From eb575d5394ed90bcb230b871907907ed709aff55 Mon Sep 17 00:00:00 2001
From: bracesproul <braceasproul@gmail.com>
Date: Mon, 29 Jul 2024 16:43:03 -0700
Subject: [PATCH] community[patch]: Fix handling parallel tool call results in
 bedrock

---
 .../tests/chatbedrock.standard.int.test.ts    |  8 ++++
 .../src/utils/bedrock/anthropic.ts            | 38 +++++++++++++------
 2 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/libs/langchain-community/src/chat_models/tests/chatbedrock.standard.int.test.ts b/libs/langchain-community/src/chat_models/tests/chatbedrock.standard.int.test.ts
index 0fc9e92e7ec8..4edd4a1ebdcc 100644
--- a/libs/langchain-community/src/chat_models/tests/chatbedrock.standard.int.test.ts
+++ b/libs/langchain-community/src/chat_models/tests/chatbedrock.standard.int.test.ts
@@ -15,6 +15,7 @@ class BedrockChatStandardIntegrationTests extends ChatModelIntegrationTests<
       Cls: BedrockChat,
       chatModelHasToolCalling: true,
       chatModelHasStructuredOutput: true,
+      supportsParallelToolCalls: true,
       constructorArgs: {
         region,
         model: "anthropic.claude-3-sonnet-20240229-v1:0",
@@ -57,6 +58,13 @@ class BedrockChatStandardIntegrationTests extends ChatModelIntegrationTests<
       "Flaky test with Bedrock not consistently returning tool calls. TODO: Fix prompting."
     );
   }
+
+  async testParallelToolCalling() {
+    // Anthropic is very flaky when calling multiple tools in parallel.
+    // Because of this, we pass `true` as the second arg to only verify
+    // it can handle parallel tools in the message history.
+    await super.testParallelToolCalling(undefined, true);
+  }
 }
 
 const testClass = new BedrockChatStandardIntegrationTests();
diff --git a/libs/langchain-community/src/utils/bedrock/anthropic.ts b/libs/langchain-community/src/utils/bedrock/anthropic.ts
index 33a7d0b48fb1..4565a2f1615d 100644
--- a/libs/langchain-community/src/utils/bedrock/anthropic.ts
+++ b/libs/langchain-community/src/utils/bedrock/anthropic.ts
@@ -55,17 +55,33 @@ function _mergeMessages(
   for (const message of messages) {
     if (message._getType() === "tool") {
       if (typeof message.content === "string") {
-        merged.push(
-          new HumanMessage({
-            content: [
-              {
-                type: "tool_result",
-                content: message.content,
-                tool_use_id: (message as ToolMessage).tool_call_id,
-              },
-            ],
-          })
-        );
+        const previousMessage = merged[merged.length - 1];
+        if (
+          previousMessage?._getType() === "human" &&
+          Array.isArray(previousMessage.content) &&
+          "type" in previousMessage.content[0] &&
+          previousMessage.content[0].type === "tool_result"
+        ) {
+          // If the previous message was a tool result, we merge this tool message into it.
+          previousMessage.content.push({
+            type: "tool_result",
+            content: message.content,
+            tool_use_id: (message as ToolMessage).tool_call_id,
+          });
+        } else {
+          // If not, we create a new human message with the tool result.
+          merged.push(
+            new HumanMessage({
+              content: [
+                {
+                  type: "tool_result",
+                  content: message.content,
+                  tool_use_id: (message as ToolMessage).tool_call_id,
+                },
+              ],
+            })
+          );
+        }
       } else {
         merged.push(new HumanMessage({ content: message.content }));
       }