--- title: streamObject description: API Reference for streamObject --- # `streamObject()` Streams a typed, structured object for a given prompt and schema using a language model. It can be used to force the language model to return structured data, e.g. for information extraction, synthetic data generation, or classification tasks. #### Example: stream an object using a schema ```ts import { openai } from '@ai-sdk/openai'; import { streamObject } from 'ai'; import { z } from 'zod'; const { partialObjectStream } = streamObject({ model: 'anthropic/claude-sonnet-4.5', schema: z.object({ recipe: z.object({ name: z.string(), ingredients: z.array(z.string()), steps: z.array(z.string()), }), }), prompt: 'Generate a lasagna recipe.', }); for await (const partialObject of partialObjectStream) { console.clear(); console.log(partialObject); } ``` #### Example: stream an array using a schema For arrays, you specify the schema of the array items. You can use `elementStream` to get the stream of complete array elements. ```ts highlight="7,18" import { openai } from '@ai-sdk/openai'; import { streamObject } from 'ai'; import { z } from 'zod'; const { elementStream } = streamObject({ model: 'anthropic/claude-sonnet-4.5', output: 'array', schema: z.object({ name: z.string(), class: z .string() .describe('Character class, e.g. warrior, mage, or thief.'), description: z.string(), }), prompt: 'Generate 3 hero descriptions for a fantasy role playing game.', }); for await (const hero of elementStream) { console.log(hero); } ``` #### Example: generate JSON without a schema ```ts import { openai } from '@ai-sdk/openai'; import { streamObject } from 'ai'; const { partialObjectStream } = streamObject({ model: 'anthropic/claude-sonnet-4.5', output: 'no-schema', prompt: 'Generate a lasagna recipe.', }); for await (const partialObject of partialObjectStream) { console.clear(); console.log(partialObject); } ``` #### Example: generate an enum When you want to generate a specific enum value, you can set the output strategy to `enum` and provide the list of possible values in the `enum` parameter. ```ts highlight="5-6" import { streamObject } from 'ai'; const { partialObjectStream } = streamObject({ model: 'anthropic/claude-sonnet-4.5', output: 'enum', enum: ['action', 'comedy', 'drama', 'horror', 'sci-fi'], prompt: 'Classify the genre of this movie plot: ' + '"A group of astronauts travel through a wormhole in search of a ' + 'new habitable planet for humanity."', }); ``` To see `streamObject` in action, check out the [additional examples](#more-examples). ## Import ## API Signature ### Parameters ', description: 'The input prompt to generate the text from.', }, { name: 'messages', type: 'Array', description: 'A list of messages that represent a conversation. Automatically converts UI messages from the useChat hook.', properties: [ { type: 'SystemModelMessage', parameters: [ { name: 'role', type: "'system'", description: 'The role for the system message.', }, { name: 'content', type: 'string', description: 'The content of the message.', }, ], }, { type: 'UserModelMessage', parameters: [ { name: 'role', type: "'user'", description: 'The role for the user message.', }, { name: 'content', type: 'string | Array', description: 'The content of the message.', properties: [ { type: 'TextPart', parameters: [ { name: 'type', type: "'text'", description: 'The type of the message part.', }, { name: 'text', type: 'string', description: 'The text content of the message part.', }, ], }, { type: 'ImagePart', parameters: [ { name: 'type', type: "'image'", description: 'The type of the message part.', }, { name: 'image', type: 'string | Uint8Array | Buffer | ArrayBuffer | URL', description: 'The image content of the message part. String are either base64 encoded content, base64 data URLs, or http(s) URLs.', }, { name: 'mediaType', type: 'string', isOptional: true, description: 'The IANA media type of the image. Optional.', }, ], }, { type: 'FilePart', parameters: [ { name: 'type', type: "'file'", description: 'The type of the message part.', }, { name: 'data', type: 'string | Uint8Array | Buffer | ArrayBuffer | URL', description: 'The file content of the message part. String are either base64 encoded content, base64 data URLs, or http(s) URLs.', }, { name: 'mediaType', type: 'string', description: 'The IANA media type of the file.', }, ], }, ], }, ], }, { type: 'AssistantModelMessage', parameters: [ { name: 'role', type: "'assistant'", description: 'The role for the assistant message.', }, { name: 'content', type: 'string | Array', description: 'The content of the message.', properties: [ { type: 'TextPart', parameters: [ { name: 'type', type: "'text'", description: 'The type of the message part.', }, { name: 'text', type: 'string', description: 'The text content of the message part.', }, ], }, { type: 'ReasoningPart', parameters: [ { name: 'type', type: "'reasoning'", description: 'The type of the message part.', }, { name: 'text', type: 'string', description: 'The reasoning text.', }, ], }, { type: 'FilePart', parameters: [ { name: 'type', type: "'file'", description: 'The type of the message