diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
index 46ad7c82128e23..bf34baaced0fd2 100644
--- a/.github/workflows/ubuntu.yml
+++ b/.github/workflows/ubuntu.yml
@@ -243,7 +243,7 @@ jobs:
           path: ruby-bench
 
       - name: Run ruby-bench
-        run: ruby run_benchmarks.rb -e "ruby::../build/install/bin/ruby" ${{ matrix.bench_opts }}
+        run: rm -rf benchmarks/lobsters && ruby run_benchmarks.rb -e "ruby::../build/install/bin/ruby" ${{ matrix.bench_opts }}
         working-directory: ruby-bench
 
       - uses: ./.github/actions/slack
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index c19d9e4aa78577..7f3e60349642e0 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -112,7 +112,7 @@ jobs:
         # https://github.com/actions/virtual-environments/issues/712#issuecomment-613004302
         run: |
           ::- Set up VC ${{ matrix.vc }}
-          set | uutils sort > old.env
+          set | sort > old.env
           call ..\src\win32\vssetup.cmd ^
             -arch=${{ matrix.target || 'amd64' }} ^
             ${{ matrix.vcvars && '-vcvars_ver=' || '' }}${{ matrix.vcvars }}
@@ -122,8 +122,8 @@ jobs:
           set MAKEFLAGS=l
           set /a TEST_JOBS=(15 * %NUMBER_OF_PROCESSORS% / 10) > nul
           set RUBY_OPT_DIR=%GITHUB_WORKSPACE:\=/%/src/vcpkg_installed/%VCPKG_DEFAULT_TRIPLET%
-          set | uutils sort > new.env
-          uutils comm -13 old.env new.env >> %GITHUB_ENV%
+          set | sort > new.env
+          comm -13 old.env new.env >> %GITHUB_ENV%
           del *.env
 
       - name: baseruby version
diff --git a/.github/workflows/zjit-macos.yml b/.github/workflows/zjit-macos.yml
index ed559d64e10d05..55bfcb30f22364 100644
--- a/.github/workflows/zjit-macos.yml
+++ b/.github/workflows/zjit-macos.yml
@@ -198,7 +198,7 @@ jobs:
           path: ruby-bench
 
       - name: Run ruby-bench
-        run: ruby run_benchmarks.rb -e "zjit::../build/install/bin/ruby ${{ matrix.ruby_opts }}" ${{ matrix.bench_opts }}
+        run: rm -rf benchmarks/lobsters && ruby run_benchmarks.rb -e "zjit::../build/install/bin/ruby ${{ matrix.ruby_opts }}" ${{ matrix.bench_opts }}
         working-directory: ruby-bench
 
       - uses: ./.github/actions/slack
diff --git a/.github/workflows/zjit-ubuntu.yml b/.github/workflows/zjit-ubuntu.yml
index 37a9000d704c5a..29b7aaad592c7e 100644
--- a/.github/workflows/zjit-ubuntu.yml
+++ b/.github/workflows/zjit-ubuntu.yml
@@ -251,7 +251,7 @@ jobs:
           path: ruby-bench
 
       - name: Run ruby-bench
-        run: ruby run_benchmarks.rb -e "zjit::../build/install/bin/ruby ${{ matrix.ruby_opts }}" ${{ matrix.bench_opts }}
+        run: rm -rf benchmarks/lobsters && ruby run_benchmarks.rb -e "zjit::../build/install/bin/ruby ${{ matrix.ruby_opts }}" ${{ matrix.bench_opts }}
         working-directory: ruby-bench
 
       - uses: ./.github/actions/slack
diff --git a/NEWS.md b/NEWS.md
index b9b5fb3ed247ca..59a2b4b49d4c44 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -19,14 +19,18 @@ 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.
+### The following bundled gems are promoted from default gems.
 
-The following default gem is added.
+### The following default gem is added.
 
-The following default gems are updated.
+### The following default gems are updated.
 
+* RubyGems 4.1.0.dev
+* bundler 4.1.0.dev
+* stringio 3.2.1.dev
+* strscan 3.1.7.dev
 
-The following bundled gems are updated.
+### The following bundled gems are updated.
 
 ### RubyGems and Bundler
 
diff --git a/doc/stringio/pread.rdoc b/doc/stringio/pread.rdoc
new file mode 100644
index 00000000000000..2dcbc18ad81a81
--- /dev/null
+++ b/doc/stringio/pread.rdoc
@@ -0,0 +1,65 @@
+**Note**: \Method +pread+ is different from other reading methods
+in that it does not modify +self+ in any way;
+thus, multiple threads may read safely from the same stream.
+
+Reads up to +maxlen+ bytes from the stream,
+beginning at 0-based byte offset +offset+;
+returns a string containing the read bytes.
+
+The returned string:
+
+- Contains +maxlen+ bytes from the stream, if available;
+  otherwise contains all available bytes.
+- Has encoding +Encoding::ASCII_8BIT+.
+
+With only arguments +maxlen+ and +offset+ given,
+returns a new string:
+
+  english = 'Hello'  # Five 1-byte characters.
+  strio = StringIO.new(english)
+  strio.pread(3, 0)  # => "Hel"
+  strio.pread(3, 2)  # => "llo"
+  strio.pread(0, 0)  # => ""
+  strio.pread(50, 0) # => "Hello"
+  strio.pread(50, 2) # => "llo"
+  strio.pread(50, 4) # => "o"
+  strio.pread(0, 0).encoding
+  # => #<Encoding:BINARY (ASCII-8BIT)>
+
+  russian = 'Привет' # Six 2-byte characters.
+  strio = StringIO.new(russian)
+  strio.pread(50, 0) # All 12 bytes.
+  # => "\xD0\x9F\xD1\x80\xD0\xB8\xD0\xB2\xD0\xB5\xD1\x82"
+  strio.pread(3, 0)  # => "\xD0\x9F\xD1"
+  strio.pread(3, 3)  # => "\x80\xD0\xB8"
+  strio.pread(0, 0).encoding
+  # => #<Encoding:BINARY (ASCII-8BIT)>
+
+  japanese = 'こんにちは' # Five 3-byte characters.
+  strio = StringIO.new(japanese)
+  strio.pread(50, 0)    # All 15 bytes.
+  # => "\xE3\x81\x93\xE3\x82\x93\xE3\x81\xAB\xE3\x81\xA1\xE3\x81\xAF"
+  strio.pread(6, 0)     # => "\xE3\x81\x93\xE3\x82\x93"
+  strio.pread(1, 2)     # => "\x93"
+  strio.pread(0, 0).encoding
+  # => #<Encoding:BINARY (ASCII-8BIT)>
+
+Raises an exception if +offset+ is out-of-range:
+
+  strio = StringIO.new(english)
+  strio.pread(5, 50) # Raises EOFError: end of file reached
+
+With string argument +out_string+ given:
+
+- Reads as above.
+- Overwrites the content of +out_string+ with the read bytes.
+
+Examples:
+
+  out_string = 'Will be overwritten'
+  out_string.encoding                # => #<Encoding:UTF-8>
+  result = StringIO.new(english).pread(50, 0, out_string)
+  result.__id__ == out_string.__id__ # => true
+  out_string                         # => "Hello"
+  out_string.encoding                # => #<Encoding:BINARY (ASCII-8BIT)>
+
diff --git a/doc/stringio/putc.rdoc b/doc/stringio/putc.rdoc
new file mode 100644
index 00000000000000..4636ffa0db8b34
--- /dev/null
+++ b/doc/stringio/putc.rdoc
@@ -0,0 +1,82 @@
+Replaces one or more bytes at position +pos+
+with bytes of the given argument;
+advances the position by the count of bytes written;
+returns the argument.
+
+\StringIO object for 1-byte characters.
+
+  strio = StringIO.new('foo')
+  strio.pos # => 0
+
+With 1-byte argument, replaces one byte:
+
+  strio.putc('b')
+  strio.string    # => "boo"
+  strio.pos       # => 1
+  strio.putc('a') # => "a"
+  strio.string    # => "bao"
+  strio.pos       # => 2
+  strio.putc('r') # => "r"
+  strio.string    # => "bar"
+  strio.pos       # => 3
+  strio.putc('n') # => "n"
+  strio.string    # => "barn"
+  strio.pos       # => 4
+
+Fills with null characters if necessary:
+
+  strio.pos = 6
+  strio.putc('x') # => "x"
+  strio.string    # => "barn\u0000\u0000x"
+  strio.pos       # => 7
+
+With integer argument, replaces one byte with the low-order byte of the integer:
+
+  strio = StringIO.new('foo')
+  strio.putc(70)
+  strio.string # => "Foo"
+  strio.putc(79)
+  strio.string # => "FOo"
+  strio.putc(79 + 1024)
+  strio.string # => "FOO"
+
+\StringIO object for Multi-byte characters:
+
+  greek = 'αβγδε' # Five 2-byte characters.
+  strio = StringIO.new(greek)
+  strio.string# => "αβγδε"
+  strio.string.b        # => "\xCE\xB1\xCE\xB2\xCE\xB3\xCE\xB4\xCE\xB5"
+  strio.string.bytesize # => 10
+  strio.string.chars    # => ["α", "β", "γ", "δ", "ε"]
+  strio.string.size     # => 5
+
+With 1-byte argument, replaces one byte of the string:
+
+  strio.putc(' ')       # 1-byte ascii space.
+  strio.pos             # => 1
+  strio.string          # => " \xB1βγδε"
+  strio.string.b        # => " \xB1\xCE\xB2\xCE\xB3\xCE\xB4\xCE\xB5"
+  strio.string.bytesize # => 10
+  strio.string.chars    # => [" ", "\xB1", "β", "γ", "δ", "ε"]
+  strio.string.size     # => 6
+
+  strio.putc(' ')
+  strio.pos             # => 2
+  strio.string          # => "  βγδε"
+  strio.string.b        # => "  \xCE\xB2\xCE\xB3\xCE\xB4\xCE\xB5"
+  strio.string.bytesize # => 10
+  strio.string.chars    # => [" ", " ", "β", "γ", "δ", "ε"]
+  strio.string.size     # => 6
+
+With 2-byte argument, replaces two bytes of the string:
+
+  strio.rewind
+  strio.putc('α')
+  strio.pos             # => 2
+  strio.string          # => "αβγδε"
+  strio.string.b        # => "\xCE\xB1\xCE\xB2\xCE\xB3\xCE\xB4\xCE\xB5"
+  strio.string.bytesize # => 10
+  strio.string.chars    # => ["α", "β", "γ", "δ", "ε"]
+  strio.string.size     # => 5
+
+Related: #getc, #ungetc.
diff --git a/doc/stringio/read.rdoc b/doc/stringio/read.rdoc
new file mode 100644
index 00000000000000..46b9fa349f284f
--- /dev/null
+++ b/doc/stringio/read.rdoc
@@ -0,0 +1,83 @@
+Reads and returns a string containing bytes read from the stream,
+beginning at the current position;
+advances the position by the count of bytes read.
+
+With no arguments given,
+reads all remaining bytes in the stream;
+returns a new string containing bytes read:
+
+  strio = StringIO.new('Hello') # Five 1-byte characters.
+  strio.read                    # => "Hello"
+  strio.pos                     # => 5
+  strio.read                    # => ""
+  StringIO.new('').read         # => ""
+
+With non-negative argument +maxlen+ given,
+reads +maxlen+ bytes as available;
+returns a new string containing the bytes read, or +nil+ if none:
+
+  strio.rewind
+  strio.read(3) # => "Hel"
+  strio.read(3) # => "lo"
+  strio.read(3) # => nil
+
+  russian = 'Привет' # Six 2-byte characters.
+  russian.b
+  # => "\xD0\x9F\xD1\x80\xD0\xB8\xD0\xB2\xD0\xB5\xD1\x82"
+  strio = StringIO.new(russian)
+  strio.read(6) # => "\xD0\x9F\xD1\x80\xD0\xB8"
+  strio.read(6) # => "\xD0\xB2\xD0\xB5\xD1\x82"
+  strio.read(6) # => nil
+
+  japanese = 'こんにちは'
+  japanese.b
+  # => "\xE3\x81\x93\xE3\x82\x93\xE3\x81\xAB\xE3\x81\xA1\xE3\x81\xAF"
+  strio = StringIO.new(japanese)
+  strio.read(9) # => "\xE3\x81\x93\xE3\x82\x93\xE3\x81\xAB"
+  strio.read(9) # => "\xE3\x81\xA1\xE3\x81\xAF"
+  strio.read(9) # => nil
+
+With argument +max_len+ as +nil+ and string argument +out_string+ given,
+reads the remaining bytes in the stream;
+clears +out_string+ and writes the bytes into it;
+returns +out_string+:
+
+  out_string = 'Will be overwritten'
+  strio = StringIO.new('Hello')
+  strio.read(nil, out_string) # => "Hello"
+  strio.read(nil, out_string) # => ""
+
+With non-negative argument +maxlen+ and string argument +out_string+ given,
+reads the +maxlen bytes from the stream, as availble;
+clears +out_string+ and writes the bytes into it;
+returns +out_string+ if any bytes were read, or +nil+ if none:
+
+  out_string = 'Will be overwritten'
+  strio = StringIO.new('Hello')
+  strio.read(3, out_string) # => "Hel"
+  strio.read(3, out_string) # => "lo"
+  strio.read(3, out_string) # => nil
+
+  out_string = 'Will be overwritten'
+  strio = StringIO.new(russian)
+  strio.read(6, out_string) # => "При"
+  strio.read(6, out_string) # => "вет"
+  strio.read(6, out_string) # => nil
+  strio.rewind
+  russian.b
+  # => "\xD0\x9F\xD1\x80\xD0\xB8\xD0\xB2\xD0\xB5\xD1\x82"
+  strio.read(3)             # => "\xD0\x9F\xD1"
+  strio.read(3)             # => "\x80\xD0\xB8"
+
+  out_string = 'Will be overwritten'
+  strio = StringIO.new(japanese)
+  strio.read(9, out_string) # => "こんに"
+  strio.read(9, out_string) # => "ちは"
+  strio.read(9, out_string) # => nil
+  strio.rewind
+  japanese.b
+  # => "\xE3\x81\x93\xE3\x82\x93\xE3\x81\xAB\xE3\x81\xA1\xE3\x81\xAF"
+  strio.read(4)             # => "\xE3\x81\x93\xE3"
+  strio.read(4)             # => "\x82\x93\xE3\x81"
+
+Related: #gets, #readlines.
diff --git a/ext/date/date_core.c b/ext/date/date_core.c
index 6bcf272b62d8b0..9755fb819eaaa9 100644
--- a/ext/date/date_core.c
+++ b/ext/date/date_core.c
@@ -452,11 +452,43 @@ do {\
 static int c_valid_civil_p(int, int, int, double,
 			   int *, int *, int *, int *);
 
