fix: lower RAG threshold, more context for better accuracy

app.py

@@ -62,7 +62,7 @@ def embed_query(text: str):
     return None
 
 # ─── RAG Search ───────────────────────────
-def rag_search(query: str, grade: str = "", subject: str = "", top_k: int = 5) -> str:
+def rag_search(query: str, grade: str = "", subject: str = "", top_k: int = 8) -> str:
     if faiss_index is None or not GEMINI_KEY:
         return ""
     vec = embed_query(query)
@@ -70,10 +70,10 @@ def rag_search(query: str, grade: str = "", subject: str = "", top_k: int = 5) -
         return ""
     q = np.array([vec], dtype=np.float32)
     faiss.normalize_L2(q)
-    scores, indices = faiss_index.search(q, top_k * 3)
+    scores, indices = faiss_index.search(q, top_k * 4)
     chunks = []
     for score, idx in zip(scores[0], indices[0]):
-        if idx < 0 or score < 0.35:
+        if idx < 0 or score < 0.25:
             continue
         meta = metadata_store[idx]
         if grade and meta.get("grade") != grade:
@@ -104,7 +104,7 @@ Give a STRUCTURED answer in Tamil+English mix with these sections:
 💡 **எளிய உதாரணம் (Simple Example):** [1 real-life example]
 📝 **நினைவில் வைக்க (Remember):** [1 key takeaway]"""
     elif mode == "📖 Story Mode":
-        user = f"""Context: {context[:500] if context else ''}
+        user = f"""Context: {context[:800] if context else ''}
 
 Write a SHORT story (exactly 6-8 sentences) about: {user_message}
 FORMAT:
@@ -114,7 +114,7 @@ FORMAT:
 📚 **கதையிலிருந்து பாடம் (Lesson from Story):**
 [1-2 sentences explaining what concept the story taught]"""
     else:
-        user = f"""Context: {context[:500] if context else ''}
+        user = f"""Context: {context[:800] if context else ''}
 
 Generate TN Board style exam questions for: {user_message}
 
@@ -146,7 +146,7 @@ FORMAT:
                     {"role": "system", "content": SYSTEM_PROMPT},
                     {"role": "user", "content": user}
                 ],
-                max_tokens=1024,
+                max_tokens=600,
                 temperature=0.7,
             )
             return response.choices[0].message.content.strip(), model_id.split("/")[-1]