Send a message to one or more recipients without supplying a from number. Linq resolves both the sending line and the target chat for you, then returns exactly which line was used, which chat the message landed in, whether a new chat was created, and every resulting message id.

This fuses "create chat" and "send message" behind a single message-centric resource. Provide only the recipients (to) and the message; the platform decides the rest.

How the from-number and chat are chosen

• Reuse — if a chat with exactly these recipients already exists on a line that can still send, the message is sent into that chat on its existing line (from_selection.reason = reused_active_chat). The most-recently-active such chat wins; chats stranded on flagged lines (e.g. by an earlier failover) are skipped.
• New — if no such chat exists, a new chat is created on the best available line (from_selection.reason = new_best_number).
• Failover — if matching chats exist but none is on a line that can send, a new chat is created on a fresh best line and the flagged chat is abandoned (from_selection.reason = failover_flagged, previous_chat_id set). If you supply continuation_message, that text is sent as the single message INSTEAD of message (useful as a fresh-number-appropriate opener). Exactly one message is sent either way.

Recipients (to) are an order-independent set: a single handle is a direct chat, multiple handles a group chat.

Excluding lines

exclude_from keeps specific lines out of this send's line pick. It only affects picking a line for a new chat — an existing chat is always reused on its own line, preferring a chat on a non-excluded line when the recipients have more than one. An exclusion never abandons a live chat or moves it to a new number, so if the only chat these recipients have is on an excluded line, that chat is still used. from tells you the line that was actually used.

Differences from POST /v3/chats

• The first message may contain a link (including for a newly created chat). Note: sending a link as the very first message on a freshly selected line can elevate that line's flagging risk — it is allowed, not recommended.
• Voice memos are not supported here. To send an iMessage voice-memo bubble, use POST /v3/chats/{chatId}/voicememo with a known chat id.

Service preference, effects, decorations, inline stickers

Set message.preferred_service (iMessage | RCS | SMS), message.effect, and per-part text_decorations and inline_stickers exactly as on the other send endpoints.

Always responds 202 Accepted — chat creation is incidental to the send.

{
  "to": [
    "+14155559876"
  ],
  "exclude_from": [
    "+12052535597"
  ],
  "message": {
    "experience": {
      "name": "agentcard",
      "action": "attach_card"
    },
    "parts": [
      {
        "type": "text",
        "value": "Check this out!"
      },
      {
        "type": "media",
        "url": "https://cdn.linqapp.com/attachments/example/photo.jpg"
      }
    ],
    "effect": {
      "type": "screen",
      "name": "confetti"
    },
    "reply_to": {
      "message_id": "550e8400-e29b-41d4-a716-446655440000"
    },
    "idempotency_key": "msg-abc123xyz",
    "preferred_service": "iMessage"
  },
  "continuation_message": {
    "text": "Hi, it's Acme Support reaching you from a new number."
  }
}

{
  "chat_id": "94c6bf33-31d9-40e3-a0e9-f94250ecedb9",
  "from": "+12052535597",
  "from_selection": {
    "reason": "reused_active_chat",
    "reused_existing_chat": true
  },
  "service": "iMessage",
  "handles": [
    {
      "id": "550e8400-e29b-41d4-a716-446655440000",
      "handle": "+15551234567",
      "service": "iMessage",
      "joined_at": "2025-05-21T15:30:00.000-05:00",
      "line_type": "iMessage"
    }
  ],
  "message": {
    "id": "69a37c7d-af4f-4b5e-af42-e28e98ce873a",
    "service": "iMessage",
    "preferred_service": "iMessage",
    "parts": [
      {
        "type": "text",
        "value": "Hello!"
      }
    ],
    "created_at": "2025-10-23T13:07:55.019-05:00",
    "delivery_status": "pending",
    "effect": {
      "type": "screen",
      "name": "confetti"
    },
    "from_handle": {
      "id": "550e8400-e29b-41d4-a716-446655440000",
      "handle": "+15551234567",
      "service": "iMessage",
      "joined_at": "2025-05-21T15:30:00.000-05:00",
      "line_type": "iMessage"
    },
    "reply_to": {
      "message_id": "550e8400-e29b-41d4-a716-446655440000"
    }
  }
}