community[minor]: Adds support for Cohere Command-R via AWS Bedrock

libs/langchain-community/src/chat_models/bedrock/web.ts

@@ -208,10 +208,7 @@ export class BedrockChat extends BaseChatModel implements BaseBedrockInput {
     this.stopSequences = fields?.stopSequences;
     this.modelKwargs = fields?.modelKwargs;
     this.streaming = fields?.streaming ?? this.streaming;
-    this.usesMessagesApi =
-      this.model.split(".")[0] === "anthropic" &&
-      !this.model.includes("claude-v2") &&
-      !this.model.includes("claude-instant-v1");
+    this.usesMessagesApi = canUseMessagesApi(this.model);
   }
 
   async _generate(
@@ -499,6 +496,29 @@ function isChatGenerationChunk(
   );
 }
 
+function canUseMessagesApi(model: string): boolean {
+  const modelProviderName = model.split(".")[0];
+
+  if (
+    modelProviderName === "anthropic" &&
+    !model.includes("claude-v2") &&
+    !model.includes("claude-instant-v1")
+  ) {
+    return true;
+  }
+
+  if (modelProviderName === "cohere") {
+    if (model.includes("command-r-v1")) {
+      return true;
+    }
+    if (model.includes("command-r-plus-v1")) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
 /**
  * @deprecated Use `BedrockChat` instead.
  */

libs/langchain-community/src/chat_models/tests/chatbedrock.int.test.ts

@@ -19,21 +19,84 @@ import { BedrockChat } from "../bedrock/web.js";
 // );
 
 void testChatModel(
-  "Test Bedrock chat model: Claude-v2",
+  "Test Bedrock chat model Generating search queries: Command-r",
+  "us-east-1",
+  "cohere.command-r-v1:0",
+  "Who is more popular: Nsync or Backstreet Boys?",
+  {
+    search_queries_only: true,
+  }
+);
+
+void testChatModel(
+  "Test Bedrock chat model: Command-r",
+  "us-east-1",
+  "cohere.command-r-v1:0",
+  "What is your name?"
+);
+
+void testChatModel(
+  "Test Bedrock chat model: Command-r",
+  "us-east-1",
+  "cohere.command-r-v1:0",
+  "What are the characteristics of the emperor penguin?",
+  {
+    documents: [
+      { title: "Tall penguins", snippet: "Emperor penguins are the tallest." },
+      {
+        title: "Penguin habitats",
+        snippet: "Emperor penguins only live in Antarctica.",
+      },
+    ],
+  }
+);
+
+void testChatStreamingModel(
+  "Test Bedrock chat model streaming: Command-r",
+  "us-east-1",
+  "cohere.command-r-v1:0",
+  "What is your name and something about yourself?"
+);
+
+void testChatStreamingModel(
+  "Test Bedrock chat model streaming: Command-r",
+  "us-east-1",
+  "cohere.command-r-v1:0",
+  "What are the characteristics of the emperor penguin?",
+  {
+    documents: [
+      { title: "Tall penguins", snippet: "Emperor penguins are the tallest." },
+      {
+        title: "Penguin habitats",
+        snippet: "Emperor penguins only live in Antarctica.",
+      },
+    ],
+  }
+);
+
+void testChatHandleLLMNewToken(
+  "Test Bedrock chat model HandleLLMNewToken: Command-r",
+  "us-east-1",
+  "cohere.command-r-v1:0",
+  "What is your name and something about yourself?"
+);
+
+void testChatModel(
+  "Test Bedrock chat model: Mistral-7b-instruct",
   "us-east-1",
   "mistral.mistral-7b-instruct-v0:2",
   "What is your name?"
 );
 
 void testChatStreamingModel(
-  "Test Bedrock chat model streaming: Claude-v2",
+  "Test Bedrock chat model streaming: Mistral-7b-instruct",
   "us-east-1",
   "mistral.mistral-7b-instruct-v0:2",
   "What is your name and something about yourself?"
 );
 
