diff --git a/src/data_collection/polymarket_readonly.py b/src/data_collection/polymarket_readonly.py
index a520b0c8..b7161111 100644
--- a/src/data_collection/polymarket_readonly.py
+++ b/src/data_collection/polymarket_readonly.py
@@ -2964,6 +2964,7 @@ class PolymarketReadOnlyLayer:
             target_date=target_date,
             primary_market=primary_market,
         )
+        logger.info("SCAN_DEBUG city={} date={} related_markets={}", city_key, target_date, len(related_markets))
         if not related_markets:
             return {
                 "rows": [],
@@ -3038,6 +3039,10 @@ class PolymarketReadOnlyLayer:
             )
 
         broad_quotes = self._batch_get_token_market_data(token_ids, include_books=False)
+        logger.info(
+            "SCAN_DEBUG city={} date={} token_ids={} broad_quotes={} entries={}",
+            city_key, target_date, len(token_ids), len(broad_quotes), len(market_entries),
+        )
         bias_inputs: List[Tuple[float, float]] = []
         for entry in market_entries:
             yes_quote = self._merge_market_quote_fallback(
@@ -3295,6 +3300,14 @@ class PolymarketReadOnlyLayer:
             ask = _clamp_probability(_safe_float(entry.get("yes_ask") if side == "yes" else entry.get("no_ask")))
             bid = _clamp_probability(_safe_float(entry.get("yes_bid") if side == "yes" else entry.get("no_bid")))
             if model_event_probability is None or ask is None:
+                logger.info(
+                    "SCAN_DEBUG row_skip city={} date={} side={} model_p={} ask={} bid={} "
+                    "yes_ask={} no_ask={} slug={}",
+                    city_key, target_date, side,
+                    model_event_probability, ask, bid,
+                    entry.get("yes_ask"), entry.get("no_ask"),
+                    str(entry.get("market", {}).get("slug") or "")[:60],
+                )
                 return None
 
             market = entry["market"]
@@ -3681,6 +3694,10 @@ class PolymarketReadOnlyLayer:
 
         primary_signal = filtered_rows[0] if filtered_rows else None
         signal_status = "ready" if primary_signal else "no_signal"
+        logger.info(
+            "SCAN_DEBUG result city={} date={} preliminary={} final={} filtered={} signal={}",
+            city_key, target_date, len(preliminary_rows), len(final_rows), len(filtered_rows), signal_status,
+        )
         return {
             "rows": filtered_rows[: filters["limit"]],
             "distribution_bias": distribution_bias,