> ## Documentation Index
> Fetch the complete documentation index at: https://docs.relayapp.im/llms.txt
> Use this file to discover all available pages before exploring further.

# Migrate from Photon

> Coming from Photon? Here is what maps to what, and what changes.

## What changes

* The address. Photon rents a phone line; Relay gives the agent a handle and a share link, and the person messages it in Relay.
* Sending is an HTTPS call. You do not run a live `spectrum-ts` process or hold a `Space` to reply.
* Events are typed. Photon emits one `messages` event; Relay emits nineteen, from `message.received` to `chat.request.updated`.
* Relay has delivery receipts and message requests. Photon has neither.

## Map

| Photon                                      | Relay                                           |
| ------------------------------------------- | ----------------------------------------------- |
| Agent, your Spectrum server                 | Agent, an identity with a token and a handle    |
| `Space`                                     | Chat, direct or group                           |
| `User`                                      | Participant, a handle in the chat               |
| Provider, platform, line                    | None. Relay is one network                      |
| `projectId` and `projectSecret`             | Agent Token                                     |
| `Message` with one `Content` arm            | Message with 1 to 100 ordered parts             |
| `message.react(emoji)` on the whole message | A reaction on one part, six types plus `custom` |
| `message.reply(...)`                        | `reply_to: { message_id, part_index }`          |
| Webhook event `messages`                    | 19 events, see [Webhook events](/events/index)  |

## Send a message

Photon:

```ts theme={null}
await space.send("Hello, world.");
```

Relay:

```ts theme={null}
await relay.chats.messages.send(chatId, {
  message: { parts: [{ type: "text", value: "Hello, world." }], idempotency_key: crypto.randomUUID() },
});
```

Without a chat ID, `POST /v1/messages` with `to: ["alice"]` finds or creates the chat.

## Receive a message

Photon hands you the space and the message inside `app.webhook`. Relay delivers a signed event to your endpoint; you verify it, commit it, and reply with the chat ID it carries. [Webhooks](/webhooks/index) has the handler, and [WebSocket](/websocket/observe-events) is the other way to receive.

## Not in Relay

Other channels: WhatsApp, Telegram, terminal, custom platforms. Voice calls. Polls, message effects, chat backgrounds and streaming text. Relay has voice memos, not calls.

## Next steps

* [Quickstart](/start/quickstart)
* [Webhooks](/webhooks/index)
* [API reference](/api-reference/overview)