diff --git a/Plan.md b/Plan.md
index 5dc860d..5c4d2a4 100644
--- a/Plan.md
+++ b/Plan.md
@@ -156,7 +156,7 @@ flowchart LR
   - PDB with minimum one available replica
   - Least-privilege CI deployer RBAC
 - Use the existing external PostgreSQL, Redis, and S3-compatible services through Kubernetes secrets; do not provision an in-cluster database or Redis instance.
-- Share a stable `NEXT_SERVER_ACTIONS_ENCRYPTION_KEY` across replicas and set a deployment ID from the immutable image revision to protect Server Actions and client navigation during rolling updates.
+- Share a stable `NEXT_SERVER_ACTIONS_ENCRYPTION_KEY` across replicas and set a deployment ID from the immutable image revision to protect Server Actions and client navigation during rolling updates. Notify active clients when that revision changes and offer a full reload into the new release.
 - Build immutable application and migration images in Gitea Actions, defaulting to `registry.neko-piranha.ts.net/astral/buzz-sheet`.
 - Run a versioned Drizzle migration Job before rollout. Use expand/contract migrations so the previous application image remains compatible during rolling deployment.
 - Produce deployment manifests and CI configuration but do not contact or mutate the production cluster during implementation.
diff --git a/README.md b/README.md
index d10a6fc..64f9ab8 100644
--- a/README.md
+++ b/README.md
@@ -225,6 +225,10 @@ NEXT_SERVER_ACTIONS_ENCRYPTION_KEY
 across replicas and rolling deployments. Do not place secret values in the
 ConfigMap or commit them to this repository.
 
+Every page also subscribes to `/api/active`. When a serving pod reports a newer
+deployment ID than the browser's current build, a persistent Thai notification
+offers a full reload into the new release.
+
 The base manifests contain deliberate `replace-me` image and deployment values.
 For initial bootstrap, the platform operator applies `k8s/base` through an
 environment overlay that supplies an existing immutable image revision. The
diff --git a/app/api/active/route.ts b/app/api/active/route.ts
new file mode 100644
index 0000000..c42b410
--- /dev/null
+++ b/app/api/active/route.ts
@@ -0,0 +1,16 @@
+import { connection } from "next/server";
+
+import { normalizeDeploymentId } from "@/lib/deployment/version";
+import { createEventStream, eventStreamHeaders } from "@/lib/events/sse";
+
+export async function GET(request: Request) {
+  await connection();
+  const deploymentId =
+    normalizeDeploymentId(process.env.NEXT_DEPLOYMENT_ID) ?? "development";
+  const channel = createEventStream({ signal: request.signal });
+  channel.sendNamed("deployment", deploymentId);
+
+  return new Response(channel.stream, {
+    headers: eventStreamHeaders(),
+  });
+}
diff --git a/app/layout.tsx b/app/layout.tsx
index 835ce4f..8fa794c 100644
--- a/app/layout.tsx
+++ b/app/layout.tsx
@@ -1,6 +1,7 @@
 import type { Metadata } from "next";
 import { Anuphan, Geist_Mono } from "next/font/google";
 
+import { DeploymentUpdateNotifier } from "@/components/deployment-update-notifier";
 import { Toaster } from "@/components/ui/sonner";
 import { TooltipProvider } from "@/components/ui/tooltip";
 
@@ -26,6 +27,9 @@ export const metadata: Metadata = {
 };
 
