genkit 0.10.0-dev.3

A type-safe Dart client library for calling Google Genkit flows with streaming support, authentication, and comprehensive error handling.

Genkit Dart

AI SDK for Dart • LLM Framework • AI Agent Toolkit

Build production-ready AI-powered applications in Dart with a unified interface for text generation, structured output, tool calling, and agentic workflows.

Documentation • API Reference • Discord

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Installation

dart pub add genkit
# For usage with Google AI (Gemini):
dart pub add genkit_google_genai

Quick Start (Framework)

Get up and running in under a minute:

import 'package:genkit/genkit.dart';
import 'package:genkit_google_genai/genkit_google_genai.dart';

void main() async {
  final ai = Genkit(plugins: [googleAI()]);

  final response = await ai.generate(
    model: googleAI.gemini('gemini-2.5-flash'),
    prompt: 'Why is Dart a great language for AI applications?',
  );

  print(response.text);
}

export GEMINI_API_KEY="your-api-key"
dart run main.dart

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Features

Genkit Dart gives you everything you need to build AI applications with confidence.

Generate Text

Call any model with a simple, unified API:

final response = await ai.generate(
  model: googleAI.gemini('gemini-2.5-flash'),
  prompt: 'Explain quantum computing in simple terms.',
);
print(response.text);

Stream Responses

Stream text as it's generated for responsive user experiences:

final stream = ai.generateStream(
  model: googleAI.gemini('gemini-2.5-flash'),
  prompt: 'Write a short story about a robot learning to paint.',
);

await for (final chunk in stream) {
  print(chunk.text);
}

Define Tools

Give models the ability to take actions and access external data:

// Define schemas for tool input
@Schematic()
abstract class WeatherInput {
  String get location;
}

// ... run build_runner to generate WeatherInputType ...

final weatherTool = ai.defineTool(
  name: 'getWeather',
  description: 'Gets the current weather for a location',
  inputType: WeatherInputType,
  fn: (input, _) async {
    // Call your weather API here
    return 'Weather in ${input.location}: 72°F and sunny';
  },
);

final response = await ai.generate(
  model: googleAI.gemini('gemini-2.5-flash'),
  prompt: 'What\'s the weather like in San Francisco?',
  tools: ['getWeather'],
);
print(response.text);

Define Flows

Wrap your AI logic in flows for better observability, testing, and deployment:

final jokeFlow = ai.defineFlow(
  name: 'tellJoke',
  inputType: StringType,
  outputType: StringType,
  fn: (topic, _) async {
    final response = await ai.generate(
      model: googleAI.gemini('gemini-2.5-flash'),
      prompt: 'Tell me a joke about $topic',
    );
    return response.text;
  },
);

final joke = await jokeFlow('programming');
print(joke);

Streaming Flows

Stream data from your flows using context.sendChunk:

final streamStory = ai.defineFlow(
  name: 'streamStory',
  inputType: StringType,
  outputType: StringType,
  streamType: StringType,
  fn: (topic, context) async {
    final stream = ai.generateStream(
      model: googleAI.gemini('gemini-2.5-flash'),
      prompt: 'Write a story about $topic',
    );

    await for (final chunk in stream) {
      context.sendChunk(chunk.text);
    }
    return 'Story complete';
  },
);

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Development Tools

Genkit CLI

Use the Genkit CLI to run your app with tracing and a local development UI:

curl -sL cli.genkit.dev | bash
genkit start -- dart run main.dart

Developer UI

The local developer UI lets you:

• Test flows with different inputs interactively
• Inspect traces to debug complex multi-step operations
• View traces of your generative AI applications

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Client SDK

This package also provides a Dart client for interacting with remote Genkit flows, enabling type-safe communication for both unary and streaming operations.

Getting Started

Import the client library and define your remote actions.

import 'package:genkit/client.dart';

### Defining Remote Actions

Remote actions represent a remote Genkit action (like flows, models and prompts) that can be invoked or streamed. You use generated `*Type` classes (from `@Schematic`) to ensure type safety.

#### Creating a remote action
final stringAction = defineRemoteAction(
  url: 'http://localhost:3400/my-flow',
  inputType: StringType,
  outputType: StringType,
);

// Create a remote action for custom objects
final customAction = defineRemoteAction(
  url: 'http://localhost:3400/custom-flow',
  inputType: MyInputType,
  outputType: MyOutputType,
);

The code assumes that you have my-flow and custom-flow deployed at those URLs. See https://genkit.dev/docs/deploy-node/ or https://genkit.dev/go/docs/deploy/ for details.

