ai-sdk/google error: enum: only allowed for STRING type

[smirea]

Description

Using z.enum() with @ai-sdk/google generates an invalid schema and throws:

AI_APICallError: * GenerateContentRequest.generation_config.response_schema.properties[value].enum: only allowed for STRING type

Steps to reproduce

import z from 'zod/v4';
import { generateObject } from 'ai';
import { google } from '@ai-sdk/google';

await generateObject({
    model: google('gemini-2.0-flash'),
    prompt: 'pick one',
    schema: z.strictObject({ value: z.enum(['foo', 'bar']), }),
})

AI SDK Version

• ai: 5.0.0-beta.1
• ai-sdk/google: 5.0.0-beta.1