diff --git a/apps/web/src/components/ChatView.tsx b/apps/web/src/components/ChatView.tsx
index 9bc4010b4b..ed8d8d6cac 100644
--- a/apps/web/src/components/ChatView.tsx
+++ b/apps/web/src/components/ChatView.tsx
@@ -162,6 +162,7 @@ import {
   renderProviderTraitsMenuContent,
   renderProviderTraitsPicker,
 } from "./chat/composerProviderRegistry";
+import { ConnectionStatusBanner } from "./chat/ConnectionStatusBanner";
 import { ProviderHealthBanner } from "./chat/ProviderHealthBanner";
 import { ThreadErrorBanner } from "./chat/ThreadErrorBanner";
 import {
@@ -3496,6 +3497,7 @@ export default function ChatView({ threadId }: ChatViewProps) {
       </header>
 
       {/* Error banner */}
+      <ConnectionStatusBanner />
       <ProviderHealthBanner status={activeProviderStatus} />
       <ThreadErrorBanner
         error={activeThread.error}
diff --git a/apps/web/src/components/chat/ConnectionStatusBanner.test.tsx b/apps/web/src/components/chat/ConnectionStatusBanner.test.tsx
new file mode 100644
index 0000000000..78f30ddf63
--- /dev/null
+++ b/apps/web/src/components/chat/ConnectionStatusBanner.test.tsx
@@ -0,0 +1,58 @@
+import { renderToStaticMarkup } from "react-dom/server";
+import { describe, expect, it, vi, beforeAll } from "vitest";
+import { ConnectionStatusBanner } from "./ConnectionStatusBanner";
+
+// Mock wsNativeApi
+vi.mock("../../wsNativeApi", () => {
+  return {
+    onTransportStateChange: vi.fn(() => {
+      return () => {};
+    }),
+  };
+});
+
+describe("ConnectionStatusBanner", () => {
+  beforeAll(() => {
+    vi.stubGlobal("navigator", {
+      onLine: true,
+    });
+  });
+
+  it("renders nothing when online and transport is open", () => {
+    const markup = renderToStaticMarkup(
+      <ConnectionStatusBanner initialIsOnline={true} initialTransportState="open" />,
+    );
+    expect(markup).toBe("");
+  });
+
+  it("renders offline message when initialIsOnline is false", async () => {
+    const markup = renderToStaticMarkup(
+      <ConnectionStatusBanner initialIsOnline={false} initialTransportState="open" />,
+    );
+    expect(markup).toContain("No internet connection");
+    expect(markup).toContain("T3 Code is offline");
+  });
+
+  it("renders disconnected message when initialTransportState is closed", async () => {
+    const markup = renderToStaticMarkup(
+      <ConnectionStatusBanner initialIsOnline={true} initialTransportState="closed" />,
+    );
+    expect(markup).toContain("Disconnected from server");
+    expect(markup).toContain("connection to the T3 Code server was lost");
+  });
+
+  it("renders reconnecting message when initialTransportState is reconnecting", async () => {
+    const markup = renderToStaticMarkup(
+      <ConnectionStatusBanner initialIsOnline={true} initialTransportState="reconnecting" />,
+    );
+    expect(markup).toContain("Disconnected from server");
+    expect(markup).toContain("Attempting to reconnect");
+  });
+
+  it("renders nothing when transport is disposed", () => {
+    const markup = renderToStaticMarkup(
+      <ConnectionStatusBanner initialIsOnline={true} initialTransportState="disposed" />,
+    );
+    expect(markup).toBe("");
+  });
+});
diff --git a/apps/web/src/components/chat/ConnectionStatusBanner.tsx b/apps/web/src/components/chat/ConnectionStatusBanner.tsx
new file mode 100644
index 0000000000..cdd159fe1a
--- /dev/null
+++ b/apps/web/src/components/chat/ConnectionStatusBanner.tsx
@@ -0,0 +1,62 @@
+import { memo, useEffect, useState } from "react";
+import { onTransportStateChange, type TransportState } from "../../wsNativeApi";
+import { Alert, AlertDescription, AlertTitle } from "../ui/alert";
+import { WifiOffIcon, CloudOffIcon } from "lucide-react";
+
+export const ConnectionStatusBanner = memo(function ConnectionStatusBanner({
+  initialIsOnline,
+  initialTransportState,
+}: {
+  initialIsOnline?: boolean;
+  initialTransportState?: TransportState;
+}) {
+  const [isOnline, setIsOnline] = useState(
+    initialIsOnline ?? (typeof navigator !== "undefined" ? navigator.onLine : true),
+  );
+  const [transportState, setTransportState] = useState<TransportState>(
+    initialTransportState ?? "open",
+  );
+
+  useEffect(() => {
+    const handleOnline = () => setIsOnline(true);
+    const handleOffline = () => setIsOnline(false);
+
+    window.addEventListener("online", handleOnline);
+    window.addEventListener("offline", handleOffline);
+
+    const unsub = onTransportStateChange((state) => {
+      setTransportState(state);
+    });
+
+    return () => {
+      window.removeEventListener("online", handleOnline);
+      window.removeEventListener("offline", handleOffline);
+      unsub();
+    };
+  }, []);
+
+  const shouldShow =
+    !isOnline ||
+    (transportState !== "open" && transportState !== "connecting" && transportState !== "disposed");
+
+  if (!shouldShow) {
+    return null;
+  }
+
+  const title = !isOnline ? "No internet connection" : "Disconnected from server";
+  const message = !isOnline
+    ? "T3 Code is offline. Please check your internet connection."
+    : transportState === "reconnecting"
+      ? "Attempting to reconnect to the T3 Code server..."
+      : "The connection to the T3 Code server was lost.";
+
+  return (
+    <div className="pt-3 mx-auto max-w-3xl">
+      <Alert variant="warning">
+        {!isOnline ? <WifiOffIcon className="size-4" /> : <CloudOffIcon className="size-4" />}
+        <AlertTitle>{title}</AlertTitle>
+        <AlertDescription>{message}</AlertDescription>
+      </Alert>
+    </div>
+  );
+});
diff --git a/apps/web/src/wsNativeApi.ts b/apps/web/src/wsNativeApi.ts
index 042875f6f7..421edf6048 100644
--- a/apps/web/src/wsNativeApi.ts
+++ b/apps/web/src/wsNativeApi.ts
@@ -11,7 +11,8 @@ import {
 } from "@t3tools/contracts";
 