part.', }, { name: 'data', type: 'string | Uint8Array | Buffer | ArrayBuffer | URL', description: 'The file content of the message part. String are either base64 encoded content, base64 data URLs, or http(s) URLs.', }, { name: 'mediaType', type: 'string', description: 'The IANA media type of the file.', }, { name: 'filename', type: 'string', description: 'The name of the file.', isOptional: true, }, ], }, { type: 'ToolCallPart', parameters: [ { name: 'type', type: "'tool-call'", description: 'The type of the message part.', }, { name: 'toolCallId', type: 'string', description: 'The id of the tool call.', }, { name: 'toolName', type: 'string', description: 'The name of the tool, which typically would be the name of the function.', }, { name: 'args', type: 'object based on zod schema', description: 'Parameters generated by the model to be used by the tool.', }, ], }, ], }, ], }, { type: 'ToolModelMessage', parameters: [ { name: 'role', type: "'tool'", description: 'The role for the assistant message.', }, { name: 'content', type: 'Array', description: 'The content of the message.', properties: [ { type: 'ToolResultPart', parameters: [ { name: 'type', type: "'tool-result'", description: 'The type of the message part.', }, { name: 'toolCallId', type: 'string', description: 'The id of the tool call the result corresponds to.', }, { name: 'toolName', type: 'string', description: 'The name of the tool the result corresponds to.', }, { name: 'result', type: 'unknown', description: 'The result returned by the tool after execution.', }, { name: 'isError', type: 'boolean', isOptional: true, description: 'Whether the result is an error or an error message.', }, ], }, ], }, ], }, ], }, { name: 'maxOutputTokens', type: 'number', isOptional: true, description: 'Maximum number of tokens to generate.', }, { name: 'temperature', type: 'number', isOptional: true, description: 'Temperature setting. The value is passed through to the provider. The range depends on the provider and model. It is recommended to set either `temperature` or `topP`, but not both.', }, { name: 'topP', type: 'number', isOptional: true, description: 'Nucleus sampling. The value is passed through to the provider. The range depends on the provider and model. It is recommended to set either `temperature` or `topP`, but not both.', }, { name: 'topK', type: 'number', isOptional: true, description: 'Only sample from the top K options for each subsequent token. Used to remove "long tail" low probability responses. Recommended for advanced use cases only. You usually only need to use temperature.', }, { name: 'presencePenalty', type: 'number', isOptional: true, description: 'Presence penalty setting. It affects the likelihood of the model to repeat information that is already in the prompt. The value is passed through to the provider. The range depends on the provider and model.', }, { name: 'frequencyPenalty', type: 'number', isOptional: true, description: 'Frequency penalty setting. It affects the likelihood of the model to repeatedly use the same words or phrases. The value is passed through to the provider. The range depends on the provider and model.', }, { name: 'seed', type: 'number', isOptional: true, description: 'The seed (integer) to use for random sampling. If set and supported by the model, calls will generate deterministic results.', }, { name: 'maxRetries', type: 'number', isOptional: true, description: 'Maximum number of retries. Set to 0 to disable retries. Default: 2.', }, { name: 'abortSignal', type: 'AbortSignal', isOptional: true, description: 'An optional abort signal that can be used to cancel the call.', }, { name: 'headers', type: 'Record', isOptional: true, description: 'Additional HTTP headers to be sent with the request. Only applicable for HTTP-based providers.', }, { name: 'experimental_repairText', type: '(options: RepairTextOptions) => Promise', isOptional: true, description: 'A function that attempts to repair the raw output of the model to enable JSON parsing. Should return the repaired text or null if the text cannot be repaired.', properties: [ { type: 'RepairTextOptions', parameters: [ { name: 'text', type: 'string', description: 'The text that was generated by the model.', }, { name: 'error', type: 'JSONParseError | TypeValidationError', description: 'The error that occurred while parsing the text.', }, ], }, ], }, { name: 'experimental_download', type: '(requestedDownloads: Array<{ url: URL; isUrlSupportedByModel: boolean }>) => Promise>', isOptional: true, description: 'Custom download function to control how URLs are fetched when they appear in prompts. By default, files are downloaded if the model does not support the URL for the given media type. Experimental feature. Return null to pass the URL directly to the model (when supported), or return downloaded content with data and media type.', }, { name: 'experimental_telemetry', type: 'TelemetrySettings', isOptional: true, description: 'Telemetry configuration. Experimental feature.', properties: [ { type: 'TelemetrySettings', parameters: [ { name: 'isEnabled', type: 'boolean', isOptional: true, description: 