LangChain chat msg and summary refactor

Author: amychisholm03

lib/llm-events-new/base.js

@@ -41,6 +41,9 @@ class LlmEvent {
     this.trace_id = transaction?.traceId
     this.vendor = vendor
     this.metadata = agent
+    // TODO: Does not appear in AIM spec, but was a
+    // requirement for LangChain instrumentation back in 2024?
+    // this.appName = agent.config.applications()[0]
 
     // Omit `error` property if no error occurred
     if (error === true) {

lib/llm-events-new/chat-summary.js

@@ -41,12 +41,13 @@ class LlmChatCompletionSummary extends LlmEvent {
     responseOrg, temperature, maxTokens, numMsgs, finishReason }) {
     super({ agent, segment, transaction, vendor, responseModel, requestId, error })
 
-    this['request.model'] = requestModel
-    this['request.max_tokens'] = maxTokens
-    this['request.temperature'] = temperature
-    this['response.number_of_messages'] = numMsgs
+    if (requestModel) this['request.model'] = requestModel
+    if (maxTokens) this['request.max_tokens'] = maxTokens
+    if (temperature) this['request.temperature'] = temperature
     if (finishReason) this['response.choices.finish_reason'] = finishReason
     if (responseOrg) this['response.organization'] = responseOrg
+
+    this['response.number_of_messages'] = numMsgs
     this.timestamp = segment.timer.start
     this.duration = segment.getDurationInMillis()
   }

lib/llm-events-new/langchain/chat-message.js

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2026 New Relic Corporation. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+'use strict'
+const LlmChatCompletionMessage = require('../chat-message')
+const { isSimpleObject } = require('../../util/objects')
+
+/**
+ * Encapsulates a LangChain LlmChatCompletionMessage.
+ */
+class LangChainLlmChatCompletionMessage extends LlmChatCompletionMessage {
+  virtual_llm = true
+  /**
+   * @param {object} params constructor parameters
+   * @param {Agent} params.agent New Relic agent instance
+   * @param {object} params.segment Current segment
+   * @param {object} params.transaction Current and active transaction
+   * @param {string} params.runId LangChain run ID (will be used as response ID)
+   * @param {number} params.sequence Index (beginning at 0) associated with
+   *    each message including the prompt and responses
+   * @param {string} params.content Content of the message
+   * @param {string} [params.role] Role of the message creator (e.g. `user`, `assistant`, `tool`)
+   * @param {string} params.completionId ID of the `LlmChatCompletionSummary` event that
+   *    this message event is connected to
+   * @param {boolean} [params.isResponse] `true` if a message is the result of a chat
+   *    completion and not an input message - omitted in `false` cases
+   * @param {object} params.metadata LangChain metadata object
+   * @param {object[]} params.tags LangChain tags
+   */
+  constructor({ agent, segment, transaction, runId, sequence, role, content, completionId, isResponse, metadata, tags }) {
+    super({ agent,
+      segment,
+      transaction,
+      vendor: 'langchain',
+      responseId: runId,
+      requestId: runId,
+      sequence,
+      content,
+      role,
+      completionId,
+      isResponse })
+
+    // TODO: Does not appear in AIM spec, but was a
+    // requirement for LangChain instrumentation back in 2024?
+    this.appName = agent.config.applications()[0]
+    this.langchainMeta = metadata
+    this.tags = Array.isArray(tags) ? tags.join(',') : tags
+  }
+
+  // eslint-disable-next-line accessor-pairs
+  set langchainMeta(value) {
+    if (isSimpleObject(value) === false) {
+      return
+    }
+    for (const [key, val] of Object.entries(value)) {
+      this[`metadata.${key}`] = val
+    }
+  }
+}
+
+module.exports = LangChainLlmChatCompletionMessage

lib/llm-events-new/langchain/chat-summary.js

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2026 New Relic Corporation. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+'use strict'
+const LlmChatCompletionSummary = require('../chat-summary')
+const { isSimpleObject } = require('../../util/objects')
+
+/**
+ * Encapsulates a LangChain LlmChatCompletionSummary.
+ */
+class LangChainLlmChatCompletionSummary extends LlmChatCompletionSummary {
+  virtual_llm = true
+  constructor({ agent, segment, transaction, error, numMsgs = 0, runId, metadata = {}, tags = '' }) {
+    super({ agent,
+      segment,
+      transaction,
+      vendor: 'langchain',
+      requestId: runId,
+      error,
+      numMsgs })
+
+    // TODO: Does not appear in AIM spec, but was a
+    // requirement for LangChain instrumentation back in 2024?
+    this.appName = agent.config.applications()[0]
+    this.langchainMeta = metadata
+    this.tags = Array.isArray(tags) ? tags.join(',') : tags
+  }
+
+  // eslint-disable-next-line accessor-pairs
+  set langchainMeta(value) {
+    if (isSimpleObject(value) === false) {
+      return
+    }
+    for (const [key, val] of Object.entries(value)) {
+      this[`metadata.${key}`] = val
+    }
+  }
+}
+
+module.exports = LangChainLlmChatCompletionSummary

lib/llm-events-new/langchain/index.js

@@ -0,0 +1,14 @@
+/*
+ * Copyright 2026 New Relic Corporation. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+'use strict'
+
+const LlmChatCompletionMessage = require('./chat-message')
+const LlmChatCompletionSummary = require('./chat-summary')
+
+module.exports = {
+  LlmChatCompletionMessage,
+  LlmChatCompletionSummary,
+}

