diff --git a/index.ts b/index.ts
index 4baf40f9..3f4f35cd 100644
--- a/index.ts
+++ b/index.ts
@@ -1615,10 +1615,14 @@ const pluginVersion = getPluginVersion();
 // Plugin Definition
 // ============================================================================
 
-// WeakSet keyed by API instance — each distinct API object tracks its own initialized state.
-// Using WeakSet instead of a module-level boolean avoids the "second register() call skips
-// hook/tool registration for the new API instance" regression that rwmjhb identified.
-const _registeredApis = new WeakSet<OpenClawPluginApi>();
+// Map keyed by API instance — each distinct API object tracks its own initialized state.
+// Using Map instead of WeakSet allows tracking per-instance state AND enables clear() for reset.
+const _registeredApis = new Map<OpenClawPluginApi, boolean>();
+
+// Helper for tests to check registered APIs
+export function _getRegisteredApisForTest(): Map<OpenClawPluginApi, boolean> {
+  return _registeredApis;
+}
 
 const memoryLanceDBProPlugin = {
   id: "memory-lancedb-pro",
@@ -1633,7 +1637,7 @@ const memoryLanceDBProPlugin = {
       api.logger.debug?.("memory-lancedb-pro: register() called again — skipping re-init (idempotent)");
       return;
     }
-    _registeredApis.add(api);
+    // Note: Map.set(api, true) is called AFTER successful init
 
     // Parse and validate configuration
     const config = parsePluginConfig(api.pluginConfig);
@@ -2113,6 +2117,9 @@ const memoryLanceDBProPlugin = {
       }
     );
 
+    // Mark as successfully initialized - only called after all init completes
+    _registeredApis.set(api, true);
+
     // Auto-compaction at gateway_start (if enabled, respects cooldown)
     if (config.memoryCompaction?.enabled) {
       api.on("gateway_start", () => {
@@ -4054,10 +4061,8 @@ export function parsePluginConfig(value: unknown): PluginConfig {
  * @public
  */
 export function resetRegistration() {
-  // Note: WeakSets cannot be cleared by design. In test scenarios where the
-  // same process reloads the module, a fresh module state means a new WeakSet.
-  // For hot-reload scenarios, the module is re-imported fresh.
-  // (WeakSet.clear() does not exist, so we do nothing here.)
+  // Clear the Map to allow re-registration after failure or hot-reload
+  _registeredApis.clear();
 }
 
 export default memoryLanceDBProPlugin;
diff --git a/src/reflection-store.ts b/src/reflection-store.ts
index 38da5ce7..7dcc91c8 100644
--- a/src/reflection-store.ts
+++ b/src/reflection-store.ts
@@ -353,6 +353,9 @@ function buildDerivedCandidates(
     const lines = sanitizeInjectableReflectionLines(toStringArray(metadata.derived));
     if (lines.length === 0) return [];
 
+    const owner = typeof metadata.agentId === "string" ? metadata.agentId.trim() : "";
+    if (owner === "main") return [];
+
     const defaults = {
       midpointDays: REFLECTION_DERIVE_LOGISTIC_MIDPOINT_DAYS,
       k: REFLECTION_DERIVE_LOGISTIC_K,
@@ -428,6 +431,21 @@ function isReflectionMetadataType(type: unknown): boolean {
 
