diff --git a/backend/internal/service/openai_gateway_response_handling.go b/backend/internal/service/openai_gateway_response_handling.go
index 2acf0a9307..7e59f778e6 100644
--- a/backend/internal/service/openai_gateway_response_handling.go
+++ b/backend/internal/service/openai_gateway_response_handling.go
@@ -967,9 +967,30 @@ func extractOpenAIUsageFromJSONBytes(body []byte) (OpenAIUsage, bool) {
 		return OpenAIUsage{}, false
 	}
 	if usage, ok := openAIUsageFromGJSON(gjson.GetBytes(body, "usage")); ok {
+		mergeHostedImageGenToolUsage(gjson.GetBytes(body, "tool_usage.image_gen"), &usage)
 		return usage, true
 	}
-	return openAIUsageFromGJSON(gjson.GetBytes(body, "response.usage"))
+	if usage, ok := openAIUsageFromGJSON(gjson.GetBytes(body, "response.usage")); ok {
+		mergeHostedImageGenToolUsage(gjson.GetBytes(body, "response.tool_usage.image_gen"), &usage)
+		return usage, true
+	}
+	return OpenAIUsage{}, false
+}
+
+func mergeHostedImageGenToolUsage(imageGen gjson.Result, usage *OpenAIUsage) {
+	if !imageGen.Exists() || !imageGen.IsObject() {
+		return
+	}
+	if usage.ImageOutputTokens == 0 {
+		if v := imageGen.Get("output_tokens_details.image_tokens").Int(); v > 0 {
+			usage.ImageOutputTokens = int(v)
+		}
+	}
+	if usage.ImageInputTokens == 0 {
+		if v := imageGen.Get("input_tokens_details.image_tokens").Int(); v > 0 {
+			usage.ImageInputTokens = int(v)
+		}
+	}
 }
 
 func extractOpenAIResponseIDFromJSONBytes(body []byte) string {
diff --git a/backend/internal/service/openai_gateway_response_handling_image_usage_test.go b/backend/internal/service/openai_gateway_response_handling_image_usage_test.go
new file mode 100644
index 0000000000..fad1e1ac62
--- /dev/null
+++ b/backend/internal/service/openai_gateway_response_handling_image_usage_test.go
@@ -0,0 +1,157 @@
+package service
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/tidwall/gjson"
+)
+
+func TestExtractOpenAIUsageFromJSONBytes_MergesHostedImageGenToolUsage(t *testing.T) {
+	// SSE response.completed event with response.usage + response.tool_usage.image_gen
+	body := []byte(`{
+		"type": "response.completed",
+		"response": {
+			"usage": {
+				"input_tokens": 43792,
+				"output_tokens": 1005,
+				"total_tokens": 44797
+			},
+			"tool_usage": {
+				"image_gen": {
+					"input_tokens": 7918,
+					"input_tokens_details": {"image_tokens": 7620, "text_tokens": 298},
+					"output_tokens": 186,
+					"output_tokens_details": {"image_tokens": 186, "text_tokens": 0},
+					"total_tokens": 8104
+				}
+			}
+		}
+	}`)
+
+	usage, ok := extractOpenAIUsageFromJSONBytes(body)
+	assert.True(t, ok)
+	assert.Equal(t, 43792, usage.InputTokens, "input_tokens from response.usage")
+	assert.Equal(t, 1005, usage.OutputTokens, "output_tokens from response.usage")
+	assert.Equal(t, 186, usage.ImageOutputTokens, "image output tokens merged from tool_usage.image_gen")
+	assert.Equal(t, 7620, usage.ImageInputTokens, "image input tokens merged from tool_usage.image_gen")
+}
+
+func TestExtractOpenAIUsageFromJSONBytes_NonStreamingMergesImageGen(t *testing.T) {
+	// Non-streaming response with top-level usage + tool_usage
+	body := []byte(`{
+		"id": "resp_abc123",
+		"object": "response",
+		"usage": {
+			"input_tokens": 5000,
+			"output_tokens": 200
+		},
+		"tool_usage": {
+			"image_gen": {
+				"input_tokens": 3000,
