sebastienros · lahma · Feb 7, 2026 · Feb 7, 2026 · Feb 7, 2026
diff --git a/Jint.Tests.Test262/Test262Harness.settings.json b/Jint.Tests.Test262/Test262Harness.settings.json
@@ -117,11 +117,8 @@
     // Many of these tests require non-English locales (Spanish, Polish, German, Chinese, etc.) or
     // advanced features like formatRange, calendar-specific formatting, or complex locale canonicalization.
 
-    // Collator - German phonebook collation and locale-specific collation data
+    // Collator - German phonebook collation
     "intl402/Collator/prototype/compare/non-normative-phonebook.js",
-    "intl402/Collator/prototype/resolvedOptions/resolved-collation-unicode-extensions-and-options.js",
-    "intl402/Collator/unicode-ext-seq-in-private-tag.js",
-    "intl402/Collator/unicode-ext-value-collation.js",
     "intl402/Collator/usage-de.js",
 
     // DateTimeFormat - hanidec numbering system has different AM/PM behavior in ICU/CLDR
@@ -132,22 +129,10 @@
     "intl402/DateTimeFormat/prototype/formatRangeToParts/dangi-calendar-dates.js",
     "intl402/DateTimeFormat/prototype/formatToParts/chinese-calendar-dates.js",
 
-    // DisplayNames - locale-specific display names and Symbol edge cases
-    "intl402/DisplayNames/locales-symbol-length.js",
-
-    // DurationFormat - formatting with specific styles and locales
-    "intl402/DurationFormat/prototype/format/duration-out-of-range-3.js",
-    "intl402/DurationFormat/prototype/format/duration-out-of-range-4.js",
+    // DurationFormat - precision formatting requires exact sub-second arithmetic
+    "intl402/DurationFormat/prototype/format/precision-exact-mathematical-values.js",
     // Requires Spanish unit patterns (ICU4N doesn't include unit data, only core locale data)
     "intl402/DurationFormat/prototype/format/mixed-non-numeric-styles-es.js",
-    "intl402/DurationFormat/prototype/format/precision-exact-mathematical-values.js",
-    "intl402/DurationFormat/prototype/resolvedOptions/resolved-numbering-system-unicode-extensions-and-options.js",
-
-    // Locale canonicalization - variant/region aliasing requires CLDR data
-    "intl402/Intl/getCanonicalLocales/complex-region-subtag-replacement.js",
-    "intl402/Intl/getCanonicalLocales/non-iana-canon.js",
-    "intl402/Intl/getCanonicalLocales/preferred-variant.js",
-    "intl402/Locale/reject-duplicate-variants-in-tlang.js",
 
     // NumberFormat - locale-specific formatting and formatRange
     "intl402/NumberFormat/prototype/format/format-significant-digits.js",
@@ -163,28 +148,15 @@
     "intl402/NumberFormat/prototype/formatToParts/unit-ko-KR.js",
     "intl402/NumberFormat/prototype/formatToParts/unit-zh-TW.js",
 
-    // PluralRules - plural categories require full CLDR data, notation requires compact support
-    "intl402/PluralRules/prototype/resolvedOptions/plural-categories-order.js",
+    // PluralRules - notation requires compact support
     "intl402/PluralRules/prototype/select/notation.js",
 
-    // String - Turkish/Lithuanian/Azeri locale-specific case conversions
-    "intl402/String/prototype/toLocaleLowerCase/capital_I_with_dot.js",
-    "intl402/String/prototype/toLocaleLowerCase/special_casing_Azeri.js",
-    "intl402/String/prototype/toLocaleLowerCase/special_casing_Lithuanian.js",
-    "intl402/String/prototype/toLocaleLowerCase/special_casing_Turkish.js",
-    "intl402/String/prototype/toLocaleLowerCase/validates-all-locale-identifiers.js",
-    "intl402/String/prototype/toLocaleUpperCase/validates-all-locale-identifiers.js",
-
-    // supportedValuesOf - currencies accepted by DisplayNames check
-    "intl402/Intl/supportedValuesOf/currencies-accepted-by-DisplayNames.js",
-
     // Misc intl402 tests requiring full locale support
     "intl402/fallback-locales-are-supported.js",
     "intl402/supportedLocalesOf-consistent-with-resolvedOptions.js",
 