 function isOwnedByAgent(metadata: Record<string, unknown>, agentId: string): boolean {
   const owner = typeof metadata.agentId === "string" ? metadata.agentId.trim() : "";
+
+  // itemKind 只存在於 memory-reflection-item 類型
+  // legacy (memory-reflection) 和 mapped (memory-reflection-mapped) 都沒有 itemKind
+  // 因此 undefined !== "derived"，會走原本的 main fallback（維持相容）
+  const itemKind = metadata.itemKind;
+
+  // 如果是 derived 項目（memory-reflection-item）：不做 main fallback，
+  // 且 derived 不允許空白 owner（空白 owner 的 derived 應完全不可見，防止洩漏）
+  // itemKind 必須是 string type，否則會錯誤進入 derived 分支（null/undefined/number 等應走 legacy fallback）
+  if (typeof itemKind === "string" && itemKind === "derived") {
+    if (!owner) return false;
+    return owner === agentId;
+  }
+
+  // invariant / legacy / mapped：允許空白 owner 可見，維持原本的 main fallback
   if (!owner) return true;
   return owner === agentId || owner === "main";
 }
diff --git a/test/isOwnedByAgent.test.mjs b/test/isOwnedByAgent.test.mjs
new file mode 100644
index 00000000..6e9a8e3b
--- /dev/null
+++ b/test/isOwnedByAgent.test.mjs
@@ -0,0 +1,66 @@
+// isOwnedByAgent unit tests — Issue #448 fix verification
+import { describe, it } from "node:test";
+import assert from "node:assert";
+
+// 從 reflection-store.ts 直接拷貝 isOwnedByAgent 函數（隔離測試）
+function isOwnedByAgent(metadata, agentId) {
+  const owner = typeof metadata.agentId === "string" ? metadata.agentId.trim() : "";
+
+  const itemKind = metadata.itemKind;
+
+  // derived：不做 main fallback，空白 owner → 完全不可見
+  if (itemKind === "derived") {
+    if (!owner) return false;
+    return owner === agentId;
+  }
+
+  // invariant / legacy / mapped：維持原本的 main fallback
+  if (!owner) return true;
+  return owner === agentId || owner === "main";
+}
+
+describe("isOwnedByAgent — derived ownership fix (Issue #448)", () => {
+  // === Must Fix 3: 缺少 derived 分支測試 ===
+  describe("itemKind === 'derived'", () => {
+    it("main's derived → main 可見", () => {
+      assert.strictEqual(isOwnedByAgent({ itemKind: "derived", agentId: "main" }, "main"), true);
+    });
+    it("main's derived → sub-agent 不可見（核心 bug fix）", () => {
+      assert.strictEqual(isOwnedByAgent({ itemKind: "derived", agentId: "main" }, "sub-agent-A"), false);
+    });
+    it("agent-x's derived → agent-x 可見", () => {
+      assert.strictEqual(isOwnedByAgent({ itemKind: "derived", agentId: "agent-x" }, "agent-x"), true);
+    });
+    it("agent-x's derived → agent-y 不可見", () => {
+      assert.strictEqual(isOwnedByAgent({ itemKind: "derived", agentId: "agent-x" }, "agent-y"), false);
+    });
+    it("derived + 空白 owner → 完全不可見（防呆）", () => {
+      assert.strictEqual(isOwnedByAgent({ itemKind: "derived", agentId: "" }, "main"), false);
+      assert.strictEqual(isOwnedByAgent({ itemKind: "derived", agentId: "" }, "sub-agent"), false);
+    });
+  });
+
+  describe("itemKind === 'invariant'（維持 fallback）", () => {
+    it("main's invariant → sub-agent 可見", () => {
+      assert.strictEqual(isOwnedByAgent({ itemKind: "invariant", agentId: "main" }, "sub-agent-A"), true);
+    });
+    it("agent-x's invariant → agent-x 可見", () => {
+      assert.strictEqual(isOwnedByAgent({ itemKind: "invariant", agentId: "agent-x" }, "agent-x"), true);
+    });
+    it("agent-x's invariant → agent-y 不可見", () => {
+      assert.strictEqual(isOwnedByAgent({ itemKind: "invariant", agentId: "agent-x" }, "agent-y"), false);
+    });
+  });
+
+  describe("legacy / mapped（無 itemKind，維持 fallback）", () => {
+    it("main legacy → sub-agent 可見", () => {
+      assert.strictEqual(isOwnedByAgent({ agentId: "main" }, "sub-agent-A"), true);
+    });
+    it("agent-x legacy → agent-x 可見", () => {
+      assert.strictEqual(isOwnedByAgent({ agentId: "agent-x" }, "agent-x"), true);
+    });
+    it("agent-x legacy → agent-y 不可見", () => {
+      assert.strictEqual(isOwnedByAgent({ agentId: "agent-x" }, "agent-y"), false);
+    });
+  });
+});