Split models: Sonnet for discoveries (accuracy), Haiku for everything else (cost)

backend/app/api/endpoints/timeline.py

@@ -101,7 +101,7 @@ Return ONLY a valid JSON object with "decades" and "insight" keys. No other text
 
     try:
         message = await client.messages.create(
-            model="claude-sonnet-4-20250514",
+            model="claude-haiku-4-5-20251001",
             max_tokens=1024,
             messages=[{"role": "user", "content": prompt}],
         )