diff --git a/graphcore/graph.py b/graphcore/graph.py
index 7ae8b5e..aae550c 100644
--- a/graphcore/graph.py
+++ b/graphcore/graph.py
@@ -249,7 +249,7 @@ def __call__(
 
 def _get_summarizer_pure(
     system_prompt: str,
-    initial_prompt: str,
+    initial_prompt: str | dict,
     state_type: type[StateT],
     context: SummaryConfig[StateT]
 ) -> PureFunction:
@@ -268,11 +268,13 @@ def to_return(state: StateT) -> PureFunctionGenerator:
             summary = msg.text
             resume_message = config.get_resume_prompt(state, summary)
             config.on_summary(state, summary, resume_message)
+            # Handle initial_prompt as either str or dict (with cache_control)
+            initial_content: list[str | dict] = [initial_prompt]
             return {
                 "messages": [
                     RemoveMessage(id="__remove_all__"),
                     SystemMessage(content=system_prompt),
-                    HumanMessage(content=initial_prompt, display_tag="initial_prompt"),
+                    HumanMessage(content=initial_content, display_tag="initial_prompt"),
                     HumanMessage(content=resume_message, display_tag="resume"),
                 ]
             }
@@ -300,7 +302,7 @@ def _get_initial_pure(
     t: Type[I],
     output_state: Type[O],
     sys_prompt: str,
-    initial_prompt: str,
+    initial_prompt: str | dict,
 ) -> PureFunction[I, O]:
     def impl(
         state: I
@@ -350,7 +352,7 @@ def impl(
 def get_summarizer(
     llm: LLM,
     system_prompt: str,
-    initial_prompt: str,
+    initial_prompt: str | dict,
     state_type: type[StateT],
     context: SummaryConfig[StateT]
 ) -> ChatNodeFunction[StateT]:
@@ -362,7 +364,7 @@ def get_summarizer(
 def get_async_summarizer(
     llm: LLM,
     system_prompt: str,
-    initial_prompt: str,
+    initial_prompt: str | dict,
     state_type: type[StateT],
     context: SummaryConfig[StateT]
 ) -> AsyncChatNodeFunction[StateT]:
@@ -376,7 +378,7 @@ def __call__(
         self,
         llm: LLM,
         system_prompt: str,
-        initial_prompt: str,
+        initial_prompt: str | dict,
         state_type: type[StateT],
         context: SummaryConfig[StateT]
     ) -> AnyChatNodeFunction[StateT]:
@@ -386,7 +388,7 @@ def initial_node(
     t: Type[InputState],
     output_state: Type[StateT],
     sys_prompt: str,
-    initial_prompt: str,
+    initial_prompt: str | dict,
     llm: LLM
 ) -> NodeFunction[InputState, StateT]:
     return _stitch_sync_impl(
@@ -398,7 +400,7 @@ def async_initial_node(
     t: Type[InputState],
     output_state: Type[StateT],
     sys_prompt: str,
-    initial_prompt: str,
+    initial_prompt: str | dict,
     llm: LLM
 ) -> AsyncNodeFunction[InputState, StateT]:
     return _stitch_async_impl(
@@ -412,7 +414,7 @@ def __call__(
         t: Type[InputState],
         output_state: Type[StateT],
         sys_prompt: str,
-        initial_prompt: str,
+        initial_prompt: str | dict,
         llm: LLM
     ) -> AnyNodeFunction[InputState, StateT]:
         ...
@@ -656,7 +658,7 @@ def build_workflow(
     input_type: Type[InputState],
     tools_list: Iterable[BaseTool | SplitTool],
     sys_prompt: str,
-    initial_prompt: str,
+    initial_prompt: str | dict,
     output_key: str,
     unbound_llm: BaseChatModel,
     output_schema: Optional[Type[OutputT]] = None,
@@ -685,7 +687,7 @@ def build_async_workflow(
     input_type: Type[InputState],
     tools_list: Iterable[BaseTool | SplitTool],
     sys_prompt: str,
-    initial_prompt: str,
+    initial_prompt: str | dict,
     output_key: str,
     unbound_llm: BaseChatModel,
     output_schema: Optional[Type[OutputT]] = None,
@@ -713,7 +715,7 @@ def _build_workflow(
     input_type: Type[InputState],
     tools_list: Iterable[BaseTool | SplitTool],
     sys_prompt: str,
-    initial_prompt: str,
+    initial_prompt: str | dict,
     output_key: str,
     unbound_llm: BaseChatModel,
     output_schema: Optional[Type[OutputT]],