+/* Check if using pure Gregorian calendar (sg == -Infinity) */
+#define c_gregorian_only_p(sg) (isinf(sg) && (sg) < 0)
+
+/*
+ * Fast path macros for pure Gregorian calendar.
+ * Sets *rjd to the JD value, *ns to 1 (new style), and returns.
+ */
+#define GREGORIAN_JD_FAST_PATH_RET(sg, jd_expr, rjd, ns) \
+    if (c_gregorian_only_p(sg)) { \
+	*(rjd) = (jd_expr); \
+	*(ns) = 1; \
+	return 1; \
+    }
+
+#define GREGORIAN_JD_FAST_PATH(sg, jd_expr, rjd, ns) \
+    if (c_gregorian_only_p(sg)) { \
+	*(rjd) = (jd_expr); \
+	*(ns) = 1; \
+	return; \
+    }
+
+/* Forward declarations for Neri-Schneider optimized functions */
+static int c_gregorian_civil_to_jd(int y, int m, int d);
+static void c_gregorian_jd_to_civil(int jd, int *ry, int *rm, int *rd);
+static int c_gregorian_fdoy(int y);
+static int c_gregorian_ldoy(int y);
+static int c_gregorian_ldom_jd(int y, int m);
+static int ns_jd_in_range(int jd);
+
 static int
 c_find_fdoy(int y, double sg, int *rjd, int *ns)
 {
     int d, rm, rd;
 
+    GREGORIAN_JD_FAST_PATH_RET(sg, c_gregorian_fdoy(y), rjd, ns);
+
+    /* Keep existing loop for Julian/reform period */
     for (d = 1; d < 31; d++)
 	if (c_valid_civil_p(y, 1, d, sg, &rm, &rd, rjd, ns))
 	    return 1;
@@ -468,6 +500,9 @@ c_find_ldoy(int y, double sg, int *rjd, int *ns)
 {
     int i, rm, rd;
 
+    GREGORIAN_JD_FAST_PATH_RET(sg, c_gregorian_ldoy(y), rjd, ns);
+
+    /* Keep existing loop for Julian/reform period */
     for (i = 0; i < 30; i++)
 	if (c_valid_civil_p(y, 12, 31 - i, sg, &rm, &rd, rjd, ns))
 	    return 1;
@@ -493,6 +528,9 @@ c_find_ldom(int y, int m, double sg, int *rjd, int *ns)
 {
     int i, rm, rd;
 
+    GREGORIAN_JD_FAST_PATH_RET(sg, c_gregorian_ldom_jd(y, m), rjd, ns);
+
+    /* Keep existing loop for Julian/reform period */
     for (i = 0; i < 30; i++)
 	if (c_valid_civil_p(y, m, 31 - i, sg, &rm, &rd, rjd, ns))
 	    return 1;
@@ -502,55 +540,69 @@ c_find_ldom(int y, int m, double sg, int *rjd, int *ns)
 static void
 c_civil_to_jd(int y, int m, int d, double sg, int *rjd, int *ns)
 {
-    double a, b, jd;
+    int jd;
+
+    GREGORIAN_JD_FAST_PATH(sg, c_gregorian_civil_to_jd(y, m, d), rjd, ns);
+
+    /* Calculate Gregorian JD using optimized algorithm */
+    jd = c_gregorian_civil_to_jd(y, m, d);
 
-    if (m <= 2) {
-	y -= 1;
-	m += 12;
-    }
-    a = floor(y / 100.0);
-    b = 2 - a + floor(a / 4.0);
-    jd = floor(365.25 * (y + 4716)) +
-	floor(30.6001 * (m + 1)) +
-	d + b - 1524;
     if (jd < sg) {
-	jd -= b;
+	/* Before Gregorian switchover - use Julian calendar */
+	int y2 = y, m2 = m;
+	if (m2 <= 2) {
+	    y2 -= 1;
+	    m2 += 12;
+	}
+	jd = (int)(floor(365.25 * (y2 + 4716)) +
+		   floor(30.6001 * (m2 + 1)) +
+		   d - 1524);
 	*ns = 0;
     }
-    else
+    else {
 	*ns = 1;
+    }
 