     // misc features that require investigation
     "intl402/NumberFormat/prototype/format/numbering-systems.js",
-    "intl402/Intl/supportedValuesOf/numberingSystems-with-simple-digit-mappings.js",
 
     // Temporal
     "intl402/Temporal/Duration/**/*.js",

diff --git a/Jint/Native/BigInt/BigIntConstructor.cs b/Jint/Native/BigInt/BigIntConstructor.cs
@@ -90,7 +90,7 @@ private JsBigInt NumberToBigInt(JsNumber value)
     {
         if (TypeConverter.IsIntegralNumber(value._value))
         {
-            return JsBigInt.Create((long) value._value);
+            return JsBigInt.Create(new BigInteger(value._value));
         }
 
         Throw.RangeError(_realm, "The number " + value + " cannot be converted to a BigInt because it is not an integer");

diff --git a/Jint/Native/Intl/CollatorConstructor.cs b/Jint/Native/Intl/CollatorConstructor.cs
@@ -26,6 +26,24 @@ internal sealed class CollatorConstructor : Constructor
         "searchjl", "stroke", "trad", "unihan", "zhuyin", "default"
     ], StringComparison.Ordinal);
 
+    // Locale-specific supported collation types (from CLDR)
+    // Only locales with non-default collation support are listed
+    private static readonly Dictionary<string, HashSet<string>> LocaleCollationSupport = new(StringComparer.OrdinalIgnoreCase)
+    {
+        ["ar"] = new(StringComparer.Ordinal) { "default", "compat", "eor" },
+        ["da"] = new(StringComparer.Ordinal) { "default", "eor" },
+        ["de"] = new(StringComparer.Ordinal) { "default", "phonebk", "eor" },
+        ["en"] = new(StringComparer.Ordinal) { "default", "ducet", "emoji", "eor" },
+        ["es"] = new(StringComparer.Ordinal) { "default", "trad", "eor" },
+        ["hi"] = new(StringComparer.Ordinal) { "default", "direct", "eor" },
+        ["ja"] = new(StringComparer.Ordinal) { "default", "unihan", "eor" },
+        ["ko"] = new(StringComparer.Ordinal) { "default", "searchjl", "unihan", "eor" },
+        ["ln"] = new(StringComparer.Ordinal) { "default", "phonetic", "eor" },
+        ["si"] = new(StringComparer.Ordinal) { "default", "dict", "eor" },
+        ["sv"] = new(StringComparer.Ordinal) { "default", "reformed", "eor" },
+        ["zh"] = new(StringComparer.Ordinal) { "default", "big5han", "gb2312", "pinyin", "stroke", "unihan", "zhuyin", "eor" },
+    };
+
     public CollatorConstructor(
         Engine engine,
         Realm realm,
@@ -90,7 +108,7 @@ public override ObjectInstance Construct(JsCallArguments arguments, JsValue newT
         // Get options (options override unicode extensions)
         var usage = GetStringOption(optionsObj, "usage", UsageValues, "sort");
         var sensitivity = GetSensitivity(optionsObj);
-        var collation = GetCollationOption(optionsObj, uCollation);
+        var collation = GetCollationOption(optionsObj, uCollation, resolvedLocale);
         var numeric = GetNumericOption(optionsObj, uNumeric);
         var caseFirst = GetCaseFirstOption(optionsObj, uCaseFirst);
 
@@ -224,13 +242,18 @@ private static void ParseUnicodeExtensions(string locale, out string? collation,
         numeric = null;
         caseFirst = null;
 
