diff --git a/apps/client/src/lightweight/messaging_provider.ts b/apps/client/src/lightweight/messaging_provider.ts
new file mode 100644
index 000000000..28b72c964
--- /dev/null
+++ b/apps/client/src/lightweight/messaging_provider.ts
@@ -0,0 +1,92 @@
+import type { WebSocketMessage } from "@triliumnext/commons";
+import type { MessagingProvider, MessageHandler } from "@triliumnext/core";
+
+/**
+ * Messaging provider for browser Worker environments.
+ * 
+ * This provider uses the Worker's postMessage API to communicate
+ * with the main thread. It's designed to be used inside a Web Worker
+ * that runs the core services.
+ * 
+ * Message flow:
+ * - Outbound (worker → main): Uses self.postMessage() with type: "WS_MESSAGE"
+ * - Inbound (main → worker): Listens to onmessage for type: "WS_MESSAGE"
+ */
+export default class WorkerMessagingProvider implements MessagingProvider {
+    private messageHandlers: MessageHandler[] = [];
+    private isDisposed = false;
+
+    constructor() {
+        // Listen for incoming messages from the main thread
+        self.addEventListener("message", this.handleIncomingMessage);
+        console.log("[WorkerMessagingProvider] Initialized");
+    }
+
+    private handleIncomingMessage = (event: MessageEvent) => {
+        if (this.isDisposed) return;
+        
+        const { type, message } = event.data || {};
+        
+        if (type === "WS_MESSAGE" && message) {
+            // Dispatch to all registered handlers
+            for (const handler of this.messageHandlers) {
+                try {
+                    handler(message as WebSocketMessage);
+                } catch (e) {
+                    console.error("[WorkerMessagingProvider] Error in message handler:", e);
+                }
+            }
+        }
+    };
+
+    /**
+     * Send a message to all clients (in this case, the main thread).
+     * The main thread is responsible for further distribution if needed.
+     */
+    sendMessageToAllClients(message: WebSocketMessage): void {
+        if (this.isDisposed) {
+            console.warn("[WorkerMessagingProvider] Cannot send message - provider is disposed");
+            return;
+        }
+
+        try {
+            self.postMessage({
+                type: "WS_MESSAGE",
+                message
+            });
+        } catch (e) {
+            console.error("[WorkerMessagingProvider] Error sending message:", e);
+        }
+    }
+
+    /**
+     * Subscribe to incoming messages from the main thread.
+     */
+    onMessage(handler: MessageHandler): () => void {
+        this.messageHandlers.push(handler);
+        
+        return () => {
+            this.messageHandlers = this.messageHandlers.filter(h => h !== handler);
+        };
+    }
+
+    /**
+     * Get the number of connected "clients".
+     * In worker context, there's always exactly 1 client (the main thread).
+     */
+    getClientCount(): number {
+        return this.isDisposed ? 0 : 1;
+    }
+
+    /**
+     * Clean up resources.
+     */
+    dispose(): void {
+        if (this.isDisposed) return;
+        
+        this.isDisposed = true;
+        self.removeEventListener("message", this.handleIncomingMessage);
+        this.messageHandlers = [];
+        console.log("[WorkerMessagingProvider] Disposed");
+    }
+}
diff --git a/apps/client/src/local-server-worker.ts b/apps/client/src/local-server-worker.ts
index 536e2a0f0..9d9a9df23 100644
--- a/apps/client/src/local-server-worker.ts
+++ b/apps/client/src/local-server-worker.ts
@@ -5,6 +5,7 @@
 import BrowserExecutionContext from './lightweight/cls_provider';
 import BrowserCryptoProvider from './lightweight/crypto_provider';
 import BrowserSqlProvider from './lightweight/sql_provider';
+import WorkerMessagingProvider from './lightweight/messaging_provider';
 import { BrowserRouter } from './lightweight/browser_router';
 import { createConfiguredRouter } from './lightweight/browser_routes';
 
@@ -50,6 +51,9 @@ console.log("[Worker] Error handlers installed");
 // Shared SQL provider instance
 const sqlProvider = new BrowserSqlProvider();
 
