fix(sdk): fetchStateHistory should not crash if thread is empty (#1397)

.changeset/solid-jars-yawn.md

@@ -0,0 +1,7 @@
+---
+"@langchain/langgraph-api": patch
+"@langchain/langgraph-cli": patch
+"@langchain/langgraph-ui": patch
+---
+
+Embed methods for obtaining state should use `getGraph(...)`

.changeset/some-deer-say.md

@@ -0,0 +1,5 @@
+---
+"@langchain/langgraph-sdk": patch
+---
+
+Fix fetching state with `fetchStateHistory: false` causing crash if thread is empty

libs/langgraph-api/src/experimental/embed.mts

@@ -156,7 +156,7 @@ export function createEmbedServer(options: {
 
       const thread = await options.threads.get(thread_id);
       const graphId = thread.metadata?.graph_id as string | undefined | null;
-      const graph = graphId ? options.graph[graphId] : undefined;
+      const graph = graphId ? await getGraph(graphId) : undefined;
 
       if (graph == null) {
         return jsonExtra(
@@ -190,7 +190,7 @@ export function createEmbedServer(options: {
 
       const thread = await options.threads.get(thread_id);
       const graphId = thread.metadata?.graph_id as string | undefined | null;
-      const graph = graphId ? options.graph[graphId] : undefined;
+      const graph = graphId ? await getGraph(graphId) : undefined;
       if (graph == null) return jsonExtra(c, []);
 
       const config = { configurable: { thread_id, ...checkpoint } };

libs/sdk/src/react/stream.tsx

@@ -244,7 +244,8 @@ function getBranchSequence<StateType extends Record<string, unknown>>(
     }
 
     for (const value of children) {
-      const id = value.checkpoint.checkpoint_id!;
+      const id = value.checkpoint?.checkpoint_id;
+      if (id == null) continue;
 
       let { sequence } = task;
       let { path } = task;
@@ -297,7 +298,10 @@ function getBranchView<StateType extends Record<string, unknown>>(
 
     if (item.type === "node") {
       history.push(item.value);
-      branchByCheckpoint[item.value.checkpoint.checkpoint_id!] = {
+      const checkpointId = item.value.checkpoint?.checkpoint_id;
+      if (checkpointId == null) continue;
+
+      branchByCheckpoint[checkpointId] = {
         branch: item.path.join(PATH_SEP),
         branchOptions: (item.path.length > 0
           ? pathMap[item.path.at(-2) ?? ROOT_ID] ?? []
@@ -312,7 +316,7 @@ function getBranchView<StateType extends Record<string, unknown>>(
           ? item.items.findIndex((value) => {
               const firstItem = value.items.at(0);
               if (!firstItem || firstItem.type !== "node") return false;
-              return firstItem.value.checkpoint.checkpoint_id === forkId;
+              return firstItem.value.checkpoint?.checkpoint_id === forkId;
             })
           : -1;
 
@@ -330,9 +334,10 @@ function fetchHistory<StateType extends Record<string, unknown>>(
   options?: { limit?: boolean | number }
 ) {
   if (options?.limit === false) {
-    return client.threads
-      .getState<StateType>(threadId)
-      .then((state) => [state]);
+    return client.threads.getState<StateType>(threadId).then((state) => {
+      if (state.checkpoint == null) return [];
+      return [state];
+    });
   }
 
   const limit = typeof options?.limit === "number" ? options.limit : 1000;
@@ -961,9 +966,11 @@ export function useStream<
           | ThreadState<StateType>
           | undefined;
 
-        let branch = firstSeen
-          ? branchByCheckpoint[firstSeen.checkpoint.checkpoint_id!]
-          : undefined;
+        const checkpointId = firstSeen?.checkpoint?.checkpoint_id;
+        let branch =
+          firstSeen && checkpointId != null
+            ? branchByCheckpoint[checkpointId]
+            : undefined;
 
         if (!branch?.branch?.length) branch = undefined;