-        var uIndex = locale.IndexOf("-u-", StringComparison.Ordinal);
+        // Only search for -u- before the private-use section (-x-)
+        var xIndex = locale.IndexOf("-x-", StringComparison.OrdinalIgnoreCase);
+        var searchRange = xIndex >= 0 ? locale.Substring(0, xIndex) : locale;
+        var uIndex = searchRange.IndexOf("-u-", StringComparison.Ordinal);
         if (uIndex < 0)
         {
             return;
         }
 
-        var parts = locale.Substring(uIndex + 3).Split('-');
+        // Extract the -u- extension content (up to private-use or next singleton)
+        var extensionContent = (xIndex >= 0 ? locale.Substring(uIndex + 3, xIndex - uIndex - 3) : locale.Substring(uIndex + 3));
+        var parts = extensionContent.Split('-');
         for (var i = 0; i < parts.Length; i++)
         {
             var key = parts[i];
@@ -270,42 +293,65 @@ private static void ParseUnicodeExtensions(string locale, out string? collation,
         }
     }
 
-    private static string GetCollationOption(ObjectInstance options, string? unicodeExtension)
+    private static string GetCollationOption(ObjectInstance options, string? unicodeExtension, string resolvedLocale)
     {
+        // Get the language code for locale-specific collation support
+        var langCode = resolvedLocale;
+        var dashIdx = resolvedLocale.IndexOf('-');
+        if (dashIdx > 0)
+        {
+            langCode = resolvedLocale.Substring(0, dashIdx);
+        }
+
         var value = options.Get("collation");
         if (!value.IsUndefined())
         {
             var collation = TypeConverter.ToString(value);
 
             // Per ECMA-402: "standard" and "search" collations are explicitly disallowed
-            // They should fall back to "default"
             if (string.Equals(collation, "standard", StringComparison.Ordinal) ||
                 string.Equals(collation, "search", StringComparison.Ordinal))
             {
-                return "default";
+                // Fall through to check unicode extension
             }
-
-            // Validate against known collation types - ignore invalid values
-            if (!ValidCollationTypes.Contains(collation))
+            // Validate against known collation types AND locale-specific support
+            else if (ValidCollationTypes.Contains(collation) && IsCollationSupportedForLocale(langCode, collation))
             {
-                return "default";
+                return collation;
             }
-
-            return collation;
+            // Options value is not supported - fall through to check unicode extension
         }
 
         // Check unicode extension, but disallow "standard", "search", and invalid values
         if (unicodeExtension != null &&
             !string.Equals(unicodeExtension, "standard", StringComparison.Ordinal) &&
             !string.Equals(unicodeExtension, "search", StringComparison.Ordinal) &&
-            ValidCollationTypes.Contains(unicodeExtension))
+            ValidCollationTypes.Contains(unicodeExtension) &&
+            IsCollationSupportedForLocale(langCode, unicodeExtension))
         {
             return unicodeExtension;
         }
 
         return "default";
     }
 
+    private static bool IsCollationSupportedForLocale(string language, string collation)
+    {
+        if (string.Equals(collation, "default", StringComparison.Ordinal))
+        {
+            return true;
+        }
+
+        // If we have explicit locale data, check against it
+        if (LocaleCollationSupport.TryGetValue(language, out var supported))
+        {
+            return supported.Contains(collation);
+        }
+
+        // For unlisted locales, only "default" and "eor" are universally supported
+        return string.Equals(collation, "eor", StringComparison.Ordinal);
+    }
+
     private static bool GetNumericOption(ObjectInstance options, bool? unicodeExtension)
     {
         var value = options.Get("numeric");

diff --git a/Jint/Native/Intl/Data/LocaleData.cs b/Jint/Native/Intl/Data/LocaleData.cs
@@ -238,14 +238,20 @@ private static void ParseComplexLanguageMapping(string key, string value)
 
