feat!: Support invoke with structured output

Author: jsonbailey

packages/ai-providers/server-ai-langchain/package.json

@@ -28,7 +28,7 @@
   "license": "Apache-2.0",
   "devDependencies": {
     "@langchain/core": "^0.3.0",
-    "@launchdarkly/server-sdk-ai": "^0.12.3",
+    "@launchdarkly/server-sdk-ai": "^0.13.0",
     "@trivago/prettier-plugin-sort-imports": "^4.1.1",
     "@types/jest": "^29.5.3",
     "@typescript-eslint/eslint-plugin": "^6.20.0",
@@ -48,7 +48,7 @@
   },
   "peerDependencies": {
     "@langchain/core": "^0.2.0 || ^0.3.0",
-    "@launchdarkly/server-sdk-ai": "^0.12.2",
+    "@launchdarkly/server-sdk-ai": "^0.13.0",
     "langchain": "^0.2.0 || ^0.3.0"
   }
 }

packages/ai-providers/server-ai-langchain/src/LangChainProvider.ts

@@ -10,6 +10,7 @@ import type {
   LDLogger,
   LDMessage,
   LDTokenUsage,
+  StructuredResponse,
 } from '@launchdarkly/server-sdk-ai';
 
 /**
@@ -79,6 +80,38 @@ export class LangChainProvider extends AIProvider {
     };
   }
 
+  /**
+   * Invoke the LangChain model with structured output support.
+   */
+  async invokeStructuredModel(
+    messages: LDMessage[],
+    responseStructure: Record<string, unknown>,
+  ): Promise<StructuredResponse> {
+    // Convert LDMessage[] to LangChain messages
+    const langchainMessages = LangChainProvider.convertMessagesToLangChain(messages);
+
+    // Get the LangChain response
+    const response = await this._llm
+      .withStructuredOutput(responseStructure)
+      .invoke(langchainMessages);
+
+    // Using structured output doesn't support metrics
+    const metrics = {
+      success: true,
+      usage: {
+        total: 0,
+        input: 0,
+        output: 0,
+      },
+    };
+
+    return {
+      data: response,
+      rawResponse: JSON.stringify(response),
+      metrics,
+    };
+  }
+
   /**
    * Get the underlying LangChain model instance.
    */