fix grok chat usage guard parity

backend/internal/service/openai_gateway_chat_completions.go

@@ -460,20 +460,14 @@ func (s *OpenAIGatewayService) handleChatBufferedStreamingResponse(
 		return nil, fmt.Errorf("upstream response failed: %s", message)
 	}
 
+	if requiresBillableGrokChatUsage(account, billingModel, upstreamModel, finalResponse.Model) && !hasBillableGrokChatUsage(usage) {
+		upstreamRequestID := firstNonEmpty(requestID, resp.Header.Get("xai-request-id"))
+		return nil, newGrokMissingUsageFailoverError(c, account, upstreamRequestID)
+	}
+
 	// When the terminal event has an empty output array, reconstruct from
 	// accumulated delta events so the client receives the full content.
 	acc.SupplementResponseOutput(finalResponse)
-	if requiresBillableGrokChatUsage(account, originalModel, billingModel, upstreamModel, finalResponse.Model) && !hasBillableOpenAIUsage(usage) {
-		return nil, s.newOpenAIStreamFailoverError(
-			c,
-			account,
-			false,
-			firstNonEmpty(requestID, resp.Header.Get("xai-request-id")),
-			nil,
-			grokMissingUsageMessage,
-			resp.Header,
-		)
-	}
 
 	chatResp := apicompat.ResponsesToChatCompletions(finalResponse, originalModel)
 

backend/internal/service/openai_gateway_chat_completions_raw.go

@@ -432,16 +432,9 @@ func (s *OpenAIGatewayService) bufferRawChatCompletions(
 		usage = parsedUsage
 	}
 	responseModel := gjson.GetBytes(respBody, "model").String()
-	if requiresBillableGrokChatUsage(account, originalModel, billingModel, upstreamModel, responseModel) && !hasBillableOpenAIUsage(usage) {
-		return nil, s.newOpenAIStreamFailoverError(
-			c,
-			account,
-			false,
-			firstNonEmpty(requestID, resp.Header.Get("xai-request-id")),
-			nil,
-			grokMissingUsageMessage,
-			resp.Header,
-		)
+	if requiresBillableGrokChatUsage(account, billingModel, upstreamModel, responseModel) && !hasBillableGrokChatUsage(usage) {
+		upstreamRequestID := firstNonEmpty(requestID, resp.Header.Get("xai-request-id"))
+		return nil, newGrokMissingUsageFailoverError(c, account, upstreamRequestID)
 	}
 
 	if s.responseHeaderFilter != nil {

backend/internal/service/openai_gateway_chat_completions_raw_test.go

@@ -158,6 +158,92 @@ func TestForwardAsChatCompletions_OpenAICompatibleGrokRawMissingUsageFailsBefore
 	require.Empty(t, recorder.Body.String())
 }
 
