diff --git a/minillmflow/__init__.py b/minillmflow/__init__.py
index af0286a..2a7ea3d 100644
--- a/minillmflow/__init__.py
+++ b/minillmflow/__init__.py
@@ -33,12 +33,26 @@ class NodeMeta(type):
                     attrs[attr_name] = _wrap_async(old_fn)
         
         return super().__new__(mcs, name, bases, attrs)
+
+
+async def hello(text):
+    print("Start")
+    await asyncio.sleep(1)  # Simulate some async work
+    print(text)
     
 class BaseNode(metaclass=NodeMeta):
     def __init__(self):
         self.parameters = {}
         self.successors = {}
 
+    # Syntactic sugar for chaining
+    def add_successor(self, node, condition="default"):
+        # warn if we're overwriting an existing successor
+        if condition in self.successors:
+            print(f"Warning: overwriting existing successor for condition '{condition}'")
+        self.successors[condition] = node
+        return node
+    
     # By default these are already async. If a subclass overrides them
     # with non-async definitions, they'll get wrapped automatically.
     def preprocess(self, shared_storage):
@@ -56,28 +70,20 @@ class BaseNode(metaclass=NodeMeta):
     async def _run_one(self, shared_storage):
         preprocess_result = await self.preprocess(shared_storage)
         process_result = await self._process(shared_storage, preprocess_result)
-        condition = await self.postprocess(shared_storage, preprocess_result, process_result)
-
-        if not self.successors:
-            return None
-        if len(self.successors) == 1:
-            return next(iter(self.successors.values()))
+        condition = await self.postprocess(shared_storage, preprocess_result, process_result) or "default"
         return self.successors.get(condition)
 
     def run(self, shared_storage=None):
-        return asyncio.run(self.run_async(shared_storage))
+        asyncio.run(self._run_async(shared_storage))
 
-    async def run_async(self, shared_storage=None):
-        shared_storage = shared_storage or {}
+    async def run_in_jupyter(self, shared_storage=None):
+        await self._run_async(shared_storage)
+        
+    async def _run_async(self, shared_storage):
         current_node = self
         while current_node:
             current_node = await current_node._run_one(shared_storage)
 
-    # Syntactic sugar for chaining
-    def add_successor(self, node, condition="default"):
-        self.successors[condition] = node
-        return node
-
     def __rshift__(self, other):
         return self.add_successor(other)
 
@@ -91,7 +97,6 @@ class BaseNode(metaclass=NodeMeta):
     def __call__(self, condition):
         return _ConditionalTransition(self, condition)
 
-
 class _ConditionalTransition:
     def __init__(self, source_node, condition):
         self.source_node = source_node
@@ -102,7 +107,6 @@ class _ConditionalTransition:
             raise TypeError("Target must be a BaseNode")
         return self.source_node.add_successor(target_node, self.condition)
 
-
 class Node(BaseNode):
     def __init__(self, max_retries=5, delay_s=0.1):
         super().__init__()
@@ -110,8 +114,8 @@ class Node(BaseNode):
         self.delay_s = delay_s
 
     def process_after_fail(self, shared_storage, data, exc):
-        print(f"[FAIL_ITEM] data={data}, error={exc}")
-        return "fail"
+        raise exc
+        # return "fail"
 
     async def _process(self, shared_storage, data):
         for attempt in range(self.max_retries):
@@ -121,6 +125,18 @@ class Node(BaseNode):
                 if attempt == self.max_retries - 1:
                     return await self.process_after_fail(shared_storage, data, e)
                 await asyncio.sleep(self.delay_s)
+                
+class Flow(BaseNode):
+    def __init__(self, start_node=None):
+        super().__init__()
+        self.start_node = start_node
+
+    async def _process(self, shared_storage, _):
+        if self.start_node:
+            current_node = self.start_node
+            while current_node:
+                current_node = await current_node._run_one(shared_storage or {})
+        return "Flow done"
 
 class BatchNode(BaseNode):
     def __init__(self, max_retries=5, delay_s=0.1):
@@ -156,18 +172,6 @@ class BatchNode(BaseNode):
             results.append(r)
         return results
 
-class Flow(BaseNode):
-    def __init__(self, start_node=None):
-        super().__init__()
-        self.start_node = start_node
-
-    async def _process(self, shared_storage, _):
-        if self.start_node:
-            current_node = self.start_node
-            while current_node:
-                current_node = await current_node._run_one(shared_storage or {})
-        return "Flow done"
-
 class BatchFlow(BaseNode):
     def __init__(self, start_node=None):
         super().__init__()
diff --git a/minillmflow/__pycache__/__init__.cpython-39.pyc b/minillmflow/__pycache__/__init__.cpython-39.pyc
index 549c726..57d50b0 100644
Binary files a/minillmflow/__pycache__/__init__.cpython-39.pyc and b/minillmflow/__pycache__/__init__.cpython-39.pyc differ