 void testChatHandleLLMNewToken(
-  "Test Bedrock chat model HandleLLMNewToken: Claude-v2",
+  "Test Bedrock chat model HandleLLMNewToken: Mistral-7b-instruct",
   "us-east-1",
   "mistral.mistral-7b-instruct-v0:2",
   "What is your name and something about yourself?"
@@ -59,6 +122,7 @@ void testChatHandleLLMNewToken(
   "anthropic.claude-3-sonnet-20240229-v1:0",
   "What is your name and something about yourself?"
 );
+
 // void testChatHandleLLMNewToken(
 //   "Test Bedrock chat model HandleLLMNewToken: Llama2 13B v1",
 //   "us-east-1",
@@ -77,13 +141,14 @@ async function testChatModel(
   title: string,
   defaultRegion: string,
   model: string,
-  message: string
+  message: string,
+  modelKwargs?: Record<string, unknown>
 ) {
   test(title, async () => {
     const region = process.env.BEDROCK_AWS_REGION ?? defaultRegion;
 
     const bedrock = new BedrockChat({
-      maxTokens: 20,
+      maxTokens: 200,
       region,
       model,
       maxRetries: 0,
@@ -92,6 +157,7 @@ async function testChatModel(
         accessKeyId: process.env.BEDROCK_AWS_ACCESS_KEY_ID!,
         sessionToken: process.env.BEDROCK_AWS_SESSION_TOKEN,
       },
+      modelKwargs,
     });
 
     const res = await bedrock.invoke([new HumanMessage(message)]);
@@ -109,7 +175,8 @@ async function testChatStreamingModel(
   title: string,
   defaultRegion: string,
   model: string,
-  message: string
+  message: string,
+  modelKwargs?: Record<string, unknown>
 ) {
   test(title, async () => {
     const region = process.env.BEDROCK_AWS_REGION ?? defaultRegion;
@@ -124,6 +191,7 @@ async function testChatStreamingModel(
         accessKeyId: process.env.BEDROCK_AWS_ACCESS_KEY_ID!,
         sessionToken: process.env.BEDROCK_AWS_SESSION_TOKEN,
       },
+      modelKwargs,
     });
 
     const stream = await bedrock.stream([

libs/langchain-community/src/utils/bedrock.ts

@@ -88,6 +88,92 @@ function formatMessagesForAnthropic(messages: BaseMessage[]): {
   };
 }
 
