ -79,9 +60,10 @@ def self.parse(wwwdir, version)
       tarballs << tarball
     end
 
-    if prev_tag
+    if teeny == 0
       # show diff shortstat
-      tag = version_tag(version)
+      tag = RubyVersion.tag(version)
+      prev_tag = RubyVersion.tag(RubyVersion.previous(version))
       rubydir = File.expand_path(File.join(__FILE__, '../../../'))
       puts %`git -C #{rubydir} diff --shortstat #{prev_tag}..#{tag}`
       stat = `git -C #{rubydir} diff --shortstat #{prev_tag}..#{tag}`
@@ -160,7 +142,7 @@ def self.update_releases_yml(ver, xy, ary, wwwdir, files_changed, insertions, de
     date = Time.now.utc # use utc to use previous day in midnight
     entry = <<eom
 - version: #{ver}
-  tag: #{version_tag(ver)}
+  tag: #{RubyVersion.tag(ver)}
   date: #{date.strftime("%Y-%m-%d")}
   post: /en/news/#{date.strftime("%Y/%m/%d")}/ruby-#{ver.tr('.', '-')}-released/
   stats:
@@ -196,15 +178,6 @@ def self.update_releases_yml(ver, xy, ary, wwwdir, files_changed, insertions, de
     end
     File.write(File.join(wwwdir, filename), data)
   end
-
-  def self.version_tag(version)
-    major_version = Integer(version.split('.', 2)[0])
-    if major_version >= 4
-      "v#{version}"
-    else
-      "v#{version.tr('.-', '_')}"
-    end
-  end
 end
 
 # Confirm current directory is www.ruby-lang.org's working directory
diff --git a/tool/ruby-version.rb b/tool/ruby-version.rb
new file mode 100755
index 00000000000000..3bbec576e13ad4
--- /dev/null
+++ b/tool/ruby-version.rb
@@ -0,0 +1,52 @@
+#!/usr/bin/env ruby
+
+module RubyVersion
+  def self.tag(version)
+    major_version = Integer(version.split('.', 2)[0])
+    if major_version >= 4
+      "v#{version}"
+    else
+      "v#{version.tr('.-', '_')}"
+    end
+  end
+
+  # Return the previous version to be used for release diff links.
+  # For a ".0" version, it returns the previous ".0" version.
+  # For a non-".0" version, it returns the previous teeny version.
+  def self.previous(version)
+    unless /\A(\d+)\.(\d+)\.(\d+)(?:-(?:preview|rc)\d+)?\z/ =~ version
+      raise "unexpected version string '#{version}'"
+    end
+    major = Integer($1)
+    minor = Integer($2)
+    teeny = Integer($3)
+
+    if teeny != 0
+      "#{major}.#{minor}.#{teeny-1}"
+    elsif minor != 0 # && teeny == 0
+      "#{major}.#{minor-1}.#{teeny}"
+    else # minor == 0 && teeny == 0
+      case major
+      when 3
+        "2.7.0"
+      when 4
+        "3.4.0"
+      else
+        raise "it doesn't know what is the previous version of '#{version}'"
+      end
+    end
+  end
+end
+
+if __FILE__ == $0
+  case ARGV[0]
+  when "tag"
+    print RubyVersion.tag(ARGV[1])
+  when "previous"
+    print RubyVersion.previous(ARGV[1])
+  when "previous-tag"
+    print RubyVersion.tag(RubyVersion.previous(ARGV[1]))
+  else
+    "#{$0}: unexpected command #{ARGV[0].inspect}"
+  end
+end
diff --git a/win32/win32.c b/win32/win32.c
index 66ce195092f5e5..97dc7148085c55 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -314,15 +314,6 @@ get_version(void)
     GetVersionEx(&osver);
 }
 
