Structured output

generateObject returns typed data validated against a JSON schema. Where a provider has native guided generation, the runtime uses it; otherwise it prompts for JSON, validates, and runs a repair retry.

const result = await ExpoAI.generateObject({
  prompt: 'Extract project name, budget, timeline, and risks.',
  schema: {
    type: 'object',
    properties: {
      projectName: { type: 'string' },
      budget: { type: 'string' },
      timeline: { type: 'string' },
      risks: {
        type: 'array',
        items: { type: 'string' },
      },
    },
    required: ['projectName', 'timeline', 'risks'],
  },
  fallback: 'cloud',
});

Strategy per provider

Provider	Strategy
Apple Foundation Models	Native guided generation where available
Android AICore	JSON prompt + validation + repair retry
LiteRT-LM	JSON prompt + validation + repair retry
Cloud	Provider-native JSON mode or tools where available

The validation and repair loop lives in expo-ai-core, so structured output behaves consistently regardless of which provider answered.

streamObject

streamObject streams a structured object as it is generated: subscribe to partialObjectStream for progressively-complete snapshots as tokens arrive, and/or await object for the validated (repaired) final value. All four views are backed by one generation; on failure the streams throw and the promises reject with the same ExpoAIError.

const { partialObjectStream, object, result } = ExpoAI.streamObject({
  prompt: 'Extract project name, budget, timeline, and risks.',
  schema: {
    type: 'object',
    properties: {
      projectName: { type: 'string' },
      risks: { type: 'array', items: { type: 'string' } },
    },
    required: ['projectName', 'risks'],
  },
  fallback: 'cloud',
});

// Render the object filling in, field by field, as tokens arrive.
for await (const partial of partialObjectStream) {
  render(partial); // DeepPartial<T> — the last snapshot equals `object`
}

const final = await object; // validated, schema-conforming
console.log((await result).provider);

The streamed text seeds the validate→repair loop, so a second generation only happens if the streamed JSON doesn't validate. Partial snapshots are best-effort and may briefly omit the field currently streaming — the final object is always validated.

In React, useObject wraps this into component state.