Update rag_retrieval.py

rag_retrieval.py

@@ -67,8 +67,11 @@ def retrieve_chunks(rewrite: str, session: dict, search_outside_thread: bool):
 
 def build_answer(user_text: str, rewrite: str, retrieved):
     """
-    Simple answer builder:
-    - Show relevant snippets with citations.
+    Answer builder with a simple 'no clear answer' heuristic.
+
+    - If scores are very low OR none of the retrieved snippets share
+      meaningful words with the question, we return a graceful fallback.
+    - Otherwise, we list relevant snippets with citations.
     """
     if not retrieved:
         return (
@@ -76,6 +79,25 @@ def build_answer(user_text: str, rewrite: str, retrieved):
             []
         )
 
+    # ---- Heuristic: check scores + keyword overlap ----
+    question_tokens = {t.lower() for t in user_text.split() if len(t) > 3}
+
+    def snippet_has_overlap(snippet: str) -> bool:
+        words = {w.lower().strip(".,!?;:()[]") for w in snippet.split()}
+        return len(question_tokens & words) > 0
+
+    best_score = max(r["score_combined"] for r in retrieved)
+    any_overlap = any(snippet_has_overlap(r["text"]) for r in retrieved)
+
+    if best_score < 0.2 or not any_overlap:
+        # Fallback: nothing strongly relevant in this thread
+        return (
+            "Within this thread, I don’t see any email that clearly answers this question. "
+            "You may need to search outside this thread or check other conversations.",
+            []
+        )
+
+    # ---- Normal snippet-based answer ----
     lines = [f"**Question:** {user_text}", "", "**Relevant information:**"]
     citations = []