+// Messaging provider for worker-to-main-thread communication
+const messagingProvider = new WorkerMessagingProvider();
+
 // Core module, router, and initialization state
 let coreModule: typeof import("@triliumnext/core") | null = null;
 let router: BrowserRouter | null = null;
@@ -100,6 +104,7 @@ async function initialize(): Promise<void> {
             coreModule.initializeCore({
                 executionContext: new BrowserExecutionContext(),
                 crypto: new BrowserCryptoProvider(),
+                messaging: messagingProvider,
                 dbConfig: {
                     provider: sqlProvider,
                     isReadOnly: false,
diff --git a/packages/trilium-core/src/index.ts b/packages/trilium-core/src/index.ts
index 561b6d8d3..3da24fa87 100644
--- a/packages/trilium-core/src/index.ts
+++ b/packages/trilium-core/src/index.ts
@@ -3,6 +3,7 @@ import { CryptoProvider, initCrypto } from "./services/encryption/crypto";
 import { getLog, initLog } from "./services/log";
 import { initSql } from "./services/sql/index";
 import { SqlService, SqlServiceParams } from "./services/sql/sql";
+import { initMessaging, MessagingProvider } from "./services/messaging/index";
 
 export type * from "./services/sql/types";
 export * from "./services/sql/index";
@@ -34,6 +35,10 @@ export { default as TaskContext } from "./services/task_context";
 export { default as revisions } from "./services/revisions";
 export { default as erase } from "./services/erase";
 
+// Messaging system
+export * from "./services/messaging/index";
+export type { MessagingProvider, ServerMessagingProvider, MessageClient, MessageHandler } from "./services/messaging/types";
+
 export { default as becca } from "./becca/becca";
 export { default as becca_loader } from "./becca/becca_loader";
 export { default as becca_service } from "./becca/becca_service";
@@ -58,13 +63,17 @@ export type { NoteParams } from "./services/notes";
 export * as sanitize from "./services/sanitizer";
 export * as routes from "./routes";
 
