add back warning when not using provider/model format

Author: tkattkat

lib/handlers/stagehandAgentHandler.ts

@@ -67,6 +67,11 @@ export class StagehandAgentHandler {
         );
       }
 
+      if (!this.llmClient.getLanguageModel) {
+        throw new Error(
+          "StagehandAgentHandler requires an AISDK-backed LLM client. Ensure your model is configured like 'openai/gpt-4.1-mini' in the provider/model format.",
+        );
+      }
       const baseModel: LanguageModel = this.llmClient.getLanguageModel();
       const wrappedModel = wrapLanguageModel({
         model: baseModel,

lib/llm/aisdk.ts

@@ -42,6 +42,10 @@ export class AISdkClient extends LLMClient {
     this.enableCaching = enableCaching;
   }
 
+  public getLanguageModel(): LanguageModel {
+    return this.model;
+  }
+
   async createChatCompletion<T = ChatCompletion>({
     options,
   }: CreateChatCompletionOptions): Promise<T> {