chat

Overview

Chat module for following the AI chat of your users’ apps in real time. Call init() to create a session and start following. A session holds one socket and up to eight app subscriptions. For each app, you get a snapshot of the app’s chat, then every change as it happens:

New and updated chat messages, with the AI’s tool calls.
The AI’s status, from processing to ready.
Preview reloads and navigation, the prompt queue, and generated images.

Methods

init()

init(options): ChatSession

Creates a session without connecting it. A session is one socket plus the app subscriptions that share it. Pass a getSession() callback in the options. The client calls it to get a socket session, which your server opens with Create socket session and returns as the response body. Each session is independent and gets its own socket session. Call connect() on the returned session to open the socket.

Parameters

ChatInitOptions

requis

Session options.

Properties

() => Promise<SocketSession>

requis

Returns a new socket session from your server.Return the response body of Create socket session as a SocketSession, and return a new session on every call. The client calls getSession() on the first connect(), and again only when the session expires or Base44 rejects its token. If a new session has a different socket_url or socket_path, the client moves to it and rejoins every active subscription.

(error: PlatformSocketError) => void

requis

Called on errors that affect the whole session, such as a failed connection or an ended session. Errors for one app go to that subscription’s onError() instead. The error codes say what each error means.

Returns

ChatSession The new session.

Example

const chat = client.chat.init({
  async getSession() {
    const response = await fetch('/api/chat-socket-session', { method: 'POST' });
    return response.json();
  },
  onError(error) {
    console.error('Live updates error', error.code);
  },
});
await chat.connect();

Session methods

A session is one socket plus the app subscriptions that share it, and it reconnects automatically if the connection drops. Use the methods below to connect the socket, follow apps, and close the session.

connect()

connect(): Promise<void>

Connects the session’s socket. The first call gets a socket session from getSession(). If the session has expired or Base44 rejects its token, the client calls getSession() once more for a new one. Concurrent calls share one attempt. The promise resolves once the socket connects, before any snapshot arrives. If the connection drops, the session retries five times and rejoins every active subscription, each with a fresh snapshot. Call connect() again after a failure or a session_replaced error.

Returns

Promise<void> A promise that resolves when the socket connects.

Throws

The promise rejects with a PlatformSocketError whose code is connection_denied, connection_failed, or session_unavailable when the session can’t connect, or client_closed when the session is closed first.

Example

try {
  await chat.connect();
} catch (error) {
  console.error('Could not connect', error.code);
}

subscribe(appId, options): PlatformSubscription

Subscribes to an app’s chat. You can subscribe before or after connecting. A session has one subscription per app, up to eight in total. A session can only follow apps your server gave the session access to, either in Create socket session or later with Add app to session. Subscribing to any other app fails with access_denied. The subscription first receives a snapshot of the app, then each live event. Pass onSnapshot(), onEvent(), and onError() callbacks in the options to receive the app’s snapshot, live events, and errors. Callbacks for an app run one at a time, in order. If a callback returns a promise, the session waits for it before calling the next callback for that app. Each app has its own queue, so a slow callback for one app doesn’t delay the others. If more than 1,000 snapshots and events are waiting for an app’s callbacks, the subscription ends with delivery_overflow.

Parameters

Properties

string

requis

ID of the app to follow, 24 lowercase hexadecimal characters.

SubscriptionOptions

requis

Callbacks for the app’s snapshots, events, and errors.

Properties

(snapshot: PlatformSnapshot) => void | Promise<void>

requis

Called with the app’s current state, a PlatformSnapshot. Replace everything you hold for the app with the snapshot.The snapshot arrives when you subscribe, after every reconnect, and after the main conversation is rewritten by an undo, restore, or sync. Live events follow it. A snapshot holds only the last 50 messages, so load older history again if you show it.

(event: PlatformEvent) => void | Promise<void>

requis

Called with each live event, a PlatformEvent. Events for an app arrive one at a time, in order. If the callback throws or rejects, the subscription ends with handler_failed.New event types can be added at any time, so ignore the types you don’t handle. An event newer than this SDK arrives with type: "unknown", and its event name is in name. Socket messages lists every event and its payload.

