test(api): add validation for unsupported models in OpenAI image handlers

- Introduced tests to ensure unsupported models are rejected in `/images/generations` and `/images/edits`.
- Added `isSupportedImagesModel` and `rejectUnsupportedImagesModel` functions for consistent model validation.
- Enhanced image handler logic to apply validation checks for model compatibility.

sdk/api/handlers/openai/openai_images_handlers.go

@@ -24,6 +24,8 @@ import (
 const (
 	defaultImagesMainModel = "gpt-5.4-mini"
 	defaultImagesToolModel = "gpt-image-2"
+	imagesGenerationsPath  = "/v1/images/generations"
+	imagesEditsPath        = "/v1/images/edits"
 )
 
 type imageCallResult struct {
@@ -99,6 +101,28 @@ func (a *sseFrameAccumulator) Flush() [][]byte {
 	return frames
 }
 
+func isSupportedImagesModel(model string) bool {
+	baseModel := strings.TrimSpace(model)
+	if idx := strings.LastIndex(baseModel, "/"); idx >= 0 && idx < len(baseModel)-1 {
+		baseModel = strings.TrimSpace(baseModel[idx+1:])
+	}
+	return baseModel == defaultImagesToolModel
+}
+
+func rejectUnsupportedImagesModel(c *gin.Context, model string) bool {
+	if isSupportedImagesModel(model) {
+		return false
+	}
+
+	c.JSON(http.StatusBadRequest, handlers.ErrorResponse{
+		Error: handlers.ErrorDetail{
+			Message: fmt.Sprintf("Model %s is not supported on %s or %s. Use %s.", model, imagesGenerationsPath, imagesEditsPath, defaultImagesToolModel),
+			Type:    "invalid_request_error",
+		},
+	})
+	return true
+}
+
 func mimeTypeFromOutputFormat(outputFormat string) string {
 	if outputFormat == "" {
 		return "image/png"
@@ -194,6 +218,14 @@ func (h *OpenAIAPIHandler) ImagesGenerations(c *gin.Context) {
 		return
 	}
 
+	imageModel := strings.TrimSpace(gjson.GetBytes(rawJSON, "model").String())
+	if imageModel == "" {
+		imageModel = defaultImagesToolModel
+	}
+	if rejectUnsupportedImagesModel(c, imageModel) {
+		return
+	}
+
 	prompt := strings.TrimSpace(gjson.GetBytes(rawJSON, "prompt").String())
 	if prompt == "" {
 		c.JSON(http.StatusBadRequest, handlers.ErrorResponse{
@@ -205,10 +237,6 @@ func (h *OpenAIAPIHandler) ImagesGenerations(c *gin.Context) {
 		return
 	}
 
-	imageModel := strings.TrimSpace(gjson.GetBytes(rawJSON, "model").String())
-	if imageModel == "" {
-		imageModel = defaultImagesToolModel
-	}
 	responseFormat := strings.TrimSpace(gjson.GetBytes(rawJSON, "response_format").String())
 	if responseFormat == "" {
 		responseFormat = "b64_json"
@@ -283,6 +311,14 @@ func (h *OpenAIAPIHandler) imagesEditsFromMultipart(c *gin.Context) {
 		return
 	}
 
+	imageModel := strings.TrimSpace(c.PostForm("model"))
+	if imageModel == "" {
+		imageModel = defaultImagesToolModel
+	}
+	if rejectUnsupportedImagesModel(c, imageModel) {
+		return
+	}
+
 	prompt := strings.TrimSpace(c.PostForm("prompt"))
 	if prompt == "" {
 		c.JSON(http.StatusBadRequest, handlers.ErrorResponse{
@@ -340,10 +376,6 @@ func (h *OpenAIAPIHandler) imagesEditsFromMultipart(c *gin.Context) {
 		maskDataURL = &dataURL
 	}
 
-	imageModel := strings.TrimSpace(c.PostForm("model"))
-	if imageModel == "" {
-		imageModel = defaultImagesToolModel
-	}
 	responseFormat := strings.TrimSpace(c.PostForm("response_format"))
 	if responseFormat == "" {
 		responseFormat = "b64_json"
@@ -412,6 +444,14 @@ func (h *OpenAIAPIHandler) imagesEditsFromJSON(c *gin.Context) {
 		return
 	}
 
+	imageModel := strings.TrimSpace(gjson.GetBytes(rawJSON, "model").String())
+	if imageModel == "" {
+		imageModel = defaultImagesToolModel
+	}
+	if rejectUnsupportedImagesModel(c, imageModel) {
+		return
+	}
+
 	prompt := strings.TrimSpace(gjson.GetBytes(rawJSON, "prompt").String())
 	if prompt == "" {
 		c.JSON(http.StatusBadRequest, handlers.ErrorResponse{
@@ -460,10 +500,6 @@ func (h *OpenAIAPIHandler) imagesEditsFromJSON(c *gin.Context) {
 		return
 	}
 
