TanStack AI version

v0.0.1

Framework/Library version

typescript v5.9.3

Describe the bug and the steps to reproduce it

The gpt-5-nano and gpt-5-mini models support reasoning tokens according to OpenAI's documentation, but @tanstack/ai-openai type definitions don't include OpenAIReasoningOptions for these models, causing TypeScript errors.

OpenAI Documentation

• https://platform.openai.com/docs/models/gpt-5-nano
• https://platform.openai.com/docs/models/gpt-5-mini

Steps to Reproduce

import { chat, toStreamResponse } from "@tanstack/ai";
import { openai } from "@tanstack/ai-openai";

const stream = chat({
  adapter: openai(),
  messages: [{ role: "user", content: "Hello" }],
  model: "gpt-5-nano", // or "gpt-5-mini"
  providerOptions: {
    reasoning: {
      effort: "medium", // ❌ Type error here
    },
  },
});

Expected Behavior

No type error - reasoning option should be allowed for gpt-5-nano and gpt-5-mini.

Actual Behavior

TypeScript error: reasoning property doesn't exist on the providerOptions type for these models.

Root Cause

In model-meta.d.ts, the type mapping excludes OpenAIReasoningOptions:

// Current (incorrect)
[GPT5_MINI.name]: OpenAIBaseOptions & OpenAIStructuredOutputOptions & OpenAIToolsOptions & OpenAIStreamingOptions & OpenAIMetadataOptions;
[GPT5_NANO.name]: OpenAIBaseOptions & OpenAIStructuredOutputOptions & OpenAIToolsOptions & OpenAIStreamingOptions & OpenAIMetadataOptions;

// Expected (should include OpenAIReasoningOptions)
[GPT5_MINI.name]: OpenAIBaseOptions & OpenAIReasoningOptions & OpenAIStructuredOutputOptions & OpenAIToolsOptions & OpenAIStreamingOptions & OpenAIMetadataOptions;
[GPT5_NANO.name]: OpenAIBaseOptions & OpenAIReasoningOptions & OpenAIStructuredOutputOptions & OpenAIToolsOptions & OpenAIStreamingOptions & OpenAIMetadataOptions;

Environment

• @tanstack/ai: 0.0.1
• @tanstack/ai-openai: 0.0.1
• typescript: 5.9.3

Your Minimal, Reproducible Example - (Sandbox Highly Recommended)

https://stackblitz.com/edit/tanstack-ai-openai-reasoning-open-ai-issue

Screenshots or Videos (Optional)

No response

Do you intend to try to help solve this bug with your own PR?

Yes, I am also opening a PR that solves the problem along side this issue

Terms & Code of Conduct

• I agree to follow this project's Code of Conduct
• I understand that if my bug cannot be reliable reproduced in a debuggable environment, it will probably not be fixed and this issue may even be closed.