-    *rjd = (int)jd;
+    *rjd = jd;
 }
 
 static void
 c_jd_to_civil(int jd, double sg, int *ry, int *rm, int *rdom)
 {
-    double x, a, b, c, d, e, y, m, dom;
-
-    if (jd < sg)
-	a = jd;
-    else {
-	x = floor((jd - 1867216.25) / 36524.25);
-	a = jd + 1 + x - floor(x / 4.0);
-    }
-    b = a + 1524;
-    c = floor((b - 122.1) / 365.25);
-    d = floor(365.25 * c);
-    e = floor((b - d) / 30.6001);
-    dom = b - d - floor(30.6001 * e);
-    if (e <= 13) {
-	m = e - 1;
-	y = c - 4716;
-    }
-    else {
-	m = e - 13;
-	y = c - 4715;
+    /* Fast path: pure Gregorian or date after switchover, within safe range */
+    if ((c_gregorian_only_p(sg) || jd >= sg) && ns_jd_in_range(jd)) {
+	c_gregorian_jd_to_civil(jd, ry, rm, rdom);
+	return;
     }
 
-    *ry = (int)y;
-    *rm = (int)m;
-    *rdom = (int)dom;
+    /* Original algorithm for Julian calendar or extreme dates */
+    {
+	double x, a, b, c, d, e, y, m, dom;
+
+	if (jd < sg)
+	    a = jd;
+	else {
+	    x = floor((jd - 1867216.25) / 36524.25);
+	    a = jd + 1 + x - floor(x / 4.0);
+	}
+	b = a + 1524;
+	c = floor((b - 122.1) / 365.25);
+	d = floor(365.25 * c);
+	e = floor((b - d) / 30.6001);
+	dom = b - d - floor(30.6001 * e);
+	if (e <= 13) {
+	    m = e - 1;
+	    y = c - 4716;
+	}
+	else {
+	    m = e - 13;
+	    y = c - 4715;
+	}
+
+	*ry = (int)y;
+	*rm = (int)m;
+	*rdom = (int)dom;
+    }
 }
 
 static void
@@ -725,6 +777,147 @@ c_gregorian_last_day_of_month(int y, int m)
     return monthtab[c_gregorian_leap_p(y) ? 1 : 0][m];
 }
 
+/*
+ * Neri-Schneider algorithm for optimized Gregorian date conversion.
+ * Reference: Neri & Schneider, "Euclidean Affine Functions and Applications
+ *            to Calendar Algorithms", Software: Practice and Experience, 2023.
+ *            https://arxiv.org/abs/2102.06959
+ *
+ * This algorithm provides ~2-3x speedup over traditional floating-point
+ * implementations by using pure integer arithmetic with multiplication
+ * and bit-shifts instead of expensive division operations.
+ */
+
+/* JDN of March 1, Year 0 in proleptic Gregorian calendar */
+#define NS_EPOCH 1721120
+
+/* Days in a 4-year cycle (3 normal years + 1 leap year) */
+#define NS_DAYS_IN_4_YEARS 1461
+
+/* Days in a 400-year Gregorian cycle (97 leap years in 400 years) */
+#define NS_DAYS_IN_400_YEARS 146097
+
+/* Years per century */
+#define NS_YEARS_PER_CENTURY 100
+
+/*
+ * Multiplier for extracting year within century using fixed-point arithmetic.
+ * This is ceil(2^32 / NS_DAYS_IN_4_YEARS) for the Euclidean affine function.
+ */
+#define NS_YEAR_MULTIPLIER 2939745
+
+/*
+ * Coefficients for month calculation from day-of-year.
+ * Maps day-of-year to month using: month = (NS_MONTH_COEFF * doy + NS_MONTH_OFFSET) >> 16
+ */
+#define NS_MONTH_COEFF 2141
+#define NS_MONTH_OFFSET 197913
+
+/*
+ * Coefficients for civil date to JDN month contribution.
+ * Maps month to accumulated days: days = (NS_CIVIL_MONTH_COEFF * m - NS_CIVIL_MONTH_OFFSET) / 32
+ */
+#define NS_CIVIL_MONTH_COEFF 979
+#define NS_CIVIL_MONTH_OFFSET 2919
+#define NS_CIVIL_MONTH_DIVISOR 32
+
+/* Days from March 1 to December 31 (for Jan/Feb year adjustment) */
+#define NS_DAYS_BEFORE_NEW_YEAR 306
+
+/*
+ * Safe bounds for Neri-Schneider algorithm to avoid integer overflow.
+ * These correspond to approximately years -1,000,000 to +1,000,000.
+ */
+#define NS_JD_MIN -364000000
+#define NS_JD_MAX  538000000
+
+inline static int
+ns_jd_in_range(int jd)
+{
+    return jd >= NS_JD_MIN && jd <= NS_JD_MAX;
+}
+
+/* Optimized: Gregorian date -> Julian Day Number */
+static int
+c_gregorian_civil_to_jd(int y, int m, int d)
+{
+    /* Shift epoch to March 1 of year 0 (Jan/Feb belong to previous year) */
+    int j = (m < 3) ? 1 : 0;
+    int y0 = y - j;
+    int m0 = j ? m + 12 : m;
+    int d0 = d - 1;
+
+    /* Calculate year contribution with leap year correction */
+    int q1 = DIV(y0, NS_YEARS_PER_CENTURY);
+    int yc = DIV(NS_DAYS_IN_4_YEARS * y0, 4) - q1 + DIV(q1, 4);
+
+    /* Calculate month contribution using integer arithmetic */
+    int mc = (NS_CIVIL_MONTH_COEFF * m0 - NS_CIVIL_MONTH_OFFSET) / NS_CIVIL_MONTH_DIVISOR;
+
+    /* Combine and add epoch offset to get JDN */
+    return yc + mc + d0 + NS_EPOCH;
+}
+
+/* Optimized: Julian Day Number -> Gregorian date */
+static void
+c_gregorian_jd_to_civil(int jd, int *ry, int *rm, int *rd)
+{
+    int r0, n1, q1, r1, n2, q2, r2, n3, q3, r3, y0, j;
+    uint64_t u2;
+
+    /* Convert JDN to rata die (March 1, Year 0 epoch) */
+    r0 = jd - NS_EPOCH;
+
+    /* Extract century and day within 400-year cycle */
+    /* Use Euclidean (floor) division for negative values */
+    n1 = 4 * r0 + 3;
+    q1 = DIV(n1, NS_DAYS_IN_400_YEARS);
+    r1 = MOD(n1, NS_DAYS_IN_400_YEARS) / 4;
+
+    /* Calculate year within century and day of year */
+    n2 = 4 * r1 + 3;
+    /* Use 64-bit arithmetic to avoid overflow */
+    u2 = (uint64_t)NS_YEAR_MULTIPLIER * (uint64_t)n2;
+    q2 = (int)(u2 >> 32);
+    r2 = (int)((uint32_t)u2 / NS_YEAR_MULTIPLIER / 4);
+
+    /* Calculate month and day using integer arithmetic */
+    n3 = NS_MONTH_COEFF * r2 + NS_MONTH_OFFSET;
+    q3 = n3 >> 16;
+    r3 = (n3 & 0xFFFF) / NS_MONTH_COEFF;
+
+    /* Combine century and year */
+    y0 = NS_YEARS_PER_CENTURY * q1 + q2;
+
+    /* Adjust for January/February (shift from fiscal year) */
+    j = (r2 >= NS_DAYS_BEFORE_NEW_YEAR) ? 1 : 0;
+
+    *ry = y0 + j;
+    *rm = j ? q3 - 12 : q3;
+    *rd = r3 + 1;
+}
+
+/* O(1) first day of year for Gregorian calendar */
+inline static int
+c_gregorian_fdoy(int y)
+{
+    return c_gregorian_civil_to_jd(y, 1, 1);
+}
+
+/* O(1) last day of year for Gregorian calendar */
+inline static int
+c_gregorian_ldoy(int y)
+{
+    return c_gregorian_civil_to_jd(y, 12, 31);
+}
+
+/* O(1) last day of month (JDN) for Gregorian calendar */
+inline static int
+c_gregorian_ldom_jd(int y, int m)
+{
+    return c_gregorian_civil_to_jd(y, m, c_gregorian_last_day_of_month(y, m));
+}
+
 static int
 c_valid_julian_p(int y, int m, int d, int *rm, int *rd)
 {
diff --git a/ext/json/lib/json.rb b/ext/json/lib/json.rb
index 43d96afa95835c..f619d93252d950 100644
--- a/ext/json/lib/json.rb
+++ b/ext/json/lib/json.rb
@@ -173,6 +173,18 @@
 # When enabled:
 #   JSON.parse('[1,]', allow_trailing_comma: true) # => [1]
 #
+# ---
+#
+# Option +allow_control_characters+ (boolean) specifies whether to allow
+# unescaped ASCII control characters, such as newlines, in strings;
+# defaults to +false+.
+#
+# With the default, +false+:
+#   JSON.parse(%{"Hello\nWorld"}) # invalid ASCII control character in string (JSON::ParserError)
+#
+# When enabled:
+#   JSON.parse(%{"Hello\nWorld"}, allow_control_characters: true) # => "Hello\nWorld"
+#
 # ====== Output Options
 #
 # Option +freeze+ (boolean) specifies whether the returned objects will be frozen;
diff --git a/ext/json/vendor/fpconv.c b/ext/json/vendor/fpconv.c
index 4888ab4b8bcefe..6c9bc2c103396d 100644
--- a/ext/json/vendor/fpconv.c
+++ b/ext/json/vendor/fpconv.c
@@ -449,7 +449,7 @@ static int filter_special(double fp, char* dest)
  * }
  *
  */
-static int fpconv_dtoa(double d, char dest[28])
+static int fpconv_dtoa(double d, char dest[32])
 {
     char digits[18];
 
diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index 05bae94529b9db..cc2294a795a378 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -13,7 +13,7 @@
 **********************************************************************/
 
 static const char *const
-STRINGIO_VERSION = "3.2.0";
+STRINGIO_VERSION = "3.2.1.dev";
 
