diff --git a/internal/client/tcp/pool_handler.go b/internal/client/tcp/pool_handler.go
index 8056ee8..ff56db0 100644
--- a/internal/client/tcp/pool_handler.go
+++ b/internal/client/tcp/pool_handler.go
@@ -117,7 +117,7 @@ func (c *PoolClient) handleHTTPStream(stream net.Conn) {
 
 	resp, err := c.httpClient.Do(outReq)
 	if err != nil {
-		httputil.WriteProxyError(cc, http.StatusBadGateway, "Local service unavailable")
+		httputil.WriteLocalServiceUnavailable(cc, c.localPort)
 		return
 	}
 	defer resp.Body.Close()
diff --git a/internal/shared/httputil/helpers.go b/internal/shared/httputil/helpers.go
index 5c92c70..d0644b7 100644
--- a/internal/shared/httputil/helpers.go
+++ b/internal/shared/httputil/helpers.go
@@ -64,6 +64,94 @@ func WriteProxyError(w io.Writer, code int, msg string) {
 	_ = resp.Body.Close()
 }
 
+func WriteLocalServiceUnavailable(w io.Writer, localPort int) {
+	html := fmt.Sprintf(`<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>502 - Local Service Unavailable</title>
+    <style>
+        * { margin: 0; padding: 0; box-sizing: border-box; }
+        body {
+            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+            background: #fff;
+            color: #24292f;
+            line-height: 1.6;
+        }
+        .container { max-width: 720px; margin: 0 auto; padding: 48px 24px; }
+        header { margin-bottom: 48px; }
+        h1 { font-size: 28px; font-weight: 600; margin-bottom: 8px; }
+        h1 span { margin-right: 8px; }
+        .desc { color: #57606a; font-size: 16px; }
+        p { margin-bottom: 16px; }
+        .info-box {
+            background: #f6f8fa;
+            border: 1px solid #d0d7de;
+            border-radius: 6px;
+            padding: 16px;
+            margin: 24px 0;
+        }
+        .info-box ul {
+            margin: 12px 0 0 20px;
+            color: #57606a;
+        }
+        .info-box li { margin-bottom: 8px; }
+        code {
+            background: #f6f8fa;
+            border: 1px solid #d0d7de;
+            border-radius: 4px;
+            padding: 2px 6px;
+            font-family: ui-monospace, SFMono-Regular, 'SF Mono', Menlo, Consolas, monospace;
+            font-size: 14px;
+        }
+        footer { margin-top: 48px; padding-top: 24px; border-top: 1px solid #d0d7de; }
+        footer a { color: #57606a; text-decoration: none; font-size: 14px; }
+        footer a:hover { color: #0969da; }
+    </style>
+</head>
+<body>
+    <div class="container">
+        <header>
+            <h1><span>⚠️</span>Local Service Unavailable</h1>
+            <p class="desc">The tunnel is active, but the local service is not responding.</p>
+        </header>
+
+        <div class="info-box">
+            <p>This could happen because:</p>
+            <ul>
+                <li>No service is running on port <code>%d</code></li>
+                <li>The local service has crashed or stopped</li>
+                <li>The service is still starting up</li>
+            </ul>
+        </div>
+
+        <p>Please ensure your local service is running on port <code>%d</code> and try again.</p>
+
+        <footer>
+            <a href="https://github.com/Gouryella/drip" target="_blank">GitHub</a>
+        </footer>
+    </div>
+</body>
+</html>`, localPort, localPort)
+
+	resp := &http.Response{
+		StatusCode:    http.StatusBadGateway,
+		Status:        "502 Bad Gateway",
+		Proto:         "HTTP/1.1",
+		ProtoMajor:    1,
+		ProtoMinor:    1,
+		Header:        make(http.Header),
+		Body:          io.NopCloser(strings.NewReader(html)),
+		ContentLength: int64(len(html)),
+		Close:         true,
+	}
+	resp.Header.Set("Content-Type", "text/html; charset=utf-8")
+	resp.Header.Set("Content-Length", fmt.Sprintf("%d", len(html)))
+	_ = resp.Write(w)
+	_ = resp.Body.Close()
+}
+
 // IsWebSocketUpgrade checks if the request is a WebSocket upgrade request.
 func IsWebSocketUpgrade(req *http.Request) bool {
 	return strings.EqualFold(req.Header.Get("Upgrade"), "websocket") &&
