diff --git a/src/MrGameEng.Content/Genetics/Phenotype.cs b/src/MrGameEng.Content/Genetics/Phenotype.cs
index ffe1dec..323c138 100644
--- a/src/MrGameEng.Content/Genetics/Phenotype.cs
+++ b/src/MrGameEng.Content/Genetics/Phenotype.cs
@@ -71,5 +71,17 @@ public static class Phenotype
 
             throw new FormulaException($"Unknown variable '{name}' while computing traits.");
         }
+
+        // Группировка генов в формулах: значения всех генов, чьи id подходят под шаблон (gsum/gavg/…).
+        public IEnumerable<float> ResolveMatching(Func<string, bool> matches)
+        {
+            foreach (var geneId in genome.Alleles.Keys)
+            {
+                if (matches(geneId) && registry.TryGetValue(geneId, out var gene))
+                {
+                    yield return genome.Express(gene);
+                }
+            }
+        }
     }
 }
diff --git a/src/MrGameEng.Content/Mods/DefDatabase.cs b/src/MrGameEng.Content/Mods/DefDatabase.cs
index 860859c..ca48b09 100644
--- a/src/MrGameEng.Content/Mods/DefDatabase.cs
+++ b/src/MrGameEng.Content/Mods/DefDatabase.cs
@@ -1,5 +1,6 @@
 using System.Text.Json;
 using System.Text.Json.Nodes;
+using System.Text.RegularExpressions;
 
 namespace MrGameEng.Mods;
 
@@ -24,6 +25,18 @@ public sealed class DefDatabase
     private readonly Dictionary<string, TypeEntry> _byKey = new(StringComparer.OrdinalIgnoreCase);
     private readonly Dictionary<Type, TypeEntry> _byType = [];
 
+    /// <summary>Reserved def-file <c>"type"</c> that carries content patches rather than defs.</summary>
+    public const string PatchTypeKey = "Patch";
+
+    private sealed record PatchRule(string DefType, Regex Match, JsonObject Set);
+
+    private sealed record ValidationRule(string Field, Regex Pattern, string Description);
+
+    private readonly List<PatchRule> _patches = [];
+    private readonly Dictionary<string, List<ValidationRule>> _validators = new(
+        StringComparer.OrdinalIgnoreCase
+    );
+
     private static readonly JsonDocumentOptions DocumentOptions = new()
     {
         CommentHandling = JsonCommentHandling.Skip,
@@ -43,6 +56,38 @@ public sealed class DefDatabase
         _byType.Add(typeof(T), entry);
     }
 
+    /// <summary>
+    /// Registers a load-time validation: the string <paramref name="field"/> of every resolved def of
+    /// type <paramref name="typeKey"/> must match <paramref name="pattern"/> (a regex), or
+    /// <see cref="Load"/> throws. Non-string or absent fields are skipped. Use it to enforce naming
+    /// conventions (e.g. gene ids start with <c>Gene</c>) or key/format rules across a mod's content.
+    /// </summary>
+    public void RegisterValidator(
+        string typeKey,
+        string field,
+        string pattern,
+        string? description = null
+    )
+    {
+        Regex regex;
+        try
+        {
+            regex = new Regex(pattern, RegexOptions.CultureInvariant);
+        }
+        catch (ArgumentException error)
+        {
+            throw new ArgumentException($"Invalid validator regex '{pattern}': {error.Message}");
+        }
+
+        if (!_validators.TryGetValue(typeKey, out var list))
+        {
+            list = [];
+            _validators[typeKey] = list;
+        }
+
+        list.Add(new ValidationRule(field, regex, description ?? $"pattern /{pattern}/"));
+    }
+
     /// <summary>
     /// Loads every <c>Defs/**/*.json</c> of <paramref name="mods"/> (in load order) and
     /// resolves inheritance. Call once after registering all def types.
@@ -66,6 +111,8 @@ public sealed class DefDatabase
             }
         }
 
+        ApplyPatches();
+
         foreach (var entry in _byKey.Values)
         {
             Resolve(entry);
@@ -133,6 +180,12 @@ public sealed class DefDatabase
             ?? throw new InvalidDataException(
                 $"Def file '{file}' (mod '{mod.Id}') has no \"type\" field."
             );
+        if (string.Equals(typeKey, PatchTypeKey, StringComparison.OrdinalIgnoreCase))
+        {
+            LoadPatches(mod, file, root);
+            return;
+        }
+
         if (!_byKey.TryGetValue(typeKey, out var entry))
         {
             throw new InvalidDataException(
@@ -169,8 +222,83 @@ public sealed class DefDatabase
         }
     }
 