     private static void ParseVariantMapping(string key, string value)
     {
-        // Format: type,replacement
-        var commaIndex = value.IndexOf(',');
-        if (commaIndex > 0)
+        // Format: type,replacement[,prefix:variant]
+        var parts = value.Split(',');
+        if (parts.Length >= 2)
         {
-            _variantMappings![key] = new VariantMapping(
-                value.Substring(0, commaIndex),
-                value.Substring(commaIndex + 1)
-            );
+            string? prefix = null;
+            for (var i = 2; i < parts.Length; i++)
+            {
+                if (parts[i].StartsWith("prefix:", StringComparison.Ordinal))
+                {
+                    prefix = parts[i].Substring(7);
+                }
+            }
+
+            _variantMappings![key] = new VariantMapping(parts[0], parts[1], prefix);
         }
     }
 
@@ -284,13 +290,19 @@ public ComplexLanguageMapping(string language, string? script, string? region)
 
     internal readonly struct VariantMapping
     {
-        public VariantMapping(string type, string replacement)
+        public VariantMapping(string type, string replacement, string? prefix = null)
         {
             Type = type;
             Replacement = replacement;
+            Prefix = prefix;
         }
 
         public string Type { get; }
         public string Replacement { get; }
+
+        /// <summary>
+        /// Optional prefix variant that should be removed when this alias is applied.
+        /// </summary>
+        public string? Prefix { get; }
     }
 }
diff --git a/Jint/Native/Intl/Data/LocaleData.txt b/Jint/Native/Intl/Data/LocaleData.txt
@@ -694,12 +694,16 @@ WK=UM
 YD=YE
 YU=RS
 ZR=CD
+810=RU
+NT=SA
+SU=RU
+AN=CW
 
 [VARIANT_MAPPINGS]
 aaland=region,AX
 arevela=language,hy
 arevmda=language,hyw
-heploc=variant,alalc97
+heploc=variant,alalc97,prefix:hepburn
 polytoni=variant,polyton
 
 [LANGUAGE_VARIANT_MAPPINGS]
@@ -715,6 +719,13 @@ Cyrl+SU=RU
 Latn+SU=RU
 Geor+SU=GE
 Arab+SU=UZ
+Armn+810=AM
+Cyrl+810=RU
+Latn+810=RU
+Geor+810=GE
+Arab+810=UZ
+Cyrl+CS=RS
+Latn+CS=RS
 
