fix(anthropic): Do not check for apiKey existence when createClient parameters are present (#6716)

Co-authored-by: Jacob Lee <[email protected]>

Author: rxliuli

docs/core_docs/docs/integrations/chat/anthropic.ipynb

@@ -953,7 +953,7 @@
     "const customClient = new AnthropicVertex();\n",
     "\n",
     "const modelWithCustomClient = new ChatAnthropic({\n",
-    "  modelName: \"claude-3-sonnet-20240229\",\n",
+    "  modelName: \"claude-3-sonnet@20240229\",\n",
     "  maxRetries: 0,\n",
     "  createClient: () => customClient,\n",
     "});\n",

libs/langchain-anthropic/src/chat_models.ts

@@ -633,7 +633,7 @@ export class ChatAnthropicMessages<
       fields?.anthropicApiKey ??
       getEnvironmentVariable("ANTHROPIC_API_KEY");
 
-    if (!this.anthropicApiKey) {
+    if (!this.anthropicApiKey && !fields?.createClient) {
       throw new Error("Anthropic API key not found");
     }
     this.clientOptions = fields?.clientOptions ?? {};
@@ -949,9 +949,6 @@ export class ChatAnthropicMessages<
   ): Promise<Anthropic.Message> {
     if (!this.batchClient) {
       const options = this.apiUrl ? { baseURL: this.apiUrl } : undefined;
-      if (!this.apiKey) {
-        throw new Error("Missing Anthropic API key.");
-      }
       this.batchClient = this.createClient({
         ...this.clientOptions,
         ...options,