Genkit Dart 0.15.0

Agents

This release introduces Agents: a first-class way to build stateful, multi-turn AI experiences in Dart. Agents wrap generate with durable sessions, tool calling, human-in-the-loop interrupts, sub-agent delegation, and a transport-agnostic client — so you can go from a one-shot prompt to a full conversational agent (running locally or served over HTTP) with a few lines of code.

Defining an agent is one call. It handles the model, tools, and session state for you:

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

final ai = Genkit(
  plugins: [googleAI()],
  model: googleAI.gemini('gemini-flash-latest'),
);

final getWeather = ai.defineTool(
  name: 'getWeather',
  description: 'Get the current weather for a given location.',
  inputSchema: GetWeatherInput.$schema,
  outputSchema: GetWeatherOutput.$schema,
  fn: (input, _) async =>
      GetWeatherOutput(weather: 'Sunny in ${input.location}', temperature: '71F'),
);

final weatherAgent = ai.defineAgent(
  name: 'weatherAgent',
  system: 'You are an assistant helping with weather information. '
      'Use the getWeather tool.',
  tools: [getWeather],
  store: FileSessionStore('.sessions'), // durable, multi-turn state
);

Talk to it - streaming, multi-turn, with state carried automatically between turns:

final chat = weatherAgent.chat(sessionId: 'user-123');

// Stream the first turn.
final turn = chat.sendStream(text: 'What is the weather like in Tokyo?');
await for (final chunk in turn.stream) {
  stdout.write(chunk.text);
}

// Follow-up turn — prior context is threaded automatically.
final res = await chat.send(text: 'What about Paris?');
print(res.text);

Serve it over HTTP with genkit_shelf, and any client (Dart, JS, browser) can
drive it:

router.post('/api/weatherAgent', shelfHandler(weatherAgent.action));

// From a Dart CLI or Flutter/web app — no server-side deps required.
import 'package:genkit/client.dart';

final weather = remoteAgent(url: 'http://localhost:8080/api/weatherAgent');
final chat = weather.chat(sessionId: 'user-123');
await for (final chunk in chat.sendStream(text: 'Weather in Tokyo?').stream) {
  stdout.write(chunk.text);
}

What agents give you

• Durable sessions & snapshots - server- or client-managed state, with
  pluggable stores: InMemorySessionStore, FileSessionStore
  (package:genkit/io.dart), and FirestoreSessionStore (new
  genkit_google_cloud package). Load any past turn from a snapshot, or fork a
  conversation into a variant.
• Streaming multi-turn chat - send / sendStream, with session state
  threaded automatically across turns.
• Tools & human-in-the-loop interrupts - tools can pause for approval
  (ctx.interrupt(...)) and be resumed/restarted with an approval payload, so
  security-critical checks live inside the tool where the model can't bypass
  them.
• Typed custom state - define a stateSchema and mutate structured session
  state from tools; each change streams a live customPatch chunk to the client.
• Sub-agent delegation - the new agents() middleware auto-injects
  delegate_to_* tools, discovers sub-agent descriptions, and adds guard rails
  (maxDelegations, historyLength) for orchestrator/worker patterns.
• Prompt-file agents - definePromptAgent wires a .prompt (dotprompt) file
  into a multi-turn agent, customizable via promptInput.
• Custom & background agents - defineCustomAgent for multi-step flows with
  live status, plus detach + status polling + abort for long-running
  background work.
• Transport-agnostic client - remoteAgent from package:genkit/client.dart
  is browser-safe and wire-compatible with the Genkit client across SDKs
  (verified by a cross-SDK conformance suite).

See the full runnable showcase in testapps/agents - 11 demo pages covering
chat, interrupts, artifacts, background/detach, branching, task state, research,
delegation, and coding agents.

Agents changelog

• feat(agents): agent & session schema types (1/8) by @pavelgj in #310
• feat(agents): session & snapshot storage + JSON Patch (2/8) by @pavelgj in #311
• feat(agents): dart:io FileSessionStore (3/8) by @pavelgj in #312
• feat(agents): transport-agnostic client core (4/8) by @pavelgj in #313
• feat(agents): server-side agent runtime (5/8) by @pavelgj in #314
• feat(agents): HTTP / remote agent client (6/8) by @pavelgj in #315
• test(agents): cross-SDK conformance suite (7/8) by @pavelgj in #316
• docs(agents): demo server + web UI (8/8) by @pavelgj in #317
• feat(google-cloud): add genkit_google_cloud with a FirestoreSessionStore by @pavelgj in #318
• feat(middleware): add agents sub-agent delegation middleware by @pavelgj in #324
• feat(genkit): type-safe agent State with schemantic parsing + agent API polish by @pavelgj in #330
• docs(testapps/agents): add reasoning display and file viewer to agents app by @pavelgj in #334

Other changes

Providers & models

• feat(genkit_firebase_ai): Support Vertex AI Gemini API by @goderbauer in #296
• feat(genkit_vertexai): support Gemini and multimodal embedders by @CorieW in #261
• feat(vertexai): curated known-model metadata + P0 Gemini 3.x registrations by @cabljac in #320
• refactor(google_genai,vertexai): model curated Gemini catalog as an enum by @cabljac in #323
• fix(genkit_openai): send non-image media as OpenAI file content parts by @irangarcia in #297

Core & prompts

• feat!: pass middleware context with GenkitAI to factories by @pavelgj in #319
• fix(core): forward init (and context) from reflection runAction to actions by @pavelgj in #321
• fix(prompt): carry resolved middleware refs on rendered options by @pavelgj in #325
• feat(prompt): surface middleware and generate options in prompt loader by @pavelgj in #333

Schemantic

• feat(schemantic): add serialize to convert typed values to JSON by @pavelgj in #332
• docs: add documentation to schemantic_builder entry point by @pavelgj in #294

Breaking changes

• feat!: pass middleware context with GenkitAI to factories (#319) - middleware factories now receive the middleware context via GenkitAI.

New Contributors

• @goderbauer made their first contribution in #296

Full Changelog: genkit-v0.14.1...genkit-v0.15.0