'Enable or disable telemetry. Disabled by default while experimental.', }, { name: 'recordInputs', type: 'boolean', isOptional: true, description: 'Enable or disable input recording. Enabled by default.', }, { name: 'recordOutputs', type: 'boolean', isOptional: true, description: 'Enable or disable output recording. Enabled by default.', }, { name: 'functionId', type: 'string', isOptional: true, description: 'Identifier for this function. Used to group telemetry data by function.', }, { name: 'metadata', isOptional: true, type: 'Record | Array | Array>', description: 'Additional information to include in the telemetry data.', }, ], }, ], }, { name: 'providerOptions', type: 'Record | undefined', isOptional: true, description: 'Provider-specific options. The outer key is the provider name. The inner values are the metadata. Details depend on the provider.', }, { name: 'onError', type: '(event: OnErrorResult) => Promise |void', isOptional: true, description: 'Callback that is called when an error occurs during streaming. You can use it to log errors.', properties: [ { type: 'OnErrorResult', parameters: [ { name: 'error', type: 'unknown', description: 'The error that occurred.', }, ], }, ], }, { name: 'onFinish', type: '(result: OnFinishResult) => void', isOptional: true, description: 'Callback that is called when the LLM response has finished.', properties: [ { type: 'OnFinishResult', parameters: [ { name: 'usage', type: 'LanguageModelUsage', description: 'The token usage of the generated text.', properties: [ { type: 'LanguageModelUsage', parameters: [ { name: 'inputTokens', type: 'number | undefined', description: 'The number of input (prompt) tokens used.', }, { name: 'outputTokens', type: 'number | undefined', description: 'The number of output (completion) tokens used.', }, { name: 'totalTokens', type: 'number | undefined', description: 'The total number of tokens as reported by the provider. This number might be different from the sum of inputTokens and outputTokens and e.g. include reasoning tokens or other overhead.', }, { name: 'reasoningTokens', type: 'number | undefined', isOptional: true, description: 'The number of reasoning tokens used.', }, { name: 'cachedInputTokens', type: 'number | undefined', isOptional: true, description: 'The number of cached input tokens.', }, ], }, ], }, { name: 'providerMetadata', type: 'ProviderMetadata | undefined', description: 'Optional metadata from the provider. The outer key is the provider name. The inner values are the metadata. Details depend on the provider.', }, { name: 'object', type: 'T | undefined', description: 'The generated object (typed according to the schema). Can be undefined if the final object does not match the schema.', }, { name: 'error', type: 'unknown | undefined', description: 'Optional error object. This is e.g. a TypeValidationError when the final object does not match the schema.', }, { name: 'warnings', type: 'Warning[] | undefined', description: 'Warnings from the model provider (e.g. unsupported settings).', }, { name: 'response', type: 'Response', isOptional: true, description: 'Response metadata.', properties: [ { type: 'Response', parameters: [ { name: 'id', type: 'string', description: 'The response identifier. The AI SDK uses the ID from the provider response when available, and generates an ID otherwise.', }, { name: 'model', type: 'string', description: 'The model that was used to generate the response. The AI SDK uses the response model from the provider response when available, and the model from the function call otherwise.', }, { name: 'timestamp', type: 'Date', description: 'The timestamp of the response. The AI SDK uses the response timestamp from the provider response when available, and creates a timestamp otherwise.', }, { name: 'headers', isOptional: true, type: 'Record', description: 'Optional response headers.', }, ], }, ], }, ], }, ], }, ]} /> ### Returns ', description: 'The token usage of the generated text. Resolved when the response is finished.', properties: [ { type: 'LanguageModelUsage', parameters: [ { name: 'inputTokens', type: 'number | undefined', description: 'The number of input (prompt) tokens used.', }, { name: 'outputTokens', type: 'number | undefined', description: 'The number of output (completion) tokens used.', }, { name: 'totalTokens', type: 'number | undefined', description: 'The total number of tokens as reported by the provider. This number might be different from the sum of inputTokens and outputTokens and e.g. include reasoning tokens or other overhead.', }, { name: 'reasoningTokens', type: 'number | undefined', isOptional: true, description: 'The number of reasoning tokens used.', }, { name: 'cachedInputTokens', type: 'number | undefined', isOptional: true, description: 'The number of cached input tokens.', }, ], }, ], }, { name: 'providerMetadata', type: 'Promise | undefined>', description: 'Optional metadata from the provider. Resolved whe the response is finished. The outer key is the provider name. The inner values are the metadata. Details depend on the provider.', }, { name: 'object', type: 'Promise', description: 'The generated