diff --git a/sdk/mod.test.ts b/sdk/mod.test.ts
index d424403..8303fc1 100644
--- a/sdk/mod.test.ts
+++ b/sdk/mod.test.ts
@@ -9,3 +9,80 @@ Deno.test("AuthSdk - initializes with config", () => {
   assertEquals(typeof sdk.validateSession, "function");
   assertEquals(typeof sdk.requireAuth, "function");
 });
+
+Deno.test("AuthSdk - Event Bus: registers, receives, and unregisters events", () => {
+  const sdk = createAuthSdk({
+    authApiUrl: "http://localhost:8000",
+    timeoutMs: 3000,
+  });
+
+  const receivedTokens: string[] = [];
+  const handler = (token: string) => {
+    receivedTokens.push(token);
+  };
+
+  sdk.on("invalidate", handler);
+
+  // Simulate Valkey push event
+  (sdk as any)._handleValkeyPush(["invalidate", ["token1", "token2"]]);
+
+  assertEquals(receivedTokens, ["token1", "token2"]);
+
+  sdk.off("invalidate", handler);
+
+  // Simulate another push event
+  (sdk as any)._handleValkeyPush(["invalidate", ["token3"]]);
+
+  // The tokens should not be added because handler was unregistered
+  assertEquals(receivedTokens, ["token1", "token2"]);
+});
+
+Deno.test("AuthSdk - Event Bus: failing async handlers do not crash bus", async () => {
+  const sdk = createAuthSdk({
+    authApiUrl: "http://localhost:8000",
+    timeoutMs: 3000,
+  });
+
+  const receivedTokens: string[] = [];
+
+  const failingHandlerAsync = async (token: string) => {
+    throw new Error(`Simulated async failure for ${token}`);
+  };
+
+  const failingHandlerSync = (token: string) => {
+    throw new Error(`Simulated sync failure for ${token}`);
+  };
+
+  const successHandler = (token: string) => {
+    receivedTokens.push(token);
+  };
+
+  sdk.on("invalidate", failingHandlerAsync);
+  sdk.on("invalidate", failingHandlerSync);
+  sdk.on("invalidate", successHandler);
+
+  // Stub console.error to avoid test noise
+  const originalConsoleError = console.error;
+  let loggedErrors = 0;
+  console.error = (...args: any[]) => {
+    const msg = args.join(" ");
+    if (msg.includes("Error in 'invalidate' listener")) {
+      loggedErrors++;
+    }
+  };
+
+  try {
+    (sdk as any)._handleValkeyPush(["invalidate", ["token4"]]);
+
+    // Give microtasks a chance to process the async rejection
+    await new Promise((resolve) => setTimeout(resolve, 0));
+
+    // The successful handler should have run despite the failures
+    assertEquals(receivedTokens, ["token4"]);
+
+    // Both the sync and async errors should have been caught and logged
+    assertEquals(loggedErrors, 2);
+  } finally {
+    console.error = originalConsoleError;
+  }
+});
diff --git a/sdk/mod.ts b/sdk/mod.ts
index a2d75c2..b3099c0 100644
--- a/sdk/mod.ts
+++ b/sdk/mod.ts
@@ -6,6 +6,16 @@ import { createClient } from "npm:@connectrpc/connect@^1.4.0";
 import { createConnectTransport } from "npm:@connectrpc/connect-node@^1.4.0";
 import { AuthService } from "./gen/auth_connect.ts";
 
+/**
+ * Supported event types for the Auth SDK.
+ */
+export type AuthSdkEvent = "invalidate";
+
+/**
+ * Handler type for invalidation events.
+ */
+export type InvalidationHandler = (token: string) => void | Promise<void>;
+
 /**
  * Configuration options for the Auth SDK.
  */
@@ -58,6 +68,7 @@ export class AuthSdk {
   private l1Cache: Map<string, SessionData>;
   private valkeyClient: Redis | null = null;
   private grpcClient: any;
+  private listeners: Map<string, Set<InvalidationHandler>> = new Map();
 
   constructor(config: AuthSdkConfig) {
     this.config = config;
@@ -84,6 +95,78 @@ export class AuthSdk {
     this.grpcClient = createClient(AuthService, transport);
   }
 