 #include <stdbool.h>
 
@@ -1615,9 +1615,10 @@ strio_write(VALUE self, VALUE str)
 
 /*
  * call-seq:
- *   strio.putc(obj)    -> obj
+ *   putc(object) -> object
+ *
+ * :include: stringio/putc.rdoc
  *
- * See IO#putc.
  */
 static VALUE
 strio_putc(VALUE self, VALUE ch)
@@ -1649,9 +1650,10 @@ strio_putc(VALUE self, VALUE ch)
 
 /*
  * call-seq:
- *   strio.read([length [, outbuf]])    -> string, outbuf, or nil
+ *   read(maxlen = nil, out_string = nil) → new_string, out_string, or nil
+ *
+ * :include: stringio/read.rdoc
  *
- * See IO#read.
  */
 static VALUE
 strio_read(int argc, VALUE *argv, VALUE self)
@@ -1723,10 +1725,10 @@ strio_read(int argc, VALUE *argv, VALUE self)
 
 /*
  *  call-seq:
- *    pread(maxlen, offset)             -> string
- *    pread(maxlen, offset, out_string) -> string
+ *    pread(maxlen, offset, out_string = nil) -> new_string or out_string
+ *
+ *  :include: stringio/pread.rdoc
  *
- *  See IO#pread.
  */
 static VALUE
 strio_pread(int argc, VALUE *argv, VALUE self)
diff --git a/ext/strscan/strscan.c b/ext/strscan/strscan.c
index 11e3d309a81757..935fce19df94e9 100644
--- a/ext/strscan/strscan.c
+++ b/ext/strscan/strscan.c
@@ -22,7 +22,7 @@ extern size_t onig_region_memsize(const struct re_registers *regs);
 
 #include <stdbool.h>
 
-#define STRSCAN_VERSION "3.1.6"
+#define STRSCAN_VERSION "3.1.7.dev"
 
 
 #ifdef HAVE_RB_DEPRECATE_CONSTANT
diff --git a/lib/bundler/current_ruby.rb b/lib/bundler/current_ruby.rb
index ab6520a106a40f..17c7655adb588f 100644
--- a/lib/bundler/current_ruby.rb
+++ b/lib/bundler/current_ruby.rb
@@ -11,7 +11,7 @@ def self.current_ruby
   end
 
   class CurrentRuby
-    ALL_RUBY_VERSIONS = [*18..27, *30..34, 40].freeze
+    ALL_RUBY_VERSIONS = [*18..27, *30..34, *40..41].freeze
     KNOWN_MINOR_VERSIONS = ALL_RUBY_VERSIONS.map {|v| v.digits.reverse.join(".") }.freeze
     KNOWN_MAJOR_VERSIONS = ALL_RUBY_VERSIONS.map {|v| v.digits.last.to_s }.uniq.freeze
     PLATFORM_MAP = {
diff --git a/lib/bundler/shared_helpers.rb b/lib/bundler/shared_helpers.rb
index 6419e4299760b7..2aa8abe0a078b0 100644
--- a/lib/bundler/shared_helpers.rb
+++ b/lib/bundler/shared_helpers.rb
@@ -105,7 +105,8 @@ def set_bundle_environment
     def filesystem_access(path, action = :write, &block)
       yield(path.dup)
     rescue Errno::EACCES => e
-      raise unless e.message.include?(path.to_s) || action == :create
+      path_basename = File.basename(path.to_s)
+      raise unless e.message.include?(path_basename) || action == :create
 
       raise PermissionError.new(path, action)
     rescue Errno::EAGAIN
diff --git a/lib/bundler/version.rb b/lib/bundler/version.rb
index 732b4a05631e84..ca7bb0719aac24 100644
--- a/lib/bundler/version.rb
+++ b/lib/bundler/version.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: false
 
 module Bundler
-  VERSION = "4.0.3".freeze
+  VERSION = "4.1.0.dev".freeze
 
   def self.bundler_major_version
     @bundler_major_version ||= gem_version.segments.first
diff --git a/lib/ipaddr.rb b/lib/ipaddr.rb
index 725ff309d27f48..6b67d7eec6706a 100644
--- a/lib/ipaddr.rb
+++ b/lib/ipaddr.rb
@@ -368,7 +368,7 @@ def _ipv4_compat?             # :nodoc:
   # into an IPv4-mapped IPv6 address.
   def ipv4_mapped
     if !ipv4?
-      raise InvalidAddressError, "not an IPv4 address: #{@addr}"
+      raise InvalidAddressError, "not an IPv4 address: #{to_s}"
     end
     clone = self.clone.set(@addr | 0xffff00000000, Socket::AF_INET6)
     clone.instance_variable_set(:@mask_addr, @mask_addr | 0xffffffffffffffffffffffff00000000)
@@ -380,7 +380,7 @@ def ipv4_mapped
   def ipv4_compat
     warn "IPAddr\##{__callee__} is obsolete", uplevel: 1 if $VERBOSE
     if !ipv4?
-      raise InvalidAddressError, "not an IPv4 address: #{@addr}"
+      raise InvalidAddressError, "not an IPv4 address: #{to_s}"
     end
     clone = self.clone.set(@addr, Socket::AF_INET6)
     clone.instance_variable_set(:@mask_addr, @mask_addr | 0xffffffffffffffffffffffff00000000)
@@ -413,7 +413,7 @@ def reverse
   # Returns a string for DNS reverse lookup compatible with RFC3172.
   def ip6_arpa
     if !ipv6?
-      raise InvalidAddressError, "not an IPv6 address: #{@addr}"
+      raise InvalidAddressError, "not an IPv6 address: #{to_s}"
     end
     return _reverse + ".ip6.arpa"
   end
@@ -421,7 +421,7 @@ def ip6_arpa
   # Returns a string for DNS reverse lookup compatible with RFC1886.
   def ip6_int
     if !ipv6?
-      raise InvalidAddressError, "not an IPv6 address: #{@addr}"
+      raise InvalidAddressError, "not an IPv6 address: #{to_s}"
     end
     return _reverse + ".ip6.int"
   end
@@ -743,19 +743,19 @@ def in6_addr(left)
       right = ''
     when RE_IPV6ADDRLIKE_COMPRESSED
       if $4
-        left.count(':') <= 6 or raise InvalidAddressError, "invalid address: #{@addr}"
+        left.count(':') <= 6 or raise InvalidAddressError, "invalid address: #{left}"
         addr = in_addr($~[4,4])
         left = $1
         right = $3 + '0:0'
       else
         left.count(':') <= ($1.empty? || $2.empty? ? 8 : 7) or
-          raise InvalidAddressError, "invalid address: #{@addr}"
+          raise InvalidAddressError, "invalid address: #{left}"
         left = $1
         right = $2
         addr = 0
       end
     else
-      raise InvalidAddressError, "invalid address: #{@addr}"
+      raise InvalidAddressError, "invalid address: #{left}"
     end
     l = left.split(':')
     r = right.split(':')
diff --git a/lib/net/protocol.rb b/lib/net/protocol.rb
index 1443f3e8b71966..8c81298c0e420a 100644
--- a/lib/net/protocol.rb
+++ b/lib/net/protocol.rb
@@ -54,6 +54,16 @@ def ssl_socket_connect(s, timeout)
         s.connect
       end
     end
+
+    tcp_socket_parameters = TCPSocket.instance_method(:initialize).parameters
+    TCP_SOCKET_NEW_HAS_OPEN_TIMEOUT = if tcp_socket_parameters != [[:rest]]
+      tcp_socket_parameters.include?([:key, :open_timeout])
+    else
+      # Use Socket.tcp to find out since there is no parameters information for TCPSocket#initialize
+      # See discussion in https://github.com/ruby/net-http/pull/224
+      Socket.method(:tcp).parameters.include?([:key, :open_timeout])
+    end
+    private_constant :TCP_SOCKET_NEW_HAS_OPEN_TIMEOUT
   end
 
 
diff --git a/lib/pp.rb b/lib/pp.rb
index fcd33ba80e9e2e..5fd29a373aa3e2 100644
--- a/lib/pp.rb
+++ b/lib/pp.rb
@@ -388,7 +388,7 @@ def pretty_print_cycle(q)
     # This method should return an array of names of instance variables as symbols or strings as:
     # +[:@a, :@b]+.
     def pretty_print_instance_variables
-      ivars = respond_to?(:instance_variables_to_inspect) ? instance_variables_to_inspect : instance_variables
+      ivars = respond_to?(:instance_variables_to_inspect, true) ? instance_variables_to_inspect || instance_variables : instance_variables
       ivars.sort
     end
 
