Claude Opus 5.5

// OpenRouter speaks the OpenAI Chat Completions format.
const res = await fetch("https://openrouter.ai/api/v1/chat/completions", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.OPENROUTER_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "model": "anthropic/claude-opus-5.5",
    "messages": [
      {
        "role": "system",
        "content": "You are a coding agent in a TypeScript monorepo. Plan first, then use tools. Stop when the tests pass."
      },
      {
        "role": "user",
        "content": "The test checkout.spec.ts fails with 'total is NaN'. Find and fix the cause."
      }
    ],
    "reasoning": {
      "effort": "high"
    },
    "tools": [
      {
        "type": "function",
        "function": {
          "name": "read_file",
          "description": "Read a file from the repository",
          "parameters": {
            "type": "object",
            "properties": {
              "path": {
                "type": "string"
              }
            },
            "required": [
              "path"
            ]
          }
        }
      }
    ]
  }),
});
const data = await res.json();
const message = data.choices[0].message;
for (const call of message.tool_calls ?? []) {
  // Run the tool yourself, then send the result back as
  // { role: "tool", tool_call_id: call.id, content: result } and call again.
  console.log(call.function.name, call.function.arguments);
}
console.log(message.content);