-export function initializeCore({ dbConfig, executionContext, crypto }: {
+export function initializeCore({ dbConfig, executionContext, crypto, messaging }: {
     dbConfig: SqlServiceParams,
     executionContext: ExecutionContext,
-    crypto: CryptoProvider
+    crypto: CryptoProvider,
+    messaging?: MessagingProvider
 }) {
     initLog();
     initCrypto(crypto);
     initSql(new SqlService(dbConfig, getLog()));
     initContext(executionContext);
+    if (messaging) {
+        initMessaging(messaging);
+    }
 };
diff --git a/packages/trilium-core/src/services/messaging/index.ts b/packages/trilium-core/src/services/messaging/index.ts
new file mode 100644
index 000000000..1fb303676
--- /dev/null
+++ b/packages/trilium-core/src/services/messaging/index.ts
@@ -0,0 +1,46 @@
+import type { WebSocketMessage } from "@triliumnext/commons";
+import type { MessagingProvider } from "./types.js";
+
+let messagingProvider: MessagingProvider | null = null;
+
+/**
+ * Initialize the messaging system with a provider.
+ * This should be called during application startup.
+ */
+export function initMessaging(provider: MessagingProvider): void {
+    messagingProvider = provider;
+}
+
+/**
+ * Get the current messaging provider.
+ * Throws if messaging hasn't been initialized.
+ */
+export function getMessagingProvider(): MessagingProvider {
+    if (!messagingProvider) {
+        throw new Error("Messaging provider not initialized. Call initMessaging() first.");
+    }
+    return messagingProvider;
+}
+
+/**
+ * Check if messaging has been initialized.
+ */
+export function isMessagingInitialized(): boolean {
+    return messagingProvider !== null;
+}
+
+/**
+ * Send a message to all connected clients.
+ * This is a convenience function that uses the current provider.
+ */
+export function sendMessageToAllClients(message: WebSocketMessage): void {
+    if (!messagingProvider) {
+        // Silently ignore if no provider - allows core to work without messaging
+        console.debug("[Messaging] No provider initialized, message not sent:", message.type);
+        return;
+    }
+    messagingProvider.sendMessageToAllClients(message);
+}
+
+// Re-export types
+export * from "./types.js";
diff --git a/packages/trilium-core/src/services/messaging/types.ts b/packages/trilium-core/src/services/messaging/types.ts
new file mode 100644
index 000000000..ae02ae061
--- /dev/null
+++ b/packages/trilium-core/src/services/messaging/types.ts
@@ -0,0 +1,97 @@
+import type { EntityChange, WebSocketMessage } from "@triliumnext/commons";
+
+/**
+ * Handler function for incoming messages from clients.
+ */
+export type MessageHandler = (message: WebSocketMessage) => void | Promise<void>;
+
+/**
+ * Represents a connected client that can receive messages.
+ */
+export interface MessageClient {
+    /** Unique identifier for this client */
+    readonly id: string;
+    /** Send a message to this specific client */
+    send(message: WebSocketMessage): void;
+    /** Check if the client is still connected */
+    isConnected(): boolean;
+}
+
+/**
+ * Provider interface for server-to-client messaging.
+ * 
+ * This abstraction allows different transport mechanisms:
+ * - WebSocket for traditional server environments
+ * - Worker postMessage for browser environments
+ * - Mock implementations for testing
+ */
+export interface MessagingProvider {
+    /**
+     * Send a message to all connected clients.
+     * This is the primary method used by core services like TaskContext.
+     */
+    sendMessageToAllClients(message: WebSocketMessage): void;
+
+    /**
+     * Send a message to a specific client by ID.
+     * Returns false if the client is not found or disconnected.
+     */
+    sendMessageToClient?(clientId: string, message: WebSocketMessage): boolean;
+
+    /**
+     * Subscribe to incoming messages from clients.
+     * Returns an unsubscribe function.
+     */
+    onMessage?(handler: MessageHandler): () => void;
+
+    /**
+     * Get the number of connected clients.
+     */
+    getClientCount?(): number;
+
+    /**
+     * Called when the provider should clean up resources.
+     */
+    dispose?(): void;
+}
+
+/**
+ * Extended interface for server-side messaging with entity change support.
+ * This is used by the WebSocket implementation to handle entity sync.
+ */
+export interface ServerMessagingProvider extends MessagingProvider {
+    /**
+     * Send entity changes to all clients (for frontend-update messages).
+     */
+    sendEntityChangesToAllClients(entityChanges: EntityChange[]): void;
+
+    /**
+     * Set the last synced push ID for sync status messages.
+     */
+    setLastSyncedPush(entityChangeId: number): void;
+
+    /**
+     * Notify clients that sync pull is in progress.
+     */
+    syncPullInProgress(): void;
+
+    /**
+     * Notify clients that sync push is in progress.
+     */
+    syncPushInProgress(): void;
+
+    /**
+     * Notify clients that sync has finished.
+     */
+    syncFinished(): void;
+
+    /**
+     * Notify clients that sync has failed.
+     */
+    syncFailed(): void;
+
+    /**
+     * Request all clients to reload their frontend.
+     */
+    reloadFrontend(reason: string): void;
+}
diff --git a/packages/trilium-core/src/services/ws.ts b/packages/trilium-core/src/services/ws.ts
index 95a41ee20..9e390a03e 100644
--- a/packages/trilium-core/src/services/ws.ts
+++ b/packages/trilium-core/src/services/ws.ts
@@ -1,5 +1,20 @@
+import type { WebSocketMessage } from "@triliumnext/commons";
+import { sendMessageToAllClients as sendMessage } from "./messaging/index.js";
+
+/**
+ * WebSocket service abstraction for core.
+ * 
+ * This module provides a simple interface for sending messages to clients.
+ * The actual transport mechanism is provided by the messaging provider
+ * configured during initialization.
+ * 
+ * @deprecated Use the messaging module directly instead.
+ */
 export default {
-    sendMessageToAllClients(message: object) {
-        console.warn("Ignored ws", message);
+    /**
+     * Send a message to all connected clients.
+     */
+    sendMessageToAllClients(message: WebSocketMessage) {
+        sendMessage(message);
     }
 }