diff --git a/docs/diffusion/api/openai_api.md b/docs/diffusion/api/openai_api.md
index 2eda86fdf..30d8d5312 100644
--- a/docs/diffusion/api/openai_api.md
+++ b/docs/diffusion/api/openai_api.md
@@ -102,7 +102,8 @@ curl -sS -X POST "http://localhost:30010/v1/images/generations" \
 ```
 
 > **Note**
-> The `response_format=url` option is not supported for `POST /v1/images/generations` and will return a `400` error.
+> If `response_format=url` is used and cloud storage is not configured, the API returns
+> a relative URL like `/v1/images/<IMAGE_ID>/content`.
 
 **Edit an image**
 
@@ -136,7 +137,8 @@ curl -sS -X POST "http://localhost:30010/v1/images/edits" \
 
 **Download image content**
 
-When `response_format=url` is used with `POST /v1/images/edits`, the API returns a relative URL like `/v1/images/<IMAGE_ID>/content`.
+When `response_format=url` is used with `POST /v1/images/generations` or `POST /v1/images/edits`,
+the API returns a relative URL like `/v1/images/<IMAGE_ID>/content`.
 
 **Endpoint:** `GET /v1/images/{image_id}/content`
 
diff --git a/python/sglang/multimodal_gen/runtime/entrypoints/openai/image_api.py b/python/sglang/multimodal_gen/runtime/entrypoints/openai/image_api.py
index 9dc2a043a..7d6f1a5db 100644
--- a/python/sglang/multimodal_gen/runtime/entrypoints/openai/image_api.py
+++ b/python/sglang/multimodal_gen/runtime/entrypoints/openai/image_api.py
@@ -159,6 +159,8 @@ async def generations(
         result,
         b64_list=b64_list,
         cloud_url=cloud_url,
+        # Provide a local fallback URL when cloud upload is unavailable, mirroring /v1/images/edits.
+        fallback_url=f"/v1/images/{request_id}/content",
     )
 
     return ImageResponse(**response_kwargs)