LangChain LLM event refactor

lib/llm-events/langchain/attach-attributes.js

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2026 New Relic Corporation. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+'use strict'
+
+module.exports = attachAttributes
+
+const { isSimpleObject } = require('#agentlib/util/objects.js')
+
+/**
+ * Applies common attributes to the various LangChain object types. We can't
+ * inline this to a common base class, because they all need to inherit from
+ * disparate base classes.
+ *
+ * @param {object} params Function parameters
+ * @param {object} params.target The LLM event object to decorate.
+ * @param {object} [params.agent] The agent instance.
+ * @param {object} [params.metadata] A set of key-value pairs to attach.
+ * @param {string|string[]} [params.tags] A comma separated list of tags, or an
+ * array of string tags.
+ */
+function attachAttributes({ target, agent = null, metadata = null, tags = null }) {
+  if (agent) {
+    target.appName = agent.config.applications()[0]
+  }
+
+  if (isSimpleObject(metadata) === true) {
+    target.langchainMeta = metadata
+    for (const [k, v] of Object.entries(metadata)) {
+      target[`metadata.${k}`] = v
+    }
+  }
+
+  if (Array.isArray(tags) === true) {
+    target.tags = tags.join(',')
+  } else if (typeof tags === 'string') {
+    target.tags = tags
+  }
+}

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

@@ -5,13 +5,14 @@
 
 'use strict'
 const LlmChatCompletionMessage = require('../chat-completion-message')
-const { isSimpleObject } = require('../../util/objects')
+const attachAttributes = require('./attach-attributes')
 
 /**
  * Encapsulates a LangChain LlmChatCompletionMessage.
  */
 class LangChainLlmChatCompletionMessage extends LlmChatCompletionMessage {
   virtual_llm = true
+
   /**
    * @param {object} params constructor parameters
    * @param {Agent} params.agent New Relic agent instance
@@ -42,20 +43,7 @@ class LangChainLlmChatCompletionMessage extends LlmChatCompletionMessage {
       completionId,
       isResponse })
 
-    // Does not appear in AIM spec as of 2/2026, but seemed
-    // to be a requirement back in 1/2024 (e.g. LangChain CDD).
-    this.appName = agent.config.applications()[0]
-
-    // `metadata.<key>` and `tags` do not appear in
-    // the AIM spec, but were a requirement for the
-    // initial LangChain instrumentation.
-    if (isSimpleObject(metadata)) {
-      this.langchainMeta = metadata
-      for (const [key, val] of Object.entries(metadata)) {
-        this[`metadata.${key}`] = val
-      }
-    }
-    this.tags = Array.isArray(tags) ? tags.join(',') : tags
+    attachAttributes({ target: this, agent, metadata, tags })
   }
 }
 

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

@@ -4,14 +4,16 @@
  */
 
 'use strict'
+
 const LlmChatCompletionSummary = require('../chat-completion-summary')
-const { isSimpleObject } = require('../../util/objects')
+const attachAttributes = require('./attach-attributes')
 
 /**
  * Encapsulates a LangChain LlmChatCompletionSummary.
  */
 class LangChainLlmChatCompletionSummary extends LlmChatCompletionSummary {
   virtual_llm = true
+
   constructor({ agent, segment, transaction, error, numMsgs = 0, runId, metadata = {}, tags = '' }) {
     super({ agent,
       segment,
@@ -21,20 +23,7 @@ class LangChainLlmChatCompletionSummary extends LlmChatCompletionSummary {
       error,
       numMsgs })
 
-    // Does not appear in AIM spec as of 2/2026, but seemed
-    // to be a requirement back in 1/2024 (e.g. LangChain CDD).
-    this.appName = agent.config.applications()[0]
-
-    // `metadata.<key>` and `tags` do not appear in
-    // the AIM spec, but were a requirement for the
-    // initial LangChain instrumentation.
-    if (isSimpleObject(metadata)) {
-      this.langchainMeta = metadata
-      for (const [key, val] of Object.entries(metadata)) {
-        this[`metadata.${key}`] = val
-      }
-    }
-    this.tags = Array.isArray(tags) ? tags.join(',') : tags
+    attachAttributes({ target: this, agent, metadata, tags })
   }
 }
 

lib/llm-events/langchain/tool.js

@@ -6,7 +6,7 @@
 'use strict'
 
 const LlmTool = require('../tool')
-const { isSimpleObject } = require('../../util/objects')
+const attachAttributes = require('./attach-attributes')
 
 /**
  * Encapsulates a LangChain LlmTool event.
@@ -35,12 +35,6 @@ module.exports = class LangChainLlmTool extends LlmTool {
     // appear in the AIM spec, but were a requirement for
     // the initial LangChain instrumentation.
     this.description = description
-    if (isSimpleObject(metadata)) {
-      this.langchainMeta = metadata
-      for (const [key, val] of Object.entries(metadata)) {
-        this[`metadata.${key}`] = val
-      }
-    }
-    this.tags = Array.isArray(tags) ? tags.join(',') : tags
+    attachAttributes({ target: this, metadata, tags })
   }
 }

lib/llm-events/langchain/vector-search-result.js

@@ -6,7 +6,7 @@
 'use strict'
 
 const LlmEvent = require('../event-base')
-const { isSimpleObject } = require('../../util/objects')
+const attachAttributes = require('./attach-attributes')
 
 /**
  * An event that captures data about a VectorStore `similaritySearch` call in LangChain.
@@ -35,18 +35,6 @@ module.exports = class LangChainLlmVectorSearchResult extends LlmEvent {
       this.page_content = pageContent
     }
 
-    // Does not appear in AIM spec as of 2/2026, but seemed
-    // to be a requirement back in 1/2024 (e.g. LangChain CDD).
-    this.appName = agent.config.applications()[0]
-
-    // `metadata.<key>` and `tags` do not appear in
-    // the AIM spec, but were a requirement for the
-    // initial LangChain instrumentation.
-    if (isSimpleObject(metadata)) {
-      this.langchainMeta = metadata
-      for (const [key, val] of Object.entries(metadata)) {
-        this[`metadata.${key}`] = val
-      }
-    }
+    attachAttributes({ target: this, agent, metadata })
   }
 }

lib/llm-events/langchain/vector-search.js

@@ -6,6 +6,7 @@
 'use strict'
 
 const LlmEvent = require('../event-base')
+const attachAttributes = require('./attach-attributes')
 
 /**
  * An event that captures data about a VectorStore `similaritySearch` call in LangChain.
@@ -33,8 +34,6 @@ module.exports = class LangChainLlmVectorSearch extends LlmEvent {
       this['request.query'] = query
     }
 
-    // Does not appear in AIM spec as of 2/2026, but seemed
-    // to be a requirement back in 1/2024 (e.g. LangChain CDD).
-    this.appName = agent.config.applications()[0]
+    attachAttributes({ target: this, agent })
   }
 }