fix: Usage for image generation is incorrect (and causes error in LiteLLM) (#7786)

* fix: Add usage fields to image generation response for OpenAI API compatibility

Fixes #7354

Added input_tokens, output_tokens, and input_tokens_details fields to the
image generation API response to comply with OpenAI's image generation API
specification. This resolves validation errors in LiteLLM and the OpenAI SDK.

Changes:
- Added InputTokensDetails struct with text_tokens and image_tokens fields
- Extended OpenAIUsage struct with input_tokens, output_tokens, and input_tokens_details
- Updated ImageEndpoint to populate usage object with required fields
- Updated InpaintingEndpoint to populate usage object with required fields
- All fields initialized to 0 as per current behavior

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: majiayu000 <1835304752@qq.com>

* fix: Correct usage field types for image generation API compatibility

Changed InputTokens and OutputTokens from pointer types (*int) to
regular int types to match OpenAI API specification. This fixes
validation errors with LiteLLM and OpenAI SDK when parsing image
generation responses.

Fixes #7354

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: majiayu000 <1835304752@qq.com>

---------

Signed-off-by: majiayu000 <1835304752@qq.com>
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

core/http/endpoints/openai/image.go

@@ -232,6 +232,17 @@ func ImageEndpoint(cl *config.ModelConfigLoader, ml *model.ModelLoader, appConfi
 			ID:      id,
 			Created: created,
 			Data:    result,
+			Usage: schema.OpenAIUsage{
+				PromptTokens:     0,
+				CompletionTokens: 0,
+				TotalTokens:      0,
+				InputTokens:      0,
+				OutputTokens:     0,
+				InputTokensDetails: &schema.InputTokensDetails{
+					TextTokens:  0,
+					ImageTokens: 0,
+				},
+			},
 		}
 
 		jsonResult, _ := json.Marshal(resp)

core/http/endpoints/openai/inpainting.go

@@ -258,6 +258,17 @@ func InpaintingEndpoint(cl *config.ModelConfigLoader, ml *model.ModelLoader, app
 			Data: []schema.Item{{
 				URL: imgPath,
 			}},
+			Usage: schema.OpenAIUsage{
+				PromptTokens:     0,
+				CompletionTokens: 0,
+				TotalTokens:      0,
+				InputTokens:      0,
+				OutputTokens:     0,
+				InputTokensDetails: &schema.InputTokensDetails{
+					TextTokens:  0,
+					ImageTokens: 0,
+				},
+			},
 		}
 
 		// mark success so defer cleanup will not remove output files

core/schema/openai.go

@@ -18,10 +18,19 @@ type ErrorResponse struct {
 	Error *APIError `json:"error,omitempty"`
 }
 
+type InputTokensDetails struct {
+	TextTokens  int `json:"text_tokens"`
+	ImageTokens int `json:"image_tokens"`
+}
+
 type OpenAIUsage struct {
 	PromptTokens     int `json:"prompt_tokens"`
 	CompletionTokens int `json:"completion_tokens"`
 	TotalTokens      int `json:"total_tokens"`
+	// Fields for image generation API compatibility
+	InputTokens        int                 `json:"input_tokens,omitempty"`
+	OutputTokens       int                 `json:"output_tokens,omitempty"`
+	InputTokensDetails *InputTokensDetails `json:"input_tokens_details,omitempty"`
 	// Extra timing data, disabled by default as is't not a part of OpenAI specification
 	TimingPromptProcessing float64 `json:"timing_prompt_processing,omitempty"`
 	TimingTokenGeneration  float64 `json:"timing_token_generation,omitempty"`
@@ -49,11 +58,11 @@ type OpenAIResponse struct {
 }
 
 type Choice struct {
-	Index        int      `json:"index"`
-	FinishReason *string  `json:"finish_reason"`
-	Message      *Message `json:"message,omitempty"`
-	Delta        *Message `json:"delta,omitempty"`
-	Text         string   `json:"text,omitempty"`
+	Index        int       `json:"index"`
+	FinishReason *string   `json:"finish_reason"`
+	Message      *Message  `json:"message,omitempty"`
+	Delta        *Message  `json:"delta,omitempty"`
+	Text         string    `json:"text,omitempty"`
 	Logprobs     *Logprobs `json:"logprobs,omitempty"`
 }