🛡️ Sentinel: [CRITICAL/HIGH] Fix bare except DoS risk

.gitignore

@@ -0,0 +1,3 @@
+__pycache__/
+*.pyc
+gh*

.jules/sentinel.md

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+## 2026-08-08 - Prevent DoS from Bare Excepts
+**Vulnerability:** Bare except blocks (`except:`) catch system-level exceptions like KeyboardInterrupt or SystemExit, potentially causing a Denial of Service and making the script unkillable.
+**Learning:** In Python, it is a security and reliability risk to catch all exceptions indiscriminately.
+**Prevention:** Always use `except Exception:` to only catch application-level errors and allow system signals to propagate.

Simulation/CancerInvasionSteppables.py

@@ -69,7 +69,7 @@ def safe_cell_removal(self, cell):
                         if self.cell_field[x, y, 0] == cell:
                             self.cell_field[x, y, 0] = None
                             pixels_cleared += 1
-                    except:
+                    except Exception:
                         continue
             return pixels_cleared > 0
         except Exception as e:
@@ -107,7 +107,7 @@ def initialize_stable_ecm(self):
                                 self.cell_field[x, y, 0] = fiber_cell
                                 self.fiber_locations.add((x, y))
                                 pixels_assigned += 1
-                        except:
+                        except Exception:
                             continue
 
                     if pixels_assigned >= 8:
@@ -202,7 +202,7 @@ def create_stable_cell(self, center_x, center_y):
                                 if self.cell_field[px, py, 0] is None:
                                     self.cell_field[px, py, 0] = cell
                                     pixels_added += 1
-                            except:
+                            except Exception:
                                 continue
 
             if pixels_added >= 20:  # Minimum viable cell
@@ -292,7 +292,7 @@ def handle_mmp_system(self):
                     if self.check_simple_fiber_contact(cell):
                         try:
                             secretor.secreteInsideCell(cell, self.mmp_secretion_rate)
-                        except:
+                        except Exception:
                             continue
 
             # Simple fiber degradation
@@ -306,7 +306,7 @@ def handle_mmp_system(self):
                             if mmp_conc >= self.degradation_threshold:
                                 fibers_to_remove.append(cell)
                                 mmp_field[cx, cy, 0] = max(0, mmp_conc - 0.5)
-                    except:
+                    except Exception:
                         continue
 
             # Remove degraded fibers
@@ -331,7 +331,7 @@ def check_simple_fiber_contact(self, cell):
                             neighbor = self.cell_field[nx, ny, 0]
                             if neighbor and neighbor.type == self.ECMFIBER:
                                 return True
-                        except:
+                        except Exception:
                             continue
             return False
 

test_no_bare_except.py

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+import ast
+import os
+
+def test_no_bare_except():
+    # Read the target file
+    filepath = os.path.join("Simulation", "CancerInvasionSteppables.py")
+    with open(filepath, "r", encoding="utf-8") as file:
+        source_code = file.read()
+
+    # Parse the source code into an AST
+    tree = ast.parse(source_code, filename=filepath)
+
+    # Walk the AST to find ExceptHandler nodes
+    bare_excepts = []
+    for node in ast.walk(tree):
+        if isinstance(node, ast.ExceptHandler):
+            # A bare 'except:' has node.type as None
+            if node.type is None:
+                bare_excepts.append(node.lineno)
+
+    # Assert that no bare excepts were found
+    assert len(bare_excepts) == 0, f"Bare 'except:' found at lines: {bare_excepts}. Use 'except Exception:' instead to avoid catching system exceptions like KeyboardInterrupt."