---
title: iMessage inline replies | Sendblue Docs
description: Reply to a specific iMessage and preserve its conversation thread
---

Inline replies let a new iMessage appear as a reply to a specific message in Messages. You can continue a thread by replying to any message whose `message_handle` was returned by Sendblue.

Inline replies require a V2 Sendblue line and an iMessage conversation. Sendblue does not downgrade replies to SMS.

## Send a reply

Add a `reply_to` object to a normal send request. Use the exact public `message_handle` returned by a Sendblue API response or webhook.

Terminal window

```
curl -X POST https://api.sendblue.com/api/send-message \
  -H "sb-api-key-id: YOUR_API_KEY" \
  -H "sb-api-secret-key: YOUR_API_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "number": "+14155550100",
    "from_number": "+14155550199",
    "content": "Yes, that works for me.",
    "reply_to": {
      "message_handle": "99DCC379-DD76-4712-BA65-11EFB33B8CD6"
    }
  }'
```

| Parameter                 | Type   | Required | Description                                   |
| ------------------------- | ------ | -------- | --------------------------------------------- |
| `reply_to`                | object | Yes      | Identifies the immediate parent message       |
| `reply_to.message_handle` | string | Yes      | Public handle of the message being replied to |

For an attachment represented by its own inbound webhook, use that webhook’s `message_handle`. Sendblue retains the authoritative Apple attachment-part identity behind the public handle, so callers do not need to infer an index from upload order.

## Reply in a group

Use the same fields with `/api/send-group-message`. The existing `group_id` and `from_number` are required, and the target must belong to that group and line.

```
{
  "group_id": "group_123456",
  "from_number": "+14155550199",
  "content": "Following up in this thread.",
  "reply_to": {
    "message_handle": "2F172CD8-C082-4A54-B9B3-D5B78CF4D0C3"
  }
}
```

Inline replies also work with `/api/send-carousel`; include the `reply_to` object alongside the normal `number`, `from_number`, and `media_urls` parameters.

## Thread fields in responses and webhooks

Reply relationships are returned on message responses, status callbacks, and inbound/outbound message webhooks.

```
{
  "message_handle": "5a17319e-cbcf-443e-897e-d8b0c04b1b09",
  "content": "Yes, that works for me.",
  "service": "iMessage",
  "reply_to": {
    "message_handle": "99DCC379-DD76-4712-BA65-11EFB33B8CD6",
    "part_index": 0
  },
  "thread_originator": {
    "message_handle": "99DCC379-DD76-4712-BA65-11EFB33B8CD6"
  }
}
```

| Field                              | Description                                                            |
| ---------------------------------- | ---------------------------------------------------------------------- |
| `reply_to.message_handle`          | Public handle of the immediate parent message                          |
| `reply_to.part_index`              | Server-reported parent part when authoritative; do not send this field |
| `thread_originator.message_handle` | Public handle of the message that started the thread                   |
| `thread_originator.part`           | Opaque Apple thread-originator part descriptor when available          |

The thread-originator fields are response fields. Do not send them when creating a reply; Sendblue derives them from the target message.

## Validation

Sendblue rejects a reply when:

- The target handle is missing or empty.
- The target belongs to another account, conversation, group, or Sendblue line.
- The target is not in a replyable sent or received state.
- The destination is not an iMessage conversation or its V2 worker does not support inline replies.

A rejected reply is not sent as a standalone message and is not downgraded to SMS. Handle the returned `400` response as a validation failure.