+				"input_tokens_details": {"image_tokens": 2800, "text_tokens": 200},
+				"output_tokens": 150,
+				"output_tokens_details": {"image_tokens": 150, "text_tokens": 0},
+				"total_tokens": 3150
+			}
+		}
+	}`)
+
+	usage, ok := extractOpenAIUsageFromJSONBytes(body)
+	assert.True(t, ok)
+	assert.Equal(t, 5000, usage.InputTokens)
+	assert.Equal(t, 200, usage.OutputTokens)
+	assert.Equal(t, 150, usage.ImageOutputTokens, "image output tokens from tool_usage.image_gen")
+	assert.Equal(t, 2800, usage.ImageInputTokens, "image input tokens from tool_usage.image_gen")
+}
+
+func TestExtractOpenAIUsageFromJSONBytes_NoToolUsageUnchanged(t *testing.T) {
+	// Standard response without tool_usage — behavior should be unchanged
+	body := []byte(`{
+		"usage": {
+			"input_tokens": 100,
+			"output_tokens": 50
+		}
+	}`)
+
+	usage, ok := extractOpenAIUsageFromJSONBytes(body)
+	assert.True(t, ok)
+	assert.Equal(t, 100, usage.InputTokens)
+	assert.Equal(t, 50, usage.OutputTokens)
+	assert.Equal(t, 0, usage.ImageOutputTokens, "no image tokens without tool_usage")
+	assert.Equal(t, 0, usage.ImageInputTokens, "no image tokens without tool_usage")
+}
+
+func TestExtractOpenAIUsageFromJSONBytes_BaseUsageHasImageTokensNoOverride(t *testing.T) {
+	// If base usage already has image tokens (e.g. from output_tokens_details),
+	// tool_usage should NOT override them.
+	body := []byte(`{
+		"usage": {
+			"input_tokens": 100,
+			"output_tokens": 50,
+			"output_tokens_details": {"image_tokens": 30}
+		},
+		"tool_usage": {
+			"image_gen": {
+				"input_tokens": 200,
+				"output_tokens": 100,
+				"output_tokens_details": {"image_tokens": 100, "text_tokens": 0},
+				"total_tokens": 300
+			}
+		}
+	}`)
+
+	usage, ok := extractOpenAIUsageFromJSONBytes(body)
+	assert.True(t, ok)
+	assert.Equal(t, 30, usage.ImageOutputTokens, "base usage image tokens preserved, not overridden")
+}
+
+func TestMergeHostedImageGenToolUsage_EmptyImageGen(t *testing.T) {
+	tests := []struct {
+		name string
+		json string
+	}{
+		{"missing", `{}`},
+		{"null", `{"image_gen": null}`},
+		{"not object", `{"image_gen": 42}`},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			usage := OpenAIUsage{InputTokens: 100, OutputTokens: 50}
+			original := usage
+			body := []byte(tt.json)
+			mergeHostedImageGenToolUsage(gjson.GetBytes(body, "image_gen"), &usage)
+			assert.Equal(t, original, usage, "usage should be unchanged")
+		})
+	}
+}
+
+func TestParseSSEUsageBytes_ResponseCompletedWithImageGen(t *testing.T) {
+	svc := &OpenAIGatewayService{}
+	data := []byte(`{
+		"type": "response.completed",
+		"response": {
+			"usage": {
+				"input_tokens": 10000,
+				"output_tokens": 500
+			},
+			"tool_usage": {
+				"image_gen": {
+					"input_tokens": 4000,
+					"input_tokens_details": {"image_tokens": 3800, "text_tokens": 200},
+					"output_tokens": 186,
+					"output_tokens_details": {"image_tokens": 186, "text_tokens": 0},
+					"total_tokens": 4186
+				}
+			}
+		}
+	}`)
+
+	usage := &OpenAIUsage{}
+	svc.parseSSEUsageBytes(data, usage)
+
+	assert.Equal(t, 10000, usage.InputTokens)
+	assert.Equal(t, 500, usage.OutputTokens)
+	assert.Equal(t, 186, usage.ImageOutputTokens, "image output tokens from SSE tool_usage")
+	assert.Equal(t, 3800, usage.ImageInputTokens, "image input tokens from SSE tool_usage")
+}