(error: PlatformSocketError) => void

requis

Called on errors for this app. Every error ends the subscription except snapshot_unavailable. The error codes say what each error means.

Returns

PlatformSubscription A subscription to an app’s chat.

Properties

string

requis

ID of the app.

boolean

requis

Whether the subscription still receives updates. The value becomes false after an error or a call to unsubscribe().

Throws

The method throws a TypeError when appId isn’t a valid app ID or the app already has a subscription.
The method throws a PlatformSocketError whose code is subscription_limit when the session already has eight subscriptions.

Example

const subscription = chat.subscribe(appId, {
  onSnapshot(snapshot) {
    renderChat(snapshot.messages);
  },
  onEvent(event) {
    if (event.type === 'message.updated') upsertMessage(event.data.message);
  },
  onError(error) {
    console.error(`App ${error.appId}`, error.code);
  },
});

close()

close(): void

Closes the session. Call close() when the page closes or you no longer need live updates. Closing ends every subscription, stops reconnecting, and disconnects the socket. Calling close() again does nothing. A closed session can’t be reused, so call init() for a new one.

Returns

void

Example

chat.close();

Type Definitions

SocketSession

The response body of Create socket session, which your getSession() callback returns. Pass the response through unchanged. The client reads the three fields below.

string

requis

Token that authenticates the socket. The client keeps it in memory and sends it only when the socket connects.

string

requis

Origin of the platform socket, with no path, query, fragment, or credentials.

string

requis

Absolute path the socket connects on, such as /ws/socket.io/.

PlatformEvent

PlatformEvent = AppEvent<"message.updated"> | AppEvent<"message.removed"> | AppEvent<"app.status_changed"> | AppEvent<"preview.reload_requested"> | AppEvent<"preview.navigation_requested"> | AppEvent<"queue.updated"> | AppEvent<"task.progressed"> | AppEvent<"image.resolved"> | AppEvent<"conversation.changed"> | AppEvent<"files.changed"> | AppEvent<"branch.deleted"> | AppEvent<"repository.changed"> | AppEvent<"pull_request.changed"> | UnknownEvent

A live event for a subscribed app. Check type to narrow data to that event’s payload. The data of an event holds only the fields that changed. Keep your value for any field the event leaves out, and clear a field the event sets to null. Socket messages lists every event and its payload. An event added to the service after this version of the SDK arrives with type: "unknown", its event name in name, and an unchecked data, so check a field before using it. After you upgrade, the event arrives under its own type.

Example

function onEvent(event: PlatformEvent) {
  if (event.type === "message.updated") {
    const { message } = event.data;
    console.log(`Message ${message.id} changed`);
  }
  // A hypothetical event this version of the SDK doesn't know yet
  if (event.type === "unknown" && event.name === "app.renamed" && typeof event.data.name === "string") {
    console.log(`App renamed to ${event.data.name}`);
  }
}

PlatformSnapshot

An app’s current state. The snapshot arrives when you subscribe, after every reconnect, and after the main conversation is rewritten. Replace everything you hold for the app with the snapshot. A snapshot holds only the last 50 messages.

StatusObject | null

requis

The app’s build status, or null when none is recorded.

Message[]

requis

The last 50 messages visible to partners, oldest first.

string

requis

Identifies the app the snapshot is for, in the form /apps/{app_id}.

QueueState

The main branch’s prompt queue. Missing when the server sends none.

Errors

PlatformSocketError

The error the SDK reports when something goes wrong with live updates. You don’t create these errors. The SDK passes them to your onError() callbacks, rejects connect() with them, and throws them from subscribe(). Check code to see what happened, then look the code up below:

Session error codes go to the onError() you pass to init(). The whole session is affected, and appId isn’t set.
App error codes go to the subscription’s onError(). Only that app is affected, and appId says which one.

