diff --git a/internal/viessmann/client.go b/internal/viessmann/client.go
index 6d40274..bc52175 100644
--- a/internal/viessmann/client.go
+++ b/internal/viessmann/client.go
@@ -17,7 +17,7 @@ import (
 
 const (
 	tokenEndpoint = "https://iam.viessmann-climatesolutions.com/idp/v3/token"
-	apiBase       = "https://api.viessmann.com/iot/v2"
+	apiBase       = "https://api.viessmann-climatesolutions.com/iot/v2"
 )
 
 // tokenFile mirrors the JSON structure stored on disk.
diff --git a/main.go b/main.go
index e595527..df498f4 100644
--- a/main.go
+++ b/main.go
@@ -361,7 +361,7 @@ func computeWWBoost(fc *forecast.Result, cfg *config.Config) float64 {
 //
 // Returns 0 on success, 1 on any failure.
 func runViessmannTest(vc *viessmann.Client) int {
-	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	ctx, cancel := context.WithTimeout(context.Background(), 120*time.Second)
 	defer cancel()
 
 	pass := func(format string, args ...any) { fmt.Printf("  PASS  "+format+"\n", args...) }
@@ -396,15 +396,18 @@ func runViessmannTest(vc *viessmann.Client) int {
 	}
 	pass("round-trip confirmed (%.1f°C)", readback)
 
-	// Stage 3: +1°C delta — heat pump won't notice (5°C hysteresis), but API change is visible
+	// Stage 3: +1°C delta — heat pump won't notice (5°C hysteresis), but API change is visible.
+	// The Viessmann cloud queues the write to the gateway; the GET endpoint returns the last
+	// *confirmed* device value, so we wait up to 30s for the change to propagate.
 	delta := original + 1
 	step("Stage 3 — +1°C delta test (%.1f°C → %.1f°C)", original, delta)
 	if err := vc.SetDHWTemperature(ctx, delta); err != nil {
 		fail("SetDHWTemperature(%.1f): %v", delta, err)
-		// Try to restore before returning
 		_ = vc.SetDHWTemperature(ctx, original)
 		return 1
 	}
+	fmt.Println("  ...waiting 30s for cloud→gateway propagation...")
+	time.Sleep(30 * time.Second)
 	readback, err = vc.GetDHWTemperature(ctx)
 	if err != nil {
 		fail("read-back after +1°C: %v", err)
@@ -412,7 +415,7 @@ func runViessmannTest(vc *viessmann.Client) int {
 		return 1
 	}
 	if readback != delta {
-		fail("+1°C mismatch: wrote %.1f, read back %.1f", delta, readback)
+		fail("+1°C mismatch: wrote %.1f, read back %.1f after 30s — gateway may be offline or propagation takes longer", delta, readback)
 		_ = vc.SetDHWTemperature(ctx, original)
 		return 1
 	}
@@ -424,6 +427,8 @@ func runViessmannTest(vc *viessmann.Client) int {
 		fail("restore SetDHWTemperature(%.1f): %v", original, err)
 		return 1
 	}
+	fmt.Println("  ...waiting 30s for cloud→gateway propagation...")
+	time.Sleep(30 * time.Second)
 	readback, err = vc.GetDHWTemperature(ctx)
 	if err != nil {
 		fail("read-back after restore: %v", err)