diff --git a/backend/internal/handler/gateway_handler.go b/backend/internal/handler/gateway_handler.go
index d07cd57e13..02e84fdcae 100644
--- a/backend/internal/handler/gateway_handler.go
+++ b/backend/internal/handler/gateway_handler.go
@@ -1307,11 +1307,15 @@ func writeGrokModelsList(c *gin.Context, modelIDs []string) {
 		if grokModelSupportsConfigurableReasoning(modelID) {
 			item.SupportsReasoningEffort = true
 			item.ReasoningEffort = "high"
-			item.ReasoningEfforts = []grokReasoningEffortOption{
+			efforts := []grokReasoningEffortOption{
 				{Value: "low", Label: "Low"},
 				{Value: "medium", Label: "Medium"},
 				{Value: "high", Label: "High", Default: true},
 			}
+			if service.GrokSupportsXHighReasoningEffort(modelID) {
+				efforts = append(efforts, grokReasoningEffortOption{Value: "xhigh", Label: "xHigh"})
+			}
+			item.ReasoningEfforts = efforts
 		}
 		models = append(models, item)
 	}
diff --git a/backend/internal/handler/gateway_models_test.go b/backend/internal/handler/gateway_models_test.go
index 05069bf25a..8059611faa 100644
--- a/backend/internal/handler/gateway_models_test.go
+++ b/backend/internal/handler/gateway_models_test.go
@@ -364,9 +364,38 @@ func TestGatewayModels_GeminiGroupFallsBackToGeminiModels(t *testing.T) {
 }
 
 func TestGatewayModels_Grok45AdvertisesReasoningEffortForGrokBuild(t *testing.T) {
+	assertGrokGatewayReasoningEfforts(t, 4409, "grok-4.5", []gatewayReasoningEffortOptionForTest{
+		{Value: "low", Label: "Low"},
+		{Value: "medium", Label: "Medium"},
+		{Value: "high", Label: "High", Default: true},
+	})
+}
+
+func TestGatewayModels_Grok46AdvertisesXHighReasoningEffortForGrokBuild(t *testing.T) {
+	xhighEfforts := []gatewayReasoningEffortOptionForTest{
+		{Value: "low", Label: "Low"},
+		{Value: "medium", Label: "Medium"},
+		{Value: "high", Label: "High", Default: true},
+		{Value: "xhigh", Label: "xHigh"},
+	}
+	tests := []struct {
+		groupID int64
+		model   string
+	}{
+		{groupID: 4410, model: "grok-4.6"},
+		{groupID: 4411, model: "grok-4.6-latest"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.model, func(t *testing.T) {
+			assertGrokGatewayReasoningEfforts(t, tt.groupID, tt.model, xhighEfforts)
+		})
+	}
+}
+
+func assertGrokGatewayReasoningEfforts(t *testing.T, groupID int64, modelID string, want []gatewayReasoningEffortOptionForTest) {
+	t.Helper()
 	gin.SetMode(gin.TestMode)
 
-	groupID := int64(4409)
 	h := newGatewayModelsHandlerForTest(
 		&gatewayModelsAccountRepoStub{
 			byGroup: map[int64][]service.Account{
@@ -375,7 +404,7 @@ func TestGatewayModels_Grok45AdvertisesReasoningEffortForGrokBuild(t *testing.T)
 						ID:       1,
 						Platform: service.PlatformGrok,
 						Credentials: map[string]any{
-							"model_mapping": map[string]any{"grok-4.5": "grok-4.5"},
+							"model_mapping": map[string]any{modelID: modelID},
 						},
 					},
 				},
@@ -397,14 +426,10 @@ func TestGatewayModels_Grok45AdvertisesReasoningEffortForGrokBuild(t *testing.T)
 	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &got))
 	require.Len(t, got.Data, 1)
 	model := got.Data[0]
-	require.Equal(t, "grok-4.5", model.ID)
+	require.Equal(t, modelID, model.ID)
 	require.True(t, model.SupportsReasoningEffort)
 	require.Equal(t, "high", model.ReasoningEffort)
-	require.Equal(t, []gatewayReasoningEffortOptionForTest{
-		{Value: "low", Label: "Low"},
-		{Value: "medium", Label: "Medium"},
-		{Value: "high", Label: "High", Default: true},
-	}, model.ReasoningEfforts)
+	require.Equal(t, want, model.ReasoningEfforts)
 }
 
 func TestGatewayModels_GeminiGroupFiltersMappedModelsByPlatform(t *testing.T) {
diff --git a/backend/internal/service/openai_codex_models_service.go b/backend/internal/service/openai_codex_models_service.go
index 95be9ebbaf..b55549e753 100644
--- a/backend/internal/service/openai_codex_models_service.go
+++ b/backend/internal/service/openai_codex_models_service.go
@@ -477,7 +477,7 @@ func configuredCodexGrokReasoningLevels(modelID string) []configuredCodexReasoni
 		{Effort: "medium", Description: "Balanced reasoning for most coding tasks"},
 		{Effort: "high", Description: "Greater reasoning depth for coding and agent tasks"},
 	}
-	if grokSupportsXHighReasoningEffort(modelID) {
+	if GrokSupportsXHighReasoningEffort(modelID) {
 		levels = append(levels, configuredCodexReasoningLevel{
 			Effort:      "xhigh",
 			Description: "Extra-high reasoning depth for difficult tasks",
diff --git a/backend/internal/service/openai_gateway_grok.go b/backend/internal/service/openai_gateway_grok.go
index 21c7342356..a99f37ac2a 100644
--- a/backend/internal/service/openai_gateway_grok.go
+++ b/backend/internal/service/openai_gateway_grok.go
@@ -723,7 +723,7 @@ func normalizeGrokReasoningEffortValue(raw, model string) (string, bool) {
 	case "minimal":
 		return "low", true
 	case "xhigh", "extrahigh":
-		if grokSupportsXHighReasoningEffort(model) {
+		if GrokSupportsXHighReasoningEffort(model) {
 			return "xhigh", true
 		}
 		return "high", true
@@ -734,7 +734,9 @@ func normalizeGrokReasoningEffortValue(raw, model string) (string, bool) {
 	}
 }
 
-func grokSupportsXHighReasoningEffort(model string) bool {
+// GrokSupportsXHighReasoningEffort reports whether the model advertises and
+// forwards the xhigh reasoning effort (Grok 4.6 and its undated alias).
+func GrokSupportsXHighReasoningEffort(model string) bool {
 	model = strings.ToLower(xai.StripGrokProviderPrefix(strings.TrimSpace(model)))
 	return model == "grok-4.6" || model == "grok-4.6-latest"
 }