+  /**
+   * Registers a callback to be invoked when a specific event occurs.
+   *
+   * @param event The event name (e.g., "invalidate").
+   * @param handler The callback function.
+   */
+  on(event: AuthSdkEvent, handler: InvalidationHandler): void {
+    let eventListeners = this.listeners.get(event);
+    if (!eventListeners) {
+      eventListeners = new Set();
+      this.listeners.set(event, eventListeners);
+    }
+    eventListeners.add(handler);
+  }
+
+  /**
+   * Unregisters a previously registered callback.
+   *
+   * @param event The event name (e.g., "invalidate").
+   * @param handler The callback function to remove.
+   */
+  off(event: AuthSdkEvent, handler: InvalidationHandler): void {
+    const eventListeners = this.listeners.get(event);
+    if (eventListeners) {
+      eventListeners.delete(handler);
+      if (eventListeners.size === 0) {
+        this.listeners.delete(event);
+      }
+    }
+  }
+
+  /**
+   * Internal method to emit an event safely to all registered listeners.
+   */
+  private emit(event: AuthSdkEvent, token: string): void {
+    const eventListeners = this.listeners.get(event);
+    if (eventListeners) {
+      for (const handler of eventListeners) {
+        try {
+          const result = handler(token);
+          if (result instanceof Promise) {
+            result.catch((err) => {
+              console.error("[AuthSdk] Error in 'invalidate' listener:", err);
+            });
+          }
+        } catch (err) {
+          console.error("[AuthSdk] Error in 'invalidate' listener:", err);
+        }
+      }
+    }
+  }
+
+  /**
+   * Internal handler for RESP3 push invalidation messages.
+   * Exposed internally/to tests via the Valkey event listener.
+   */
+  _handleValkeyPush(msg: unknown): void {
+    if (
+      Array.isArray(msg) && msg.length >= 2 && msg[0] === "invalidate"
+    ) {
+      const keysToInvalidate = msg[1];
+      if (Array.isArray(keysToInvalidate)) {
+        for (const key of keysToInvalidate) {
+          // SIDE EFFECT: Delete the invalidated key from the local Map
+          this.l1Cache.delete(key);
+          // Emit invalidate event for real-time consumers
+          this.emit("invalidate", key);
+        }
+      }
+    }
+  }
+
   private initValkeyClient() {
     this.valkeyClient = new Redis(this.config.valkeyUrl!, {
       enableOfflineQueue: false,
@@ -102,19 +185,7 @@ export class AuthSdk {
     });
 
     // Listen for RESP3 push invalidation messages
-    this.valkeyClient.on("push", (msg: unknown) => {
-      if (
-        Array.isArray(msg) && msg.length >= 2 && msg[0] === "invalidate"
-      ) {
-        const keysToInvalidate = msg[1];
-        if (Array.isArray(keysToInvalidate)) {
-          for (const key of keysToInvalidate) {
-            // SIDE EFFECT: Delete the invalidated key from the local Map
-            this.l1Cache.delete(key);
-          }
-        }
-      }
-    });
+    this.valkeyClient.on("push", (msg: unknown) => this._handleValkeyPush(msg));
 
     this.valkeyClient.on("error", (err: unknown) => {
       console.error("Valkey SDK Client error:", err);
diff --git a/tasks/new/2026-0824.02.jul.feat.sdk.realtime-invalidation-bus-1200.md b/tasks/complete/2026-0824.02.jul.feat.sdk.realtime-invalidation-bus-1200.md
similarity index 100%
rename from tasks/new/2026-0824.02.jul.feat.sdk.realtime-invalidation-bus-1200.md
rename to tasks/complete/2026-0824.02.jul.feat.sdk.realtime-invalidation-bus-1200.md