 import { showContextMenuFallback } from "./contextMenuFallback";
-import { WsTransport } from "./wsTransport";
+import { WsTransport, type TransportState } from "./wsTransport";
+export type { TransportState };
 
 let instance: { api: NativeApi; transport: WsTransport } | null = null;
 const welcomeListeners = new Set<(payload: WsWelcomePayload) => void>();
@@ -64,6 +65,17 @@ export function onServerConfigUpdated(
   };
 }
 
+/**
+ * Subscribe to WebSocket transport state changes.
+ */
+export function onTransportStateChange(listener: (state: TransportState) => void): () => void {
+  if (!instance) {
+    // Force instance creation if it doesn't exist
+    createWsNativeApi();
+  }
+  return instance!.transport.onStateChange(listener);
+}
+
 export function createWsNativeApi(): NativeApi {
   if (instance) return instance.api;
 
diff --git a/apps/web/src/wsTransport.ts b/apps/web/src/wsTransport.ts
index 12c9a6d958..445ce7eaa5 100644
--- a/apps/web/src/wsTransport.ts
+++ b/apps/web/src/wsTransport.ts
@@ -25,7 +25,7 @@ interface RequestOptions {
   readonly timeoutMs?: number | null;
 }
 
-type TransportState = "connecting" | "open" | "reconnecting" | "closed" | "disposed";
+export type TransportState = "connecting" | "open" | "reconnecting" | "closed" | "disposed";
 
 const REQUEST_TIMEOUT_MS = 60_000;
 const RECONNECT_DELAYS_MS = [500, 1_000, 2_000, 4_000, 8_000];
@@ -55,6 +55,7 @@ export class WsTransport {
   private nextId = 1;
   private readonly pending = new Map<string, PendingRequest>();
   private readonly listeners = new Map<string, Set<(message: WsPush) => void>>();
+  private readonly stateListeners = new Set<(state: TransportState) => void>();
   private readonly latestPushByChannel = new Map<string, WsPush>();
   private readonly outboundQueue: string[] = [];
   private reconnectAttempt = 0;
@@ -76,6 +77,26 @@ export class WsTransport {
     this.connect();
   }
 
+  onStateChange(listener: (state: TransportState) => void): () => void {
+    listener(this.state);
+    this.stateListeners.add(listener);
+    return () => {
+      this.stateListeners.delete(listener);
+    };
+  }
+
+  private setState(next: TransportState) {
+    if (this.state === next) return;
+    this.state = next;
+    for (const listener of this.stateListeners) {
+      try {
+        listener(next);
+      } catch {
+        // Swallow listener errors
+      }
+    }
+  }
+
   async request<T = unknown>(
     method: string,
     params?: unknown,
@@ -152,7 +173,7 @@ export class WsTransport {
 
   dispose() {
     this.disposed = true;
-    this.state = "disposed";
+    this.setState("disposed");
     if (this.reconnectTimer !== null) {
       clearTimeout(this.reconnectTimer);
       this.reconnectTimer = null;
@@ -174,12 +195,12 @@ export class WsTransport {
       return;
     }
 
-    this.state = this.reconnectAttempt > 0 ? "reconnecting" : "connecting";
+    this.setState(this.reconnectAttempt > 0 ? "reconnecting" : "connecting");
     const ws = new WebSocket(this.url);
 
     ws.addEventListener("open", () => {
       this.ws = ws;
-      this.state = "open";
+      this.setState("open");
       this.reconnectAttempt = 0;
       this.flushQueue();
     });
@@ -201,10 +222,10 @@ export class WsTransport {
         }
       }
       if (this.disposed) {
-        this.state = "disposed";
+        this.setState("disposed");
         return;
       }
-      this.state = "closed";
+      this.setState("closed");
       this.scheduleReconnect();
     });