Predicted Outputs | OpenAI API

Predicted Outputs enable you to speed up API responses from Chat Completions when many of the output tokens are known ahead of time. This is most common when you are regenerating a text or code file with minor modifications. You can provide your prediction using the prediction request parameter in Chat Completions.

Predicted Outputs are available today using the latest gpt-4o, gpt-4o-mini, gpt-4.1, gpt-4.1-mini, and gpt-4.1-nano models. Read on to learn how to use Predicted Outputs to reduce latency in your applications.

Code refactoring example

Predicted Outputs are particularly useful for regenerating text documents and code files with small modifications. Let’s say you want the GPT-4o model to refactor a piece of JavaScript code, and convert the username property of the User class to be email instead:

1
2
3
4
5
6
7class User {
  firstName = "";
  lastName = "";
  username = "";
}

export default User;

Most of the file will be unchanged, except for line 4 above. If you use the current text of the code file as your prediction, you can regenerate the entire file with lower latency. These time savings add up quickly for larger files.

Below is an example of using the prediction parameter in our SDKs to predict that the final output of the model will be very similar to our original code file, which we use as the prediction text.

Refactor a JavaScript class with a Predicted Output

JavaScript

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41import OpenAI from "openai";

const code = `
class User {
  firstName = "";
  lastName = "";
  username = "";
}

export default User;
`.trim();

const openai = new OpenAI();

const refactorPrompt = `
Replace the "username" property with an "email" property. Respond only
with code, and with no markdown formatting.
`;

const completion = await openai.chat.completions.create({
  model: "gpt-4.1",
  messages: [
    {
      role: "user",
      content: refactorPrompt,
    },
    {
      role: "user",
      content: code,
    },
  ],
  store: true,
  prediction: {
    type: "content",
    content: code,
  },
});

// Inspect returned data
console.log(completion);
console.log(completion.choices[0].message.content);

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30from openai import OpenAI

code = """
class User {
  firstName = "";
  lastName = "";
  username = "";
}

export default User;
""".strip()

refactor_prompt = """
Replace the "username" property with an "email" property. Respond only
with code, and with no markdown formatting.
"""

client = OpenAI()

completion = client.chat.completions.create(
    model="gpt-4.1",
    messages=[
        {"role": "user", "content": refactor_prompt},
        {"role": "user", "content": code},
    ],
    prediction={"type": "content", "content": code},
)

print(completion)
print(completion.choices[0].message.content)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42package main

import (
	"context"
	"fmt"
	"strings"

	"github.com/openai/openai-go/v3"
	"github.com/openai/openai-go/v3/shared"
)

func main() {
	client := openai.NewClient()
	code := strings.TrimSpace(`
class User {
  firstName = "";
  lastName = "";
  username = "";
}

export default User;
`)
	refactorPrompt := strings.TrimSpace(`
Replace the "username" property with an "email" property. Respond only
with code, and with no markdown formatting.
`)
	completion, err := client.Chat.Completions.New(context.Background(), openai.ChatCompletionNewParams{
		Model: shared.ChatModelGPT4_1,
		Messages: []openai.ChatCompletionMessageParamUnion{
			openai.UserMessage(refactorPrompt),
			openai.UserMessage(code),
		},
		Store: openai.Bool(true),
		Prediction: openai.ChatCompletionPredictionContentParam{
			Content: openai.ChatCompletionPredictionContentContentUnionParam{OfString: openai.String(code)},
		},
	})
	if err != nil {
		panic(err)
	}
	fmt.Println(completion.Choices[0].Message.Content)
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31import com.openai.client.OpenAIClient;
import com.openai.client.okhttp.OpenAIOkHttpClient;
import com.openai.models.chat.completions.ChatCompletionCreateParams;
import com.openai.models.chat.completions.ChatCompletionPredictionContent;

String code =
    """
    class User {
      firstName: string = "";
      lastName: string = "";
      username: string = "";
    }

    export default User;
    """;
String refactorPrompt =
    "Replace the \"username\" property with an \"email\" property. "
        + "Respond only with code, and with no markdown formatting.";

ChatCompletionCreateParams params =
    ChatCompletionCreateParams.builder()
        .model("gpt-4.1")
        .addUserMessage(refactorPrompt)
        .addUserMessage(code)
        .prediction(ChatCompletionPredictionContent.builder().content(code).build())
        .store(true)
        .build();

client.chat().completions().create(params).choices().stream()
    .flatMap(choice -> choice.message().content().stream())
    .forEach(System.out::println);