-    private static void Resolve(TypeEntry entry)
+    // Парсит файл-патч: операции { defType, match (регэксп по defName), set: {поля} }.
+    private void LoadPatches(Mod mod, string file, JsonNode root)
     {
+        if (root["patches"] is not JsonArray patches)
+        {
+            throw new InvalidDataException(
+                $"Patch file '{file}' (mod '{mod.Id}') has no \"patches\" array."
+            );
+        }
+
+        foreach (var node in patches)
+        {
+            if (node is not JsonObject patch)
+            {
+                throw new InvalidDataException(
+                    $"Patch file '{file}' (mod '{mod.Id}') contains a non-object patch."
+                );
+            }
+
+            var defType =
+                patch["defType"]?.GetValue<string>()
+                ?? throw new InvalidDataException($"A patch in '{file}' has no \"defType\".");
+            var match =
+                patch["match"]?.GetValue<string>()
+                ?? throw new InvalidDataException($"A patch in '{file}' has no \"match\".");
+            if (patch["set"] is not JsonObject set)
+            {
+                throw new InvalidDataException($"A patch in '{file}' has no \"set\" object.");
+            }
+
+            Regex regex;
+            try
+            {
+                regex = new Regex(match, RegexOptions.CultureInvariant);
+            }
+            catch (ArgumentException error)
+            {
+                throw new InvalidDataException(
+                    $"Patch in '{file}' has invalid regex '{match}': {error.Message}"
+                );
+            }
+
+            _patches.Add(new PatchRule(defType, regex, (JsonObject)set.DeepClone()));
+        }
+    }
+
+    // Применяет патчи к сырым дефам (до резолва), в порядке загрузки: каждому дефу нужного типа,
+    // чьё имя подходит под регэксп, проставляются поля set. Поля наследуются детьми как обычно.
+    private void ApplyPatches()
+    {
+        foreach (var patch in _patches)
+        {
+            if (!_byKey.TryGetValue(patch.DefType, out var entry))
+            {
+                throw new InvalidDataException(
+                    $"A patch targets unknown def type '{patch.DefType}'."
+                );
+            }
+
+            foreach (var raw in entry.Raw)
+            {
+                if (!patch.Match.IsMatch(raw.Key))
+                {
+                    continue;
+                }
+
+                foreach (var (key, value) in patch.Set)
+                {
+                    raw.Value[key] = value?.DeepClone();
+                }
+            }
+        }
+    }
+
+    private void Resolve(TypeEntry entry)
+    {
+        _validators.TryGetValue(entry.Key, out var rules);
         foreach (var defName in entry.Raw.Keys.Order(StringComparer.Ordinal))
         {
             var merged = MergeChain(entry, defName, []);
@@ -179,6 +307,11 @@ public sealed class DefDatabase
                 continue;
             }
 
+            if (rules is not null)
+            {
+                Validate(entry.Key, defName, merged, rules);
+            }
+
             var def =
                 (Def?)merged.Deserialize(entry.ClrType, ModInfo.JsonOptions)
                 ?? throw new InvalidDataException(
@@ -188,6 +321,28 @@ public sealed class DefDatabase
         }
     }
 
+    private static void Validate(
+        string typeKey,
+        string defName,
+        JsonObject merged,
+        List<ValidationRule> rules
+    )
+    {
+        foreach (var rule in rules)
+        {
+            if (
+                merged[rule.Field] is JsonValue value
+                && value.TryGetValue<string>(out var text)
+                && !rule.Pattern.IsMatch(text)
+            )
+            {
+                throw new InvalidDataException(
+                    $"Def '{defName}' ({typeKey}) field '{rule.Field}'=\"{text}\" violates {rule.Description}."
+                );
+            }
+        }
+    }
+
     private static JsonObject MergeChain(TypeEntry entry, string defName, HashSet<string> seen)
     {
         if (!seen.Add(defName))
diff --git a/src/MrGameEng.Core/Formulas/FormulaContext.cs b/src/MrGameEng.Core/Formulas/FormulaContext.cs
index 25b7d6f..2d696b3 100644
--- a/src/MrGameEng.Core/Formulas/FormulaContext.cs
+++ b/src/MrGameEng.Core/Formulas/FormulaContext.cs
@@ -12,6 +12,13 @@ public interface IFormulaContext
     /// if the name is unknown — the engine does not invent a default.
     /// </summary>
     float Resolve(string name);
+
+    /// <summary>
+    /// Returns the values of every variable whose name satisfies <paramref name="matches"/> — the
+    /// backing for the group functions (<c>gsum</c>, <c>gavg</c>, …) that aggregate over a name
+    /// pattern, e.g. all <c>leaf_*</c> genes. Contexts with no enumerable variables return nothing.
+    /// </summary>
+    IEnumerable<float> ResolveMatching(Func<string, bool> matches) => [];
 }
 
