fix(grok): proxy signed video status URLs

backend/internal/service/grok_media.go

@@ -845,7 +845,11 @@ func rewriteGrokMediaVideoContentURLs(body []byte, requestID, proxyURL string) [
 	if err := decoder.Decode(&value); err != nil {
 		return body
 	}
-	if !rewriteGrokMediaVideoContentURLValue(&value, requestID, proxyURL) {
+	changed := rewriteGrokMediaKnownVideoURL(&value, proxyURL)
+	if rewriteGrokMediaVideoContentURLValue(&value, requestID, proxyURL) {
+		changed = true
+	}
+	if !changed {
 		return body
 	}
 	rewritten, err := json.Marshal(value)
@@ -855,6 +859,26 @@ func rewriteGrokMediaVideoContentURLs(body []byte, requestID, proxyURL string) [
 	return rewritten
 }
 
+func rewriteGrokMediaKnownVideoURL(value *any, proxyURL string) bool {
+	if value == nil {
+		return false
+	}
+	root, ok := (*value).(map[string]any)
+	if !ok {
+		return false
+	}
+	video, ok := root["video"].(map[string]any)
+	if !ok {
+		return false
+	}
+	rawURL, ok := video["url"].(string)
+	if !ok || strings.TrimSpace(rawURL) == "" {
+		return false
+	}
+	video["url"] = proxyURL
+	return true
+}
+
 func rewriteGrokMediaVideoContentURLValue(value *any, requestID, proxyURL string) bool {
 	if value == nil {
 		return false

backend/internal/service/grok_media_content_test.go

@@ -193,3 +193,13 @@ func TestRewriteGrokMediaVideoContentURLsPreservesOtherIDsAndHandlesNestedEscape
 	require.Equal(t, "/v1/videos/task%2Fone/content", gjson.GetBytes(rewritten, "nested.0.url").String())
 	require.Equal(t, "https://relay.example/v1/videos/task-two/content", gjson.GetBytes(rewritten, "nested.1.url").String())
 }
+
+func TestRewriteGrokMediaVideoContentURLsRewritesSignedVideoURL(t *testing.T) {
+	body := []byte(`{"status":"done","video":{"url":"https://vidgen.x.ai/signed-token/xai-video-request-1.mp4","duration":8}}`)
+
+	rewritten := rewriteGrokMediaVideoContentURLs(body, "request-1", "/v1/videos/request-1/content")
+
+	require.Equal(t, "/v1/videos/request-1/content", gjson.GetBytes(rewritten, "video.url").String())
+	require.Equal(t, "8", gjson.GetBytes(rewritten, "video.duration").String())
+	require.Equal(t, "done", gjson.GetBytes(rewritten, "status").String())
+}