 [UNICODE_MAPPINGS]
 ca:ethiopic-amete-alem=ethioaa

diff --git a/Jint/Native/Intl/Data/NumberingSystemData.cs b/Jint/Native/Intl/Data/NumberingSystemData.cs
@@ -24,9 +24,11 @@ internal static class NumberingSystemData
         ["deva"] = "\u0966\u0967\u0968\u0969\u096A\u096B\u096C\u096D\u096E\u096F",
         ["diak"] = "\U00011950\U00011951\U00011952\U00011953\U00011954\U00011955\U00011956\U00011957\U00011958\U00011959",
         ["fullwide"] = "\uFF10\uFF11\uFF12\uFF13\uFF14\uFF15\uFF16\uFF17\uFF18\uFF19",
+        ["gara"] = "\U00010D40\U00010D41\U00010D42\U00010D43\U00010D44\U00010D45\U00010D46\U00010D47\U00010D48\U00010D49",
         ["gong"] = "\U00011DA0\U00011DA1\U00011DA2\U00011DA3\U00011DA4\U00011DA5\U00011DA6\U00011DA7\U00011DA8\U00011DA9",
         ["gonm"] = "\U00011D50\U00011D51\U00011D52\U00011D53\U00011D54\U00011D55\U00011D56\U00011D57\U00011D58\U00011D59",
         ["gujr"] = "\u0AE6\u0AE7\u0AE8\u0AE9\u0AEA\u0AEB\u0AEC\u0AED\u0AEE\u0AEF",
+        ["gukh"] = "\U00016130\U00016131\U00016132\U00016133\U00016134\U00016135\U00016136\U00016137\U00016138\U00016139",
         ["guru"] = "\u0A66\u0A67\u0A68\u0A69\u0A6A\u0A6B\u0A6C\u0A6D\u0A6E\u0A6F",
         ["hanidec"] = "\u3007\u4E00\u4E8C\u4E09\u56DB\u4E94\u516D\u4E03\u516B\u4E5D",
         ["hmng"] = "\U00016B50\U00016B51\U00016B52\U00016B53\U00016B54\U00016B55\U00016B56\U00016B57\U00016B58\U00016B59",
@@ -36,6 +38,7 @@ internal static class NumberingSystemData
         ["kawi"] = "\U00011F50\U00011F51\U00011F52\U00011F53\U00011F54\U00011F55\U00011F56\U00011F57\U00011F58\U00011F59",
         ["khmr"] = "\u17E0\u17E1\u17E2\u17E3\u17E4\u17E5\u17E6\u17E7\u17E8\u17E9",
         ["knda"] = "\u0CE6\u0CE7\u0CE8\u0CE9\u0CEA\u0CEB\u0CEC\u0CED\u0CEE\u0CEF",
+        ["krai"] = "\U00016D70\U00016D71\U00016D72\U00016D73\U00016D74\U00016D75\U00016D76\U00016D77\U00016D78\U00016D79",
         ["lana"] = "\u1A80\u1A81\u1A82\u1A83\u1A84\u1A85\u1A86\u1A87\u1A88\u1A89",
         ["lanatham"] = "\u1A90\u1A91\u1A92\u1A93\u1A94\u1A95\u1A96\u1A97\u1A98\u1A99",
         ["laoo"] = "\u0ED0\u0ED1\u0ED2\u0ED3\u0ED4\u0ED5\u0ED6\u0ED7\u0ED8\u0ED9",
@@ -53,14 +56,18 @@ internal static class NumberingSystemData
         ["mroo"] = "\U00016A60\U00016A61\U00016A62\U00016A63\U00016A64\U00016A65\U00016A66\U00016A67\U00016A68\U00016A69",
         ["mtei"] = "\uABF0\uABF1\uABF2\uABF3\uABF4\uABF5\uABF6\uABF7\uABF8\uABF9",
         ["mymr"] = "\u1040\u1041\u1042\u1043\u1044\u1045\u1046\u1047\u1048\u1049",
+        ["mymrepka"] = "\U000116DA\U000116DB\U000116DC\U000116DD\U000116DE\U000116DF\U000116E0\U000116E1\U000116E2\U000116E3",
+        ["mymrpao"] = "\U000116D0\U000116D1\U000116D2\U000116D3\U000116D4\U000116D5\U000116D6\U000116D7\U000116D8\U000116D9",
         ["mymrshan"] = "\u1090\u1091\u1092\u1093\u1094\u1095\u1096\u1097\u1098\u1099",
         ["mymrtlng"] = "\uA9F0\uA9F1\uA9F2\uA9F3\uA9F4\uA9F5\uA9F6\uA9F7\uA9F8\uA9F9",
