diff --git a/src/assets/AssetGraph.ts b/src/assets/AssetGraph.ts
index 85b93ae..bd88baa 100644
--- a/src/assets/AssetGraph.ts
+++ b/src/assets/AssetGraph.ts
@@ -20,6 +20,27 @@ export class AssetGraph {
     this.ownerToSessions.set(owner, sessions);
   }
 
+  hasSession(sessionId: string): boolean {
+    return this.sessions.has(sessionId);
+  }
+
+  removeSession(sessionId: string): void {
+    const session = this.sessions.get(sessionId);
+    if (!session) {
+      return;
+    }
+
+    this.sessions.delete(sessionId);
+    const sessions = this.ownerToSessions.get(session.owner);
+    if (!sessions) {
+      return;
+    }
+    sessions.delete(sessionId);
+    if (sessions.size === 0) {
+      this.ownerToSessions.delete(session.owner);
+    }
+  }
+
   trackBundle(sessionId: string, bundleName: string): void {
     const session = this.sessions.get(sessionId);
     if (!session) {
diff --git a/src/assets/AssetSession.ts b/src/assets/AssetSession.ts
index c5e8a51..6720750 100644
--- a/src/assets/AssetSession.ts
+++ b/src/assets/AssetSession.ts
@@ -5,6 +5,7 @@ export class AssetSession {
   readonly id: string;
   readonly owner: string;
   private manager: AssetManager;
+  private closed = false;
 
   constructor(manager: AssetManager, id: string, owner: string) {
     this.manager = manager;
@@ -16,17 +17,34 @@ export class AssetSession {
     name: string,
     onProgress?: (progress: number) => void
   ): Promise<AssetsBundle | null> {
+    this.assertOpen();
     return this.manager.acquireBySession(this.id, name, onProgress);
   }
 
   releaseBundle(name: string): Promise<void> {
+    this.assertOpen();
     return this.manager.releaseBySession(this.id, name);
   }
 
   async releaseAll(): Promise<void> {
+    this.assertOpen();
     const bundles = this.manager.getSessionBundles(this.id);
     for (const bundle of bundles) {
       await this.releaseBundle(bundle);
     }
   }
+
+  async destroy(): Promise<void> {
+    if (this.closed) {
+      return;
+    }
+    this.closed = true;
+    await this.manager.destroySession(this.id);
+  }
+
+  private assertOpen(): void {
+    if (this.closed) {
+      throw new Error(`AssetSession "${this.id}" is already destroyed`);
+    }
+  }
 }
diff --git a/src/core/AssetManager.ts b/src/core/AssetManager.ts
index b738cd9..e5af916 100644
--- a/src/core/AssetManager.ts
+++ b/src/core/AssetManager.ts
@@ -32,9 +32,11 @@ export class AssetManager {
   private adapter: AssetRuntimeAdapter;
   private bundleRefCounts: Map<string, number> = new Map();
   private bundleCache: Map<string, AssetsBundle> = new Map();
+  private pendingLoads: Map<string, Promise<AssetsBundle | null>> = new Map();
   private sessionBundleRefs: Map<string, Map<string, number>> = new Map();
   private graph: AssetGraph = new AssetGraph();
   private sessionIdSeed = 0;
+  private defaultSessionId = "";
   private defaultSession: AssetSession;
 
   constructor(adapter?: AssetRuntimeAdapter) {
@@ -57,6 +59,9 @@ export class AssetManager {
     const sessionId = `session-${this.sessionIdSeed}`;
     this.graph.registerSession(sessionId, normalizedOwner);
     this.sessionBundleRefs.set(sessionId, new Map());
+    if (this.defaultSessionId === "") {
+      this.defaultSessionId = sessionId;
+    }
     return new AssetSession(this, sessionId, normalizedOwner);
   }
 
@@ -68,6 +73,23 @@ export class AssetManager {
     return this.graph.getSessionBundles(sessionId);
   }
 
+  async destroySession(sessionId: string): Promise<void> {
+    if (!this.graph.hasSession(sessionId)) {
+      return;
+    }
+    if (sessionId === this.defaultSessionId) {
+      throw new Error("AssetManager: default session cannot be destroyed");
+    }
+
+    const bundles = this.getSessionBundles(sessionId);
+    for (const bundle of bundles) {
+      await this.releaseBySession(sessionId, bundle);
+    }
+
+    this.sessionBundleRefs.delete(sessionId);
+    this.graph.removeSession(sessionId);
+  }
+
   async acquireBySession(
     sessionId: string,
     name: string,
@@ -86,29 +108,71 @@ export class AssetManager {
 
     const totalRefCount = this.bundleRefCounts.get(name) ?? 0;
     const sessionRefCount = sessionRefs.get(name) ?? 0;
+    this.bundleRefCounts.set(name, totalRefCount + 1);
+    sessionRefs.set(name, sessionRefCount + 1);
+    this.graph.trackBundle(sessionId, name);
+
+    const pendingLoad = this.pendingLoads.get(name);
+    if (pendingLoad) {
+      const bundle = await pendingLoad;
+      if (!bundle) {
+        this.rollbackFailedAcquire(sessionId, name);
+      }
+      return bundle;
+    }
+
     if (totalRefCount > 0) {
-      this.bundleRefCounts.set(name, totalRefCount + 1);
-      sessionRefs.set(name, sessionRefCount + 1);
-      this.graph.trackBundle(sessionId, name);
       logger.debug(
         `AssetManager: reuse bundle "${name}", refCount = ${totalRefCount + 1}`
       );
       onProgress?.(1);
-      return this.bundleCache.get(name) ?? this.adapter.loadBundle(name);
+      return this.bundleCache.get(name) ?? null;
     }
 
