diff --git a/lavague-core/lavague/core/navigation.py b/lavague-core/lavague/core/navigation.py
index cc15f0ae..c8b52f79 100644
--- a/lavague-core/lavague/core/navigation.py
+++ b/lavague-core/lavague/core/navigation.py
@@ -166,7 +166,14 @@ def get_action_from_context(self, context: str, query: str) -> str:
         """
         Generate the code from a query and a context
         """
-        prompt = self.prompt_template.format(context_str=context, query_str=query)
+        authorized_xpaths = extract_xpaths_from_html(context)
+
+        prompt = self.prompt_template.format(
+            context_str=context,
+            query_str=query,
+            authorized_xpaths=authorized_xpaths,
+        )
+
         response = self.llm.complete(prompt).text
         code = self.extractor.extract(response)
         return code
@@ -241,8 +248,11 @@ def execute_instruction_gradio(self, instruction: str, action_engine: Any):
                 except:
                     pass
             start = time.time()
+            authorized_xpaths = extract_xpaths_from_html(llm_context)
             prompt = self.prompt_template.format(
-                context_str=llm_context, query_str=instruction
+                context_str=llm_context,
+                query_str=instruction,
+                authorized_xpaths=authorized_xpaths,
             )
             response = self.llm.complete(prompt).text
             end = time.time()
diff --git a/lavague-core/lavague/core/python_engine.py b/lavague-core/lavague/core/python_engine.py
index 5d2fdae2..9a763d51 100644
--- a/lavague-core/lavague/core/python_engine.py
+++ b/lavague-core/lavague/core/python_engine.py
@@ -21,6 +21,7 @@
 from llama_index.core.base.llms.base import BaseLLM
 from llama_index.core.embeddings import BaseEmbedding
 import re
+from lavague.core.extractors import DynamicExtractor
 
 DEFAULT_TEMPERATURE = 0.0
 
@@ -39,6 +40,7 @@ class PythonEngine(BaseEngine):
     ocr_llm: BaseLLM
     batch_size: int
     confidence_threshold: float
+    fallback_theshold: float
     temp_screenshots_path: str
     n_search_attempts: int
 
@@ -54,6 +56,7 @@ def __init__(
         display: bool = False,
         batch_size: int = 5,
         confidence_threshold: float = 0.85,
+        fallback_threshold: float = 0.85,
         temp_screenshots_path="./tmp_screenshots",
         n_search_attemps=10,
     ):
@@ -71,24 +74,19 @@ def __init__(
         self.confidence_threshold = confidence_threshold
         self.temp_screenshots_path = temp_screenshots_path
         self.n_search_attempts = n_search_attemps
+        self.fallback_theshold = fallback_threshold
 
     @classmethod
     def from_context(cls, context: Context, driver: BaseDriver):
         return cls(llm=context.llm, embedding=context.embedding, driver=driver)
 
     def extract_json(self, output: str) -> Optional[dict]:
-        clean = (
-            output.replace("'ret'", '"ret"')
-            .replace("'score'", '"score"')
-            .replace("```json", "")
-            .replace("```", "")
-            .strip()
-        )
-        clean = re.sub(r"\n+", "\n", clean)
+        extractor = DynamicExtractor()
+        clean = extractor.extract(output)
         try:
             output_dict = json.loads(clean)
         except json.JSONDecodeError as e:
-            print(f"Error extracting JSON: {e}")
+            print(f"Error extracting Json: {e}")
             return None
         return output_dict
 
@@ -121,7 +119,7 @@ def perform_fallback(self, prompt, instruction) -> str:
         context_score = -1
 
         prompt = f"""
-        You must respond with a dictionary in the following format:
+        You must respond with a JSON object in the following format:
         {{
             "ret": "[any relevant text transcribed from the image in order to answer the query {instruction} - make sure to answer with full sentences so the reponse can be understood out of context.]",
             "score": [a confidence score between 0 and 1 that the necessary context has been captured in order to answer the following query]
@@ -152,9 +150,10 @@ def perform_fallback(self, prompt, instruction) -> str:
                 image_documents=screenshots, prompt=prompt
             ).text.strip()
             output_dict = self.extract_json(output)
-            context_score = output_dict.get("score")
-            output = output_dict.get("ret")
-            memory += output
+            if output_dict:
+                context_score = output_dict.get("score", 0)
+                output = output_dict.get("ret")
+                memory += output
 
             # delete temp image folder
             shutil.rmtree(Path(self.temp_screenshots_path))
@@ -208,7 +207,7 @@ def execute_instruction(self, instruction: str) -> ActionResult:
 
         try:
             if (
-                output_dict.get("score", 0) < self.confidence_threshold
+                output_dict.get("score", 0) < self.fallback_theshold
             ):  # use fallback method
                 output = self.perform_fallback(prompt=prompt, instruction=instruction)