diff --git a/src/ytdl_sub/script/script.py b/src/ytdl_sub/script/script.py
index 3b54c9c1..acaa5d8a 100644
--- a/src/ytdl_sub/script/script.py
+++ b/src/ytdl_sub/script/script.py
@@ -1,4 +1,5 @@
 # pylint: disable=missing-raises-doc
+import copy
 from typing import Dict
 from typing import List
 from typing import Optional
@@ -696,6 +697,11 @@ class Script:
         """
         return set(to_function_definition_name(name) for name in self._functions.keys())
 
+    def _to_syntax_tree(self, maybe_resolved: SyntaxTree | Resolvable) -> SyntaxTree:
+        if isinstance(maybe_resolved, Resolvable):
+            return ResolvedSyntaxTree(ast=[maybe_resolved])
+        return maybe_resolved
+
     def resolve_partial(
         self,
         unresolvable: Optional[Set[str]] = None,
@@ -739,8 +745,8 @@ class Script:
                 # which means we can iterate again
                 partially_resolved |= definition != maybe_resolved
 
-        return Script({}).add_parsed(
-            self._functions
-            | {var.name: definition for var, definition in resolved.items()}
-            | unresolved
+        return copy.deepcopy(self).add_parsed(
+            {var.name: self._variables[var.name] for var in unresolvable}
+            | {var.name: self._to_syntax_tree(definition) for var, definition in resolved.items()}
+            | {var.name: self._to_syntax_tree(definition) for var, definition in unresolved.items()}
         )
diff --git a/src/ytdl_sub/script/types/function.py b/src/ytdl_sub/script/types/function.py
index 593e6a8e..9e69c01a 100644
--- a/src/ytdl_sub/script/types/function.py
+++ b/src/ytdl_sub/script/types/function.py
@@ -39,25 +39,6 @@ class Function(FunctionType, VariableDependency, ABC):
     def _iterable_arguments(self) -> List[Argument]:
         return self.args
 
-    def partial_resolve(
-        self: TypeT,
-        resolved_variables: Dict[Variable, Resolvable],
-        custom_functions: Dict[str, "VariableDependency"],
-    ) -> TypeT | Resolvable:
-        maybe_resolvable_values, is_resolvable = VariableDependency.try_partial_resolve(
-            args=self.args,
-            resolved_variables=resolved_variables,
-            custom_functions=custom_functions,
-        )
-
-        if is_resolvable:
-            return self.resolve(
-                resolved_variables=resolved_variables,
-                custom_functions=custom_functions,
-            )
-
-        return BuiltInFunction(name=self.name, args=maybe_resolvable_values)
-
 
 class CustomFunction(Function, NamedCustomFunction):
     def resolve(
@@ -104,6 +85,28 @@ class CustomFunction(Function, NamedCustomFunction):
         # been checked in the parser with
         raise UNREACHABLE
 
+    def partial_resolve(
+        self,
+        resolved_variables: Dict[Variable, Resolvable],
+        custom_functions: Dict[str, "VariableDependency"],
+    ) -> TypeT | Resolvable:
+        maybe_resolvable_values, is_resolvable = VariableDependency.try_partial_resolve(
+            args=self.args,
+            resolved_variables=resolved_variables,
+            custom_functions=custom_functions,
+        )
+
+        if any(var not in resolved_variables for var in custom_functions[self.name].variables):
+            is_resolvable = False
+
+        if is_resolvable:
+            return self.resolve(
+                resolved_variables=resolved_variables,
+                custom_functions=custom_functions,
+            )
+
+        return CustomFunction(name=self.name, args=maybe_resolvable_values)
+
 
 class BuiltInFunction(Function, BuiltInFunctionType):
     def validate_args(self) -> "BuiltInFunction":
@@ -332,5 +335,37 @@ class BuiltInFunction(Function, BuiltInFunctionType):
                 f"Runtime error occurred when executing the function %{self.name}: {str(exc)}"
             ) from exc
 
+    def partial_resolve(
+        self,
+        resolved_variables: Dict[Variable, Resolvable],
+        custom_functions: Dict[str, "VariableDependency"],
+    ) -> TypeT | Resolvable:
+        conditional_return_args = self.function_spec.conditional_arg_indices(
+            num_input_args=len(self.args)
+        )
+
+        # If the function is conditional, only run if its entirety is resolvable
+        if conditional_return_args:
+            if self.is_subset_of(variables=resolved_variables, custom_function_definitions=custom_functions):
+                return self.resolve(
+                    resolved_variables=resolved_variables,
+                    custom_functions=custom_functions,
+                )
+            return self
+        else:
+            maybe_resolvable_values, is_resolvable = VariableDependency.try_partial_resolve(
+                args=self.args,
+                resolved_variables=resolved_variables,
+                custom_functions=custom_functions,
+            )
+
+            if is_resolvable:
+                return self.resolve(
+                    resolved_variables=resolved_variables,
+                    custom_functions=custom_functions,
+                )
+
+        return BuiltInFunction(name=self.name, args=maybe_resolvable_values)
+
     def __hash__(self):
         return hash((self.name, *self.args))
diff --git a/src/ytdl_sub/utils/script.py b/src/ytdl_sub/utils/script.py
index 027a0bd8..5c0264f9 100644
--- a/src/ytdl_sub/utils/script.py
+++ b/src/ytdl_sub/utils/script.py
@@ -144,6 +144,12 @@ class ScriptUtils:
         """
         Converts any JSON-compatible value into equivalent script syntax
         """
+        if isinstance(value, SyntaxTree):
+            output = ""
+            for arg in value.ast:
+                output += cls._to_script_code(arg, top_level=True)
+            return output
+
         return cls._to_script_code(cls._to_script_argument(value), top_level=True)
 
     @classmethod
diff --git a/tests/unit/config/test_subscription.py b/tests/unit/config/test_subscription.py
index 418e1d31..127c94b8 100644
--- a/tests/unit/config/test_subscription.py
+++ b/tests/unit/config/test_subscription.py
@@ -11,6 +11,7 @@ from ytdl_sub.config.config_file import ConfigFile
 from ytdl_sub.plugins.nfo_tags import NfoTagsOptions
 from ytdl_sub.subscriptions.subscription import Subscription
 from ytdl_sub.utils.exceptions import ValidationException
+from ytdl_sub.utils.script import ScriptUtils
 
 
 @contextmanager
@@ -616,4 +617,6 @@ def test_default_docker_config_and_subscriptions(
     unresolvable.add("sibling_metadata")
 
     out = default_subs[0].overrides.script.resolve_partial(unresolvable=unresolvable)
+    prev = ScriptUtils.to_native_script(out._variables['episode_file_name'])
+
     print("hi")