-	imageModel := strings.TrimSpace(gjson.GetBytes(rawJSON, "model").String())
-	if imageModel == "" {
-		imageModel = defaultImagesToolModel
-	}
 	responseFormat := strings.TrimSpace(gjson.GetBytes(rawJSON, "response_format").String())
 	if responseFormat == "" {
 		responseFormat = "b64_json"

sdk/api/handlers/openai/openai_images_handlers_test.go

@@ -0,0 +1,95 @@
+package openai
+
+import (
+	"bytes"
+	"io"
+	"mime/multipart"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/tidwall/gjson"
+)
+
+func performImagesEndpointRequest(t *testing.T, endpointPath string, contentType string, body io.Reader, handler gin.HandlerFunc) *httptest.ResponseRecorder {
+	t.Helper()
+
+	gin.SetMode(gin.TestMode)
+	router := gin.New()
+	router.POST(endpointPath, handler)
+
+	req := httptest.NewRequest(http.MethodPost, endpointPath, body)
+	if contentType != "" {
+		req.Header.Set("Content-Type", contentType)
+	}
+	resp := httptest.NewRecorder()
+	router.ServeHTTP(resp, req)
+	return resp
+}
+
+func assertUnsupportedImagesModelResponse(t *testing.T, resp *httptest.ResponseRecorder, model string) {
+	t.Helper()
+
+	if resp.Code != http.StatusBadRequest {
+		t.Fatalf("status = %d, want %d: %s", resp.Code, http.StatusBadRequest, resp.Body.String())
+	}
+
+	message := gjson.GetBytes(resp.Body.Bytes(), "error.message").String()
+	expectedMessage := "Model " + model + " is not supported on " + imagesGenerationsPath + " or " + imagesEditsPath + ". Use " + defaultImagesToolModel + "."
+	if message != expectedMessage {
+		t.Fatalf("error message = %q, want %q", message, expectedMessage)
+	}
+	if errorType := gjson.GetBytes(resp.Body.Bytes(), "error.type").String(); errorType != "invalid_request_error" {
+		t.Fatalf("error type = %q, want invalid_request_error", errorType)
+	}
+}
+
+func TestImagesModelValidationAllowsGPTImage2WithOptionalPrefix(t *testing.T) {
+	for _, model := range []string{"gpt-image-2", "codex/gpt-image-2"} {
+		if !isSupportedImagesModel(model) {
+			t.Fatalf("expected %s to be supported", model)
+		}
+	}
+	if isSupportedImagesModel("gpt-5.4-mini") {
+		t.Fatal("expected gpt-5.4-mini to be rejected")
+	}
+}
+
+func TestImagesGenerationsRejectsUnsupportedModel(t *testing.T) {
+	handler := &OpenAIAPIHandler{}
+	body := strings.NewReader(`{"model":"gpt-5.4-mini","prompt":"draw a square"}`)
+
+	resp := performImagesEndpointRequest(t, imagesGenerationsPath, "application/json", body, handler.ImagesGenerations)
+
+	assertUnsupportedImagesModelResponse(t, resp, "gpt-5.4-mini")
+}
+
+func TestImagesEditsJSONRejectsUnsupportedModel(t *testing.T) {
+	handler := &OpenAIAPIHandler{}
+	body := strings.NewReader(`{"model":"gpt-5.4-mini","prompt":"edit this","images":[{"image_url":"data:image/png;base64,AA=="}]}`)
+
+	resp := performImagesEndpointRequest(t, imagesEditsPath, "application/json", body, handler.ImagesEdits)
+
+	assertUnsupportedImagesModelResponse(t, resp, "gpt-5.4-mini")
+}
+
+func TestImagesEditsMultipartRejectsUnsupportedModel(t *testing.T) {
+	handler := &OpenAIAPIHandler{}
+	var body bytes.Buffer
+	writer := multipart.NewWriter(&body)
+	if err := writer.WriteField("model", "gpt-5.4-mini"); err != nil {
+		t.Fatalf("write model field: %v", err)
+	}
+	if err := writer.WriteField("prompt", "edit this"); err != nil {
+		t.Fatalf("write prompt field: %v", err)
+	}
+	if errClose := writer.Close(); errClose != nil {
+		t.Fatalf("close multipart writer: %v", errClose)
+	}
+
+	resp := performImagesEndpointRequest(t, imagesEditsPath, writer.FormDataContentType(), &body, handler.ImagesEdits)
+
+	assertUnsupportedImagesModelResponse(t, resp, "gpt-5.4-mini")
+}