Upload - SDK - Zod invalid_union error before it ever reaches the OpenRouter API #83

Problem
When using @openrouter/sdk to send a chat request with a file content item (as shown in the official documentation for PDF processing), the SDK rejects the request with a SDKValidationError / Zod invalid_union error before it ever reaches the OpenRouter API.

Concretely, this payload:

await openRouter.chat.send({
  model: 'anthropic/claude-sonnet-4',
  messages: [
    {
      role: 'user',
      content: [
        { type: 'text', text: 'What are the main points in this document?' },
        {
          type: 'file',
          file: {
            filename: 'document.pdf',
            fileData: 'https://bitcoin.org/bitcoin.pdf',
          },
        },
      ],
    },
  ],
  plugins: [
    {
      id: 'file-parser',
      pdf: { engine: 'mistral-ocr' },
    },
  ],
});

fails with a Zod validation error on messages[0].content[1].type: "file".

Root Cause
The installed SDK’s runtime schema and TypeScript types do not match the documented API:

• In node_modules/@openrouter/sdk/esm/models/chatmessagecontentitem.d.ts:

  export type ChatMessageContentItem =
    (ChatMessageContentItemText  & { type: "text" })      |
    (ChatMessageContentItemImage & { type: "image_url" }) |
    (ChatMessageContentItemAudio & { type: "input_audio" }) |
    (ChatMessageContentItemVideo & { type: "input_video" });

There is no variant for type: "file".

The corresponding Zod schema used internally by chat.send enforces this union at runtime. As a result, any content item with type: "file" is considered invalid, even if it matches the structure shown in the official docs.

In short: the SDK’s validation layer and type definitions lag behind the documented feature (PDF/file support via type: 'file' + file: { filename, fileData }), so all such requests are rejected client‑side by the SDK before reaching OpenRouter.