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iMessage inline replies

iMessage inline replies

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.

Send a reply

Section titled “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"
    }
  }'
ParameterTypeRequiredDescription
reply_toobjectYesIdentifies the immediate parent message
reply_to.message_handlestringYesPublic 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

Section titled “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

Section titled “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"
  }
}
FieldDescription
reply_to.message_handlePublic handle of the immediate parent message
reply_to.part_indexServer-reported parent part when authoritative; do not send this field
thread_originator.message_handlePublic handle of the message that started the thread
thread_originator.partOpaque 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

Section titled “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.