diff --git a/libs/langgraph/src/graph/graph.ts b/libs/langgraph/src/graph/graph.ts
index 1b121ee8..02650f9a 100644
--- a/libs/langgraph/src/graph/graph.ts
+++ b/libs/langgraph/src/graph/graph.ts
@@ -41,7 +41,7 @@ export interface BranchOptions<IO, N extends string> {
 export class Branch<IO, N extends string> {
   condition: (
     input: IO,
-    config?: RunnableConfig
+    config: RunnableConfig
   ) =>
     | string
     | Send
diff --git a/libs/langgraph/src/prebuilt/agent_executor.ts b/libs/langgraph/src/prebuilt/agent_executor.ts
index 21611833..d6a6e462 100644
--- a/libs/langgraph/src/prebuilt/agent_executor.ts
+++ b/libs/langgraph/src/prebuilt/agent_executor.ts
@@ -44,10 +44,7 @@ export function createAgentExecutor({
     return "continue";
   };
 
-  const runAgent = async (
-    data: AgentExecutorState,
-    config?: RunnableConfig
-  ) => {
+  const runAgent = async (data: AgentExecutorState, config: RunnableConfig) => {
     const agentOutcome = await agentRunnable.invoke(data, config);
     return {
       agentOutcome,
@@ -56,7 +53,7 @@ export function createAgentExecutor({
 
   const executeTools = async (
     data: AgentExecutorState,
-    config?: RunnableConfig
+    config: RunnableConfig
   ): Promise<Partial<AgentExecutorState>> => {
     const agentAction = data.agentOutcome;
     if (!agentAction || "returnValues" in agentAction) {
diff --git a/libs/langgraph/src/prebuilt/chat_agent_executor.ts b/libs/langgraph/src/prebuilt/chat_agent_executor.ts
index 861d7f68..6cdd0715 100644
--- a/libs/langgraph/src/prebuilt/chat_agent_executor.ts
+++ b/libs/langgraph/src/prebuilt/chat_agent_executor.ts
@@ -70,7 +70,7 @@ export function createFunctionCallingExecutor<Model extends object>({
   // Define the function that calls the model
   const callModel = async (
     state: FunctionCallingExecutorState,
-    config?: RunnableConfig
+    config: RunnableConfig
   ) => {
     const { messages } = state;
     const response = await newModel.invoke(messages, config);
@@ -104,7 +104,7 @@ export function createFunctionCallingExecutor<Model extends object>({
 
   const callTool = async (
     state: FunctionCallingExecutorState,
-    config?: RunnableConfig
+    config: RunnableConfig
   ) => {
     const action = _getAction(state);
     // We call the tool_executor and get back a response
diff --git a/libs/langgraph/src/prebuilt/react_agent_executor.ts b/libs/langgraph/src/prebuilt/react_agent_executor.ts
index bba625aa..4463c090 100644
--- a/libs/langgraph/src/prebuilt/react_agent_executor.ts
+++ b/libs/langgraph/src/prebuilt/react_agent_executor.ts
@@ -154,7 +154,7 @@ export function createReactAgent(
     }
   };
 
