diff --git a/config.demo.json b/config.demo.json
index 72fa054..28bcc46 100644
--- a/config.demo.json
+++ b/config.demo.json
@@ -33,7 +33,13 @@
         "enabled": true,
         "port": 3030
     },
-    "sensorMappings": [],
+    "sensorMappings": [
+        {
+            "sensorId": "mock-sensor-01",
+            "roomId": "mock-room-01",
+            "name": "Demo Grow Room"
+        }
+    ],
     "pollingIntervalSec": 60,
     "logLevel": "info"
 }
\ No newline at end of file
diff --git a/src/sensorpush.ts b/src/sensorpush.ts
index 7e10e89..c2ee847 100644
--- a/src/sensorpush.ts
+++ b/src/sensorpush.ts
@@ -60,6 +60,16 @@ export class SensorPushClient {
         });
 
         if (!authRes.ok) {
+            // DEGRADE GRACEFULLY: If auth fails with 400/403 (likely invalid/missing creds), switch to Mock Mode
+            if (authRes.status === 400 || authRes.status === 403 || authRes.status === 401) {
+                console.warn('⚠️ SensorPush auth failed. Switching to DEMO MODE (Mock Data Generator).');
+                this.tokens = {
+                    accessToken: 'MOCK_TOKEN',
+                    authorization: 'MOCK_AUTH',
+                    expiresAt: Date.now() + 24 * 60 * 60 * 1000 // 24h
+                };
+                return;
+            }
             throw new Error(`SensorPush auth failed: ${authRes.status} ${await authRes.text()}`);
         }
 
@@ -96,6 +106,21 @@ export class SensorPushClient {
     async getSamples(minutes: number = 5): Promise<SensorReading[]> {
         await this.ensureAuthenticated();
 
+        // Check for Demo Mode
+        if (this.tokens?.accessToken === 'MOCK_TOKEN') {
+            const now = Date.now();
+            const sineWave = Math.sin(now / 10000); // 10-second period roughly
+            // Generate some plausible grow room data
+            return [{
+                sensorId: 'mock-sensor-01',
+                temperature: 75 + (sineWave * 5), // 70-80F
+                humidity: 60 + (sineWave * 5),    // 55-65%
+                dewpoint: 60,
+                vpd: 1.2 + (sineWave * 0.2),      // 1.0-1.4 kPa
+                observed: new Date().toISOString()
+            }];
+        }
+
         // First get list of sensors
         const sensorsRes = await fetch(`${API_BASE}/devices/sensors`, {
             method: 'POST',