resolves server-side error when a Gemini prompt is blocked due to safety

src/proxy/middleware/common.ts

@@ -264,7 +264,15 @@ export function getCompletionFromBody(req: Request, body: Record<string, any>) {
       if ("choices" in body) {
         return body.choices[0].message.content;
       }
-      return body.candidates[0].content.parts[0].text;
+      const text = body.candidates[0].content?.parts?.[0]?.text;
+      if (!text) {
+        req.log.warn(
+          { body: JSON.stringify(body) },
+          "Received empty Google AI text completion"
+        );
+        return "";
+      }
+      return text;
     case "openai-image":
       return body.data?.map((item: any) => item.url).join("\n");
     default:

src/proxy/middleware/response/streaming/transformers/google-ai-to-openai.ts

@@ -9,7 +9,7 @@ const log = logger.child({
 
 type GoogleAIStreamEvent = {
   candidates: {
-    content: { parts: { text: string }[]; role: string };
+    content?: { parts?: { text: string }[]; role: string };
     finishReason?: "STOP" | "MAX_TOKENS" | "SAFETY" | "RECITATION" | "OTHER";
     index: number;
     tokenCount?: number;
@@ -34,9 +34,15 @@ export const googleAIToOpenAI: StreamingCompletionTransformer = (params) => {
     return { position: -1 };
   }
 
-  const parts = completionEvent.candidates[0].content.parts;
+  const parts = completionEvent.candidates[0].content?.parts || [];
   let content = parts[0]?.text ?? "";
 
+  if (isSafetyStop(completionEvent)) {
+    content = `[Proxy Warning] Gemini safety filter triggered: ${JSON.stringify(
+      completionEvent.candidates[0].safetyRatings
+    )}`;
+  }
+
   // If this is the first chunk, try stripping speaker names from the response
   // e.g. "John: Hello" -> "Hello"
   if (index === 0) {
@@ -60,6 +66,14 @@ export const googleAIToOpenAI: StreamingCompletionTransformer = (params) => {
   return { position: -1, event: newEvent };
 };
 
+function isSafetyStop(completion: GoogleAIStreamEvent) {
+  const isSafetyStop = ["SAFETY", "OTHER"].includes(
+    completion.candidates[0].finishReason ?? ""
+  );
+  const hasNoContent = completion.candidates[0].content?.parts?.length === 0;
+  return isSafetyStop && hasNoContent;
+}
+
 function asCompletion(event: ServerSentEvent): GoogleAIStreamEvent | null {
   try {
     const parsed = JSON.parse(event.data) as GoogleAIStreamEvent;