-  const callModel = async (state: AgentState, config?: RunnableConfig) => {
+  const callModel = async (state: AgentState, config: RunnableConfig) => {
     const { messages } = state;
     // TODO: Auto-promote streaming.
     return { messages: [await modelRunnable.invoke(messages, config)] };
diff --git a/libs/langgraph/src/prebuilt/tool_executor.ts b/libs/langgraph/src/prebuilt/tool_executor.ts
index a0366082..bbe03a98 100644
--- a/libs/langgraph/src/prebuilt/tool_executor.ts
+++ b/libs/langgraph/src/prebuilt/tool_executor.ts
@@ -50,7 +50,7 @@ export class ToolExecutor extends RunnableBinding<
       ...fields,
     };
     const bound = RunnableLambda.from(
-      async (input: ToolInvocationInterface, config?: RunnableConfig) =>
+      async (input: ToolInvocationInterface, config: RunnableConfig) =>
         this._execute(input, config)
     );
     super({
@@ -74,7 +74,7 @@ export class ToolExecutor extends RunnableBinding<
    */
   async _execute(
     toolInvocation: ToolInvocationInterface,
-    config?: RunnableConfig
+    config: RunnableConfig
   ): Promise<ToolExecutorOutputType> {
     if (!(toolInvocation.tool in this.toolMap)) {
       return this.invalidToolMsgTemplate
diff --git a/libs/langgraph/src/pregel/write.ts b/libs/langgraph/src/pregel/write.ts
index 9c276443..0d306834 100644
--- a/libs/langgraph/src/pregel/write.ts
+++ b/libs/langgraph/src/pregel/write.ts
@@ -53,8 +53,8 @@ export class ChannelWrite<
       .join(",")}>`;
     super({
       ...{ writes, name, tags },
-      func: async (input: RunInput, config?: RunnableConfig) => {
-        return this._write(input, config ?? {});
+      func: async (input: RunInput, config: RunnableConfig) => {
+        return this._write(input, config);
       },
     });
 
diff --git a/libs/langgraph/src/tests/pregel.test.ts b/libs/langgraph/src/tests/pregel.test.ts
index f1a675e6..8b384a09 100644
--- a/libs/langgraph/src/tests/pregel.test.ts
+++ b/libs/langgraph/src/tests/pregel.test.ts
@@ -3787,20 +3787,14 @@ describe("StateGraph", () => {
       hello: Annotation<string>,
     });
 
-    const nodeA = (
-      _: typeof StateAnnotation.State,
-      config?: RunnableConfig
-    ) => {
+    const nodeA = (_: typeof StateAnnotation.State, config: RunnableConfig) => {
       // Unfortunately can't infer input types at runtime :(
-      expect(config?.configurable?.foo).toEqual("bar");
+      expect(config.configurable?.foo).toEqual("bar");
       return {};
     };
 
-    const nodeB = (
-      _: typeof StateAnnotation.State,
-      config?: RunnableConfig
-    ) => {
-      expect(config?.configurable?.foo).toEqual("bar");
+    const nodeB = (_: typeof StateAnnotation.State, config: RunnableConfig) => {
+      expect(config.configurable?.foo).toEqual("bar");
       return {
         hello: "again",
         now: 123,
@@ -3897,6 +3891,20 @@ describe("StateGraph", () => {
       hello: "again",
     });
   });
+
+  it("can be passed a conditional edge with required config arg", async () => {
+    const workflow = new StateGraph(MessagesAnnotation)
+      .addNode("nodeOne", () => ({}))
+      .addConditionalEdges("nodeOne", (_, config) => {
+        expect(config).toBeDefined();
+        if (!config) {
+          throw new Error("config must be defined.");
+        }
+        return END;
+      });
+    const app = workflow.compile();
+    await app.invoke({ messages: [] });
+  });
 });
 
 describe("PreBuilt", () => {
@@ -5252,11 +5260,8 @@ describe("Managed Values (context) can be passed through state", () => {
   it("should be passed through state but not stored in checkpointer", async () => {
     const nodeOne = async (
       data: typeof AgentAnnotation.State,
-      config?: RunnableConfig
+      config: RunnableConfig
     ): Promise<Partial<typeof AgentAnnotation.State>> => {
-      if (!config) {
-        throw new Error("config is undefined");
-      }
       expect(config.configurable?.thread_id).toEqual(threadId);
 
       expect(data.sharedStateKey).toEqual({});
@@ -5272,13 +5277,8 @@ describe("Managed Values (context) can be passed through state", () => {
     };
 
