diff --git a/py/src/braintrust/functions/invoke.py b/py/src/braintrust/functions/invoke.py
index 9bd0a41a8..e473870ee 100644
--- a/py/src/braintrust/functions/invoke.py
+++ b/py/src/braintrust/functions/invoke.py
@@ -211,13 +211,20 @@ def init_function(project_name: str, slug: str, version: Optional[str] = None):
     :return: A function that can be used as a task or scorer.
     """
 
-    def f(*args: Any, **kwargs: Any) -> Any:
-        if len(args) > 0:
-            # Task.
-            return invoke(project_name=project_name, slug=slug, version=version, input=args[0])
+    def f(input, hooks=None):
+        # When used as a task, hooks may be provided with metadata
+        # When used as a scorer, all args come via kwargs in the input dict
+        if hooks is not None and not isinstance(hooks, str):
+            # Task mode with hooks object
+            metadata = hooks.metadata if hasattr(hooks, 'metadata') else None
+            return invoke(project_name=project_name, slug=slug, version=version, input=input, metadata=metadata)
+        elif isinstance(input, dict) and ('output' in input or 'expected' in input or 'metadata' in input):
+            # Scorer mode - input is a dict with scorer args
+            metadata = input.get('metadata')
+            return invoke(project_name=project_name, slug=slug, version=version, input=input, metadata=metadata)
         else:
-            # Scorer.
-            return invoke(project_name=project_name, slug=slug, version=version, input=kwargs)
+            # Task mode without hooks (backward compatibility) or hooks is not actually hooks
+            return invoke(project_name=project_name, slug=slug, version=version, input=input)
 
     f.__name__ = f"init_function-{project_name}-{slug}-{version or 'latest'}"
     return f