fix: don't pass response_format to gpt-image-* models

gpt-image-* models return b64_json by default and reject the
response_format parameter with a 400 error. Only pass it for
DALL-E models which default to url.

bulkgen/providers/openai_image.py

@@ -145,7 +145,22 @@ async def _generate_new(
     model: str,
     size: _SIZE | None,
 ) -> ImagesResponse:
-    """Generate a new image from a text prompt."""
+    """Generate a new image from a text prompt.
+
+    gpt-image-* models return b64 by default and reject ``response_format``,
+    so we only pass it for DALL-E models.
+    """
+    # gpt-image-* returns b64 by default; DALL-E defaults to url.
+    if model.startswith("gpt-image-"):
+        if size is not None:
+            return await client.images.generate(
+                prompt=prompt,
+                model=model,
+                n=1,
+                size=size,
+            )
+        return await client.images.generate(prompt=prompt, model=model, n=1)
+
     if size is not None:
         return await client.images.generate(
             prompt=prompt,
@@ -170,10 +185,30 @@ async def _generate_edit(
     project_dir: Path,
     size: _SIZE | None,
 ) -> ImagesResponse:
-    """Generate an image using a reference image via the edits endpoint."""
+    """Generate an image using a reference image via the edits endpoint.
+
+    gpt-image-* models return b64 by default and reject ``response_format``,
+    so we only pass it for DALL-E models.
+    """
     ref_path = project_dir / reference_images[0]
     image_bytes = ref_path.read_bytes()
 
+    if model.startswith("gpt-image-"):
+        if size is not None:
+            return await client.images.edit(
+                image=image_bytes,
+                prompt=prompt,
+                model=model,
+                n=1,
+                size=size,  # pyright: ignore[reportArgumentType]
+            )
+        return await client.images.edit(
+            image=image_bytes,
+            prompt=prompt,
+            model=model,
+            n=1,
+        )
+
     if size is not None:
         return await client.images.edit(
             image=image_bytes,