diff --git a/backend/internal/service/image_generation_intent.go b/backend/internal/service/image_generation_intent.go
index b6ef106509d..4b278481a01 100644
--- a/backend/internal/service/image_generation_intent.go
+++ b/backend/internal/service/image_generation_intent.go
@@ -173,6 +173,7 @@ func cloneRequestMapForImageIntent(body []byte) map[string]any {
 func resolveOpenAIResponsesImageBillingConfig(reqBody map[string]any, fallbackModel string) (string, string, error) {
 	imageModel := ""
 	imageSize := ""
+	imageQuality := ""
 	hasImageTool := false
 	if reqBody != nil {
 		rawTools, _ := reqBody["tools"].([]any)
@@ -184,11 +185,15 @@ func resolveOpenAIResponsesImageBillingConfig(reqBody map[string]any, fallbackMo
 			hasImageTool = true
 			imageModel = strings.TrimSpace(firstNonEmptyString(toolMap["model"]))
 			imageSize = strings.TrimSpace(firstNonEmptyString(toolMap["size"]))
+			imageQuality = strings.TrimSpace(firstNonEmptyString(toolMap["quality"]))
 			break
 		}
 		if imageSize == "" {
 			imageSize = strings.TrimSpace(firstNonEmptyString(reqBody["size"]))
 		}
+		if imageQuality == "" {
+			imageQuality = strings.TrimSpace(firstNonEmptyString(reqBody["quality"]))
+		}
 	}
 	if imageModel == "" && reqBody != nil {
 		bodyModel := strings.TrimSpace(firstNonEmptyString(reqBody["model"]))
@@ -202,7 +207,7 @@ func resolveOpenAIResponsesImageBillingConfig(reqBody map[string]any, fallbackMo
 	if imageModel == "" {
 		imageModel = strings.TrimSpace(fallbackModel)
 	}
-	sizeTier := normalizeOpenAIImageSizeTier(imageSize)
+	sizeTier := normalizeOpenAIImageSizeTier(imageSize, imageQuality)
 	return imageModel, sizeTier, nil
 }
 
diff --git a/backend/internal/service/openai_images.go b/backend/internal/service/openai_images.go
index afa94156867..9b7f5aeaba7 100644
--- a/backend/internal/service/openai_images.go
+++ b/backend/internal/service/openai_images.go
@@ -218,7 +218,7 @@ func (s *OpenAIGatewayService) ParseOpenAIImagesRequest(c *gin.Context, body []b
 	if err := validateOpenAIImagesModel(req.Model); err != nil {
 		return nil, err
 	}
-	req.SizeTier = normalizeOpenAIImageSizeTier(req.Size)
+	req.SizeTier = normalizeOpenAIImageSizeTier(req.Size, req.Quality)
 	req.RequiredCapability = classifyOpenAIImagesCapability(req)
 	return req, nil
 }
@@ -531,7 +531,24 @@ func isOpenAINativeImageOption(name string) bool {
 	}
 }
 
-func normalizeOpenAIImageSizeTier(size string) string {
+// normalizeOpenAIImageSizeTier maps an image request to a billing tier
+// ("1K"/"2K"/"4K") consumed by BillingService.CalculateImageCost and the
+// Group.ImagePrice1K/2K/4K subscription pricing fields.
+//
+// gpt-image-2's image_tokens scale primarily with `quality`, not pixel size
+// (low ≈ 1k tokens, medium ≈ 2k, high ≈ 4k), so an explicit quality value
+// takes precedence. When quality is empty / "auto" / unrecognized we fall
+// back to size-dimension classification for legacy callers (older
+// gpt-image-1, dall-e flows).
+func normalizeOpenAIImageSizeTier(size, quality string) string {
+	switch strings.ToLower(strings.TrimSpace(quality)) {
+	case "low":
+		return "1K"
+	case "medium":
+		return "2K"
+	case "high":
+		return "4K"
+	}
 	trimmed := strings.TrimSpace(size)
 	normalized := strings.ToLower(trimmed)
 	switch normalized {
diff --git a/backend/internal/service/openai_images_test.go b/backend/internal/service/openai_images_test.go
index 45fb24e975e..28eea8c5e37 100644
--- a/backend/internal/service/openai_images_test.go
+++ b/backend/internal/service/openai_images_test.go
@@ -51,7 +51,7 @@ func TestOpenAIGatewayServiceParseOpenAIImagesRequest_JSON(t *testing.T) {
 	require.Equal(t, "draw a cat", parsed.Prompt)
 	require.True(t, parsed.Stream)
 	require.Equal(t, "1024x1024", parsed.Size)
-	require.Equal(t, "1K", parsed.SizeTier)
+	require.Equal(t, "4K", parsed.SizeTier)
 	require.Equal(t, OpenAIImagesCapabilityNative, parsed.RequiredCapability)
 	require.False(t, parsed.Multipart)
 }