## Send a message (auto-selected from-number) **post** `/v3/messages` 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 and the line it lives on is healthy, the message is sent into that chat on its existing line (`from_selection.reason = reused_active_chat`). - **New** — if no such chat exists, a new chat is created on the best available line (`from_selection.reason = new_best_number`). - **Failover** — if a matching chat exists but its line has been flagged, 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. ## 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 Set `message.preferred_service` (`iMessage` | `RCS` | `SMS`), `message.effect`, and per-part `text_decorations` exactly as on the other send endpoints. Always responds `202 Accepted` — chat creation is incidental to the send. ### Header Parameters - `"Idempotency-Key": optional string` ### Body Parameters - `message: MessageContent` Message content container. Groups all message-related fields together, separating the "what" (message content) from the "where" (routing fields like from/to). - `parts: array of TextPart or MediaPart or LinkPart or object { app, layout, type, 3 more }` Array of message parts. Each part can be text, media, or link. Parts are displayed in order. Text and media can be mixed freely, but a `link` part must be the only part in the message. **Rich Link Previews:** - Use a `link` part to send a URL with a rich preview card - A `link` part must be the **only** part in the message - To send a URL as plain text (no preview), use a `text` part instead **Supported Media:** - Images: .jpg, .jpeg, .png, .gif, .heic, .heif, .tif, .tiff, .bmp - Videos: .mp4, .mov, .m4v, .mpeg, .mpg, .3gp - Audio: .m4a, .mp3, .aac, .caf, .wav, .aiff, .amr - Documents: .pdf, .txt, .rtf, .csv, .doc, .docx, .xls, .xlsx, .ppt, .pptx, .pages, .numbers, .key, .epub, .zip, .html, .htm - Contact & Calendar: .vcf, .ics **Audio:** - Audio files (.m4a, .mp3, .aac, .caf, .wav, .aiff, .amr) are fully supported as media parts - To send audio as an **iMessage voice memo bubble** (inline playback UI), use the dedicated `/v3/chats/{chatId}/voicememo` endpoint instead **Validation Rules:** - A `link` part must be the **only** part in the message. It cannot be combined with text or media parts. - Consecutive text parts are not allowed. Text parts must be separated by media parts. For example, [text, text] is invalid, but [text, media, text] is valid. - Maximum of **100 parts** total. - Media parts using a public `url` (downloaded by the server on send) are capped at **40**. Parts using `attachment_id` or presigned URLs are exempt from this sub-limit. For bulk media sends exceeding 40 files, pre-upload via `POST /v3/attachments` and reference by `attachment_id` or `download_url`. - `TextPart object { type, value, text_decorations }` - `type: "text"` Indicates this is a text message part - `"text"` - `value: string` The text content of the message. This value is sent as-is with no parsing or transformation — Markdown syntax will be delivered as plain text. Use `text_decorations` to apply inline formatting and animations (iMessage only). - `text_decorations: optional array of TextDecoration` Optional array of text decorations applied to character ranges in the `value` field (iMessage only). Each decoration specifies a character range `[start, end)` and exactly one of `style` or `animation`. **Styles:** `bold`, `italic`, `strikethrough`, `underline` **Animations:** `big`, `small`, `shake`, `nod`, `explode`, `ripple`, `bloom`, `jitter` Style ranges may overlap (e.g. bold + italic on the same text), but animation ranges must not overlap with other animations or styles. *Characters are measured as UTF-16 code units. Most characters count as 1; some emoji count as 2.* **Note:** Text decorations only render for iMessage recipients. For SMS/RCS, text decorations are not applied. - `range: array of number` Character range `[start, end)` in the `value` string where the decoration applies. `start` is inclusive, `end` is exclusive. *Characters are measured as UTF-16 code units. Most characters count as 1; some emoji count as 2.* - `animation: optional "big" or "small" or "shake" or 5 more` Animated text effect to apply. Mutually exclusive with `style`. - `"big"` - `"small"` - `"shake"` - `"nod"` - `"explode"` - `"ripple"` - `"bloom"` - `"jitter"` - `style: optional "bold" or "italic" or "strikethrough" or "underline"` Text style to apply. Mutually exclusive with `animation`. - `"bold"` - `"italic"` - `"strikethrough"` - `"underline"` - `MediaPart object { type, attachment_id, url }` - `type: "media"` Indicates this is a media attachment part - `"media"` - `attachment_id: optional string` Reference to a file pre-uploaded via `POST /v3/attachments` (optional). The file is already stored, so sends using this ID skip the download step — useful when sending the same file to many recipients. Either `url` or `attachment_id` must be provided, but not both. - `url: optional string` Any publicly accessible HTTPS URL to the media file. The server downloads and sends the file automatically — no pre-upload step required. **Size limit:** 10MB maximum for URL-based downloads. For larger files (up to 100MB), use the pre-upload flow: `POST /v3/attachments` to get a presigned URL, upload directly, then reference by `attachment_id`. **Requirements:** - URL must use HTTPS - File content must be a supported format (the server validates the actual file content) **Supported formats:** - Images: .jpg, .jpeg, .png, .gif, .heic, .heif, .tif, .tiff, .bmp - Videos: .mp4, .mov, .m4v, .mpeg, .mpg, .3gp - Audio: .m4a, .mp3, .aac, .caf, .wav, .aiff, .amr - Documents: .pdf, .txt, .rtf, .csv, .doc, .docx, .xls, .xlsx, .ppt, .pptx, .pages, .numbers, .key, .epub, .zip, .html, .htm - Contact & Calendar: .vcf, .ics **Tip:** Audio sent here appears as a regular file attachment. To send audio as an iMessage voice memo bubble (with inline playback), use `/v3/chats/{chatId}/voicememo`. For repeated sends of the same file, use `attachment_id` to avoid redundant downloads. Either `url` or `attachment_id` must be provided, but not both. - `LinkPart object { type, value }` - `type: "link"` Indicates this is a rich link preview part - `"link"` - `value: string` URL to send with a rich link preview. The recipient will see an inline card with the page's title, description, and preview