feat: add anthropic-reasoning example with Claude-style messages

Demonstrates multi-turn conversations using:
- ClaudeMessageParam type for Claude-style message format
- fromClaudeMessages() to convert to OpenResponses input format
- toClaudeMessage() to convert responses back to Claude format

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: mattapperson

examples/anthropic-reasoning.example.ts

@@ -0,0 +1,158 @@
+/*
+ * Code generated by Speakeasy (https://speakeasy.com). DO NOT EDIT.
+ */
+
+import dotenv from "dotenv";
+
+dotenv.config();
+
+/**
+ * Example demonstrating multi-turn conversations using Claude-style messages
+ * with the anthropic-compat helper functions.
+ *
+ * This example shows how to:
+ * 1. Use Claude-style message format (ClaudeMessageParam)
+ * 2. Convert between Claude format and OpenResponses format
+ * 3. Build a 3-turn conversation carrying message history forward
+ *
+ * To run this example from the examples directory with Bun:
+ * bun run anthropic-reasoning.example.ts
+ */
+
+import type { ClaudeMessageParam } from "../src/models/claude-message.js";
+import {
+  OpenRouter,
+  fromClaudeMessages,
+  toClaudeMessage,
+} from "../src/index.js";
+
+if (!process.env["OPENROUTER_API_KEY"]) {
+  throw new Error("Missing OPENROUTER_API_KEY environment variable");
+}
+
+const openRouter = new OpenRouter({
+  apiKey: process.env["OPENROUTER_API_KEY"] ?? "",
+});
+
+async function multiTurnClaudeConversation() {
+  const model = "anthropic/claude-sonnet-4";
+
+  // Initialize message history with Claude-style message format
+  const messages: ClaudeMessageParam[] = [
+    {
+      role: "user",
+      content: "What are the key differences between functional and object-oriented programming?",
+    },
+  ];
+
+  console.log("=== Turn 1 ===");
+  console.log("User:", messages[0].content);
+  console.log();
+
+  // First turn - convert Claude messages to OpenResponses format
+  const result1 = await openRouter.callModel({
+    model,
+    input: fromClaudeMessages(messages),
+  });
+
+  // Get the response and convert back to Claude format
+  const response1 = await result1.getResponse();
+  const claudeMessage1 = toClaudeMessage(response1);
+
+  // Extract text content from Claude message
+  const content1 = extractTextContent(claudeMessage1.content);
+  console.log("Assistant:", content1);
+  console.log();
+
+  // Add assistant response to history (as Claude-style message)
+  messages.push({
+    role: "assistant",
+    content: content1,
+  });
+
+  // Add next user message
+  messages.push({
+    role: "user",
+    content: "Can you show me an example of how the same problem would be solved differently in each paradigm?",
+  });
+
+  console.log("=== Turn 2 ===");
+  console.log("User:", messages[messages.length - 1].content);
+  console.log();
+
+  // Second turn
+  const result2 = await openRouter.callModel({
+    model,
+    input: fromClaudeMessages(messages),
+  });
+
+  const response2 = await result2.getResponse();
+  const claudeMessage2 = toClaudeMessage(response2);
+  const content2 = extractTextContent(claudeMessage2.content);
+  console.log("Assistant:", content2);
+  console.log();
+
+  // Add to history
+  messages.push({
+    role: "assistant",
+    content: content2,
+  });
+
+  messages.push({
+    role: "user",
+    content: "Which paradigm would you recommend for building a large-scale web application and why?",
+  });
+
+  console.log("=== Turn 3 ===");
+  console.log("User:", messages[messages.length - 1].content);
+  console.log();
+
+  // Third turn
+  const result3 = await openRouter.callModel({
+    model,
+    input: fromClaudeMessages(messages),
+  });
+
+  const response3 = await result3.getResponse();
+  const claudeMessage3 = toClaudeMessage(response3);
+  const content3 = extractTextContent(claudeMessage3.content);
+  console.log("Assistant:", content3);
+  console.log();
+
+  // Final message history
+  messages.push({
+    role: "assistant",
+    content: content3,
+  });
+
+  console.log("=== Conversation Complete ===");
+  console.log(`Total messages in history: ${messages.length}`);
+
+  // Show the final Claude message structure
+  console.log("\n=== Final Claude Message Structure ===");
+  console.log("Stop reason:", claudeMessage3.stop_reason);
+  console.log("Model:", claudeMessage3.model);
+  console.log("Usage:", claudeMessage3.usage);
+}
+
+/**
+ * Helper to extract text content from Claude message content blocks
+ */
+function extractTextContent(
+  content: Array<{ type: string; text?: string }>
+): string {
+  return content
+    .filter((block) => block.type === "text" && block.text)
+    .map((block) => block.text)
+    .join("");
+}
+
+async function main() {
+  try {
+    await multiTurnClaudeConversation();
+  } catch (error) {
+    console.error("Error:", error);
+  }
+}
+
+main();