diff --git a/comfy_api/latest/_io.py b/comfy_api/latest/_io.py
index a7228acac..d6e92c17b 100644
--- a/comfy_api/latest/_io.py
+++ b/comfy_api/latest/_io.py
@@ -1369,36 +1369,7 @@ _DynamicInputFunc = Callable[
 ]
 DYNAMIC_INPUT_LOOKUP: dict[str, _DynamicInputFunc] = {}
 def register_dynamic_input_func(io_type: str, func: _DynamicInputFunc):
-    """Register a dynamic-input expansion callback.
-
-    Accepts both the current 6-argument form and the legacy 5-argument form
-    (without ``live_input_types``). Legacy callables are silently wrapped so
-    custom nodes that registered against the older signature continue to work.
-    """
-    try:
-        sig = inspect.signature(func)
-        param_count = sum(
-            1 for p in sig.parameters.values()
-            if p.kind in (inspect.Parameter.POSITIONAL_ONLY,
-                          inspect.Parameter.POSITIONAL_OR_KEYWORD,
-                          inspect.Parameter.VAR_POSITIONAL)
-        )
-        # 5 = legacy signature (no live_input_types). If the callable has
-        # *args we can't be certain, so treat it as new-style.
-        has_varargs = any(p.kind is inspect.Parameter.VAR_POSITIONAL for p in sig.parameters.values())
-        is_legacy = (param_count == 5 and not has_varargs)
-    except (TypeError, ValueError):
-        # Builtins / C-implemented callables without introspectable signatures
-        # are assumed to be new-style.
-        is_legacy = False
-
-    if is_legacy:
-        _legacy = func
-        def _adapter(out_dict, live_inputs, value, input_type, curr_prefix, live_input_types=None):
-            _legacy(out_dict, live_inputs, value, input_type, curr_prefix)
-        DYNAMIC_INPUT_LOOKUP[io_type] = _adapter
-    else:
-        DYNAMIC_INPUT_LOOKUP[io_type] = func
+    DYNAMIC_INPUT_LOOKUP[io_type] = func
 
 def get_dynamic_input_func(io_type: str) -> _DynamicInputFunc:
     return DYNAMIC_INPUT_LOOKUP[io_type]
diff --git a/tests-unit/comfy_api_test/test_register_dynamic_input_func.py b/tests-unit/comfy_api_test/test_register_dynamic_input_func.py
deleted file mode 100644
index afabf9fe7..000000000
--- a/tests-unit/comfy_api_test/test_register_dynamic_input_func.py
+++ /dev/null
@@ -1,79 +0,0 @@
-"""Backward-compat tests for ``register_dynamic_input_func``.
-
-When ``live_input_types`` was added as a sixth argument to the dynamic-input
-expansion callback, third-party custom nodes that registered against the
-original 5-argument signature would otherwise crash with ``TypeError`` the
-first time their input was expanded. ``register_dynamic_input_func`` wraps
-such legacy callables transparently.
-"""
-
-from __future__ import annotations
-
-from comfy_api.latest import _io
-
-
-def test_legacy_5arg_callback_is_wrapped_transparently():
-    received = {}
-
-    def legacy(out_dict, live_inputs, value, input_type, curr_prefix):
-        received["args"] = (out_dict, live_inputs, value, input_type, curr_prefix)
-
-    io_type = "TEST_LEGACY_5ARG_V3"
-    try:
-        _io.register_dynamic_input_func(io_type, legacy)
-        fn = _io.get_dynamic_input_func(io_type)
-
-        # Caller invokes with 6 arguments (current signature). The shim must
-        # strip the trailing live_input_types argument before delegating.
-        fn({"required": {}}, {"a": 1}, ("X", {}), "required", ["p"], {"a": "INT"})
-
-        assert received["args"] == (
-            {"required": {}}, {"a": 1}, ("X", {}), "required", ["p"]
-        )
-    finally:
-        _io.DYNAMIC_INPUT_LOOKUP.pop(io_type, None)
-
-
-def test_new_6arg_callback_passes_live_input_types_through():
-    received = {}
-
-    def modern(out_dict, live_inputs, value, input_type, curr_prefix, live_input_types=None):
-        received["live_input_types"] = live_input_types
-
-    io_type = "TEST_MODERN_6ARG_V3"
-    try:
-        _io.register_dynamic_input_func(io_type, modern)
-        fn = _io.get_dynamic_input_func(io_type)
-        fn({}, {}, ("X", {}), "required", None, {"foo": "IMAGE"})
-        assert received["live_input_types"] == {"foo": "IMAGE"}
-    finally:
-        _io.DYNAMIC_INPUT_LOOKUP.pop(io_type, None)
-
-
-def test_callable_with_uninspectable_signature_assumed_modern():
-    """``functools.partial`` and C builtins may have no introspectable signature.
-
-    The shim must not blow up; falling back to the new signature is the safe
-    choice (we get a clean TypeError if the callable really is too old, which
-    is no worse than the pre-shim behavior).
-    """
-    calls = []
-
-    class _CallableObj:
-        # Lambdas / objects with __call__ are introspectable; partial with
-        # opaque builtins are not. Simulate the latter by raising in __signature__.
-        def __call__(self, *args, **kwargs):
-            calls.append((args, kwargs))
-
-        @property
-        def __signature__(self):
-            raise ValueError("uninspectable")
-
-    io_type = "TEST_UNINSPECTABLE_V3"
-    try:
-        _io.register_dynamic_input_func(io_type, _CallableObj())
-        fn = _io.get_dynamic_input_func(io_type)
-        fn({}, {}, ("X", {}), "required", None, {"x": "INT"})
-        assert calls and len(calls[0][0]) == 6
-    finally:
-        _io.DYNAMIC_INPUT_LOOKUP.pop(io_type, None)