     logger.debug(`AssetManager: loading bundle "${name}"`);
-    try {
-      const bundle = await this.adapter.loadBundle(name, onProgress);
-      this.bundleRefCounts.set(name, 1);
-      this.bundleCache.set(name, bundle);
-      sessionRefs.set(name, 1);
-      this.graph.trackBundle(sessionId, name);
-      return bundle;
-    } catch (error) {
-      logger.error(`AssetManager: Failed to load bundle "${name}":`, error);
+    const loadPromise = this.adapter
+      .loadBundle(name, onProgress)
+      .then((bundle) => {
+        this.bundleCache.set(name, bundle);
+        return bundle;
+      })
+      .catch((error) => {
+        logger.error(`AssetManager: Failed to load bundle "${name}":`, error);
+        return null;
+      })
+      .finally(() => {
+        this.pendingLoads.delete(name);
+      });
+    this.pendingLoads.set(name, loadPromise);
+
+    const bundle = await loadPromise;
+    if (!bundle) {
+      this.rollbackFailedAcquire(sessionId, name);
       return null;
     }
+    return bundle;
+  }
+
+  private rollbackFailedAcquire(sessionId: string, name: string): void {
+    const sessionRefs = this.sessionBundleRefs.get(sessionId);
+    if (!sessionRefs) {
+      return;
+    }
+
+    const sessionRefCount = sessionRefs.get(name) ?? 0;
+    if (sessionRefCount <= 1) {
+      sessionRefs.delete(name);
+      this.graph.untrackBundle(sessionId, name);
+    } else {
+      sessionRefs.set(name, sessionRefCount - 1);
+    }
+
+    const totalRefCount = (this.bundleRefCounts.get(name) ?? 0) - 1;
+    if (totalRefCount <= 0) {
+      this.bundleRefCounts.delete(name);
+      return;
+    }
+    this.bundleRefCounts.set(name, totalRefCount);
   }
 
   async releaseBySession(sessionId: string, name: string): Promise<void> {
@@ -181,9 +245,11 @@ export class AssetManager {
   clearAll(): void {
     this.bundleRefCounts.clear();
     this.bundleCache.clear();
+    this.pendingLoads.clear();
     this.sessionBundleRefs.clear();
     this.sessionIdSeed = 0;
     this.graph = new AssetGraph();
+    this.defaultSessionId = "";
     this.defaultSession = this.createSession("global");
     logger.debug("AssetManager: Reference count map cleared");
   }
diff --git a/tests/assets/asset-session.test.ts b/tests/assets/asset-session.test.ts
index 83010a8..99c27be 100644
--- a/tests/assets/asset-session.test.ts
+++ b/tests/assets/asset-session.test.ts
@@ -4,6 +4,35 @@ import { AssetManager } from "@/core/AssetManager";
 type FakeBundle = Record<string, unknown>;
 
 describe("AssetSession", () => {
+  it("deduplicates concurrent first-time bundle loads", async () => {
+    const loadCalls: string[] = [];
+    let resolveLoad: ((bundle: FakeBundle) => void) | null = null;
+    const manager = new AssetManager({
+      init: async () => undefined,
+      loadBundle: (name: string) =>
+        new Promise<FakeBundle>((resolve) => {
+          loadCalls.push(name);
+          resolveLoad = resolve;
+        }),
+      unloadBundle: async () => undefined,
+    });
+
+    const sessionA = manager.createSession("scene");
+    const sessionB = manager.createSession("ui");
+
+    const pendingA = sessionA.loadBundle("shared");
+    const pendingB = sessionB.loadBundle("shared");
+
+    expect(loadCalls).toEqual(["shared"]);
+
+    resolveLoad?.({ shared: true });
+    const [bundleA, bundleB] = await Promise.all([pendingA, pendingB]);
+
+    expect(bundleA).toEqual({ shared: true });
+    expect(bundleB).toEqual({ shared: true });
+    expect(manager.getRefCount("shared")).toBe(2);
+  });
+
   it("tracks owner/session relationships in inspector snapshot", async () => {
     const loadCalls: string[] = [];
     const unloadCalls: string[] = [];
@@ -65,4 +94,31 @@ describe("AssetSession", () => {
     expect(snapshot.bundles).toEqual({});
     expect(unloadCalls.sort()).toEqual(["fx", "music"]);
   });
+
+  it("cleans up destroyed sessions and keeps mixed default/explicit semantics consistent", async () => {
+    const unloadCalls: string[] = [];
+    const manager = new AssetManager({
+      init: async () => undefined,
+      loadBundle: async (name: string) => ({ name }) as FakeBundle,
+      unloadBundle: async (name: string) => {
+        unloadCalls.push(name);
+      },
+    });
+
+    const explicit = manager.createSession("scene");
+    await manager.loadBundle("shared");
+    await explicit.loadBundle("shared");
+
+    await manager.unloadBundle("shared");
+    expect(unloadCalls).toEqual([]);
+    expect(manager.getInspectorSnapshot().activeBundles).toEqual(["shared"]);
+
+    await explicit.destroy();
+    const snapshot = manager.getInspectorSnapshot();
+
+    expect(snapshot.sessions[explicit.id]).toBeUndefined();
+    expect(snapshot.owners.scene).toBeUndefined();
+    expect(snapshot.activeBundles).toEqual([]);
+    expect(unloadCalls).toEqual(["shared"]);
+  });
 });