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32using OpenAI.Chat;
#pragma warning disable OPENAI001

string key = Environment.GetEnvironmentVariable("OPENAI_API_KEY")!;
string model = "gpt-4.1";
ChatClient client = new(model, key);

string code =
    """
    class User {
      firstName = "";
      lastName = "";
      username = "";
    }

    export default User;
    """;
ChatCompletionOptions options = new()
{
    OutputPrediction = ChatOutputPrediction.CreateStaticContentPrediction(code),
};
ChatCompletion completion = await client.CompleteChatAsync(
    [
        new UserChatMessage(
            "Replace the username property with an email property. Respond only with code, and with no markdown formatting."
        ),
        new UserChatMessage(code),
    ],
    options
);

Console.WriteLine(completion.Content[0].Text);

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27require "openai"

client = OpenAI::Client.new
code = <<~CODE
  class User {
    firstName: string = "";
    lastName: string = "";
    username: string = "";
  }

  export default User;
CODE
refactor_prompt = <<~PROMPT
  Replace the "username" property with an "email" property. Respond only
  with code, and with no markdown formatting.
PROMPT
completion = client.chat.completions.create(
  model: "gpt-4.1",
  messages: [
    {role: :user, content: refactor_prompt},
    {role: :user, content: code}
  ],
  prediction: {type: :content, content: code},
  store: true
)

puts(completion.choices.fetch(0).message.content)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20curl https://api.openai.com/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -d '{
    "model": "gpt-4.1",
    "messages": [
      {
        "role": "user",
        "content": "Replace the username property with an email property. Respond only with code, and with no markdown formatting."
      },
      {
        "role": "user",
        "content": "$CODE_CONTENT_HERE"
      }
    ],
    "prediction": {
        "type": "content",
        "content": "$CODE_CONTENT_HERE"
    }
  }'

In addition to the refactored code, an abridged model response without the choices field contains usage data like this:

12345678910111213141516171819{
  "id": "chatcmpl-xxx",
  "object": "chat.completion",
  "created": 1786652188,
  "model": "gpt-4.1-2025-04-14",
  "usage": {
    "prompt_tokens": 59,
    "completion_tokens": 24,
    "total_tokens": 83,
    "prompt_tokens_details": { "cached_tokens": 0, "audio_tokens": 0 },
    "completion_tokens_details": {
      "reasoning_tokens": 0,
      "audio_tokens": 0,
      "accepted_prediction_tokens": 14,
      "rejected_prediction_tokens": 2
    }
  },
  "system_fingerprint": "fp_6ddb4f7408"
}

Note both the accepted_prediction_tokens and rejected_prediction_tokens in the usage object. In this example, 14 tokens from the prediction were used to speed up the response, while 2 were rejected.

Note that any rejected tokens are still billed like other completion tokens generated by the API, so Predicted Outputs can introduce higher costs for your requests.

Streaming example

The latency gains of Predicted Outputs are even greater when you use streaming for API responses. Here is an example of the same code refactoring use case, but using streaming in the OpenAI SDKs instead.

Predicted Outputs with streaming

JavaScript

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43import OpenAI from "openai";

const code = `
class User {
  firstName = "";
  lastName = "";
  username = "";
}

export default User;
`.trim();

const openai = new OpenAI();

const refactorPrompt = `
Replace the "username" property with an "email" property. Respond only
with code, and with no markdown formatting.
`;

const completion = await openai.chat.completions.create({
  model: "gpt-4.1",
  messages: [
    {
      role: "user",
      content: refactorPrompt,
    },
    {
      role: "user",
      content: code,
    },
  ],
  store: true,
  prediction: {
    type: "content",
    content: code,
  },
  stream: true,
});

// Inspect returned data
for await (const chunk of completion) {
  process.stdout.write(chunk.choices[0]?.delta?.content || "");
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32from openai import OpenAI

code = """
class User {
  firstName = "";
  lastName = "";
  username = "";
}

export default User;
""".strip()

refactor_prompt = """
Replace the "username" property with an "email" property. Respond only
with code, and with no markdown formatting.
"""

client = OpenAI()

stream = client.chat.completions.create(
    model="gpt-4.1",
    messages=[
        {"role": "user", "content": refactor_prompt},
        {"role": "user", "content": code},
    ],
    prediction={"type": "content", "content": code},
    stream=True,
)

for chunk in stream:
    if chunk.choices[0].delta.content is not None:
        print(chunk.choices[0].delta.content, end="")