     const nodeTwo = async (
-      data: typeof AgentAnnotation.State,
-      config?: RunnableConfig
+      data: typeof AgentAnnotation.State
     ): Promise<Partial<typeof AgentAnnotation.State>> => {
-      if (!config) {
-        throw new Error("config is undefined");
-      }
-
       expect(data.sharedStateKey).toEqual({
         sharedStateValue: {
           value: "shared",
@@ -5314,13 +5314,8 @@ describe("Managed Values (context) can be passed through state", () => {
     };
 
     const nodeThree = async (
-      data: typeof AgentAnnotation.State,
-      config?: RunnableConfig
+      data: typeof AgentAnnotation.State
     ): Promise<Partial<typeof AgentAnnotation.State>> => {
-      if (!config) {
-        throw new Error("config is undefined");
-      }
-
       expect(data.sharedStateKey).toEqual({
         sharedStateValue: {
           value: "updated",
@@ -5389,11 +5384,8 @@ describe("Managed Values (context) can be passed through state", () => {
   it("can not access shared values from other 'on' keys", async () => {
     const nodeOne = async (
       data: typeof AgentAnnotation.State,
-      config?: RunnableConfig
+      config: RunnableConfig
     ): Promise<Partial<typeof AgentAnnotation.State>> => {
-      if (!config) {
-        throw new Error("config is undefined");
-      }
       expect(config.configurable?.thread_id).toBe(threadId);
       expect(config.configurable?.assistant_id).toBe("a");
 
@@ -5410,11 +5402,8 @@ describe("Managed Values (context) can be passed through state", () => {
 
     const nodeTwo = async (
       data: typeof AgentAnnotation.State,
-      config?: RunnableConfig
+      config: RunnableConfig
     ): Promise<Partial<typeof AgentAnnotation.State>> => {
-      if (!config) {
-        throw new Error("config is undefined");
-      }
       expect(config.configurable?.thread_id).toBe(threadId);
       expect(config.configurable?.assistant_id).toBe("b");
 
@@ -5431,12 +5420,8 @@ describe("Managed Values (context) can be passed through state", () => {
 
     const nodeThree = async (
       data: typeof AgentAnnotation.State,
-      config?: RunnableConfig
+      config: RunnableConfig
     ): Promise<Partial<typeof AgentAnnotation.State>> => {
-      if (!config) {
-        throw new Error("config is undefined");
-      }
-
       expect(config.configurable?.thread_id).toBe(threadId);
       expect(config.configurable?.assistant_id).toBe("a");
 
@@ -5451,12 +5436,8 @@ describe("Managed Values (context) can be passed through state", () => {
 
     const nodeFour = async (
       data: typeof AgentAnnotation.State,
-      config?: RunnableConfig
+      config: RunnableConfig
     ): Promise<Partial<typeof AgentAnnotation.State>> => {
-      if (!config) {
-        throw new Error("config is undefined");
-      }
-
       expect(config.configurable?.thread_id).toBe(threadId);
       expect(config.configurable?.assistant_id).toBe("b");
 
@@ -5611,11 +5592,8 @@ describe("Managed Values (context) can be passed through state", () => {
     // Define nodeOne that sets sharedStateKey and adds a message
     const nodeOne = async (
       data: typeof AgentAnnotation.State,
-      config?: RunnableConfig
+      config: RunnableConfig
     ): Promise<Partial<typeof AgentAnnotation.State>> => {
-      if (!config) {
-        throw new Error("config is undefined");
-      }
       expect(config.configurable?.thread_id).toEqual(threadId);
 
       expect(data.sharedStateKey).toEqual({});
@@ -5632,13 +5610,8 @@ describe("Managed Values (context) can be passed through state", () => {
 
     // Define nodeTwo that updates sharedStateKey
     const nodeTwo = async (
-      data: typeof AgentAnnotation.State,
-      config?: RunnableConfig
+      data: typeof AgentAnnotation.State
     ): Promise<Partial<typeof AgentAnnotation.State>> => {
-      if (!config) {
-        throw new Error("config is undefined");
-      }
-
       expect(data.sharedStateKey).toEqual({
         data: {
           value: "shared",