fix(openai): fix content in AIMessage for tool and function calls (#9636)

Co-authored-by: Hunter Lovell <40191806+hntrl@users.noreply.github.com>

Author: christian-bromann

.changeset/cold-laws-matter.md

@@ -0,0 +1,5 @@
+---
+"@langchain/openai": patch
+---
+
+fix content in AIMessage for tool and function calls

libs/providers/langchain-openai/src/converters/completions.ts

@@ -811,13 +811,11 @@ export const convertMessagesToCompletionsMessageParams: Converter<
     }
     if (message.additional_kwargs.function_call != null) {
       completionParam.function_call = message.additional_kwargs.function_call;
-      completionParam.content = "";
     }
     if (AIMessage.isInstance(message) && !!message.tool_calls?.length) {
       completionParam.tool_calls = message.tool_calls.map(
         convertLangChainToolCallToOpenAI
       );
-      completionParam.content = "";
     } else {
       if (message.additional_kwargs.tool_calls != null) {
         completionParam.tool_calls = message.additional_kwargs.tool_calls;

libs/providers/langchain-openai/src/converters/tests/completions.test.ts

@@ -1,9 +1,11 @@
 /* eslint-disable @typescript-eslint/no-explicit-any */
 import { describe, it, expect } from "vitest";
 import { ChatCompletionMessage } from "openai/resources";
+import { AIMessage } from "@langchain/core/messages";
 import {
   completionsApiContentBlockConverter,
   convertCompletionsMessageToBaseMessage,
+  convertMessagesToCompletionsMessageParams,
   convertStandardContentBlockToCompletionsContentPart,
 } from "../completions.js";
 
@@ -194,6 +196,102 @@ describe("convertCompletionsMessageToBaseMessage", () => {
     });
   });
 
+  describe("convertMessagesToCompletionsMessageParams", () => {
+    it("should preserve AIMessage content when tool_calls are present", () => {
+      const message = new AIMessage({
+        content:
+          "I'll check the status of item 730 for identifier X1110 to find out why it's not active.",
+        tool_calls: [
+          {
+            id: "call_zGKlzVl2Ee3Lyob4AsyqfGXb",
+            name: "getStatus",
+            args: { identifier: "X1110", itemId: "730" },
+          },
+        ],
+      });
+
+      const result = convertMessagesToCompletionsMessageParams({
+        messages: [message],
+      });
+
+      expect(result).toHaveLength(1);
+      expect(result[0]).toEqual({
+        role: "assistant",
+        content:
+          "I'll check the status of item 730 for identifier X1110 to find out why it's not active.",
+        tool_calls: [
+          {
+            id: "call_zGKlzVl2Ee3Lyob4AsyqfGXb",
+            type: "function",
+            function: {
+              name: "getStatus",
+              arguments: '{"identifier":"X1110","itemId":"730"}',
+            },
+          },
+        ],
+      });
+    });
+
+    it("should handle AIMessage with empty content and tool_calls", () => {
+      const message = new AIMessage({
+        content: "",
+        tool_calls: [
+          {
+            id: "call_123",
+            name: "someFunction",
+            args: { key: "value" },
+          },
+        ],
+      });
+
+      const result = convertMessagesToCompletionsMessageParams({
+        messages: [message],
+      });
+
+      expect(result).toHaveLength(1);
+      expect(result[0]).toEqual({
+        role: "assistant",
+        content: "",
+        tool_calls: [
+          {
+            id: "call_123",
+            type: "function",
+            function: {
+              name: "someFunction",
+              arguments: '{"key":"value"}',
+            },
+          },
+        ],
+      });
+    });
+
+    it("should preserve content with function_call in additional_kwargs", () => {
+      const message = new AIMessage({
+        content: "Let me call a function for you.",
+        additional_kwargs: {
+          function_call: {
+            name: "myFunction",
+            arguments: '{"arg":"value"}',
+          },
+        },
+      });
+
+      const result = convertMessagesToCompletionsMessageParams({
+        messages: [message],
+      });
+
+      expect(result).toHaveLength(1);
+      expect(result[0]).toEqual({
+        role: "assistant",
+        content: "Let me call a function for you.",
+        function_call: {
+          name: "myFunction",
+          arguments: '{"arg":"value"}',
+        },
+      });
+    });
+  });
+
   describe("completionsApiContentBlockConverter.fromStandardFileBlock", () => {
     it("throws when base64 file block is missing filename/name/title metadata", () => {
       const block = {