 /// <summary>An <see cref="IFormulaContext"/> backed by a lookup delegate — handy for tests and ad-hoc use.</summary>
diff --git a/src/MrGameEng.Core/Formulas/FormulaGroups.cs b/src/MrGameEng.Core/Formulas/FormulaGroups.cs
new file mode 100644
index 0000000..2b53870
--- /dev/null
+++ b/src/MrGameEng.Core/Formulas/FormulaGroups.cs
@@ -0,0 +1,98 @@
+using System.Text.RegularExpressions;
+using Node = System.Func<MrGameEng.Formulas.IFormulaContext, float>;
+
+namespace MrGameEng.Formulas;
+
+/// <summary>
+/// The group functions — <c>gsum</c>, <c>gcount</c>, <c>gavg</c>, <c>gmin</c>, <c>gmax</c> — which
+/// aggregate over every context variable whose name matches a regex literal, e.g.
+/// <c>gsum('leaf_.*')</c> sums all <c>leaf_*</c> genes. The pattern is a string literal compiled to a
+/// <see cref="Regex"/> once at parse time; aggregation reads <see cref="IFormulaContext.ResolveMatching"/>.
+/// </summary>
+internal static class FormulaGroups
+{
+    private static readonly HashSet<string> Names = new(StringComparer.Ordinal)
+    {
+        "gsum",
+        "gcount",
+        "gavg",
+        "gmin",
+        "gmax",
+    };
+
+    public static bool IsGroupFunction(string name) => Names.Contains(name);
+
+    public static Node Build(string name, string pattern)
+    {
+        Regex regex;
+        try
+        {
+            regex = new Regex(pattern, RegexOptions.CultureInvariant);
+        }
+        catch (ArgumentException error)
+        {
+            throw new FormulaException($"Invalid regex '{pattern}': {error.Message}");
+        }
+
+        bool Match(string variable) => regex.IsMatch(variable);
+        return name switch
+        {
+            "gsum" => ctx => Aggregate(ctx.ResolveMatching(Match), sum: true),
+            "gavg" => ctx => Aggregate(ctx.ResolveMatching(Match), average: true),
+            "gcount" => ctx => Count(ctx.ResolveMatching(Match)),
+            "gmin" => ctx => Extreme(ctx.ResolveMatching(Match), max: false),
+            "gmax" => ctx => Extreme(ctx.ResolveMatching(Match), max: true),
+            _ => throw new FormulaException($"Unknown group function '{name}'."),
+        };
+    }
+
+    private static float Aggregate(
+        IEnumerable<float> values,
+        bool sum = false,
+        bool average = false
+    )
+    {
+        var total = 0f;
+        var count = 0;
+        foreach (var value in values)
+        {
+            total += value;
+            count++;
+        }
+
+        if (average)
+        {
+            return count == 0 ? 0f : total / count;
+        }
+
+        return total; // sum (count==0 → 0)
+    }
+
+    private static float Count(IEnumerable<float> values)
+    {
+        var count = 0;
+        foreach (var _ in values)
+        {
+            count++;
+        }
+
+        return count;
+    }
+
+    private static float Extreme(IEnumerable<float> values, bool max)
+    {
+        var has = false;
+        var best = 0f;
+        foreach (var value in values)
+        {
+            if (!has || (max ? value > best : value < best))
+            {
+                best = value;
+            }
+
+            has = true;
+        }
+
+        return best; // empty → 0
+    }
+}
diff --git a/src/MrGameEng.Core/Formulas/FormulaLexer.cs b/src/MrGameEng.Core/Formulas/FormulaLexer.cs
index 423fbce..467de9e 100644
--- a/src/MrGameEng.Core/Formulas/FormulaLexer.cs
+++ b/src/MrGameEng.Core/Formulas/FormulaLexer.cs
@@ -6,6 +6,7 @@ internal enum TokenType
 {
     Number,
     Identifier,
+    String,
     Plus,
     Minus,
     Star,
@@ -99,6 +100,27 @@ internal static class FormulaLexer
                 continue;
             }
 
