buster/packages/ai/src/utils/models/gpt-5-mini.ts

import type { LanguageModelV1 } from '@ai-sdk/provider';
import { createFallback } from './ai-fallback';
import { openaiModel } from './providers/openai';

// Lazy initialization to allow mocking in tests
let _gpt5Instance: ReturnType<typeof createFallback> | null = null;

function initializeGPT5() {
  if (_gpt5Instance) {
    return _gpt5Instance;
  }

  // Build models array based on available credentials
  const models: LanguageModelV1[] = [];

  // Only include OpenAI if API key is available
  if (process.env.OPENAI_API_KEY) {
    try {
      models.push(openaiModel('gpt-5-mini-2025-08-07'));
      console.info('GPT5: OpenAI model added to fallback chain');
    } catch (error) {
      console.warn('GPT5: Failed to initialize OpenAI model:', error);
    }
  }

  // Ensure we have at least one model
  if (models.length === 0) {
    throw new Error('No AI models available. Please set OPENAI_API_KEY environment variable.');
  }

  console.info(`GPT5: Initialized with ${models.length} model(s) in fallback chain`);

  _gpt5Instance = createFallback({
    models,
    modelResetInterval: 60000,
    retryAfterOutput: true,
    onError: (err) => console.error(`FALLBACK.  Here is the error: ${err}`),
  });

  return _gpt5Instance;
}

// Export a proxy that initializes on first use
export const GPT5Mini = new Proxy({} as ReturnType<typeof createFallback>, {
  get(_target, prop) {
    const instance = initializeGPT5();
    // Direct property access without receiver to avoid proxy conflicts
    return instance[prop as keyof typeof instance];
  },
  has(_target, prop) {
    const instance = initializeGPT5();
    return prop in instance;
  },
  ownKeys(_target) {
    const instance = initializeGPT5();
    return Reflect.ownKeys(instance);
  },
  getOwnPropertyDescriptor(_target, prop) {
    const instance = initializeGPT5();
    return Reflect.getOwnPropertyDescriptor(instance, prop);
  },
});