diff --git a/lib/prism/translation/parser_current.rb b/lib/prism/translation/parser_current.rb
index ac6daf7082e416..f13eff6bbe2d90 100644
--- a/lib/prism/translation/parser_current.rb
+++ b/lib/prism/translation/parser_current.rb
@@ -16,7 +16,7 @@ module Translation
       ParserCurrent = Parser41
     else
       # Keep this in sync with released Ruby.
-      parser = Parser34
+      parser = Parser40
       major, minor, _patch = Gem::Version.new(RUBY_VERSION).segments
       warn "warning: `Prism::Translation::Current` is loading #{parser.name}, " \
            "but you are running #{major}.#{minor}."
diff --git a/lib/resolv.rb b/lib/resolv.rb
index 0e62aaf8510496..fa7d4e2e4753b3 100644
--- a/lib/resolv.rb
+++ b/lib/resolv.rb
@@ -721,7 +721,8 @@ def request(sender, tout)
           begin
             reply, from = recv_reply(select_result[0])
           rescue Errno::ECONNREFUSED, # GNU/Linux, FreeBSD
-                 Errno::ECONNRESET # Windows
+                 Errno::ECONNRESET, # Windows
+                 EOFError
             # No name server running on the server?
             # Don't wait anymore.
             raise ResolvTimeout
@@ -930,8 +931,11 @@ def initialize(host, port=Port)
         end
 
         def recv_reply(readable_socks)
-          len = readable_socks[0].read(2).unpack('n')[0]
+          len_data = readable_socks[0].read(2)
+          raise EOFError if len_data.nil? || len_data.bytesize != 2
+          len = len_data.unpack('n')[0]
           reply = @socks[0].read(len)
+          raise EOFError if reply.nil? || reply.bytesize != len
           return reply, nil
         end
 
diff --git a/lib/rubygems.rb b/lib/rubygems.rb
index e99176fec0e107..b52dd1b9d3e99a 100644
--- a/lib/rubygems.rb
+++ b/lib/rubygems.rb
@@ -9,7 +9,7 @@
 require "rbconfig"
 
 module Gem
-  VERSION = "4.0.3"
+  VERSION = "4.1.0.dev"
 end
 
 require_relative "rubygems/defaults"
@@ -17,6 +17,7 @@ module Gem
 require_relative "rubygems/errors"
 require_relative "rubygems/target_rbconfig"
 require_relative "rubygems/win_platform"
+require_relative "rubygems/util/atomic_file_writer"
 
 ##
 # RubyGems is the Ruby standard for publishing and managing third party
@@ -833,14 +834,12 @@ def self.read_binary(path)
   end
 
   ##
-  # Safely write a file in binary mode on all platforms.
+  # Atomically write a file in binary mode on all platforms.
 
   def self.write_binary(path, data)
-    File.binwrite(path, data)
-  rescue Errno::ENOSPC
-    # If we ran out of space but the file exists, it's *guaranteed* to be corrupted.
-    File.delete(path) if File.exist?(path)
-    raise
+    Gem::AtomicFileWriter.open(path) do |file|
+      file.write(data)
+    end
   end
 
   ##
diff --git a/lib/rubygems/resolver.rb b/lib/rubygems/resolver.rb
index ed4cbde3bab12c..bc4fef893ead65 100644
--- a/lib/rubygems/resolver.rb
+++ b/lib/rubygems/resolver.rb
@@ -2,7 +2,6 @@
 
 require_relative "dependency"
 require_relative "exceptions"
-require_relative "util/list"
 
 ##
 # Given a set of Gem::Dependency objects as +needed+ and a way to query the
diff --git a/lib/rubygems/specification.rb b/lib/rubygems/specification.rb
index a9ec6aa3a3c84c..3d1f2dad910485 100644
--- a/lib/rubygems/specification.rb
+++ b/lib/rubygems/specification.rb
@@ -11,7 +11,6 @@
 require_relative "stub_specification"
 require_relative "platform"
 require_relative "specification_record"
-require_relative "util/list"
 
 require "rbconfig"
 
diff --git a/lib/rubygems/util/atomic_file_writer.rb b/lib/rubygems/util/atomic_file_writer.rb
new file mode 100644
index 00000000000000..7d1d6a74168f95
--- /dev/null
+++ b/lib/rubygems/util/atomic_file_writer.rb
@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+# Based on ActiveSupport's AtomicFile implementation
+# Copyright (c) David Heinemeier Hansson
+# https://github.com/rails/rails/blob/main/activesupport/lib/active_support/core_ext/file/atomic.rb
+# Licensed under the MIT License
+
+module Gem
+  class AtomicFileWriter
+    ##
+    # Write to a file atomically. Useful for situations where you don't
+    # want other processes or threads to see half-written files.
+
+    def self.open(file_name)
+      temp_dir = File.dirname(file_name)
+      require "tempfile" unless defined?(Tempfile)
+
+      Tempfile.create(".#{File.basename(file_name)}", temp_dir) do |temp_file|
+        temp_file.binmode
+        return_value = yield temp_file
+        temp_file.close
+
+        original_permissions = if File.exist?(file_name)
+          File.stat(file_name)
+        else
+          # If not possible, probe which are the default permissions in the
+          # destination directory.
+          probe_permissions_in(File.dirname(file_name))
+        end
+
+        # Set correct permissions on new file
+        if original_permissions
+          begin
+            File.chown(original_permissions.uid, original_permissions.gid, temp_file.path)
+            File.chmod(original_permissions.mode, temp_file.path)
+          rescue Errno::EPERM, Errno::EACCES
+            # Changing file ownership failed, moving on.
+          end
+        end
+
+        # Overwrite original file with temp file
+        File.rename(temp_file.path, file_name)
+        return_value
+      end
+    end
+
+    def self.probe_permissions_in(dir) # :nodoc:
+      basename = [
+        ".permissions_check",
+        Thread.current.object_id,
+        Process.pid,
+        rand(1_000_000),
+      ].join(".")
+
+      file_name = File.join(dir, basename)
+      File.open(file_name, "w") {}
+      File.stat(file_name)
+    rescue Errno::ENOENT
+      nil
+    ensure
+      begin
+        File.unlink(file_name) if File.exist?(file_name)
+      rescue SystemCallError
+      end
+    end
+  end
+end
diff --git a/lib/rubygems/util/list.rb b/lib/rubygems/util/list.rb
deleted file mode 100644
index 2899e8a2b9ed70..00000000000000
--- a/lib/rubygems/util/list.rb
+++ /dev/null
@@ -1,40 +0,0 @@
-# frozen_string_literal: true
-
-module Gem
-  # The Gem::List class is currently unused and will be removed in the next major rubygems version
-  class List # :nodoc:
-    include Enumerable
-    attr_accessor :value, :tail
-
-    def initialize(value = nil, tail = nil)
-      @value = value
-      @tail = tail
-    end
-
-    def each
-      n = self
-      while n
-        yield n.value
-        n = n.tail
-      end
-    end
-
-    def to_a
-      super.reverse
-    end
-
-    def prepend(value)
-      List.new value, self
-    end
-
-    def pretty_print(q) # :nodoc:
-      q.pp to_a
-    end
-
-    def self.prepend(list, value)
-      return List.new(value) unless list
-      List.new value, list
-    end
-  end
-  deprecate_constant :List
-end
diff --git a/set.c b/set.c
index 469078ee9968af..d7704e9cf38a4f 100644
--- a/set.c
+++ b/set.c
@@ -116,7 +116,7 @@ static ID id_class_methods;
 #define RSET_SIZE(set) set_table_size(RSET_TABLE(set))
 #define RSET_EMPTY(set) (RSET_SIZE(set) == 0)
 #define RSET_SIZE_NUM(set) SIZET2NUM(RSET_SIZE(set))
-#define RSET_IS_MEMBER(sobj, item) set_table_lookup(RSET_TABLE(set), (st_data_t)(item))
+#define RSET_IS_MEMBER(set, item) set_table_lookup(RSET_TABLE(set), (st_data_t)(item))
 #define RSET_COMPARE_BY_IDENTITY(set) (RSET_TABLE(set)->type == &identhash)
 
 struct set_object {
diff --git a/spec/bundler/bundler/current_ruby_spec.rb b/spec/bundler/bundler/current_ruby_spec.rb
index aa19a414076508..79eb802aa52215 100644
--- a/spec/bundler/bundler/current_ruby_spec.rb
+++ b/spec/bundler/bundler/current_ruby_spec.rb
@@ -23,6 +23,7 @@
         ruby_33: Gem::Platform::RUBY,
         ruby_34: Gem::Platform::RUBY,
         ruby_40: Gem::Platform::RUBY,
+        ruby_41: Gem::Platform::RUBY,
         mri: Gem::Platform::RUBY,
         mri_18: Gem::Platform::RUBY,
         mri_19: Gem::Platform::RUBY,
@@ -40,6 +41,7 @@
         mri_33: Gem::Platform::RUBY,
         mri_34: Gem::Platform::RUBY,
         mri_40: Gem::Platform::RUBY,
+        mri_41: Gem::Platform::RUBY,
         rbx: Gem::Platform::RUBY,
         truffleruby: Gem::Platform::RUBY,
         jruby: Gem::Platform::JAVA,
@@ -61,7 +63,8 @@
         windows_32: Gem::Platform::WINDOWS,
         windows_33: Gem::Platform::WINDOWS,
         windows_34: Gem::Platform::WINDOWS,
-        windows_40: Gem::Platform::WINDOWS }
+        windows_40: Gem::Platform::WINDOWS,
+        windows_41: Gem::Platform::WINDOWS }
     end
 
