Fix issue when cond edge visited after multiple executions of Send

- cond edge will run for each execution of Send, so target channels need to support multiple publishes

libs/langgraph/langgraph/graph/state.py

@@ -610,7 +610,7 @@ def branch_writer(packets: list[Union[str, Send]]) -> Optional[ChannelWrite]:
                 if branch.then and branch.then != END:
                     writes.append(
                         ChannelWriteEntry(
-                            f"branch:{start}:{name}:then",
+                            f"branch:{start}:{name}::then",
                             WaitForNames(
                                 {p.node if isinstance(p, Send) else p for p in filtered}
                             ),
@@ -630,12 +630,12 @@ def branch_writer(packets: list[Union[str, Send]]) -> Optional[ChannelWrite]:
         for end in ends:
             if end != END:
                 channel_name = f"branch:{start}:{name}:{end}"
-                self.channels[channel_name] = EphemeralValue(Any)
+                self.channels[channel_name] = EphemeralValue(Any, guard=False)
                 self.nodes[end].triggers.append(channel_name)
 
         # attach then subscriber
         if branch.then and branch.then != END:
-            channel_name = f"branch:{start}:{name}:then"
+            channel_name = f"branch:{start}:{name}::then"
             self.channels[channel_name] = DynamicBarrierValue(str)
             self.nodes[branch.then].triggers.append(channel_name)
             for end in ends:

libs/langgraph/tests/test_pregel.py

@@ -1134,23 +1134,23 @@ def __init__(self, name: str):
             setattr(self, "__name__", name)
 
         def __call__(self, state):
-            return state + [self.name]
+            return [self.name]
 
     def send_for_fun(state):
-        return [Send("2", state)]
+        return [Send("2", state), Send("2", state)]
 
     def route_to_three(state) -> Literal["3"]:
         return "3"
 
-    builder = StateGraph(list)
+    builder = StateGraph(Annotated[list, operator.add])
     builder.add_node(Node("1"))
     builder.add_node(Node("2"))
     builder.add_node(Node("3"))
     builder.add_edge(START, "1")
     builder.add_conditional_edges("1", send_for_fun)
     builder.add_conditional_edges("2", route_to_three)
     graph = builder.compile()
-    assert graph.invoke(["0"]) == ["0", "1", "2", "3"]
+    assert graph.invoke(["0"]) == ["0", "1", "2", "2", "3"]
 
 
 async def test_checkpointer_null_pending_writes() -> None:
@@ -6536,18 +6536,18 @@ class State(TypedDict):
                 "timestamp": AnyStr(),
                 "step": 3,
                 "payload": {
-                    "id": "ceada3c5-5f25-59e4-9ea5-544599ce1d2f",
+                    "id": "9b590c54-15ef-54b1-83a7-140d27b0bc52",
                     "name": "finish",
                     "input": {"my_key": "value prepared slow", "market": "DE"},
-                    "triggers": ["branch:prepare:condition:then"],
+                    "triggers": ["branch:prepare:condition::then"],
                 },
             },
             {
                 "type": "task_result",
                 "timestamp": AnyStr(),
                 "step": 3,
                 "payload": {
-                    "id": "ceada3c5-5f25-59e4-9ea5-544599ce1d2f",
+                    "id": "9b590c54-15ef-54b1-83a7-140d27b0bc52",
                     "name": "finish",
                     "result": [("my_key", " finished")],
                 },

libs/langgraph/tests/test_pregel_async.py

@@ -1257,15 +1257,15 @@ def __init__(self, name: str):
             setattr(self, "__name__", name)
 
         async def __call__(self, state):
-            return state + [self.name]
+            return [self.name]
 
     async def send_for_fun(state):
-        return [Send("2", state)]
+        return [Send("2", state), Send("2", state)]
 
     async def route_to_three(state) -> Literal["3"]:
         return "3"
 
-    builder = StateGraph(list)
+    builder = StateGraph(Annotated[list, operator.add])
     builder.add_node(Node("1"))
     builder.add_node(Node("2"))
     builder.add_node(Node("3"))
@@ -1274,7 +1274,7 @@ async def route_to_three(state) -> Literal["3"]:
     builder.add_conditional_edges("2", route_to_three)
     graph = builder.compile()
 
-    assert await graph.ainvoke(["0"]) == ["0", "1", "2", "3"]
+    assert await graph.ainvoke(["0"]) == ["0", "1", "2", "2", "3"]
 
 
 async def test_invoke_checkpoint_aiosqlite(mocker: MockerFixture) -> None:
@@ -5119,18 +5119,18 @@ class State(TypedDict):
                 "timestamp": AnyStr(),
                 "step": 3,
                 "payload": {
-                    "id": "ceada3c5-5f25-59e4-9ea5-544599ce1d2f",
+                    "id": "9b590c54-15ef-54b1-83a7-140d27b0bc52",
                     "name": "finish",
                     "input": {"my_key": "value prepared slow", "market": "DE"},
-                    "triggers": ["branch:prepare:condition:then"],
+                    "triggers": ["branch:prepare:condition::then"],
                 },
             },
             {
                 "type": "task_result",
                 "timestamp": AnyStr(),
                 "step": 3,
                 "payload": {
-                    "id": "ceada3c5-5f25-59e4-9ea5-544599ce1d2f",
+                    "id": "9b590c54-15ef-54b1-83a7-140d27b0bc52",
                     "name": "finish",
                     "result": [("my_key", " finished")],
                 },