lib/llm-events/langchain/chat-completion-message.js

@@ -7,8 +7,6 @@
 
 module.exports = {
   LangChainEvent: require('./event'),
-  LangChainCompletionMessage: require('./chat-completion-message'),
-  LangChainCompletionSummary: require('./chat-completion-summary'),
   LangChainVectorSearch: require('./vector-search'),
   LangChainVectorSearchResult: require('./vector-search-result'),
   LangChainTool: require('./tool')

lib/llm-events/langchain/chat-completion-summary.js

@@ -6,9 +6,9 @@
 const { AiMonitoringChatSubscriber } = require('../ai-monitoring')
 const { AI: { LANGCHAIN } } = require('../../metrics/names')
 const {
-  LangChainCompletionMessage,
-  LangChainCompletionSummary
-} = require('#agentlib/llm-events/langchain/index.js')
+  LlmChatCompletionMessage,
+  LlmChatCompletionSummary
+} = require('#agentlib/llm-events-new/langchain/index.js')
 const { langchainRunId } = require('#agentlib/symbols.js')
 
 class LangchainRunnableSubscriber extends AiMonitoringChatSubscriber {
@@ -42,15 +42,15 @@ class LangchainRunnableSubscriber extends AiMonitoringChatSubscriber {
     // Stream calls that error on initial call lack a response message
     // so create an empty array in that case
     const messages = response ? [response] : []
-    return new LangChainCompletionSummary({
+    return new LlmChatCompletionSummary({
       agent: this.agent,
       segment,
       transaction,
       error: !!err,
-      messages,
+      numMsgs: messages?.length,
+      runId: segment[langchainRunId],
       metadata,
-      tags,
-      runId: segment[langchainRunId]
+      tags
     })
   }
 
@@ -85,7 +85,7 @@ class LangchainRunnableSubscriber extends AiMonitoringChatSubscriber {
     const isResponse = message === response
     const { content, role } = this.extractContentAndRole(message)
 
-    return new LangChainCompletionMessage({
+    return new LlmChatCompletionMessage({
       sequence: index,
       agent: this.agent,
       content,

lib/llm-events/langchain/index.js

@@ -7,7 +7,7 @@
 
 const test = require('node:test')
 const assert = require('node:assert')
-const LangChainCompletionMessage = require('../../../../lib/llm-events/langchain/chat-completion-message')
+const LlmChatCompletionMessage = require('#agentlib/llm-events-new/langchain/chat-message.js')
 
 test.beforeEach((ctx) => {
   ctx.nr = {}
@@ -49,12 +49,13 @@ test.beforeEach((ctx) => {
     }
   }
 
+  ctx.nr.completionId = '4bea415a30e702d45f5dd521c74b6216d209'
   ctx.nr.runId = 'run-1'
   ctx.nr.metadata = { foo: 'foo' }
 })
 
 test('creates entity', async (t) => {
-  const msg = new LangChainCompletionMessage({
+  const msg = new LlmChatCompletionMessage({
     ...t.nr,
     sequence: 1,
     content: 'hello world',
@@ -73,12 +74,12 @@ test('creates entity', async (t) => {
   assert.equal(msg.sequence, 1)
   assert.equal(msg.role, 'assistant', 'should assume assistant role based on isResponse=true')
   assert.equal(msg.content, 'hello world')
-  assert.match(msg.completion_id, /[a-z0-9-]{36}/)
+  assert.equal(msg.completion_id, t.nr.completionId)
   assert.equal(msg.timestamp, undefined, 'should not have a timestamp defined if isResponse=true')
 })
 
 test('assigns role if given', async(t) => {
-  const msg = new LangChainCompletionMessage({
+  const msg = new LlmChatCompletionMessage({
     ...t.nr,
     sequence: 1,
     content: 'hello world',
@@ -88,7 +89,7 @@ test('assigns role if given', async(t) => {
 })
 
 test('assigns role and timestamp correctly if isResponse is false', async(t) => {
-  const msg = new LangChainCompletionMessage({
+  const msg = new LlmChatCompletionMessage({
     ...t.nr,
     sequence: 0,
     content: 'hello world',
@@ -99,16 +100,16 @@ test('assigns role and timestamp correctly if isResponse is false', async(t) =>
 })
 
 test('assigns id correctly', async (t) => {
-  let msg = new LangChainCompletionMessage({ ...t.nr, runId: '', sequence: 1 })
-  assert.match(msg.id, /[a-z0-9-]{36}-1/)
+  let msg = new LlmChatCompletionMessage({ ...t.nr, runId: '', sequence: 1 })
+  assert.match(msg.id, /[a-z0-9-]{36}/)
 
-  msg = new LangChainCompletionMessage({ ...t.nr, runId: '123456', sequence: 42 })
+  msg = new LlmChatCompletionMessage({ ...t.nr, runId: '123456', sequence: 42 })
   assert.equal(msg.id, '123456-42')
 })
 
 test('respects record_content setting', async (t) => {
   t.nr.agent.config.ai_monitoring.record_content.enabled = false
-  const search = new LangChainCompletionMessage({
+  const search = new LlmChatCompletionMessage({
     ...t.nr,
     sequence: 1,
     content: 'hello world'