 export default function RootLayout({ children }: LayoutProps<"/">) {
+  const deploymentId =
+    process.env.NEXT_DEPLOYMENT_ID?.trim() || "development";
+
   return (
     <html
       lang="th"
@@ -34,6 +38,7 @@ export default function RootLayout({ children }: LayoutProps<"/">) {
       <body className="flex min-h-full flex-col">
         <TooltipProvider>
           {children}
+          <DeploymentUpdateNotifier deploymentId={deploymentId} />
           <Toaster position="bottom-right" />
         </TooltipProvider>
       </body>
diff --git a/components/deployment-update-notifier.tsx b/components/deployment-update-notifier.tsx
new file mode 100644
index 0000000..1584ab2
--- /dev/null
+++ b/components/deployment-update-notifier.tsx
@@ -0,0 +1,57 @@
+"use client";
+
+import { useEffect, useRef } from "react";
+import { toast } from "sonner";
+
+import {
+  hasDeploymentChanged,
+  normalizeDeploymentId,
+} from "@/lib/deployment/version";
+
+const UPDATE_TOAST_ID = "deployment-update";
+
+export function DeploymentUpdateNotifier({
+  deploymentId,
+}: {
+  deploymentId: string;
+}) {
+  const currentDeployment = useRef(normalizeDeploymentId(deploymentId));
+  const updateAvailable = useRef(false);
+
+  useEffect(() => {
+    const source = new EventSource("/api/active");
+    const receiveDeployment = (event: Event) => {
+      if (
+        updateAvailable.current ||
+        !(event instanceof MessageEvent) ||
+        typeof event.data !== "string"
+      ) {
+        return;
+      }
+
+      const nextDeployment = normalizeDeploymentId(event.data);
+      if (!hasDeploymentChanged(currentDeployment.current, nextDeployment)) {
+        return;
+      }
+
+      updateAvailable.current = true;
+      toast("มีอัปเดตใหม่พร้อมใช้งาน", {
+        id: UPDATE_TOAST_ID,
+        description: "รีโหลดเพื่ออัปเดตเป็นเวอร์ชันล่าสุด",
+        action: {
+          label: "รีโหลด",
+          onClick: () => window.location.reload(),
+        },
+        duration: Infinity,
+      });
+    };
+
+    source.addEventListener("deployment", receiveDeployment);
+    return () => {
+      source.removeEventListener("deployment", receiveDeployment);
+      source.close();
+    };
+  }, []);
+
+  return null;
+}
diff --git a/lib/deployment/version.test.ts b/lib/deployment/version.test.ts
new file mode 100644
index 0000000..0445b1c
--- /dev/null
+++ b/lib/deployment/version.test.ts
@@ -0,0 +1,20 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  hasDeploymentChanged,
+  normalizeDeploymentId,
+} from "./version";
+
+describe("deployment version comparison", () => {
+  it("normalizes identifiers before comparing them", () => {
+    expect(normalizeDeploymentId("  release-2  ")).toBe("release-2");
+    expect(normalizeDeploymentId("   ")).toBeNull();
+    expect(hasDeploymentChanged("release-1", " release-2 ")).toBe(true);
+  });
+
+  it("does not announce the initial or unchanged deployment", () => {
+    expect(hasDeploymentChanged(null, "release-2")).toBe(false);
+    expect(hasDeploymentChanged("release-2", "release-2")).toBe(false);
+    expect(hasDeploymentChanged("release-2", "")).toBe(false);
+  });
+});
diff --git a/lib/deployment/version.ts b/lib/deployment/version.ts
new file mode 100644
index 0000000..b2e4367
--- /dev/null
+++ b/lib/deployment/version.ts
@@ -0,0 +1,15 @@
+export function normalizeDeploymentId(
+  value: string | null | undefined,
+): string | null {
+  const normalized = value?.trim();
+  return normalized ? normalized : null;
+}
+
+export function hasDeploymentChanged(
+  current: string | null | undefined,
+  next: string | null | undefined,
+): boolean {
+  const currentId = normalizeDeploymentId(current);
+  const nextId = normalizeDeploymentId(next);
+  return currentId !== null && nextId !== null && currentId !== nextId;
+}
diff --git a/lib/events/sse.test.ts b/lib/events/sse.test.ts
index 6a4099b..c39ed27 100644
--- a/lib/events/sse.test.ts
+++ b/lib/events/sse.test.ts
@@ -38,10 +38,22 @@ describe("SSE stream", () => {
     expect(decoder.decode((await reader.read()).value)).toBe(
       'event: invalidation\ndata: {"type":"page.updated","id":"opaque","version":7}\n\n',
     );
+    channel.sendNamed("deployment", "release-2");
+    expect(decoder.decode((await reader.read()).value)).toBe(
+      "event: deployment\ndata: release-2\n\n",
+    );
     await vi.advanceTimersByTimeAsync(50);
     expect(decoder.decode((await reader.read()).value)).toMatch(/^: heartbeat /u);
     await vi.advanceTimersByTimeAsync(49);
     expect((await reader.read()).done).toBe(true);
     expect(onClose).toHaveBeenCalledTimes(1);
   });
+
+  it("rejects event names that could inject another SSE field", () => {
+    const channel = createEventStream();
+    expect(() => channel.sendNamed("deployment\ndata", "release-2")).toThrow(
+      "SSE event names",
+    );
+    channel.close();
+  });
 });
diff --git a/lib/events/sse.ts b/lib/events/sse.ts
index b23491c..bc6ed61 100644
--- a/lib/events/sse.ts
+++ b/lib/events/sse.ts
@@ -5,6 +5,20 @@ export const SSE_MAX_LIFETIME_MS = 30 * 60 * 1_000;
 
 const encoder = new TextEncoder();
 
+function namedEvent(eventName: string, data: string): string {
+  if (!/^[a-z0-9_-]+$/iu.test(eventName)) {
+    throw new Error(
+      "SSE event names may contain only letters, numbers, underscores, and hyphens.",
+    );
+  }
+  const lines = data
+    .replace(/\r\n?/gu, "\n")
+    .split("\n")
+    .map((line) => `data: ${line}`)
+    .join("\n");
+  return `event: ${eventName}\n${lines}\n\n`;
+}
+
 export interface EventStreamOptions {
   signal?: AbortSignal;
   heartbeatMs?: number;
@@ -15,6 +29,7 @@ export interface EventStreamOptions {
 export interface EventStreamChannel {
   stream: ReadableStream<Uint8Array>;
   send(event: InvalidationEvent): boolean;
+  sendNamed(eventName: string, data: string): boolean;
   close(): void;
 }
 
@@ -87,6 +102,9 @@ export function createEventStream(
     send(event) {
       return enqueue(`event: invalidation\ndata: ${JSON.stringify(event)}\n\n`);
     },
+    sendNamed(eventName, data) {
+      return enqueue(namedEvent(eventName, data));
+    },
     close() {
       close(true);
     },
diff --git a/tests/deployment-contract.test.ts b/tests/deployment-contract.test.ts
index 780aba7..362a337 100644
--- a/tests/deployment-contract.test.ts
+++ b/tests/deployment-contract.test.ts
@@ -110,6 +110,20 @@ describe("production deployment contract", () => {
     );
     expect(workflow).not.toMatch(/playwright|chromium/iu);
   });
+
+  it("mounts the deployment stream and offers a full reload for new releases", async () => {
+    const [layout, notifier, route] = await Promise.all([
+      repositoryFile("app/layout.tsx"),
+      repositoryFile("components/deployment-update-notifier.tsx"),
+      repositoryFile("app/api/active/route.ts"),
+    ]);
+
+    expect(layout).toContain("<DeploymentUpdateNotifier");
+    expect(notifier).toContain('new EventSource("/api/active")');
+    expect(notifier).toContain("window.location.reload()");
+    expect(notifier).toContain('label: "รีโหลด"');
+    expect(route).toContain('channel.sendNamed("deployment", deploymentId)');
+  });
 });
 
 describe("environment template contract", () => {