+/**
+ * format messages for Cohere Command-R and CommandR+ via AWS Bedrock.
+ *
+ * @param messages messages The base messages to format as a prompt.
+ *
+ * @returns The formatted prompt for Cohere.
+ *
+ * `system`: user system prompts. Overrides the default preamble for search query generation. Has no effect on tool use generations.\
+ * `message`: (Required) Text input for the model to respond to.\
+ * `chatHistory`: A list of previous messages between the user and the model, meant to give the model conversational context for responding to the user's message.\
+ * The following are required fields.
+ * - `role` - The role for the message. Valid values are USER or CHATBOT.\
+ * - `message` – Text contents of the message.\
+ *
+ * The following is example JSON for the chat_history field.\
+ * "chat_history": [
+ * {"role": "USER", "message": "Who discovered gravity?"},
+ * {"role": "CHATBOT", "message": "The man who is widely credited with discovering gravity is Sir Isaac Newton"}]\
+ *
+ * docs: https://docs.aws.amazon.com/bedrock/latest/userguide/model-parameters-cohere-command-r-plus.html
+ */
+function formatMessagesForCohere(messages: BaseMessage[]): {
+  system?: string;
+  message: string;
+  chatHistory: Record<string, unknown>[];
+} {
+  const systemMessages = messages.filter(
+    (system) => system._getType() === "system"
+  );
+
+  const system = systemMessages
+    .filter((m) => typeof m.content === "string")
+    .map((m) => m.content)
+    .join("\n\n");
+
+  const conversationMessages = messages.filter(
+    (message) => message._getType() !== "system"
+  );
+
+  const questionContent = conversationMessages.slice(-1);
+
+  if (!questionContent.length || questionContent[0]._getType() !== "human") {
+    throw new Error("question message content must be a human message.");
+  }
+
+  if (typeof questionContent[0].content !== "string") {
+    throw new Error("question message content must be a string.");
+  }
+
+  const formattedMessage = questionContent[0].content;
+
+  const formattedChatHistories = conversationMessages
+    .slice(0, -1)
+    .map((message) => {
+      let role;
+      switch (message._getType()) {
+        case "human":
+          role = "USER" as const;
+          break;
+        case "ai":
+          role = "CHATBOT" as const;
+          break;
+        case "system":
+          throw new Error("chat_history can not include system prompts.");
+        default:
+          throw new Error(
+            `Message type "${message._getType()}" is not supported.`
+          );
+      }
+
+      if (typeof message.content !== "string") {
+        throw new Error("message content must be a string.");
+      }
+      return {
+        role,
+        message: message.content,
+      };
+    });
+
+  return {
+    chatHistory: formattedChatHistories,
+    message: formattedMessage,
+    system,
+  };
+}
+
 /** Bedrock models.
     To authenticate, the AWS client uses the following methods to automatically load credentials:
     https://boto3.amazonaws.com/v1/documentation/api/latest/guide/credentials.html
@@ -221,9 +307,25 @@ export class BedrockLLMInputOutputAdapter {
       inputBody.temperature = temperature;
       inputBody.stop_sequences = stopSequences;
       return { ...inputBody, ...modelKwargs };
+    } else if (provider === "cohere") {
+      const {
+        system,
+        message: formattedMessage,
+        chatHistory: formattedChatHistories,
+      } = formatMessagesForCohere(messages);
+
+      if (system !== undefined && system.length > 0) {
+        inputBody.preamble = system;
+      }
+      inputBody.message = formattedMessage;
+      inputBody.chat_history = formattedChatHistories;
+      inputBody.max_tokens = maxTokens;
+      inputBody.temperature = temperature;
+      inputBody.stop_sequences = stopSequences;
+      return { ...inputBody, ...modelKwargs };
     } else {
       throw new Error(
-        "The messages API is currently only supported by Anthropic"
+        "The messages API is currently only supported by Anthropic or Cohere"
       );
     }
   }
@@ -298,9 +400,48 @@ export class BedrockLLMInputOutputAdapter {
       } else {
         return undefined;
       }
+    } else if (provider === "cohere") {
+      if (responseBody.event_type === "stream-start") {
+        return parseMessageCohere(responseBody.message, true);
+      } else if (
+        responseBody.event_type === "text-generation" &&
+        typeof responseBody?.text === "string"
+      ) {
+        return new ChatGenerationChunk({
+          message: new AIMessageChunk({
+            content: responseBody.text,
+          }),
+          text: responseBody.text,
+        });
+      } else if (responseBody.event_type === "search-queries-generation") {
+        return parseMessageCohere(responseBody);
+      } else if (
+        responseBody.event_type === "stream-end" &&
+        responseBody.response !== undefined &&
+        responseBody["amazon-bedrock-invocationMetrics"] !== undefined
+      ) {
+        return new ChatGenerationChunk({
+          message: new AIMessageChunk({ content: "" }),
+          text: "",
+          generationInfo: {
+            response: responseBody.response,
+            "amazon-bedrock-invocationMetrics":
+              responseBody["amazon-bedrock-invocationMetrics"],
+          },
+        });
+      } else {
+        if (
+          responseBody.finish_reason === "COMPLETE" ||
+          responseBody.finish_reason === "MAX_TOKENS"
+        ) {
+          return parseMessageCohere(responseBody);
+        } else {
+          return undefined;
+        }
+      }
     } else {
       throw new Error(
-        "The messages API is currently only supported by Anthropic."
+        "The messages API is currently only supported by Anthropic or Cohere."
       );
     }
   }
@@ -341,3 +482,31 @@ function parseMessage(responseBody: any, asChunk?: boolean): ChatGeneration {
     };
   }
 }
+
+function parseMessageCohere(
+  responseBody: any,
+  asChunk?: boolean
+): ChatGeneration {
+  const { text, ...generationInfo } = responseBody;
+  let parsedContent = text;
+  if (typeof text !== "string") {
+    parsedContent = "";
+  }
+  if (asChunk) {
+    return new ChatGenerationChunk({
+      message: new AIMessageChunk({
+        content: parsedContent,
+      }),
+      text: parsedContent,
+      generationInfo,
+    });
+  } else {
+    return {
+      message: new AIMessage({
+        content: parsedContent,
+      }),
+      text: parsedContent,
+      generationInfo,
+    };
+  }
+}