+            if (c == '\'')
+            {
+                var open = i;
+                var start = ++i;
+                while (i < source.Length && source[i] != '\'')
+                {
+                    i++;
+                }
+
+                if (i >= source.Length)
+                {
+                    throw new FormulaException($"Unterminated string at position {open}.");
+                }
+
+                tokens.Add(
+                    new Token(TokenType.String, open, text: source.Substring(start, i - start))
+                );
+                i++; // пропускаем закрывающую кавычку
+                continue;
+            }
+
             var pos = i;
             switch (c)
             {
diff --git a/src/MrGameEng.Core/Formulas/FormulaParser.cs b/src/MrGameEng.Core/Formulas/FormulaParser.cs
index b897191..4ed99bd 100644
--- a/src/MrGameEng.Core/Formulas/FormulaParser.cs
+++ b/src/MrGameEng.Core/Formulas/FormulaParser.cs
@@ -232,6 +232,20 @@ internal sealed class FormulaParser(List<Token> tokens)
     private Node ParseCall(string name)
     {
         Expect(TokenType.LParen);
+        if (FormulaGroups.IsGroupFunction(name))
+        {
+            var pattern = Current;
+            if (!Match(TokenType.String))
+            {
+                throw new FormulaException(
+                    $"Group function '{name}' expects a quoted regex pattern at position {pattern.Position}."
+                );
+            }
+
+            Expect(TokenType.RParen);
+            return FormulaGroups.Build(name, pattern.Text);
+        }
+
         var args = new List<Node>();
         if (!Peek(TokenType.RParen))
         {
diff --git a/tests/MrGameEng.Content.Tests/Mods/DefDatabaseTests.cs b/tests/MrGameEng.Content.Tests/Mods/DefDatabaseTests.cs
index 841614b..661568d 100644
--- a/tests/MrGameEng.Content.Tests/Mods/DefDatabaseTests.cs
+++ b/tests/MrGameEng.Content.Tests/Mods/DefDatabaseTests.cs
@@ -143,4 +143,73 @@ public sealed class DefDatabaseTests : IDisposable
         Assert.Throws<KeyNotFoundException>(() => database.Get<AnimalDef>("Dodo"));
         Assert.False(database.TryGet<AnimalDef>("Dodo", out _));
     }
+
+    private Mod WriteMod(string fileName, string json)
+    {
+        var id = $"mod{_modCounter++:D2}";
+        var modDir = Path.Combine(_root, id);
+        Directory.CreateDirectory(Path.Combine(modDir, "Defs"));
+        File.WriteAllText(Path.Combine(modDir, "Defs", fileName), json);
+        return new Mod(new ModInfo { Id = id }, modDir);
+    }
+
+    [Fact]
+    public void Patch_SetsFields_OnDefsMatchingNamePattern()
+    {
+        var defs = WriteDefsMod(
+            """
+            { "type": "Animal", "defs": [
+                { "defName": "Wolf", "speed": 9 },
+                { "defName": "WolfPup", "speed": 4 },
+                { "defName": "Bear", "speed": 6 }
+            ]}
+            """
+        );
+        var patch = WriteMod(
+            "patches.json",
+            """{ "type": "Patch", "patches": [ { "defType": "Animal", "match": "Wolf.*", "set": { "legs": 6 } } ] }"""
+        );
+
+        var database = LoadAnimals(defs, patch);
+
+        Assert.Equal(6, database.Get<AnimalDef>("Wolf").Legs); // matched
+        Assert.Equal(6, database.Get<AnimalDef>("WolfPup").Legs); // matched
+        Assert.Equal(4, database.Get<AnimalDef>("Bear").Legs); // unmatched → default
+    }
+
+    [Fact]
+    public void Patch_UnknownDefType_Throws()
+    {
+        var patch = WriteMod(
+            "patches.json",
+            """{ "type": "Patch", "patches": [ { "defType": "Ghost", "match": ".*", "set": {} } ] }"""