Calling Actions

Example: String to String

final action = defineRemoteAction(
  url: 'http://localhost:3400/echo-string',
  inputType: StringType,
  outputType: StringType,
);

try {
  final response = await action(input: 'Hello from Dart!');
  print('Flow Response: $response');
} catch (e) {
  print('Error calling flow: $e');
}

Example: Custom Object Input and Output

First, define your schemas and run build_runner to generate the types.

@Schematic()
abstract class MyInput {
  String get message;
  int get count;
}

@Schematic()
abstract class MyOutput {
  String get reply;
  int get newCount;
}

// ... run build_runner ...

Then define and call the action:

final action = defineRemoteAction(
  url: 'http://localhost:3400/process-object',
  inputType: MyInputType,
  outputType: MyOutputType,
);

final input = MyInput.from(message: 'Process this data', count: 10);

try {
  final output = await action(input: input);
  print('Flow Response: ${output.reply}, ${output.newCount}');
} catch (e) {
  print('Error calling flow: $e');
}

Calling Streaming Flows

Use the stream method for flows that stream multiple chunks of data and then return a final response. Specify streamType to handle typed chunks.

Example 1: Using onResult (Recommended)

final streamAction = defineRemoteAction(
  url: 'http://localhost:3400/stream-story',
  inputType: StringType,
  outputType: StringType,
  streamType: StringType,
);

try {
  final stream = streamAction.stream(
    input: 'Tell me a short story about a Dart developer.',
  );

  print('Streaming chunks:');
  await for (final chunk in stream) {
    print('Chunk: $chunk'); // chunk is String
  }

  // Use onResult to asynchronously get the final response.
  final finalResult = await stream.onResult;
  print('\nFinal Response: $finalResult');
} catch (e) {
  print('Error calling streamFlow: $e');
}

Example: Custom Object Streaming

@Schematic()
abstract class StreamChunk {
  String get content;
}

// ... generated StreamChunkType ...

final streamAction = defineRemoteAction(
  url: 'http://localhost:3400/stream-process',
  inputType: MyInputType,
  outputType: MyOutputType,
  streamType: StreamChunkType,
);

final input = MyInput.from(message: 'Stream this data', count: 5);

try {
  final stream = streamAction.stream(input: input);

  print('Streaming chunks:');
  await for (final chunk in stream) {
    print('Chunk: ${chunk.content}');
  }

  final finalResult = await stream.onResult;
  print('\nFinal Response: ${finalResult.reply}');
} catch (e) {
  print('Error calling streaming flow: $e');
}

Custom Headers

You can provide custom headers for individual requests:

final response = await action(
  input: 'test input',
  headers: {'Authorization': 'Bearer your-token'},
);

// For streaming
final streamResponse = action.stream(
  input: 'test input',
  headers: {'Authorization': 'Bearer your-token'},
);

You can also set default headers when creating the remote action:

final action = defineRemoteAction(
  url: 'http://localhost:3400/my-flow',
  inputType: StringType,
  outputType: StringType,
  defaultHeaders: {'Authorization': 'Bearer your-token'},
);

Error Handling

The library throws GenkitException for various error conditions:

try {
  final result = await action(input: 'test');
} on GenkitException catch (e) {
  print('Genkit error: ${e.message}');
  print('Status code: ${e.statusCode}');
  print('Details: ${e.details}');
} catch (e) {
  print('Other error: $e');
}

Advanced: Manual Data Conversion

For advanced use cases where generated types are not available, you can still use fromResponse and fromStreamChunk for manual conversion:

final action = defineRemoteAction(
  url: 'http://localhost:3400/my-flow',
  fromResponse: (data) => data as String,
);

Working with Genkit Data Objects

When interacting with Genkit models, you'll often work with a set of standardized data classes that represent the inputs and outputs of generative models.

Example: Streaming with Genkit Data Objects

import 'package:genkit/client.dart';

final generateFlow = defineRemoteAction(
  url: 'http://localhost:3400/generate',
  inputType: ModelRequestType,
  outputType: ModelResponseType,
  streamType: ModelResponseChunkType,
);

final stream = generateFlow.stream(
  input: ModelRequest.from(
    messages: [Message.from(role: Role.user, content: [TextPart.from(text: "hello")])],
  ),
);

print('Streaming chunks:');
await for (final chunk in stream) {
  print('Chunk: ${chunk.text}');
}

final finalResult = await stream.onResult;
print('Final Response: ${finalResult.text}');

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Built by Google with contributions from the Open Source Community