fix: replace self-chaining exception raise with 'from None' in retry loop

dotflow/core/action.py

@@ -166,7 +166,7 @@ def _run_action(self, *args, task=None, **kwargs):
                     raise ExecutionWithClassError() from None
 
                 if attempt == self.retry:
-                    raise last_exception from last_exception
+                    raise last_exception from None
 
                 if task is not None:
                     task.retry_count += 1

tests/core/test_action.py

@@ -79,6 +79,21 @@ def flaky_step():
         self.assertEqual(len(statuses), 1)
         self.assertEqual(statuses[0], TypeStatus.RETRY)
 
+    def test_retry_exception_does_not_chain_to_itself(self):
+        def always_fail():
+            raise ValueError("fail")
+
+        inside = Action(always_fail, retry=2, retry_delay=0)
+
+        try:
+            inside()
+        except ValueError as error:
+            self.assertIsNot(
+                error.__cause__,
+                error,
+                "Exception must not be its own __cause__ (circular chain)",
+            )
+
     def test_backoff_does_not_mutate_retry_delay(self):
         def always_fail():
             raise RuntimeError("fail")