# Genkit 1.39 Retires the Chat Beta, Lands Production Agents

> Source: <https://firerun.io/blog/genkit-1-39-agents-api-2026/>
> Published: 2026-06-28 00:00:00+00:00

# Genkit 1.39 Retires the Chat Beta, Lands Production Agents

Genkit JS v1.39.0 removes the beta Chat API and ships defineAgent, a production multi-turn agent framework with Firestore session persistence.

Genkit JS v1.39.0, released June 26, 2026, removes the beta Chat API entirely and replaces it with a production-ready Agents framework. If your app uses `ai.chat()`

or the `Chat`

class, migration is not optional. That code no longer compiles against 1.39.

The change is documented in the [v1.39.0 release notes on GitHub](https://github.com/genkit-ai/genkit/releases) (June 26, 2026).

## What Changed

The beta `Chat`

class and `ai.chat(...)`

method are gone. The replacement is `ai.defineAgent()`

, which provides everything Chat offered plus the infrastructure developers were building around it manually: stateful sessions, pluggable persistence, streaming, and human-in-the-loop controls.

The new surface looks like this:

``` js
import { genkit } from 'genkit';
import { googleAI } from '@genkit-ai/googleai';

const ai = genkit({ plugins: [googleAI()] });

const supportAgent = ai.defineAgent({
  name: 'supportAgent',
  model: googleAI.model('gemini-2.5-flash'),
  system: 'You are a helpful support agent.',
});

const session = await supportAgent.createSession();
const response = await session.chat('What plans do you offer?');
```

The `defineAgent()`

call replaces the old `ai.chat()`

entry point. Sessions are now explicit objects, not implicit chat instances. That gives you a place to attach persistence, pass custom state schemas via Zod, and re-open sessions by ID across requests.

## Key Takeaways

**Migration is required**:`ai.chat()`

and the`Chat`

class are removed in 1.39. Pin`genkit`

to`<1.39.0`

if you need time to migrate, then move fast.is the new entry point for multi-turn AI conversations in Genkit JS.`defineAgent()`

**SessionStore** is pluggable: in-memory and file-based options ship in the core package; ais available for production deployments where session state must survive restarts and scale horizontally.`FirestoreSessionStore`

**Streaming** now delivers JSON Patch state updates, so clients can show incremental state changes (not just token deltas) without polling.**Human-in-the-loop** flows use an interrupt/resume pattern: an agent step can pause for external approval and resume from the same conversation state when the decision arrives.**Multi-agent delegation:** agent middleware handles it; one agent passes context to another without manual state threading.**Vercel AI SDK integration** ships via`GenkitChatTransport`

, wiring`defineAgent`

sessions directly into React chat UIs.

## Migration Path

The mechanical migration from Chat to Agents is straightforward for most apps:

| Before (≤1.38) | After (1.39+) |
|---|---|
`const chat = ai.chat(options)` |
`const agent = ai.defineAgent(options)` |
`await chat.send(message)` |
`const session = await agent.createSession(); await session.chat(message)` |
| No built-in persistence | Pass `sessionStore: new FirestoreSessionStore(db)` to defineAgent |

If you were managing conversation history manually on top of Chat, the new `session.chat()`

interface maintains that history automatically and exposes the full session snapshot for inspection or custom storage.

## Production Session Persistence

`FirestoreSessionStore`

is the production addition that matters most for server-side apps. Sessions persist to Firestore using incremental JSON Patch diffs, so a session that spans multiple HTTP requests or scales across Cloud Run instances stays consistent without any additional plumbing.

For local development and testing, the file-based store (`FileSessionStore`

) or the default in-memory store are sufficient.

## What This Doesn’t Change

Genkit flows, RAG, tool calling, and MCP support are unaffected by this release. The Chat API was one entry point to multi-turn conversations; everything else in the Genkit stack continues to work as documented. TypeScript and Go remain the two production-stable Genkit runtimes; Python and Dart remain in Preview.

## Related

— the other major SDK update from June 2026.[Firebase SQL Connect Streaming Lands in the JavaScript SDK](/blog/firebase-sql-connect-streaming-2026/)