Don't add outgoing tool call with content == ''

Author: amychisholm03

lib/subscribers/langchain/runnable-stream.js

@@ -115,20 +115,21 @@ class LangchainRunnableStreamSubscriber extends LangchainRunnableSubscriber {
    * Concats streamed content from various LangChain/LangGraph result formats.
    *
    * @param {object} result the stream result chunk
-   * @param {string} content the concated response as a string
-   * @returns {string} updated content
+   * @param {string|object} content the response so far
+   * @returns {string|object} updated response content. For LangGraph, it will return an object
+   * (e.g. AIMessage), so we have more info if we need to drop this response if it is incomplete
+   * (e.g outgoing tool call).
    */
   concatResponseContent(result, content) {
     if (result?.value?.messages || result?.value?.agent?.messages) {
       // LangGraph case:
       // The result.value.%messages field contains all messages,
       // request and response, and appends new events at the
-      // end of the array. The last result chunk will contain all messages
-      // in the stream with the final response at the end.
+      // end of the array. Therefore the las message is the most
+      // recent response.
       const langgraphMessages = result?.value?.messages ?? result?.value?.agent?.messages
       if (langgraphMessages.length > 0) {
-        const lastMsg = langgraphMessages[langgraphMessages.length - 1]
-        content = lastMsg?.content
+        content = langgraphMessages[langgraphMessages.length - 1]
       }
     } else if (typeof result?.value?.content === 'string') {
       // LangChain MessageChunk case

lib/subscribers/langchain/runnable.js

@@ -55,13 +55,20 @@ class LangchainRunnableSubscriber extends AiMonitoringChatSubscriber {
 
   getMessages({ request, response }) {
     const messages = []
-    // check if request is truthy and an empty string
     if (request || request === '') {
       messages.push(request)
     }
 
-    // check if response is truthy and an empty string
     if (response || response === '') {
+    // via langgraph api, response object lives at `messages[0]`
+      if (response.messages?.length > 0) {
+        response = response.messages[0]
+      }
+      if (response.content === '' && response?.tool_calls?.length > 0) {
+        // Do not create a LlmChatCompletionMessage for an outgoing
+        // tool call with no result yet
+        return [request]
+      }
       messages.push(response)
     }
 
@@ -94,11 +101,6 @@ class LangchainRunnableSubscriber extends AiMonitoringChatSubscriber {
    * @returns {object} an object with `content` (string) and `role` (string)
    */
   extractContentAndRole(msg) {
-    if (msg?.messages) {
-      // Typical structure for LangGraph
-      msg = msg.messages[0]
-    }
-
     // Get message content
     let content = ''
     if (typeof msg === 'string') {

test/versioned/langgraph/graph-stream.test.js

@@ -265,6 +265,11 @@ test('should have LlmTool events from LangChain instrumentation', async (t) => {
     const chatEvents = events.filter((e) => e[0].type === 'LlmChatCompletionMessage' && e[1].role === 'tool')
     assert.equal(chatEvents.length, 2, 'should have one tool message for openai and another for langchain')
 
+    const langchainEvents = events.filter((e) => e[0].type === 'LlmChatCompletionMessage' && e[1].vendor === 'langchain')
+    langchainEvents.forEach((msg) => {
+      assert.ok(msg?.[1]?.content?.length > 0, 'should have non-empty content')
+    })
+
     tx.end()
   })
 })