These errors never carry the session token, a callback’s exception, or the server’s exception text.

Example

const chat = client.chat.init({
  async getSession() {
    const response = await fetch('/api/chat-socket-session', { method: 'POST' });
    return response.json();
  },
  // Session error codes: the whole session is affected
  onError(error) {
    if (error.code === 'session_revoked') showSignedOut();
  },
});

chat.subscribe(appId, {
  onSnapshot: renderChat,
  onEvent: applyEvent,
  // App error codes: only this app is affected, and error.appId says which
  onError(error) {
    if (error.code === 'access_revoked') hideLiveUpdates(error.appId);
  },
});

PlatformSocketErrorCode

requis

What happened. One of the session error codes or app error codes.

Session error codes

Codes of errors that affect the whole session. They go to the onError() you pass to init(), and connect() rejects with them. A retryable error is one where the same call can succeed again without changing anything.

The getSession() callback threw, took longer than 20 seconds, or returned a session without a valid session_token, a socket_url that is an HTTP or HTTPS origin, or a socket_path that is an absolute path.Check the endpoint that opens sessions, then call connect() again. Retryable. If a field is invalid, fix it on your server first.

Base44 refused the session even with a fresh token. Either the token is invalid, or live updates aren’t turned on for the workspace.Check that your server opens a new session on every call. Not retryable.

The socket couldn’t connect after five retries, or the server closed the connection.Call connect() again, for example when the tab next gets focus. Retryable.

Your server or an admin ended the session, or the workspace API key that opened the session lost access.Open a new session from your server if the page should still follow apps. Not retryable.

Another socket connected with the same session token.Use one session per tab. Don’t reconnect automatically. Call connect() only to take the session back on purpose. Not retryable.

A message about the whole session didn’t match the protocol.Update the SDK, then call connect() again. Not retryable.

You called connect() or subscribe() after close().Create a new session with init(). Not retryable.

App error codes

Codes of errors for a single app. They go to the subscription’s onError(), and subscribe() throws subscription_limit. Every one ends the subscription except snapshot_unavailable.

The session doesn’t have access to the app, or the connection subscribed to apps too often.Add the app to the session from your server, then subscribe again. Not retryable.

The session lost access to the app. Your server removed the app from the session, or the app left the workspace.Stop showing the app’s live updates. Not retryable.

The subscription is active, but its snapshot failed. Events keep arriving.Load the app’s messages from the Apps API instead.

The session already has eight subscriptions.Unsubscribe from an app, or open another session. Not retryable.

More than 1,000 snapshots and events were waiting for your callbacks.Make the callbacks faster, then subscribe again for a fresh snapshot. Retryable.

Your onSnapshot() or onEvent() callback threw or rejected.Fix the callback, then subscribe again. Not retryable.

An event for this app didn’t match the protocol.Update the SDK, then subscribe again. Not retryable.

string

ID of the app the error is about. Set for app error codes, and not set for session error codes.

Base44 SDKs

App SDK

Platform SDK (Beta)

Overview

Methods

init()

Parameters

Returns

Example

Session methods

connect()

Returns

Throws

Example

Parameters

Returns

Throws

Example

close()

Returns

Example

Type Definitions

SocketSession

PlatformEvent

Example

PlatformSnapshot

Errors

PlatformSocketError

Example

​Overview

​Methods

​init()

​Parameters

​Returns

​Example

​Session methods

​connect()

​Returns

​Throws

​Example

​subscribe()

​Parameters

​Returns

​Throws

​Example

​close()

​Returns

​Example

​Type Definitions

​SocketSession

​PlatformEvent

​Example

​PlatformSnapshot

​Errors

​PlatformSocketError

​Example

Overview

Methods

init()

Parameters

Returns

Example

Session methods

connect()

Returns

Throws

Example

subscribe()

Parameters

Returns

Throws

Example

close()

Returns

Example

Type Definitions

SocketSession

PlatformEvent

Example

PlatformSnapshot

Errors

PlatformSocketError

Example