+func TestForwardAsChatCompletions_OpenAICompatibleRawUsageGuard(t *testing.T) {
+	tests := []struct {
+		name             string
+		model            string
+		upstreamResponse string
+		modelMapping     map[string]any
+		wantGuarded      bool
+	}{
+		{
+			name:             "Grok response without usage",
+			model:            "grok-4.5",
+			upstreamResponse: `{"id":"resp_missing","object":"chat.completion","model":"grok-4.5","choices":[{"index":0,"message":{"role":"assistant","content":"hello"},"finish_reason":"stop"}]}`,
+			wantGuarded:      true,
+		},
+		{
+			name:             "namespaced Grok response without usage",
+			model:            "x-ai/grok-4.5",
+			upstreamResponse: `{"id":"resp_namespaced","object":"chat.completion","model":"x-ai/grok-4.5","choices":[{"index":0,"message":{"role":"assistant","content":"hello"},"finish_reason":"stop"}]}`,
+			wantGuarded:      true,
+		},
+		{
+			name:             "Grok response with aggregate usage passes",
+			model:            "grok-4.5",
+			upstreamResponse: `{"id":"resp_usage","object":"chat.completion","model":"grok-4.5","choices":[{"index":0,"message":{"role":"assistant","content":"hello"},"finish_reason":"stop"}],"usage":{"prompt_tokens":9,"completion_tokens":3,"total_tokens":12}}`,
+			wantGuarded:      false,
+		},
+		{
+			name:             "Grok alias mapped to non-Grok remains unchanged",
+			model:            "grok-alias",
+			upstreamResponse: `{"id":"resp_mapped","object":"chat.completion","model":"gpt-5.4","choices":[{"index":0,"message":{"role":"assistant","content":"hello"},"finish_reason":"stop"}]}`,
+			modelMapping:     map[string]any{"grok-alias": "gpt-5.4"},
+			wantGuarded:      false,
+		},
+		{
+			name:             "Grok response with detail-only usage",
+			model:            "grok-4.5",
+			upstreamResponse: `{"id":"resp_detail_only","object":"chat.completion","model":"grok-4.5","choices":[{"index":0,"message":{"role":"assistant","content":"hello"},"finish_reason":"stop"}],"usage":{"input_tokens_details":{"text_tokens":9,"image_tokens":2},"output_tokens_details":{"image_tokens":1}}}`,
+			wantGuarded:      true,
+		},
+		{
+			name:             "non-Grok response without usage remains unchanged",
+			model:            "gpt-5.4",
+			upstreamResponse: `{"id":"resp_openai","object":"chat.completion","model":"gpt-5.4","choices":[{"index":0,"message":{"role":"assistant","content":"hello"},"finish_reason":"stop"}]}`,
+			wantGuarded:      false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gin.SetMode(gin.TestMode)
+			body := []byte(`{"model":"` + tt.model + `","messages":[{"role":"user","content":"hello"}],"stream":false}`)
+			recorder := httptest.NewRecorder()
+			c, _ := gin.CreateTestContext(recorder)
+			c.Request = httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(body))
+
+			upstream := &httpUpstreamRecorder{resp: &http.Response{
+				StatusCode: http.StatusOK,
+				Header:     http.Header{"Content-Type": []string{"application/json"}, "X-Request-Id": []string{"rid-openai-compatible"}},
+				Body:       io.NopCloser(strings.NewReader(tt.upstreamResponse)),
+			}}
+			svc := &OpenAIGatewayService{cfg: rawChatCompletionsTestConfig(), httpUpstream: upstream}
+			account := rawChatCompletionsTestAccount()
+			account.Name = "openai-compatible"
+			account.Extra = map[string]any{openai_compat.ExtraKeyResponsesSupported: false}
+			if tt.modelMapping != nil {
+				account.Credentials["model_mapping"] = tt.modelMapping
+			}
+
+			result, err := svc.ForwardAsChatCompletions(context.Background(), c, account, body, "", "")
+
+			if !tt.wantGuarded {
+				require.NoError(t, err)
+				require.NotNil(t, result)
+				require.True(t, c.Writer.Written())
+				return
+			}
+			require.Nil(t, result)
+			var failoverErr *UpstreamFailoverError
+			require.ErrorAs(t, err, &failoverErr)
+			require.Equal(t, http.StatusBadGateway, failoverErr.StatusCode)
+			require.Equal(t, "grok_missing_usage", gjson.GetBytes(failoverErr.ResponseBody, "error.code").String())
+			require.False(t, c.Writer.Written(), "unbilled Grok content must not be returned")
+		})
+	}
+}
+
 func TestForwardAsRawChatCompletions_PreservesMappedGPT56MaxEffort(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 

backend/internal/service/openai_gateway_grok_chat_bridge_test.go

@@ -308,6 +308,8 @@ func TestForwardGrokChatViaResponsesNonStreamingRejectsCompletedResponseWithoutU
 	require.Nil(t, result)
 	var failoverErr *UpstreamFailoverError
 	require.ErrorAs(t, err, &failoverErr)
+	require.Equal(t, http.StatusBadGateway, failoverErr.StatusCode)
+	require.Equal(t, grokMissingUsageErrorCode, gjson.GetBytes(failoverErr.ResponseBody, "error.code").String())
 	require.False(t, c.Writer.Written(), "an unbillable response must not be committed to the client")
 	require.Empty(t, recorder.Body.String())
 }

