diff --git a/app/routes/debug_fb.py b/app/routes/debug_fb.py
new file mode 100644
index 0000000..5c211a4
--- /dev/null
+++ b/app/routes/debug_fb.py
@@ -0,0 +1,67 @@
+from fastapi import APIRouter, Request, Depends
+from fastapi.responses import JSONResponse
+from app.database import get_connection
+from app.auth import get_current_user
+from app.services.firebird_service import get_firebird_from_config
+
+router = APIRouter(prefix="/debug-fb", tags=["debug"])
+
+
+def _cfg():
+    conn = get_connection()
+    c = {r["key"]: r["value"] for r in conn.execute("SELECT * FROM config").fetchall()}
+    conn.close()
+    return c
+
+
+@router.get("/cups")
+async def find_cups(request: Request, user: dict = Depends(get_current_user)):
+    cfg = _cfg()
+    fb, ok, msg = get_firebird_from_config(cfg)
+    if not ok:
+        return JSONResponse({"error": msg})
+
+    results = {}
+
+    # 1. Tablas/campos que contengan "CUP" en el nombre
+    ok1, _, rows1 = fb.execute_query("""
+        SELECT DISTINCT TRIM(f.RDB$RELATION_NAME) AS tabla, TRIM(f.RDB$FIELD_NAME) AS campo
+        FROM RDB$RELATION_FIELDS f
+        WHERE f.RDB$FIELD_NAME CONTAINING 'CUP'
+        ORDER BY 1, 2
+    """)
+    results["campos_cup"] = rows1 if ok1 else []
+
+    # 2. Columnas de la tabla ARTICULO
+    ok2, _, rows2 = fb.execute_query("""
+        SELECT TRIM(f.RDB$FIELD_NAME) AS campo
+        FROM RDB$RELATION_FIELDS f
+        WHERE f.RDB$RELATION_NAME = 'ARTICULO'
+        ORDER BY f.RDB$FIELD_POSITION
+    """)
+    results["columnas_articulo"] = [r["campo"] for r in rows2] if ok2 else "no existe"
+
+    # 3. Columnas de la tabla EXAMEN (si existe)
+    ok3, _, rows3 = fb.execute_query("""
+        SELECT TRIM(f.RDB$FIELD_NAME) AS campo
+        FROM RDB$RELATION_FIELDS f
+        WHERE f.RDB$RELATION_NAME = 'EXAMEN'
+        ORDER BY f.RDB$FIELD_POSITION
+    """)
+    results["columnas_examen"] = [r["campo"] for r in rows3] if ok3 else "no existe"
+
+    # 4. Muestra de ARTICULO con el primer examen de RELACION
+    ok4, _, rows4 = fb.execute_query("""
+        SELECT FIRST 1 rel.COD_EXAMEN FROM RELACION rel WHERE rel.COD_EXAMEN IS NOT NULL
+    """)
+    if ok4 and rows4:
+        cod = rows4[0]["COD_EXAMEN"]
+        ok5, _, rows5 = fb.execute_query(
+            "SELECT FIRST 1 a.* FROM ARTICULO a WHERE a.CODIGO = :cod",
+            {"cod": cod}
+        )
+        results["muestra_articulo"] = rows5[0] if (ok5 and rows5) else "sin datos"
+        results["cod_examen_muestra"] = cod
+
+    fb.disconnect()
+    return JSONResponse(results)
diff --git a/app/services/json_generator.py b/app/services/json_generator.py
index 479d5ac..6156263 100644
--- a/app/services/json_generator.py
+++ b/app/services/json_generator.py
@@ -197,7 +197,7 @@ def generar_rda_paciente(rows: list, default_profesional: str = "", default_espe
     vigencia = 30
 
     result = {
-        "codigoPrefijo": default_prefijo or str(h.get("PREFIJO") or "00").strip(),
+        "codigoPrefijo": str(h.get("PREFIJO") or "").strip() or default_prefijo or "00",
         "numero": numero_override if numero_override else (
             str(h.get("NUM_FACTURA") or "").strip() if (h.get("NUM_FACTURA") or 0) != 0 else ""
         ),
diff --git a/main.py b/main.py
index eaa3ce8..540249a 100644
--- a/main.py
+++ b/main.py
@@ -65,7 +65,7 @@ async def root():
     return RedirectResponse(url="/dashboard")
 
 
-from app.routes import auth, dashboard, config, queries, terceros, transaccion, logs, automation, test_rda
+from app.routes import auth, dashboard, config, queries, terceros, transaccion, logs, automation, test_rda, debug_fb
 
 app.include_router(auth.router)
 app.include_router(dashboard.router)
@@ -76,6 +76,7 @@ app.include_router(transaccion.router)
 app.include_router(logs.router)
 app.include_router(automation.router)
 app.include_router(test_rda.router)
+app.include_router(debug_fb.router)
 
 
 if __name__ == "__main__":