     let(:deprecated) do
@@ -82,6 +85,7 @@
         mswin_33: Gem::Platform::MSWIN,
         mswin_34: Gem::Platform::MSWIN,
         mswin_40: Gem::Platform::MSWIN,
+        mswin_41: Gem::Platform::MSWIN,
         mswin64: Gem::Platform::MSWIN64,
         mswin64_19: Gem::Platform::MSWIN64,
         mswin64_20: Gem::Platform::MSWIN64,
@@ -98,6 +102,7 @@
         mswin64_33: Gem::Platform::MSWIN64,
         mswin64_34: Gem::Platform::MSWIN64,
         mswin64_40: Gem::Platform::MSWIN64,
+        mswin64_41: Gem::Platform::MSWIN64,
         mingw: Gem::Platform::UNIVERSAL_MINGW,
         mingw_18: Gem::Platform::UNIVERSAL_MINGW,
         mingw_19: Gem::Platform::UNIVERSAL_MINGW,
@@ -115,6 +120,7 @@
         mingw_33: Gem::Platform::UNIVERSAL_MINGW,
         mingw_34: Gem::Platform::UNIVERSAL_MINGW,
         mingw_40: Gem::Platform::UNIVERSAL_MINGW,
+        mingw_41: Gem::Platform::UNIVERSAL_MINGW,
         x64_mingw: Gem::Platform::UNIVERSAL_MINGW,
         x64_mingw_20: Gem::Platform::UNIVERSAL_MINGW,
         x64_mingw_21: Gem::Platform::UNIVERSAL_MINGW,
@@ -129,7 +135,8 @@
         x64_mingw_32: Gem::Platform::UNIVERSAL_MINGW,
         x64_mingw_33: Gem::Platform::UNIVERSAL_MINGW,
         x64_mingw_34: Gem::Platform::UNIVERSAL_MINGW,
-        x64_mingw_40: Gem::Platform::UNIVERSAL_MINGW }
+        x64_mingw_40: Gem::Platform::UNIVERSAL_MINGW,
+        x64_mingw_41: Gem::Platform::UNIVERSAL_MINGW }
     end
     # rubocop:enable Naming/VariableNumber
 
diff --git a/spec/bundler/realworld/fixtures/tapioca/Gemfile.lock b/spec/bundler/realworld/fixtures/tapioca/Gemfile.lock
index 2db720a69f4632..4ce06de722cfaa 100644
--- a/spec/bundler/realworld/fixtures/tapioca/Gemfile.lock
+++ b/spec/bundler/realworld/fixtures/tapioca/Gemfile.lock
@@ -46,4 +46,4 @@ DEPENDENCIES
   tapioca
 
 BUNDLED WITH
-  4.0.3
+  4.1.0.dev
diff --git a/spec/bundler/realworld/fixtures/warbler/Gemfile.lock b/spec/bundler/realworld/fixtures/warbler/Gemfile.lock
index c37fbbb7eed556..2f2deea99408cc 100644
--- a/spec/bundler/realworld/fixtures/warbler/Gemfile.lock
+++ b/spec/bundler/realworld/fixtures/warbler/Gemfile.lock
@@ -36,4 +36,4 @@ DEPENDENCIES
   warbler!
 
 BUNDLED WITH
-  4.0.3
+  4.1.0.dev
diff --git a/test/resolv/test_dns.rb b/test/resolv/test_dns.rb
index d5d2648e1bc649..7a01909eeb9a4b 100644
--- a/test/resolv/test_dns.rb
+++ b/test/resolv/test_dns.rb
@@ -822,4 +822,124 @@ def test_multiple_servers_with_timeout_and_truncated_tcp_fallback
       end
     end
   end
+
+  def test_tcp_connection_closed_before_length
+    with_tcp('127.0.0.1', 0) do |t|
+      _, server_port, _, server_address = t.addr
+
+      server_thread = Thread.new do
+        ct = t.accept
+        ct.recv(512)
+        ct.close
+      end
+
+      client_thread = Thread.new do
+        requester = Resolv::DNS::Requester::TCP.new(server_address, server_port)
+        begin
+          msg = Resolv::DNS::Message.new
+          msg.add_question('example.org', Resolv::DNS::Resource::IN::A)
+          sender = requester.sender(msg, msg)
+          assert_raise(Resolv::ResolvTimeout) do
+            requester.request(sender, 2)
+          end
+        ensure
+          requester.close
+        end
+      end
+
+      server_thread.join
+      client_thread.join
+    end
+  end
+
+  def test_tcp_connection_closed_after_length
+    with_tcp('127.0.0.1', 0) do |t|
+      _, server_port, _, server_address = t.addr
+
+      server_thread = Thread.new do
+        ct = t.accept
+        ct.recv(512)
+        ct.send([100].pack('n'), 0)
+        ct.close
+      end
+
+      client_thread = Thread.new do
+        requester = Resolv::DNS::Requester::TCP.new(server_address, server_port)
+        begin
+          msg = Resolv::DNS::Message.new
+          msg.add_question('example.org', Resolv::DNS::Resource::IN::A)
+          sender = requester.sender(msg, msg)
+          assert_raise(Resolv::ResolvTimeout) do
+            requester.request(sender, 2)
+          end
+        ensure
+          requester.close
+        end
+      end
+
+      server_thread.join
+      client_thread.join
+    end
+  end
+
+  def test_tcp_connection_closed_with_partial_length_prefix
+    with_tcp('127.0.0.1', 0) do |t|
+      _, server_port, _, server_address = t.addr
+
+      server_thread = Thread.new do
+        ct = t.accept
+        ct.recv(512)
+        ct.write "A" # 1 byte
+        ct.close
+      end
+
+      client_thread = Thread.new do
+        requester = Resolv::DNS::Requester::TCP.new(server_address, server_port)
+        begin
+          msg = Resolv::DNS::Message.new
+          msg.add_question('example.org', Resolv::DNS::Resource::IN::A)
+          sender = requester.sender(msg, msg)
+          assert_raise(Resolv::ResolvTimeout) do
+            requester.request(sender, 2)
+          end
+        ensure
+          requester.close
+        end
+      end
+
+      server_thread.join
+      client_thread.join
+    end
+  end
+
+  def test_tcp_connection_closed_with_partial_message_body
+    with_tcp('127.0.0.1', 0) do |t|
+      _, server_port, _, server_address = t.addr
+
+      server_thread = Thread.new do
+        ct = t.accept
+        ct.recv(512)
+        ct.write([10].pack('n')) # length 10
+        ct.write "12345" # 5 bytes (partial)
+        ct.close
+      end
+
+      client_thread = Thread.new do
+        requester = Resolv::DNS::Requester::TCP.new(server_address, server_port)
+        begin
+          msg = Resolv::DNS::Message.new
+          msg.add_question('example.org', Resolv::DNS::Resource::IN::A)
+          sender = requester.sender(msg, msg)
+          assert_raise(Resolv::ResolvTimeout) do
+            requester.request(sender, 2)
+          end
+        ensure
+          requester.close
+        end
+      end
+
+      server_thread.join
+      client_thread.join
+    end
+  end
 end
diff --git a/test/ruby/test_rubyoptions.rb b/test/ruby/test_rubyoptions.rb
index 735d2681fb6a13..cd2dd5d3ff7412 100644
--- a/test/ruby/test_rubyoptions.rb
+++ b/test/ruby/test_rubyoptions.rb
@@ -47,10 +47,15 @@ def test_source_file
     assert_in_out_err([], "", [], [])
   end
 
+  # This constant enforces the traditional 80x25 terminal size standard
+  TRADITIONAL_TERM_COLS = 80 # DO NOT MODIFY!
+  TRADITIONAL_TERM_ROWS = 25 # DO NOT MODIFY!
+
   def test_usage
+    # This test checks if the output of `ruby -h` fits in 80x25
     assert_in_out_err(%w(-h)) do |r, e|
-      assert_operator(r.size, :<=, 25)
-      longer = r[1..-1].select {|x| x.size >= 80}
+      assert_operator(r.size, :<=, TRADITIONAL_TERM_ROWS)
+      longer = r[1..-1].select {|x| x.size >= TRADITIONAL_TERM_COLS}
       assert_equal([], longer)
       assert_equal([], e)
     end
diff --git a/test/rubygems/test_gem_installer.rb b/test/rubygems/test_gem_installer.rb
index 293fe1e823dd1a..0220a41f88a4f2 100644
--- a/test/rubygems/test_gem_installer.rb
+++ b/test/rubygems/test_gem_installer.rb
@@ -2385,25 +2385,31 @@ def test_leaves_no_empty_cached_spec_when_no_more_disk_space
     installer = Gem::Installer.for_spec @spec
     installer.gem_home = @gemhome
 
-    File.singleton_class.class_eval do
-      alias_method :original_binwrite, :binwrite
-
-      def binwrite(path, data)
+    assert_raise(Errno::ENOSPC) do
+      Gem::AtomicFileWriter.open(@spec.spec_file) do
         raise Errno::ENOSPC
       end
     end
 
-    assert_raise Errno::ENOSPC do
-      installer.write_spec
-    end
-
     assert_path_not_exist @spec.spec_file
-  ensure
-    File.singleton_class.class_eval do
-      remove_method :binwrite
-      alias_method :binwrite, :original_binwrite
-      remove_method :original_binwrite
-    end
+  end
+
+  def test_write_default_spec
+    @spec = setup_base_spec
+    @spec.files = %w[a.rb b.rb c.rb]
+
+    installer = Gem::Installer.for_spec @spec
+    installer.gem_home = @gemhome
+
+    installer.write_default_spec
+
+    assert_path_exist installer.default_spec_file
+
+    loaded = Gem::Specification.load installer.default_spec_file
+
+    assert_equal @spec.files, loaded.files
+    assert_equal @spec.name, loaded.name
+    assert_equal @spec.version, loaded.version
   end
 
   def test_dir
diff --git a/test/rubygems/test_gem_remote_fetcher.rb b/test/rubygems/test_gem_remote_fetcher.rb
index 5c1d89fad6934a..9badd75b427169 100644
--- a/test/rubygems/test_gem_remote_fetcher.rb
+++ b/test/rubygems/test_gem_remote_fetcher.rb
@@ -60,7 +60,7 @@ def test_cache_update_path
     uri = Gem::URI "http://example/file"
     path = File.join @tempdir, "file"
 