backend/internal/service/openai_gateway_grok_test.go

@@ -1968,6 +1968,8 @@ func TestForwardAsChatCompletionsForGrokAPIKeyRejectsNonStreamingResponseWithout
 	require.Nil(t, result)
 	var failoverErr *UpstreamFailoverError
 	require.ErrorAs(t, err, &failoverErr)
+	require.Equal(t, http.StatusBadGateway, failoverErr.StatusCode)
+	require.Equal(t, grokMissingUsageErrorCode, gjson.GetBytes(failoverErr.ResponseBody, "error.code").String())
 	require.False(t, c.Writer.Written(), "an unbillable response must not be committed to the client")
 	require.Empty(t, recorder.Body.String())
 }

backend/internal/service/openai_gateway_usage_integrity.go

@@ -1,18 +1,26 @@
 package service
 
-const grokMissingUsageMessage = "Grok upstream returned a successful response without billable usage"
+import (
+	"encoding/json"
+	"net/http"
+	"strings"
 
-// hasBillableOpenAIUsage distinguishes a usable accounting result from the
-// zero value produced when an upstream omits usage entirely. A successful Grok
-// completion without any positive usage cannot be safely charged, so callers
-// must fail over before committing the response to the client.
-func hasBillableOpenAIUsage(usage OpenAIUsage) bool {
+	"github.com/gin-gonic/gin"
+)
+
+const (
+	grokMissingUsageErrorCode = "grok_missing_usage"
+	grokMissingUsageMessage   = "xAI upstream returned a successful chat completion without billable usage"
+)
+
+// hasBillableGrokChatUsage stays aligned with the aggregate token buckets used
+// to account for chat completions. Detail fields alone do not prove that the
+// successful response can be settled safely.
+func hasBillableGrokChatUsage(usage OpenAIUsage) bool {
 	return usage.InputTokens > 0 ||
-		usage.ImageInputTokens > 0 ||
 		usage.OutputTokens > 0 ||
 		usage.CacheCreationInputTokens > 0 ||
-		usage.CacheReadInputTokens > 0 ||
-		usage.ImageOutputTokens > 0
+		usage.CacheReadInputTokens > 0
 }
 
 // requiresBillableGrokChatUsage identifies Grok traffic by both account
@@ -24,9 +32,50 @@ func requiresBillableGrokChatUsage(account *Account, models ...string) bool {
 		return true
 	}
 	for _, model := range models {
-		if platform, ok := DetectModelPlatform(model); ok && platform == PlatformGrok {
+		normalized := strings.ToLower(strings.TrimSpace(model))
+		if separator := strings.LastIndex(normalized, "/"); separator >= 0 {
+			normalized = strings.TrimSpace(normalized[separator+1:])
+		}
+		if normalized == "grok" || strings.HasPrefix(normalized, "grok-") {
 			return true
 		}
 	}
 	return false
 }
+
+func newGrokMissingUsageFailoverError(c *gin.Context, account *Account, upstreamRequestID string) *UpstreamFailoverError {
+	accountID := int64(0)
+	accountName := ""
+	if account != nil {
+		accountID = account.ID
+		accountName = account.Name
+	}
+
+	setOpsUpstreamError(c, http.StatusBadGateway, grokMissingUsageMessage, "")
+	appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
+		Platform:           PlatformGrok,
+		AccountID:          accountID,
+		AccountName:        accountName,
+		UpstreamStatusCode: http.StatusBadGateway,
+		UpstreamRequestID:  strings.TrimSpace(upstreamRequestID),
+		Kind:               "failover",
+		Message:            grokMissingUsageMessage,
+	})
+
+	body, _ := json.Marshal(gin.H{
+		"error": gin.H{
+			"type":    "upstream_error",
+			"code":    grokMissingUsageErrorCode,
+			"message": grokMissingUsageMessage,
+		},
+	})
+	headers := http.Header{}
+	if requestID := strings.TrimSpace(upstreamRequestID); requestID != "" {
+		headers.Set("x-request-id", requestID)
+	}
+	return &UpstreamFailoverError{
+		StatusCode:      http.StatusBadGateway,
+		ResponseBody:    body,
+		ResponseHeaders: headers,
+	}
+}