diff --git a/js/src/anisette.ts b/js/src/anisette.ts
index c4dd264..0842904 100644
--- a/js/src/anisette.ts
+++ b/js/src/anisette.ts
@@ -149,10 +149,12 @@ export class Anisette {
   async provision(): Promise<void> {
     await this.provisioning.provision(this.dsid);
     // Sync provisioning state to IndexedDB (browser only)
-    try {
-      await this.bridge.syncIdbfsToStorage();
-    } catch {
-      // Ignore errors in Node.js or if IDBFS unavailable
+    if (this.bridge.isIdbfsAvailable()) {
+      try {
+        await this.bridge.syncIdbfsToStorage();
+      } catch (err) {
+        console.error("[anisette] Failed to sync to IDBFS:", err);
+      }
     }
   }
 
@@ -171,11 +173,15 @@ export class Anisette {
     const deviceJsonBytes = encodeUtf8(JSON.stringify(this.device.toJson(), null, 2));
 
     this.bridge = new WasmBridge(this.wasmModule);
-    mountIdbfsPaths(this.bridge, this.libraryPath, this.provisioningPath);
-    try {
-      await this.bridge.syncIdbfsFromStorage();
-    } catch {
-      // Ignore errors - might be first run or Node.js
+
+    // Mount + load persisted IDBFS in browser environment
+    if (this.bridge.isIdbfsAvailable()) {
+      mountIdbfsPaths(this.bridge, this.libraryPath, this.provisioningPath);
+      try {
+        await this.bridge.syncIdbfsFromStorage();
+      } catch {
+        // Ignore errors - might be first run or no existing data
+      }
     }
 
     if (adiPb) {
diff --git a/js/src/wasm-bridge.ts b/js/src/wasm-bridge.ts
index ec50d09..a83456b 100644
--- a/js/src/wasm-bridge.ts
+++ b/js/src/wasm-bridge.ts
@@ -216,13 +216,24 @@ export class WasmBridge {
     };
   }
 
+  /**
+   * Check if IDBFS is available (browser environment only).
+   */
+  isIdbfsAvailable(): boolean {
+    try {
+      return !!(this.m.FS && this.m.FS.filesystems?.IDBFS);
+    } catch {
+      return false;
+    }
+  }
+
   /**
    * Initialize IDBFS for browser persistence.
    * Only works in browser environments with IDBFS available.
    */
   initIdbfs(path: string): void {
     // Check if FS and IDBFS are available (browser only)
-    if (!this.m.FS || !this.m.FS.filesystems?.IDBFS) {
+    if (!this.isIdbfsAvailable()) {
       return; // Node.js or environment without IDBFS
     }
 
@@ -248,10 +259,11 @@ export class WasmBridge {
   /**
    * Sync IDBFS from IndexedDB to memory (async).
    * Must be called after initIdbfs to load existing data from IndexedDB.
+   * Only works in browser environments with IDBFS available.
    */
   async syncIdbfsFromStorage(): Promise<void> {
-    if (!this.m.FS) {
-      return; // FS not available
+    if (!this.isIdbfsAvailable()) {
+      return; // IDBFS not available, skip silently
     }
 
     return new Promise((resolve, reject) => {
@@ -269,10 +281,11 @@ export class WasmBridge {
   /**
    * Sync IDBFS from memory to IndexedDB (async).
    * Must be called after modifying files to persist them.
+   * Only works in browser environments with IDBFS available.
    */
   async syncIdbfsToStorage(): Promise<void> {
-    if (!this.m.FS) {
-      return; // FS not available
+    if (!this.isIdbfsAvailable()) {
+      return; // IDBFS not available, skip silently
     }
 
     return new Promise((resolve, reject) => {