diff --git a/app/routes/debug_fb.py b/app/routes/debug_fb.py
index 980f30f..c8e6d8e 100644
--- a/app/routes/debug_fb.py
+++ b/app/routes/debug_fb.py
@@ -18,22 +18,37 @@ async def find_cups(request: Request, user: dict = Depends(get_current_user)):
         return JSONResponse({"error": msg})
 
     results = {}
-    try:
-        ok1, err1, rows1 = fb.execute_query(
-            "SELECT TRIM(f.RDB$FIELD_NAME) AS campo "
-            "FROM RDB$RELATION_FIELDS f "
-            "WHERE TRIM(f.RDB$RELATION_NAME) = 'ITEM' "
-            "ORDER BY f.RDB$FIELD_POSITION"
-        )
-        results["columnas_item"] = [r["campo"] for r in rows1] if ok1 else err1
-    except Exception as e:
-        results["columnas_item"] = str(e)
 
-    try:
-        ok2, err2, rows2 = fb.execute_query("SELECT FIRST 2 i.* FROM ITEM i")
-        results["item_muestra"] = list(rows2) if ok2 else err2
-    except Exception as e:
-        results["item_muestra"] = str(e)
+    # Columnas de ITEM via sistema
+    ok1, err1, rows1 = fb.execute_query(
+        "SELECT TRIM(f.RDB$FIELD_NAME) AS c FROM RDB$RELATION_FIELDS f "
+        "WHERE TRIM(f.RDB$RELATION_NAME)='ITEM' ORDER BY f.RDB$FIELD_POSITION"
+    )
+    cols_item = [r["c"] for r in rows1] if ok1 else []
+    results["columnas_item"] = cols_item if cols_item else f"error: {err1}"
+
+    # Probar cada posible campo clave contra COD_EXAMEN de RELACION
+    candidatos = ["COD_ITEM", "CODITEM", "CODIGO", "COD", "ID", "CODARTICULO", "ARTICULO"]
+    joins_ok = {}
+    for campo in candidatos:
+        if campo not in cols_item:
+            continue
+        ok2, _, rows2 = fb.execute_query(
+            f"SELECT FIRST 3 rel.COD_EXAMEN, i.CUPS_DETALLE "
+            f"FROM RELACION rel "
+            f"LEFT JOIN ITEM i ON TRIM(i.{campo}) = TRIM(rel.COD_EXAMEN) "
+            f"WHERE i.CUPS_DETALLE IS NOT NULL AND TRIM(i.CUPS_DETALLE)<>'' "
+        )
+        if ok2 and rows2:
+            joins_ok[campo] = rows2
+            break
+        else:
+            joins_ok[campo] = "sin resultados"
+    results["join_pruebas"] = joins_ok
+
+    # Primera fila de ITEM sin JOIN
+    ok3, err3, rows3 = fb.execute_query("SELECT FIRST 1 i.* FROM ITEM i")
+    results["item_primera_fila"] = rows3[0] if (ok3 and rows3) else f"error: {err3}"
 
     fb.disconnect()
     return JSONResponse(results)