-#ifdef _M_IX86
-/* License: Artistic or GPL */
-DWORD
-rb_w32_osid(void)
-{
-    return osver.dwPlatformId;
-}
-#endif
-
 /* License: Artistic or GPL */
 DWORD
 rb_w32_osver(void)
@@ -7223,9 +7214,6 @@ rb_w32_read_internal(int fd, void *buf, size_t size, rb_off_t *offset)
     size_t len;
     size_t ret;
     OVERLAPPED ol;
-    BOOL isconsole;
-    BOOL islineinput = FALSE;
-    int start = 0;
 
     if (is_socket(sock))
         return rb_w32_recv(fd, buf, size, 0);
@@ -7248,25 +7236,8 @@ rb_w32_read_internal(int fd, void *buf, size_t size, rb_off_t *offset)
     }
 
     ret = 0;
-    isconsole = is_console(_osfhnd(fd)) && (osver.dwMajorVersion < 6 || (osver.dwMajorVersion == 6 && osver.dwMinorVersion < 2));
-    if (isconsole) {
-        DWORD mode;
-        GetConsoleMode((HANDLE)_osfhnd(fd),&mode);
-        islineinput = (mode & ENABLE_LINE_INPUT) != 0;
-    }
   retry:
-    /* get rid of console reading bug */
-    if (isconsole) {
-        constat_reset((HANDLE)_osfhnd(fd));
-        if (start)
-            len = 1;
-        else {
-            len = 0;
-            start = 1;
-        }
-    }
-    else
-        len = size;
+    len = size;
     size -= len;
 
     if (setup_overlapped(&ol, fd, FALSE, offset)) {
@@ -7337,8 +7308,7 @@ rb_w32_read_internal(int fd, void *buf, size_t size, rb_off_t *offset)
     ret += read;
     if (read >= len) {
         buf = (char *)buf + read;
-        if (err != ERROR_OPERATION_ABORTED &&
-            !(isconsole && len == 1 && (!islineinput || *((char *)buf - 1) == '\n')) && size > 0)
+        if (err != ERROR_OPERATION_ABORTED && size > 0)
             goto retry;
     }
     if (read == 0)
diff --git a/zjit/src/hir.rs b/zjit/src/hir.rs
index 4992f177991d47..1cdc5e003a7cf2 100644
--- a/zjit/src/hir.rs
+++ b/zjit/src/hir.rs
@@ -5229,6 +5229,7 @@ fn unspecializable_c_call_type(flags: u32) -> bool {
 /// If a given call uses overly complex arguments, then we won't specialize.
 fn unspecializable_call_type(flags: u32) -> bool {
     ((flags & VM_CALL_ARGS_SPLAT) != 0) ||
+    ((flags & VM_CALL_KW_SPLAT) != 0) ||
     ((flags & VM_CALL_ARGS_BLOCKARG) != 0)
 }
 
diff --git a/zjit/src/hir/opt_tests.rs b/zjit/src/hir/opt_tests.rs
index a602121a0cc51d..3946c9d03c0714 100644
--- a/zjit/src/hir/opt_tests.rs
+++ b/zjit/src/hir/opt_tests.rs
@@ -2993,6 +2993,33 @@ mod hir_opt_tests {
         ");
     }
 
+    #[test]
+    fn dont_specialize_call_to_iseq_with_call_kwsplat() {
+        eval("
+            def foo(a:) = a
+            def test = foo(**{a: 1})
+            test
+            test
+        ");
+        assert_snapshot!(hir_string("test"), @r"
+        fn test@<compiled>:3:
+        bb0():
+          EntryPoint interpreter
+          v1:BasicObject = LoadSelf
+          Jump bb2(v1)
+        bb1(v4:BasicObject):
+          EntryPoint JIT(0)
+          Jump bb2(v4)
+        bb2(v6:BasicObject):
+          v11:HashExact[VALUE(0x1000)] = Const Value(VALUE(0x1000))
+          v12:HashExact = HashDup v11
+          IncrCounter complex_arg_pass_caller_kw_splat
+          v14:BasicObject = SendWithoutBlock v6, :foo, v12 # SendFallbackReason: Complex argument passing
+          CheckInterrupts
+          Return v14
+        ");
+    }
+
     #[test]
     fn dont_specialize_call_to_iseq_with_param_kwrest() {
         eval("