diff --git a/Assets/Tests/EditMode/AI/AiDefinitionRegistryTests.cs b/Assets/Tests/EditMode/AI/AiDefinitionRegistryTests.cs
new file mode 100644
index 00000000..b9e40fb5
--- /dev/null
+++ b/Assets/Tests/EditMode/AI/AiDefinitionRegistryTests.cs
@@ -0,0 +1,48 @@
+using NUnit.Framework;
+using BaseGames.AI;
+
+namespace BaseGames.Tests.EditMode.AI
+{
+    // 顶层测试定义，供反射注册表发现
+    [AiDefinition("__test_grunt")]
+    internal sealed class TestGruntAi : AiScript
+    {
+        protected override void Build(BrainBuilder b)
+        {
+            b.Entry("A");
+            b.State("A").To("B").When(c => c.Sensor.SeesPlayer(), "SeesPlayer");
+            b.State("B");
+        }
+    }
+
+    public class AiDefinitionRegistryTests
+    {
+        [Test]
+        public void Has_FindsRegisteredDefinition()
+        {
+            Assert.IsTrue(AiDefinitionRegistry.Has("__test_grunt"));
+        }
+
+        [Test]
+        public void GetGraph_ResolvesById()
+        {
+            var g = AiDefinitionRegistry.GetGraph("__test_grunt");
+            Assert.AreEqual("A", g.EntryState);
+        }
+
+        [Test]
+        public void GetGraph_SameId_ReturnsSharedInstance()
+        {
+            Assert.AreSame(
+                AiDefinitionRegistry.GetGraph("__test_grunt"),
+                AiDefinitionRegistry.GetGraph("__test_grunt"));
+        }
+
+        [Test]
+        public void GetGraph_UnknownId_Throws()
+        {
+            Assert.Throws<System.InvalidOperationException>(
+                () => AiDefinitionRegistry.GetGraph("__nope__"));
+        }
+    }
+}
diff --git a/Assets/Tests/EditMode/AI/AiDefinitionRegistryTests.cs.meta b/Assets/Tests/EditMode/AI/AiDefinitionRegistryTests.cs.meta
new file mode 100644
index 00000000..1aa02327
--- /dev/null
+++ b/Assets/Tests/EditMode/AI/AiDefinitionRegistryTests.cs.meta
@@ -0,0 +1,11 @@
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diff --git a/Assets/_Game/Scripts/AI/AiDefinitionRegistry.cs b/Assets/_Game/Scripts/AI/AiDefinitionRegistry.cs
new file mode 100644
index 00000000..ddf4a9b0
--- /dev/null
+++ b/Assets/_Game/Scripts/AI/AiDefinitionRegistry.cs
@@ -0,0 +1,65 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using UnityEngine;
+
+namespace BaseGames.AI
+{
+    /// <summary>
+    /// 反射收集所有 [AiDefinition] 的 AiScript 子类，按 id 提供共享 AiGraph（flyweight）。
+    /// 同一 id 全实例共享同一 AiScript 实例 → 同一张不可变 AiGraph。
+    /// </summary>
+    public static class AiDefinitionRegistry
+    {
+        static Dictionary<string, AiScript> _byId;
+
+        // 项目已关闭 Domain Reload：静态缓存需在进入播放时重置，保证按最新类型重建。
+        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
+        static void ResetOnPlay() => _byId = null;
+
+        static void EnsureBuilt()
+        {
+            if (_byId != null) return;
+            _byId = new Dictionary<string, AiScript>();
+            foreach (var asm in AppDomain.CurrentDomain.GetAssemblies())
+            {
+                Type[] types;
+                try { types = asm.GetTypes(); }
+                catch (ReflectionTypeLoadException e) { types = e.Types; }
+                if (types == null) continue;
+                for (int i = 0; i < types.Length; i++)
+                {
+                    var t = types[i];
+                    if (t == null || t.IsAbstract || !typeof(AiScript).IsAssignableFrom(t)) continue;
+                    var attr = t.GetCustomAttribute<AiDefinitionAttribute>();
+                    if (attr == null) continue;
+                    if (_byId.ContainsKey(attr.Id))
+                        throw new InvalidOperationException(
+                            $"AiDefinitionRegistry: 重复的 AI 定义 id '{attr.Id}'（{t.FullName}）。");
+                    _byId[attr.Id] = (AiScript)Activator.CreateInstance(t);
+                }
+            }
+        }
+
+        public static bool Has(string id)
+        {
+            EnsureBuilt();
+            return _byId.ContainsKey(id);
+        }
+
+        /// <summary>取 id 对应的共享 AiGraph；不存在则显式抛错（根因暴露，不做兜底）。</summary>
+        public static AiGraph GetGraph(string id)
+        {
+            EnsureBuilt();
+            if (!_byId.TryGetValue(id, out var script))
+                throw new InvalidOperationException(
+                    $"AiDefinitionRegistry: 未找到 AI 定义 id '{id}'。请确认存在 [AiDefinition(\"{id}\")] 的 AiScript 子类。");
+            return script.GetOrBuildGraph();
+        }
+
+        public static IEnumerable<string> Ids
+        {
+            get { EnsureBuilt(); return _byId.Keys; }
+        }
+    }
+}
diff --git a/Assets/_Game/Scripts/AI/AiDefinitionRegistry.cs.meta b/Assets/_Game/Scripts/AI/AiDefinitionRegistry.cs.meta
new file mode 100644
index 00000000..32cb47d6
--- /dev/null
+++ b/Assets/_Game/Scripts/AI/AiDefinitionRegistry.cs.meta
@@ -0,0 +1,11 @@
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