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46package main

import (
	"context"
	"fmt"
	"strings"

	"github.com/openai/openai-go/v3"
	"github.com/openai/openai-go/v3/shared"
)

func main() {
	client := openai.NewClient()
	code := strings.TrimSpace(`
class User {
  firstName = "";
  lastName = "";
  username = "";
}

export default User;
`)
	refactorPrompt := strings.TrimSpace(`
Replace the "username" property with an "email" property. Respond only
with code, and with no markdown formatting.
`)
	stream := client.Chat.Completions.NewStreaming(context.Background(), openai.ChatCompletionNewParams{
		Model: shared.ChatModelGPT4_1,
		Messages: []openai.ChatCompletionMessageParamUnion{
			openai.UserMessage(refactorPrompt),
			openai.UserMessage(code),
		},
		Store: openai.Bool(true),
		Prediction: openai.ChatCompletionPredictionContentParam{
			Content: openai.ChatCompletionPredictionContentContentUnionParam{OfString: openai.String(code)},
		},
	})
	for stream.Next() {
		if len(stream.Current().Choices) > 0 {
			fmt.Print(stream.Current().Choices[0].Delta.Content)
		}
	}
	if err := stream.Err(); err != nil {
		panic(err)
	}
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37import com.openai.client.OpenAIClient;
import com.openai.client.okhttp.OpenAIOkHttpClient;
import com.openai.core.http.StreamResponse;
import com.openai.models.chat.completions.ChatCompletionChunk;
import com.openai.models.chat.completions.ChatCompletionCreateParams;
import com.openai.models.chat.completions.ChatCompletionPredictionContent;

String code =
    """
    class User {
      firstName: string = "";
      lastName: string = "";
      username: string = "";
    }

    export default User;
    """;
String refactorPrompt =
    "Replace the \"username\" property with an \"email\" property. "
        + "Respond only with code, and with no markdown formatting.";

ChatCompletionCreateParams params =
    ChatCompletionCreateParams.builder()
        .model("gpt-4.1")
        .addUserMessage(refactorPrompt)
        .addUserMessage(code)
        .prediction(ChatCompletionPredictionContent.builder().content(code).build())
        .store(true)
        .build();

try (StreamResponse<ChatCompletionChunk> stream =
    client.chat().completions().createStreaming(params)) {
  stream.stream()
      .flatMap(chunk -> chunk.choices().stream())
      .flatMap(choice -> choice.delta().content().stream())
      .forEach(System.out::print);
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39using OpenAI.Chat;
#pragma warning disable OPENAI001

string key = Environment.GetEnvironmentVariable("OPENAI_API_KEY")!;
string model = "gpt-4.1";
ChatClient client = new(model, key);

string code =
    """
    class User {
      firstName = "";
      lastName = "";
      username = "";
    }

    export default User;
    """;
ChatCompletionOptions options = new()
{
    OutputPrediction = ChatOutputPrediction.CreateStaticContentPrediction(code),
};

await foreach (
    StreamingChatCompletionUpdate update in client.CompleteChatStreamingAsync(
        [
            new UserChatMessage(
                "Replace the username property with an email property. Respond only with code, and with no markdown formatting."
            ),
            new UserChatMessage(code),
        ],
        options
    )
)
{
    foreach (ChatMessageContentPart part in update.ContentUpdate)
    {
        Console.Write(part.Text);
    }
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27require "openai"

client = OpenAI::Client.new
code = <<~CODE
  class User {
    firstName: string = "";
    lastName: string = "";
    username: string = "";
  }

  export default User;
CODE
refactor_prompt = <<~PROMPT
  Replace the "username" property with an "email" property. Respond only
  with code, and with no markdown formatting.
PROMPT
stream = client.chat.completions.stream(
  model: "gpt-4.1",
  messages: [
    {role: :user, content: refactor_prompt},
    {role: :user, content: code}
  ],
  prediction: {type: :content, content: code},
  store: true
)

stream.text.each { |text| print(text) }

Position of predicted text in response

When providing prediction text, your prediction can appear anywhere within the generated response, and still provide latency reduction for the response. Let’s say your predicted text is the simple Hono server shown below:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25import { serve } from "@hono/node-server";
import { serveStatic } from "@hono/node-server/serve-static";
import { Hono } from "hono";

const app = new Hono();

app.get("/api", (c) => {
  return c.text("Hello Hono!");
});