-    fetcher = util_fuck_with_fetcher "hello"
+    fetcher = fake_fetcher(uri.to_s, "hello")
 
     data = fetcher.cache_update_path uri, path
 
@@ -75,7 +75,7 @@ def test_cache_update_path_with_utf8_internal_encoding
       path = File.join @tempdir, "file"
       data = String.new("\xC8").force_encoding(Encoding::BINARY)
 
-      fetcher = util_fuck_with_fetcher data
+      fetcher = fake_fetcher(uri.to_s, data)
 
       written_data = fetcher.cache_update_path uri, path
 
@@ -88,7 +88,7 @@ def test_cache_update_path_no_update
     uri = Gem::URI "http://example/file"
     path = File.join @tempdir, "file"
 
-    fetcher = util_fuck_with_fetcher "hello"
+    fetcher = fake_fetcher(uri.to_s, "hello")
 
     data = fetcher.cache_update_path uri, path, false
 
@@ -97,103 +97,79 @@ def test_cache_update_path_no_update
     assert_path_not_exist path
   end
 
-  def util_fuck_with_fetcher(data, blow = false)
-    fetcher = Gem::RemoteFetcher.fetcher
-    fetcher.instance_variable_set :@test_data, data
-
-    if blow
-      def fetcher.fetch_path(arg, *rest)
-        # OMG I'm such an ass
-        class << self; remove_method :fetch_path; end
-        def self.fetch_path(arg, *rest)
-          @test_arg = arg
-          @test_data
-        end
+  def test_cache_update_path_overwrites_existing_file
+    uri = Gem::URI "http://example/file"
+    path = File.join @tempdir, "file"
 
-        raise Gem::RemoteFetcher::FetchError.new("haha!", "")
-      end
-    else
-      def fetcher.fetch_path(arg, *rest)
-        @test_arg = arg
-        @test_data
-      end
-    end
+    # Create existing file with old content
+    File.write(path, "old content")
+    assert_equal "old content", File.read(path)
+
+    fetcher = fake_fetcher(uri.to_s, "new content")
 
-    fetcher
+    data = fetcher.cache_update_path uri, path
+
+    assert_equal "new content", data
+    assert_equal "new content", File.read(path)
   end
 
   def test_download
-    a1_data = nil
-    File.open @a1_gem, "rb" do |fp|
-      a1_data = fp.read
-    end
+    a1_data = File.open @a1_gem, "rb", &:read
+    a1_url = "http://gems.example.com/gems/a-1.gem"
 
-    fetcher = util_fuck_with_fetcher a1_data
+    fetcher = fake_fetcher(a1_url, a1_data)
 
     a1_cache_gem = @a1.cache_file
     assert_equal a1_cache_gem, fetcher.download(@a1, "http://gems.example.com")
-    assert_equal("http://gems.example.com/gems/a-1.gem",
-                 fetcher.instance_variable_get(:@test_arg).to_s)
+    assert_equal a1_url, fetcher.paths.last
     assert File.exist?(a1_cache_gem)
   end
 
   def test_download_with_auth
-    a1_data = nil
-    File.open @a1_gem, "rb" do |fp|
-      a1_data = fp.read
-    end
+    a1_data = File.open @a1_gem, "rb", &:read
+    a1_url = "http://user:password@gems.example.com/gems/a-1.gem"
 
-    fetcher = util_fuck_with_fetcher a1_data
+    fetcher = fake_fetcher(a1_url, a1_data)
 
     a1_cache_gem = @a1.cache_file
     assert_equal a1_cache_gem, fetcher.download(@a1, "http://user:password@gems.example.com")
-    assert_equal("http://user:password@gems.example.com/gems/a-1.gem",
-                 fetcher.instance_variable_get(:@test_arg).to_s)
+    assert_equal a1_url, fetcher.paths.last
     assert File.exist?(a1_cache_gem)
   end
 
   def test_download_with_token
-    a1_data = nil
-    File.open @a1_gem, "rb" do |fp|
-      a1_data = fp.read
-    end
+    a1_data = File.open @a1_gem, "rb", &:read
+    a1_url = "http://token@gems.example.com/gems/a-1.gem"
 
-    fetcher = util_fuck_with_fetcher a1_data
+    fetcher = fake_fetcher(a1_url, a1_data)
 
     a1_cache_gem = @a1.cache_file
     assert_equal a1_cache_gem, fetcher.download(@a1, "http://token@gems.example.com")
-    assert_equal("http://token@gems.example.com/gems/a-1.gem",
-                 fetcher.instance_variable_get(:@test_arg).to_s)
+    assert_equal a1_url, fetcher.paths.last
     assert File.exist?(a1_cache_gem)
   end
 
   def test_download_with_x_oauth_basic
-    a1_data = nil
-    File.open @a1_gem, "rb" do |fp|
-      a1_data = fp.read
-    end
+    a1_data = File.open @a1_gem, "rb", &:read
+    a1_url = "http://token:x-oauth-basic@gems.example.com/gems/a-1.gem"
 
-    fetcher = util_fuck_with_fetcher a1_data
+    fetcher = fake_fetcher(a1_url, a1_data)
 
     a1_cache_gem = @a1.cache_file
     assert_equal a1_cache_gem, fetcher.download(@a1, "http://token:x-oauth-basic@gems.example.com")
-    assert_equal("http://token:x-oauth-basic@gems.example.com/gems/a-1.gem",
-                 fetcher.instance_variable_get(:@test_arg).to_s)
+    assert_equal a1_url, fetcher.paths.last
     assert File.exist?(a1_cache_gem)
   end
 
   def test_download_with_encoded_auth
-    a1_data = nil
-    File.open @a1_gem, "rb" do |fp|
-      a1_data = fp.read
-    end
+    a1_data = File.open @a1_gem, "rb", &:read
+    a1_url = "http://user:%25pas%25sword@gems.example.com/gems/a-1.gem"
 
-    fetcher = util_fuck_with_fetcher a1_data
+    fetcher = fake_fetcher(a1_url, a1_data)
 
     a1_cache_gem = @a1.cache_file
     assert_equal a1_cache_gem, fetcher.download(@a1, "http://user:%25pas%25sword@gems.example.com")
-    assert_equal("http://user:%25pas%25sword@gems.example.com/gems/a-1.gem",
-                 fetcher.instance_variable_get(:@test_arg).to_s)
+    assert_equal a1_url, fetcher.paths.last
     assert File.exist?(a1_cache_gem)
   end
 
@@ -235,8 +211,9 @@ def test_download_local_space
 
   def test_download_install_dir
     a1_data = File.open @a1_gem, "rb", &:read
+    a1_url = "http://gems.example.com/gems/a-1.gem"
 
-    fetcher = util_fuck_with_fetcher a1_data
+    fetcher = fake_fetcher(a1_url, a1_data)
 
     install_dir = File.join @tempdir, "more_gems"
 
@@ -245,8 +222,7 @@ def test_download_install_dir
     actual = fetcher.download(@a1, "http://gems.example.com", install_dir)
 
     assert_equal a1_cache_gem, actual
-    assert_equal("http://gems.example.com/gems/a-1.gem",
-                 fetcher.instance_variable_get(:@test_arg).to_s)
+    assert_equal a1_url, fetcher.paths.last
 
     assert File.exist?(a1_cache_gem)
   end
@@ -282,7 +258,12 @@ def test_download_read_only
       FileUtils.chmod 0o555, @a1.cache_dir
       FileUtils.chmod 0o555, @gemhome
 
-      fetcher = util_fuck_with_fetcher File.read(@a1_gem)
+      fetcher = Gem::RemoteFetcher.fetcher
+      def fetcher.fetch_path(uri, *rest)
+        File.read File.join(@test_gem_dir, "a-1.gem")
+      end
+      fetcher.instance_variable_set(:@test_gem_dir, File.dirname(@a1_gem))
+
       fetcher.download(@a1, "http://gems.example.com")
       a1_cache_gem = File.join Gem.user_dir, "cache", @a1.file_name
       assert File.exist? a1_cache_gem
@@ -301,19 +282,21 @@ def test_download_platform_legacy
     end
     e1.loaded_from = File.join(@gemhome, "specifications", e1.full_name)
 
-    e1_data = nil
-    File.open e1_gem, "rb" do |fp|
-      e1_data = fp.read
-    end
+    e1_data = File.open e1_gem, "rb", &:read
 
-    fetcher = util_fuck_with_fetcher e1_data, :blow_chunks
+    fetcher = Gem::RemoteFetcher.fetcher
+    def fetcher.fetch_path(uri, *rest)
+      @call_count ||= 0
+      @call_count += 1
+      raise Gem::RemoteFetcher::FetchError.new("error", uri) if @call_count == 1
+      @test_data
+    end
+    fetcher.instance_variable_set(:@test_data, e1_data)
 
     e1_cache_gem = e1.cache_file
 
     assert_equal e1_cache_gem, fetcher.download(e1, "http://gems.example.com")
 
