simplify: handlers always receive state as first arg, drop takes_input flag

libs/langgraph/langgraph/_internal/_runnable.py

@@ -342,17 +342,6 @@ class RunnableCallable(Runnable):
             # If the kwarg is accepted by the function, store the key / runtime attribute to inject
             self.func_accepts[kw] = (runtime_key, default)
 
-        # True when the function expects a "state" or "input" first arg.
-        # False only when ALL non-VAR_POSITIONAL params are injected kwargs, e.g.
-        # `def handler(error: NodeError) -> T` — passing input positionally would
-        # conflict with the kwarg injection.
-        injected_names = set(self.func_accepts)
-        self.takes_input: bool = not self.explode_args and any(
-            p.kind == inspect.Parameter.VAR_POSITIONAL
-            or (p.kind in VALID_KINDS and p.name not in injected_names)
-            for p in params.values()
-        )
-
     def __repr__(self) -> str:
         repr_args = {
             k: v
@@ -375,11 +364,8 @@ class RunnableCallable(Runnable):
         if self.explode_args:
             args, _kwargs = input
             kwargs = {**self.kwargs, **_kwargs, **kwargs}
-        elif self.takes_input:
-            args = (input,)
-            kwargs = {**self.kwargs, **kwargs}
         else:
-            args = ()
+            args = (input,)
             kwargs = {**self.kwargs, **kwargs}
 
         runtime = config.get(CONF, {}).get(CONFIG_KEY_RUNTIME)
@@ -452,11 +438,8 @@ class RunnableCallable(Runnable):
         if self.explode_args:
             args, _kwargs = input
             kwargs = {**self.kwargs, **_kwargs, **kwargs}
-        elif self.takes_input:
-            args = (input,)
-            kwargs = {**self.kwargs, **kwargs}
         else:
-            args = ()
+            args = (input,)
             kwargs = {**self.kwargs, **kwargs}
 
         runtime = config.get(CONF, {}).get(CONFIG_KEY_RUNTIME)