// You will need to build the client code first: `pnpm run ui:build`.
app.use(
  "/*",
  serveStatic({
    rewriteRequestPath: (path) => `./dist${path}`,
  })
);

const port = 3000;
console.log(`Server is running on port ${port}`);

serve({
  fetch: app.fetch,
  port,
});

You could prompt the model to regenerate the file with a prompt like:

Add a get route to this application that responds with
the text "hello world". Generate the entire application
file again with this route added, and with no other
markdown formatting.

The response to the prompt might look something like this:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29import { serve } from "@hono/node-server";
import { serveStatic } from "@hono/node-server/serve-static";
import { Hono } from "hono";

const app = new Hono();

app.get("/api", (c) => {
  return c.text("Hello Hono!");
});

app.get("/hello", (c) => {
  return c.text("hello world");
});

// You will need to build the client code first: `pnpm run ui:build`.
app.use(
  "/*",
  serveStatic({
    rewriteRequestPath: (path) => `./dist${path}`,
  })
);

const port = 3000;
console.log(`Server is running on port ${port}`);

serve({
  fetch: app.fetch,
  port,
});

An abridged model response without the choices field would still show accepted prediction tokens, even though the prediction text appeared both before and after the new content added to the response:

12345678910111213141516171819{
  "id": "chatcmpl-xxx",
  "object": "chat.completion",
  "created": 1731014771,
  "model": "gpt-4o-2024-08-06",
  "usage": {
    "prompt_tokens": 203,
    "completion_tokens": 159,
    "total_tokens": 362,
    "prompt_tokens_details": { "cached_tokens": 0, "audio_tokens": 0 },
    "completion_tokens_details": {
      "reasoning_tokens": 0,
      "audio_tokens": 0,
      "accepted_prediction_tokens": 60,
      "rejected_prediction_tokens": 0
    }
  },
  "system_fingerprint": "fp_9ee9e968ea"
}

This time, there were no rejected prediction tokens, because the entire content of the file we predicted was used in the final response. Nice! 🔥

Limitations

When using Predicted Outputs, you should consider the following factors and limitations.

Predicted Outputs are only supported with the GPT-4o, GPT-4o-mini, GPT-4.1, GPT-4.1-mini, and GPT-4.1-nano series of models.
When providing a prediction, any tokens provided that are not part of the final completion are still charged at completion token rates. See the rejected_prediction_tokens property of the usage object to see how many tokens are not used in the final response.
The following API parameters are not supported when using Predicted Outputs:
- n: values higher than 1 are not supported
- logprobs: not supported
- presence_penalty: values greater than 0 are not supported
- frequency_penalty: values greater than 0 are not supported
- audio: Predicted Outputs are not compatible with audio inputs and outputs
- modalities: Only text modalities are supported
- max_completion_tokens: not supported
- tools: Function calling is not currently supported with Predicted Outputs

Suggested

Get started

Core concepts

SDKs and CLI

Resources

Legacy APIs

Choose a model

Text and code

Prompting

Reasoning

Images and video

Realtime and audio

Specialized models

Agents SDK

ChatKit

Search and retrieval

Connect tools and data

Build tool workflows

Computer and code

Media

Get started

Audio

Connection methods

Sessions and operations

Go live

Performance and quality

Cost and throughput

Safety and governance

Infrastructure and access

Operations

Core concepts

Plan

Build

Test and publish

Conversion specs

Guides

Resources

Get started

Guides

File Upload

API

Measurement

Advertiser API

API Reference

Get started

Foundations

Explore

Available on

Releases

Workflows

Capabilities

Reference

Customization

Config file

Agent configuration

Extend ChatGPT and Codex

Linux

Windows

Development workflows

Extend and automate

Environments

Build with Codex

Third-party integrations

Reference

Permissions

Codex Security

Cyber safety

Getting started

ChatGPT Work

Identity and authentication

Workspace access, policy, and models

Plugin and connector controls

Usage, governance, and compliance

Deployment and model providers

Community

Blog

Community

Blog

Recent

Topics