         ["nagm"] = "\U0001E4F0\U0001E4F1\U0001E4F2\U0001E4F3\U0001E4F4\U0001E4F5\U0001E4F6\U0001E4F7\U0001E4F8\U0001E4F9",
         ["newa"] = "\U00011450\U00011451\U00011452\U00011453\U00011454\U00011455\U00011456\U00011457\U00011458\U00011459",
         ["nkoo"] = "\u07C0\u07C1\u07C2\u07C3\u07C4\u07C5\u07C6\u07C7\u07C8\u07C9",
         ["olck"] = "\u1C50\u1C51\u1C52\u1C53\u1C54\u1C55\u1C56\u1C57\u1C58\u1C59",
+        ["onao"] = "\U0001E5F1\U0001E5F2\U0001E5F3\U0001E5F4\U0001E5F5\U0001E5F6\U0001E5F7\U0001E5F8\U0001E5F9\U0001E5FA",
         ["orya"] = "\u0B66\u0B67\u0B68\u0B69\u0B6A\u0B6B\u0B6C\u0B6D\u0B6E\u0B6F",
         ["osma"] = "\U000104A0\U000104A1\U000104A2\U000104A3\U000104A4\U000104A5\U000104A6\U000104A7\U000104A8\U000104A9",
+        ["outlined"] = "\U0001CCF0\U0001CCF1\U0001CCF2\U0001CCF3\U0001CCF4\U0001CCF5\U0001CCF6\U0001CCF7\U0001CCF8\U0001CCF9",
         ["rohg"] = "\U00010D30\U00010D31\U00010D32\U00010D33\U00010D34\U00010D35\U00010D36\U00010D37\U00010D38\U00010D39",
         ["saur"] = "\uA8D0\uA8D1\uA8D2\uA8D3\uA8D4\uA8D5\uA8D6\uA8D7\uA8D8\uA8D9",
         ["segment"] = "\U0001FBF0\U0001FBF1\U0001FBF2\U0001FBF3\U0001FBF4\U0001FBF5\U0001FBF6\U0001FBF7\U0001FBF8\U0001FBF9",
@@ -69,6 +76,7 @@ internal static class NumberingSystemData
         ["sinh"] = "\u0DE6\u0DE7\u0DE8\u0DE9\u0DEA\u0DEB\u0DEC\u0DED\u0DEE\u0DEF",
         ["sora"] = "\U000110F0\U000110F1\U000110F2\U000110F3\U000110F4\U000110F5\U000110F6\U000110F7\U000110F8\U000110F9",
         ["sund"] = "\u1BB0\u1BB1\u1BB2\u1BB3\u1BB4\u1BB5\u1BB6\u1BB7\u1BB8\u1BB9",
+        ["sunu"] = "\U00011BF0\U00011BF1\U00011BF2\U00011BF3\U00011BF4\U00011BF5\U00011BF6\U00011BF7\U00011BF8\U00011BF9",
         ["takr"] = "\U000116C0\U000116C1\U000116C2\U000116C3\U000116C4\U000116C5\U000116C6\U000116C7\U000116C8\U000116C9",
         ["talu"] = "\u19D0\u19D1\u19D2\u19D3\u19D4\u19D5\u19D6\u19D7\u19D8\u19D9",
         ["tamldec"] = "\u0BE6\u0BE7\u0BE8\u0BE9\u0BEA\u0BEB\u0BEC\u0BED\u0BEE\u0BEF",
@@ -77,6 +85,7 @@ internal static class NumberingSystemData
         ["tibt"] = "\u0F20\u0F21\u0F22\u0F23\u0F24\u0F25\u0F26\u0F27\u0F28\u0F29",
         ["tirh"] = "\U000114D0\U000114D1\U000114D2\U000114D3\U000114D4\U000114D5\U000114D6\U000114D7\U000114D8\U000114D9",
         ["tnsa"] = "\U00016AC0\U00016AC1\U00016AC2\U00016AC3\U00016AC4\U00016AC5\U00016AC6\U00016AC7\U00016AC8\U00016AC9",
+        ["tols"] = "\U00011DE0\U00011DE1\U00011DE2\U00011DE3\U00011DE4\U00011DE5\U00011DE6\U00011DE7\U00011DE8\U00011DE9",
         ["vaii"] = "\uA620\uA621\uA622\uA623\uA624\uA625\uA626\uA627\uA628\uA629",
         ["wara"] = "\U000118E0\U000118E1\U000118E2\U000118E3\U000118E4\U000118E5\U000118E6\U000118E7\U000118E8\U000118E9",
         ["wcho"] = "\U0001E2F0\U0001E2F1\U0001E2F2\U0001E2F3\U0001E2F4\U0001E2F5\U0001E2F6\U0001E2F7\U0001E2F8\U0001E2F9",