+        );
+
+        Assert.Throws<InvalidDataException>(() => LoadAnimals(patch));
+    }
+
+    [Fact]
+    public void Validator_RejectsField_NotMatchingPattern()
+    {
+        var database = new DefDatabase();
+        database.RegisterType<AnimalDef>("Animal");
+        database.RegisterValidator("Animal", "defName", "^[A-Z]");
+        var bad = WriteDefsMod("""{ "type": "Animal", "defs": [ { "defName": "wolf" } ] }""");
+
+        var error = Assert.Throws<InvalidDataException>(() => database.Load([bad]));
+        Assert.Contains("wolf", error.Message);
+    }
+
+    [Fact]
+    public void Validator_Passes_WhenFieldMatches()
+    {
+        var database = new DefDatabase();
+        database.RegisterType<AnimalDef>("Animal");
+        database.RegisterValidator("Animal", "defName", "^[A-Z]");
+        database.Load([
+            WriteDefsMod("""{ "type": "Animal", "defs": [ { "defName": "Wolf", "speed": 7 } ] }"""),
+        ]);
+
+        Assert.Equal(7f, database.Get<AnimalDef>("Wolf").Speed);
+    }
 }
diff --git a/tests/MrGameEng.Core.Tests/FormulaTests.cs b/tests/MrGameEng.Core.Tests/FormulaTests.cs
index e126106..2ac85a9 100644
--- a/tests/MrGameEng.Core.Tests/FormulaTests.cs
+++ b/tests/MrGameEng.Core.Tests/FormulaTests.cs
@@ -109,4 +109,66 @@ public class FormulaTests
         var formula = Formula.Compile("x + 1");
         Assert.Throws<FormulaException>(() => formula.Evaluate());
     }
+
+    // --- Group functions (regex aggregation over matching variables) ---
+
+    private sealed class GroupContext(Dictionary<string, float> values) : IFormulaContext
+    {
+        public float Resolve(string name) => values[name];
+
+        public IEnumerable<float> ResolveMatching(Func<string, bool> matches)
+        {
+            foreach (var (name, value) in values)
+            {
+                if (matches(name))
+                {
+                    yield return value;
+                }
+            }
+        }
+    }
+
+    [Fact]
+    public void Evaluate_GroupFunctions_AggregateMatchingVariables()
+    {
+        var ctx = new GroupContext(
+            new()
+            {
+                ["leaf_a"] = 2f,
+                ["leaf_b"] = 4f,
+                ["leaf_c"] = 6f,
+                ["root_a"] = 100f,
+            }
+        );
+
+        Assert.Equal(12f, Formula.Compile("gsum('leaf_.*')").Evaluate(ctx), 4); // 2+4+6
+        Assert.Equal(3f, Formula.Compile("gcount('leaf_.*')").Evaluate(ctx), 4);
+        Assert.Equal(4f, Formula.Compile("gavg('leaf_.*')").Evaluate(ctx), 4);
+        Assert.Equal(2f, Formula.Compile("gmin('leaf_.*')").Evaluate(ctx), 4);
+        Assert.Equal(6f, Formula.Compile("gmax('leaf_.*')").Evaluate(ctx), 4);
+    }
+
+    [Fact]
+    public void Evaluate_GroupFunction_ComposesWithArithmetic()
+    {
+        var ctx = new GroupContext(new() { ["g1"] = 3f, ["g2"] = 5f });
+        Assert.Equal(16f, Formula.Compile("gsum('g.*') * 2").Evaluate(ctx), 4); // (3+5)*2
+    }
+
+    [Fact]
+    public void Evaluate_GroupFunction_NoMatches_IsZero()
+    {
+        var ctx = new GroupContext(new() { ["x"] = 1f });
+        Assert.Equal(0f, Formula.Compile("gsum('none_.*')").Evaluate(ctx), 4);
+        Assert.Equal(0f, Formula.Compile("gavg('none_.*')").Evaluate(ctx), 4);
+    }
+
+    [Theory]
+    [InlineData("gsum(leaf)")] // pattern must be a quoted string
+    [InlineData("gsum('[')")] // invalid regex
+    [InlineData("gsum('a' 'b')")] // extra token
+    public void Compile_BadGroupCall_Throws(string expr)
+    {
+        Assert.Throws<FormulaException>(() => Formula.Compile(expr));
+    }
 }