diff --git a/archive/scanner.py b/archive/scanner.py
index ca91511..4d2f8a0 100644
--- a/archive/scanner.py
+++ b/archive/scanner.py
@@ -25,7 +25,7 @@ def __init__(self):
         }
 
     def scan_directory(self, root_path):
-        inventory = {
+        inventory: dict = {
             "meta": {"root": str(root_path), "total_files": 0, "algorithms_found": 0},
             "files": [],
         }
@@ -59,15 +59,13 @@ def analyze_file(self, file_path):
             # print(f"Error parsing {file_path}: {e}") # Reduce noise
             return None
 
-        file_data = {"path": str(file_path), "functions": []}
+        file_data: dict = {"path": str(file_path), "functions": []}
 
         # Find all function definitions (simplified traversal)
         # Note: Ideally this should be language-agnostic node type checking
         # For now relying on tree-sitter standard naming common in supported langs
-        cursor = tree.walk()
-
         def traverse(node):
-            if node.type == "function_definition" or node.type == "method_declaration":
+            if node.type in {"function_definition", "method_declaration"}:
                 self._analyze_function_node(node, code_bytes, file_data)
 
             for child in node.children:
@@ -80,7 +78,7 @@ def traverse(node):
     def _analyze_function_node(self, node, code_bytes, file_data):
         try:
             func_name = node.child_by_field_name("name").text.decode("utf-8")
-        except:
+        except Exception:
             func_name = "anonymous"
 
         function_entry = {"name": func_name, "line": node.start_point[0] + 1, "algorithms": []}
diff --git a/dissect/cli.py b/dissect/cli.py
index cf132d0..d1dea4a 100644
--- a/dissect/cli.py
+++ b/dissect/cli.py
@@ -14,6 +14,8 @@
 from .exporters.mermaid import save_mermaid
 from .trace_receiver import parse_trace_file
 
+TRACE_FILE_HELP = "Path to trace file (JSON)"
+
 
 def explain_command(args):
     """Generate AI summary of the trace."""
@@ -138,12 +140,12 @@ def main():
 
     # Trace command
     trace_parser = subparsers.add_parser("trace", help="Parse and inspect a trace file")
-    trace_parser.add_argument("--file", "-f", required=True, help="Path to trace file (JSON)")
+    trace_parser.add_argument("--file", "-f", required=True, help=TRACE_FILE_HELP)
     trace_parser.set_defaults(func=trace_command)
 
     # Visualize command
     viz_parser = subparsers.add_parser("visualize", help="Generate visualization from trace")
-    viz_parser.add_argument("--file", "-f", required=True, help="Path to trace file (JSON)")
+    viz_parser.add_argument("--file", "-f", required=True, help=TRACE_FILE_HELP)
     viz_parser.add_argument(
         "--format",
         "-t",
@@ -160,7 +162,7 @@ def main():
     explain_parser = subparsers.add_parser(
         "explain", help="Generate AI-powered insights from trace"
     )
-    explain_parser.add_argument("--file", "-f", required=True, help="Path to trace file (JSON)")
+    explain_parser.add_argument("--file", "-f", required=True, help=TRACE_FILE_HELP)
     explain_parser.add_argument(
         "--provider",
         "-p",
diff --git a/dissect/graph.py b/dissect/graph.py
index ea2539c..28174aa 100644
--- a/dissect/graph.py
+++ b/dissect/graph.py
@@ -127,10 +127,11 @@ def dfs(node_id: str, visited: set) -> tuple:
 
             return (node_duration + max_child_duration, [node] + max_child_path)
 
-        roots = self.get_root_nodes()
-        if not roots:
-            return []
+        return self._best_root_path(self.get_root_nodes(), dfs)
 
+    @staticmethod
+    def _best_root_path(roots, dfs):
+        """Racine au plus long chemin (extrait pour complexite)."""
         max_duration = 0
         critical_path = []
         for root in roots:
@@ -138,7 +139,6 @@ def dfs(node_id: str, visited: set) -> tuple:
             if duration > max_duration:
                 max_duration = duration
                 critical_path = path
-
         return critical_path
 
     def to_dict(self) -> Dict[str, Any]:
diff --git a/dissect/trace_receiver.py b/dissect/trace_receiver.py
index b696726..f3bbd7e 100644
--- a/dissect/trace_receiver.py
+++ b/dissect/trace_receiver.py
@@ -6,10 +6,18 @@
 """
 
 import json
+from datetime import datetime
 from typing import Any, Dict, List, Optional
 
 from .graph import Edge, Node, NodeType, OrchestrationGraph
 
+UTC_SUFFIX = "+00:00"
+
+
+def _parse_ts(ts):
+    """ISO-8601 tolerant Z (meme regle aux 3 sites d appel)."""
+    return datetime.fromisoformat(ts.replace("Z", UTC_SUFFIX))
+
 
 class TraceParser:
     """
@@ -210,11 +218,8 @@ def _parse_timestamp(self, ts: Any) -> Optional[float]:
             return ts
         if isinstance(ts, str):
             # Try ISO format
-            from datetime import datetime
-
             try:
-                dt = datetime.fromisoformat(ts.replace("Z", "+00:00"))
-                return dt.timestamp()
+                return _parse_ts(ts).timestamp()
             except Exception:
                 return None
         return None
@@ -352,11 +357,8 @@ def _parse_timestamp(self, ts: Any) -> Optional[float]:
                 return ts / 1000
             return ts
         if isinstance(ts, str):
-            from datetime import datetime
-
             try:
-                dt = datetime.fromisoformat(ts.replace("Z", "+00:00"))
-                return dt.timestamp()
+                return _parse_ts(ts).timestamp()
             except Exception:
                 return None
         return None
@@ -454,11 +456,8 @@ def _parse_timestamp(self, ts: Any) -> Optional[float]:
                 return ts / 1000
             return ts
         if isinstance(ts, str):
-            from datetime import datetime
-
             try:
-                dt = datetime.fromisoformat(ts.replace("Z", "+00:00"))
-                return dt.timestamp()
+                return _parse_ts(ts).timestamp()
             except Exception:
                 return None
         return None