generateObject throws error with o3-mini when schema has an optional param

[benhylak]

Description

Any optional property in a schema causes the following error:

Error in streaming examples: Error [AI_APICallError]: Invalid schema for response_format 'response': In context=('properties', 'recipe'), 'required' is required to be supplied and to be an array including every key in properties. Missing 'steps'.

The same schema works fine with Flash/Claude/4o. We rely on optional properties pretty heavily.

Code example

const test = await generateObject({
  model: openai("o3-mini"),
  schema: z.object({
    recipe: z.object({
      name: z.string(),
      ingredients: z.array(z.string()),
      steps: z.array(z.string()).optional(),
    }),
  }),
  prompt: 'Generate a lasagna recipe.',
});

AI provider

@ai-sdk/openai 1.1.9

Additional context

No response

[lgrammel]

Duplicates #4662