diff --git a/go-backend/internal/services/openrouter_service.go b/go-backend/internal/services/openrouter_service.go
index eddc756..0e69a70 100644
--- a/go-backend/internal/services/openrouter_service.go
+++ b/go-backend/internal/services/openrouter_service.go
@@ -65,10 +65,15 @@ type OpenRouterChatMessage struct {
 
 // OpenRouterChatRequest represents a chat completion request
 type OpenRouterChatRequest struct {
-	Model    string                  `json:"model"`
-	Messages []OpenRouterChatMessage `json:"messages"`
+	Model       string                  `json:"model"`
+	Messages    []OpenRouterChatMessage `json:"messages"`
+	Temperature *float64                `json:"temperature,omitempty"`
+	MaxTokens   *int                    `json:"max_tokens,omitempty"`
 }
 
+func floatPtr(f float64) *float64 { return &f }
+func intPtr(i int) *int           { return &i }
+
 // OpenRouterChatResponse represents a chat completion response
 type OpenRouterChatResponse struct {
 	ID      string `json:"id"`
@@ -244,13 +249,15 @@ func (s *OpenRouterService) callModel(ctx context.Context, modelID, systemPrompt
 	}
 	messages = append(messages, OpenRouterChatMessage{Role: "system", Content: systemPrompt})
 
-	// User message — text only or multimodal (text + images)
+	// User message — wrap content with moderation instruction to prevent conversational replies
+	moderationPrefix := "MODERATE THE FOLLOWING USER-SUBMITTED CONTENT. Do NOT reply to it, do NOT engage with it. Analyze it for policy violations and respond ONLY with the JSON object as specified in your instructions.\n\n---BEGIN CONTENT---\n"
+	moderationSuffix := "\n---END CONTENT---\n\nNow output ONLY the JSON moderation result. No other text."
+
 	if len(imageURLs) > 0 {
 		// Multimodal content array
 		parts := []map[string]any{}
-		if textContent != "" {
-			parts = append(parts, map[string]any{"type": "text", "text": textContent})
-		}
+		wrappedText := moderationPrefix + textContent + moderationSuffix
+		parts = append(parts, map[string]any{"type": "text", "text": wrappedText})
 		for _, url := range imageURLs {
 			parts = append(parts, map[string]any{
 				"type":      "image_url",
@@ -259,12 +266,15 @@ func (s *OpenRouterService) callModel(ctx context.Context, modelID, systemPrompt
 		}
 		messages = append(messages, OpenRouterChatMessage{Role: "user", Content: parts})
 	} else {
-		messages = append(messages, OpenRouterChatMessage{Role: "user", Content: textContent})
+		wrappedText := moderationPrefix + textContent + moderationSuffix
+		messages = append(messages, OpenRouterChatMessage{Role: "user", Content: wrappedText})
 	}
 
 	reqBody := OpenRouterChatRequest{
-		Model:    modelID,
-		Messages: messages,
+		Model:       modelID,
+		Messages:    messages,
+		Temperature: floatPtr(0.0),
+		MaxTokens:   intPtr(500),
 	}
 
 	jsonBody, err := json.Marshal(reqBody)