-    assert_equal("http://gems.example.com/gems/#{e1.original_name}.gem",
-                 fetcher.instance_variable_get(:@test_arg).to_s)
     assert File.exist?(e1_cache_gem)
   end
 
@@ -592,6 +575,8 @@ def test_yaml_error_on_size
     end
   end
 
+  private
+
   def assert_error(exception_class = Exception)
     got_exception = false
 
@@ -603,4 +588,13 @@ def assert_error(exception_class = Exception)
 
     assert got_exception, "Expected exception conforming to #{exception_class}"
   end
+
+  def fake_fetcher(url, data)
+    original_fetcher = Gem::RemoteFetcher.fetcher
+    fetcher = Gem::FakeFetcher.new
+    fetcher.data[url] = data
+    Gem::RemoteFetcher.fetcher = fetcher
+  ensure
+    Gem::RemoteFetcher.fetcher = original_fetcher
+  end
 end
diff --git a/test/test_ipaddr.rb b/test/test_ipaddr.rb
index 005927cd054cd9..4b7229fc17b686 100644
--- a/test/test_ipaddr.rb
+++ b/test/test_ipaddr.rb
@@ -207,6 +207,15 @@ def test_ipv4_compat
     assert_equal(112, b.prefix)
   end
 
+  def test_ipv4_compat_with_error_message
+    e = assert_raise(IPAddr::InvalidAddressError) do
+      assert_warning(/obsolete/) {
+        IPAddr.new('2001:db8::').ipv4_compat
+      }
+    end
+    assert_equal('not an IPv4 address: 2001:db8::', e.message)
+  end
+
   def test_ipv4_mapped
     a = IPAddr.new("::ffff:192.168.1.2")
     assert_equal("::ffff:192.168.1.2", a.to_s)
@@ -224,6 +233,13 @@ def test_ipv4_mapped
     assert_equal(Socket::AF_INET6, b.family)
   end
 
+  def test_ipv4_mapped_with_error_message
+    e = assert_raise(IPAddr::InvalidAddressError) do
+      IPAddr.new('2001:db8::').ipv4_mapped
+    end
+    assert_equal('not an IPv4 address: 2001:db8::', e.message)
+  end
+
   def test_reverse
     assert_equal("f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.0.0.0.5.0.5.0.e.f.f.3.ip6.arpa", IPAddr.new("3ffe:505:2::f").reverse)
     assert_equal("1.2.168.192.in-addr.arpa", IPAddr.new("192.168.2.1").reverse)
@@ -231,16 +247,18 @@ def test_reverse
 
   def test_ip6_arpa
     assert_equal("f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.0.0.0.5.0.5.0.e.f.f.3.ip6.arpa", IPAddr.new("3ffe:505:2::f").ip6_arpa)
-    assert_raise(IPAddr::InvalidAddressError) {
+    e = assert_raise(IPAddr::InvalidAddressError) {
       IPAddr.new("192.168.2.1").ip6_arpa
     }
+    assert_equal('not an IPv6 address: 192.168.2.1', e.message)
   end
 
   def test_ip6_int
     assert_equal("f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.0.0.0.5.0.5.0.e.f.f.3.ip6.int", IPAddr.new("3ffe:505:2::f").ip6_int)
-    assert_raise(IPAddr::InvalidAddressError) {
+    e = assert_raise(IPAddr::InvalidAddressError) {
       IPAddr.new("192.168.2.1").ip6_int
     }
+    assert_equal('not an IPv6 address: 192.168.2.1', e.message)
   end
 
   def test_prefix_writer
@@ -631,5 +649,10 @@ def test_raises_invalid_address_error_with_error_message
       IPAddr.new('192.168.01.100')
     end
     assert_equal('zero-filled number in IPv4 address is ambiguous: 192.168.01.100', e.message)
+
+    e = assert_raise(IPAddr::InvalidAddressError) do
+      IPAddr.new('INVALID')
+    end
+    assert_equal('invalid address: INVALID', e.message)
   end
 end
diff --git a/test/test_pp.rb b/test/test_pp.rb
index 4a273e6edd0aec..922ed371af3e8f 100644
--- a/test/test_pp.rb
+++ b/test/test_pp.rb
@@ -146,7 +146,9 @@ def a.pretty_print_instance_variables() [:@b] end
 
   def test_iv_hiding_via_ruby
     a = Object.new
-    def a.instance_variables_to_inspect() [:@b] end
+    a.singleton_class.class_eval do
+      private def instance_variables_to_inspect() [:@b] end
+    end
     a.instance_eval { @a = "aaa"; @b = "bbb" }
     assert_match(/\A#<Object:0x[\da-f]+ @b="bbb">\n\z/, PP.pp(a, ''.dup))
   end
diff --git a/test/test_timeout.rb b/test/test_timeout.rb
index fead81f571929d..b11fc92aeab1cb 100644
--- a/test/test_timeout.rb
+++ b/test/test_timeout.rb
@@ -54,6 +54,12 @@ def test_raise_for_neg_second
     end
   end
 
+  def test_raise_for_string_argument
+    assert_raise(NoMethodError) do
+      Timeout.timeout("1") { sleep(0.01) }
+    end
+  end
+
   def test_included
     c = Class.new do
       include Timeout
diff --git a/tool/bundler/dev_gems.rb.lock b/tool/bundler/dev_gems.rb.lock
index fff9cfe70cb104..72abb0efcbe1f6 100644
--- a/tool/bundler/dev_gems.rb.lock
+++ b/tool/bundler/dev_gems.rb.lock
@@ -129,4 +129,4 @@ CHECKSUMS
   turbo_tests (2.2.5) sha256=3fa31497d12976d11ccc298add29107b92bda94a90d8a0a5783f06f05102509f
 
 BUNDLED WITH
-  4.0.3
+  4.1.0.dev
diff --git a/tool/bundler/rubocop_gems.rb.lock b/tool/bundler/rubocop_gems.rb.lock
index 70704bfc38896c..251abc37dd0f23 100644
--- a/tool/bundler/rubocop_gems.rb.lock
+++ b/tool/bundler/rubocop_gems.rb.lock
@@ -156,4 +156,4 @@ CHECKSUMS
   unicode-emoji (4.1.0) sha256=4997d2d5df1ed4252f4830a9b6e86f932e2013fbff2182a9ce9ccabda4f325a5
 
 BUNDLED WITH
-  4.0.3
+  4.1.0.dev
diff --git a/tool/bundler/standard_gems.rb.lock b/tool/bundler/standard_gems.rb.lock
index 669e5492a8a0f0..1b48fe058257f4 100644
--- a/tool/bundler/standard_gems.rb.lock
+++ b/tool/bundler/standard_gems.rb.lock
@@ -176,4 +176,4 @@ CHECKSUMS
   unicode-emoji (4.1.0) sha256=4997d2d5df1ed4252f4830a9b6e86f932e2013fbff2182a9ce9ccabda4f325a5
 
 BUNDLED WITH
-  4.0.3
+  4.1.0.dev
diff --git a/tool/bundler/test_gems.rb.lock b/tool/bundler/test_gems.rb.lock
index d8f7d77122846d..6fb9d1c0c5eb77 100644
--- a/tool/bundler/test_gems.rb.lock
+++ b/tool/bundler/test_gems.rb.lock
@@ -103,4 +103,4 @@ CHECKSUMS
   tilt (2.6.1) sha256=35a99bba2adf7c1e362f5b48f9b581cce4edfba98117e34696dde6d308d84770
 
 BUNDLED WITH
-  4.0.3
+  4.1.0.dev
diff --git a/tool/rbs_skip_tests_windows b/tool/rbs_skip_tests_windows
index 1b9f930e846624..35e78e237f1668 100644
--- a/tool/rbs_skip_tests_windows
+++ b/tool/rbs_skip_tests_windows
@@ -107,3 +107,7 @@ test_new(TempfileSingletonTest)
 test_open(ZlibGzipReaderSingletonTest)
 
 test_reachable_objects_from_root(ObjectSpaceTest) To avoid NoMemoryError with test-unit 3.7.5
+
+# Errno::EACCES: Permission denied @ rb_file_s_rename
+# D:/a/ruby/ruby/src/lib/rubygems/util/atomic_file_writer.rb:42:in 'File.rename'
+test_write_binary(GemSingletonTest)
diff --git a/tool/update-NEWS-gemlist.rb b/tool/update-NEWS-gemlist.rb
index e1535eb400bc7e..0b5503580d3de9 100755
--- a/tool/update-NEWS-gemlist.rb
+++ b/tool/update-NEWS-gemlist.rb
@@ -6,10 +6,10 @@
 
 update = ->(list, type, desc = "updated") do
   item = ->(mark = "* ") do
-    "The following #{type} gem#{list.size == 1 ? ' is' : 's are'} #{desc}.\n\n" +
+    "### The following #{type} gem#{list.size == 1 ? ' is' : 's are'} #{desc}.\n\n" +
       list.map {|g, v|"#{mark}#{g} #{v}\n"}.join("") + "\n"
   end
-  news.sub!(/^(?:\*( +))?The following #{type} gems? (?:are|is) #{desc}\.\n+(?:(?(1) \1)\*( *).*\n)*\n*/) do
+  news.sub!(/^(?:\*( +)|#+ *)?The following #{type} gems? (?:are|is) #{desc}\.\n+(?:(?(1) \1)\*( *).*\n)*\n*/) do
     item["#{$1&.<< " "}*#{$2 || ' '}"]
   end or news.sub!(/^## Stdlib updates(?:\n+The following.*(?:\n+( *\* *).*)*)*\n+\K/) do
     item[$1 || "* "]