object (typed according to the schema). Resolved when the response is finished.', }, { name: 'partialObjectStream', type: 'AsyncIterableStream>', description: 'Stream of partial objects. It gets more complete as the stream progresses. Note that the partial object is not validated. If you want to be certain that the actual content matches your schema, you need to implement your own validation for partial results.', }, { name: 'elementStream', type: 'AsyncIterableStream', description: 'Stream of array elements. Only available in "array" mode.', }, { name: 'textStream', type: 'AsyncIterableStream', description: 'Text stream of the JSON representation of the generated object. It contains text chunks. When the stream is finished, the object is valid JSON that can be parsed.', }, { name: 'fullStream', type: 'AsyncIterableStream>', description: 'Stream of different types of events, including partial objects, errors, and finish events. Only errors that stop the stream, such as network errors, are thrown.', properties: [ { type: 'ObjectPart', parameters: [ { name: 'type', type: "'object'", }, { name: 'object', type: 'DeepPartial', description: 'The partial object that was generated.', }, ], }, { type: 'TextDeltaPart', parameters: [ { name: 'type', type: "'text-delta'", }, { name: 'textDelta', type: 'string', description: 'The text delta for the underlying raw JSON text.', }, ], }, { type: 'ErrorPart', parameters: [ { name: 'type', type: "'error'", }, { name: 'error', type: 'unknown', description: 'The error that occurred.', }, ], }, { type: 'FinishPart', parameters: [ { name: 'type', type: "'finish'", }, { name: 'finishReason', type: 'FinishReason', }, { name: 'logprobs', type: 'Logprobs', isOptional: true, }, { name: 'usage', type: 'Usage', description: 'Token usage.', }, { name: 'response', type: 'Response', isOptional: true, description: 'Response metadata.', properties: [ { type: 'Response', parameters: [ { name: 'id', type: 'string', description: 'The response identifier. The AI SDK uses the ID from the provider response when available, and generates an ID otherwise.', }, { name: 'model', type: 'string', description: 'The model that was used to generate the response. The AI SDK uses the response model from the provider response when available, and the model from the function call otherwise.', }, { name: 'timestamp', type: 'Date', description: 'The timestamp of the response. The AI SDK uses the response timestamp from the provider response when available, and creates a timestamp otherwise.', }, ], }, ], }, ], }, ], }, { name: 'request', type: 'Promise', description: 'Request metadata.', properties: [ { type: 'LanguageModelRequestMetadata', parameters: [ { name: 'body', type: 'string', description: 'Raw request HTTP body that was sent to the provider API as a string (JSON should be stringified).', }, ], }, ], }, { name: 'response', type: 'Promise', description: 'Response metadata. Resolved when the response is finished.', properties: [ { type: 'LanguageModelResponseMetadata', parameters: [ { name: 'id', type: 'string', description: 'The response identifier. The AI SDK uses the ID from the provider response when available, and generates an ID otherwise.', }, { name: 'model', type: 'string', description: 'The model that was used to generate the response. The AI SDK uses the response model from the provider response when available, and the model from the function call otherwise.', }, { name: 'timestamp', type: 'Date', description: 'The timestamp of the response. The AI SDK uses the response timestamp from the provider response when available, and creates a timestamp otherwise.', }, { name: 'headers', isOptional: true, type: 'Record', description: 'Optional response headers.', }, ], }, ], }, { name: 'warnings', type: 'CallWarning[] | undefined', description: 'Warnings from the model provider (e.g. unsupported settings).', }, { name: 'pipeTextStreamToResponse', type: '(response: ServerResponse, init?: ResponseInit => void', description: 'Writes text delta output to a Node.js response-like object. It sets a `Content-Type` header to `text/plain; charset=utf-8` and writes each text delta as a separate chunk.', properties: [ { type: 'ResponseInit', parameters: [ { name: 'status', type: 'number', isOptional: true, description: 'The response status code.', }, { name: 'statusText', type: 'string', isOptional: true, description: 'The response status text.', }, { name: 'headers', type: 'Record', isOptional: true, description: 'The response headers.', }, ], }, ], }, { name: 'toTextStreamResponse', type: '(init?: ResponseInit) => Response', description: 'Creates a simple text stream response. Each text delta is encoded as UTF-8 and sent as a separate chunk. Non-text-delta events are ignored.', properties: [ { type: 'ResponseInit', parameters: [ { name: 'status', type: 'number', isOptional: true, description: 'The response status code.', }, { name: 'statusText', type: 'string', isOptional: true, description: 'The response status text.', }, { name: 'headers', type: 'Record', isOptional: true, description: 'The response headers.', }, ], }, ], }, ]} /> ## More Examples