diff --git a/src/anthropic/_base_client.py b/src/anthropic/_base_client.py
index 98d154c0..c8d2b051 100644
--- a/src/anthropic/_base_client.py
+++ b/src/anthropic/_base_client.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import sys
+import os
 import json
 import time
 import uuid
@@ -35,6 +36,7 @@
     overload,
 )
 from typing_extensions import Literal, override, get_origin
+from ._heuristics import HeuristicGuard
 
 import anyio
 import httpx
@@ -1530,10 +1532,24 @@ def post(
                 DeprecationWarning,
                 stacklevel=2,
             )
+
+        if os.environ.get("ANTHROPIC_ENABLE_HEURISTIC_GUARD"):
+            if isinstance(body, dict):
+                body_dict = cast(Dict[str, Any], body)
+                messages: List[Dict[str, Any]] = body_dict.get("messages", [])
+                last_msg: Any = next(
+                    (m.get("content", "") for m in reversed(messages) if m.get("role") == "user"),
+                    "",
+                )
+                if isinstance(last_msg, str) and last_msg:
+                    analysis: Dict[str, Any] = HeuristicGuard.analyze(last_msg)
+                    if not analysis.get("valid", True):
+                        raise ValueError(f"BLOCKED: Score {analysis.get('S', 0)}")
+
         opts = FinalRequestOptions.construct(
             method="post", url=path, json_data=body, content=content, files=to_httpx_files(files), **options
         )
-        return cast(ResponseT, self.request(cast_to, opts, stream=stream, stream_cls=stream_cls))
+        return self.request(cast_to, opts, stream=stream, stream_cls=stream_cls)
 
     def patch(
         self,
@@ -2270,6 +2286,20 @@ async def post(
                 DeprecationWarning,
                 stacklevel=2,
             )
+
+        if os.environ.get("ANTHROPIC_ENABLE_HEURISTIC_GUARD"):
+            if isinstance(body, dict):
+                body_dict = cast(Dict[str, Any], body)
+                messages: List[Dict[str, Any]] = body_dict.get("messages", [])
+                last_msg: Any = next(
+                    (m.get("content", "") for m in reversed(messages) if m.get("role") == "user"),
+                    "",
+                )
+                if isinstance(last_msg, str) and last_msg:
+                    analysis: Dict[str, Any] = HeuristicGuard.analyze(last_msg)
+                    if not analysis.get("valid", True):
+                        raise ValueError(f"BLOCKED: Score {analysis.get('S', 0)}")
+
         opts = FinalRequestOptions.construct(
             method="post", url=path, json_data=body, content=content, files=await async_to_httpx_files(files), **options
         )
diff --git a/src/anthropic/_heuristics.py b/src/anthropic/_heuristics.py
new file mode 100644
index 00000000..c7cb91ba
--- /dev/null
+++ b/src/anthropic/_heuristics.py
@@ -0,0 +1,57 @@
+import typing
+
+class HeuristicGuard:
+    """
+    Filtre heuristique pour requêtes LLM en Français.
+    """
+    
+    OPERANTS: typing.Set[str] = {
+        'donne', 'fais', 'analyse', 'génère', 'genere', 'calcule', 
+        'audit', 'verdict', 'système', 'crée', 'cree', 'optimise', 
+        'explique', 'compare', 'résume', 'resume', 'évalue', 'evalue', 
+        'teste', 'montre', 'prouve', 'liste', 'décris', 'decris', 'generate'
+    }
+    
+    FORMATS: typing.Set[str] = {
+        'json', 'tableau', 'liste', 'markdown', 'csv', 'expert', 
+        'physique', 'code', 'python', 'sql'
+    }
+
+    THRESH_OPTIMAL: float = 2.3
+    THRESH_ADMISSIBLE: float = 0.3  # To adjust the threshold for admissible prompts, we can change this value.
+
+    @classmethod
+    def analyze(cls, prompt: str) -> typing.Dict[str, typing.Any]:
+        prompt = prompt.strip()
+        if len(prompt) < 3:
+            return {"S": 0.0, "verdict": "INCOHERENCE", "valid": False}
+
+        tokens: typing.List[str] = prompt.lower().split()
+        t_len: int = len(tokens)
+        
+        beta: float = 1.0
+        if t_len < 4: beta *= 0.6
+        if t_len > 100: beta *= 0.85
+        
+        complex_terms = len([t for t in tokens if len(t) > 7])
+        if t_len > 0 and (complex_terms / t_len) > 0.4:
+            beta *= 1.15
+        
+        score_delta: float = 0.1
+        if any(op in tokens for op in cls.OPERANTS): score_delta += 0.45
+        if any(fmt in tokens for fmt in cls.FORMATS): score_delta += 0.35
+        
+        delta_c: float = min(1.0, score_delta + 0.1)
+        lambda_val: float = max(0.08, 1.1 - (score_delta * 0.85))
+        
+        s_score: float = (beta * delta_c) / lambda_val
+        
+        verdict: str = "INCOHERENCE"
+        if s_score >= cls.THRESH_OPTIMAL: verdict = "OPTIMAL"
+        elif s_score >= cls.THRESH_ADMISSIBLE: verdict = "ADMISSIBLE"
+        
+        return {
+            "S": round(s_score, 2),
+            "verdict": verdict,
+            "valid": s_score >= cls.THRESH_ADMISSIBLE
+        }
\ No newline at end of file