image (when available). A `link` part must be the **only** part in the message. To send a URL as plain text (no preview card), use a `text` part instead. - `IMessageApp object { app, layout, type, 3 more }` An iMessage app card, backed by a Messages app extension. iMessage only — an `imessage_app` part must be the **only** part in the message and is never delivered over SMS/RCS. See the IMessageAppServiceUnsupported (2018) and RecipientUnsupportedMessageType (4005) error codes. - `app: object { bundle_id, name, team_id, app_store_id }` Identifies the iMessage app (Messages app extension) that backs the card. - `bundle_id: string` Bundle identifier of the Messages app extension. Must not contain `:`. - `name: string` Display name of the app, shown by Messages' fallback UI. - `team_id: string` The app's 10-character uppercase alphanumeric team identifier. - `app_store_id: optional number` The owning app's App Store id (optional). When set, recipients without the iMessage app installed see a "Get the app" affordance. - `layout: object { caption, subcaption, trailing_caption, trailing_subcaption }` Visible layout of the card. At least one of `caption`, `subcaption`, `trailing_caption`, or `trailing_subcaption` must be set, otherwise the card renders as an empty bubble. These four caption fields are the complete set of layout properties. The `image`, `mediaFileURL`, `imageTitle`, and `imageSubtitle` fields belong to your app's own Messages extension, not this API: they only render when an app composes the message on-device, and cannot be set here (a sender-supplied image, even delivered as an attachment, does not render). The small icon beside the caption is likewise the app's own icon, not a settable field. - `caption: optional string` Primary label, top-left and bold. - `subcaption: optional string` Secondary label, below `caption` on the left. - `trailing_caption: optional string` Label shown top-right. - `trailing_subcaption: optional string` Label shown below `trailing_caption`, on the right. - `type: "imessage_app"` Indicates this is an iMessage app card part. - `"imessage_app"` - `fallback_text: optional string` Text shown on surfaces that cannot render the card (notifications, lock screen). Defaults to the caption when omitted. - `interactive: optional boolean` Whether the card renders as your app's interactive balloon for recipients who have your iMessage app installed. `true` (default) lets your installed extension draw its live, interactive view for those recipients; everyone else sees the static card built from `layout`. `false` always shows the static `layout` card, even to recipients who have the app installed. Recipients without your app always see the static card regardless of this flag. - `url: optional string` URL the recipient's app opens when they tap the card. - `effect: optional MessageEffect` iMessage effect to apply to this message (screen or bubble effect) - `name: optional string` Name of the effect. Common values: - Screen effects: confetti, fireworks, lasers, sparkles, celebration, hearts, love, balloons, happy_birthday, echo, spotlight - Bubble effects: slam, loud, gentle, invisible - `type: optional "screen" or "bubble"` Type of effect - `"screen"` - `"bubble"` - `idempotency_key: optional string` Optional idempotency key for this message. Use this to prevent duplicate sends of the same message. - `preferred_service: optional ServiceType` Messaging service type - `"iMessage"` - `"SMS"` - `"RCS"` - `reply_to: optional ReplyTo` Reply to another message to create a threaded conversation - `message_id: string` The ID of the message to reply to - `part_index: optional number` The specific message part to reply to (0-based index). Defaults to 0 (first part) if not provided. Use this when replying to a specific part of a multipart message. - `to: array of string` Recipient handles (E.164 phone numbers or email addresses). One handle is a direct chat; multiple handles a group chat. Order-independent — the set identifies the chat. - `continuation_message: optional object { text }` Text-only fallback that **replaces** `message` ONLY on the failover branch — when a chat with these recipients already existed but its line was flagged, so a new chat is created on a fresh line. On that branch this text is sent as the single message instead of `message` (the recipient is on a new number, so you typically want a fresh-number-appropriate opener rather than the original content). Ignored otherwise (a healthy reuse, or genuine first contact). Carries no parts, media, or effects — exactly one message is ever sent. - `text: string` The replacement message text, sent as the single message on failover. ### Returns - `chat_id: string` The resolved chat (reused or newly created) the message landed in. - `created_new_chat: boolean` True when a new chat was created (new or failover), false on reuse. - `from: string` The line (E.164) the message was actually sent from. - `from_selection: object { reason, reused_existing_chat }` Why this line/chat was chosen. - `reason: "reused_active_chat" or "new_best_number" or "failover_flagged"` - `reused_active_chat` — reused an existing chat on its healthy line - `new_best_number` — created a new chat on the best available line - `failover_flagged` — prior chat's line was flagged; created a new chat on a fresh line - `"reused_active_chat"` - `"new_best_number"` - `"failover_flagged"` - `reused_existing_chat: boolean` True only when an existing chat was reused. - `handles: array of ChatHandle` Participants of the resolved chat. - `id: string` Unique identifier for this handle - `handle: string` Phone number (E.164) or email address of the participant - `joined_at: string` When this participant joined the chat - `service: ServiceType` Messaging service type - `"iMessage"` - `"SMS"` - `"RCS"` - `is_me: optional boolean` Whether this handle belongs to the sender (your phone number) - `left_at: optional string` When they left (if applicable) - `status: optional "active" or "left" or "removed"` Participant status - `"active"` - `"left"` - `"removed"` - `is_group: boolean` Whether the resolved chat is a group chat. - `message: SentMessage` A message that was sent (used in CreateChat and SendMessage responses) - `id: string` Message identifier (UUID) - `created_at: string` When the message was created - `delivery_status: "pending" or "queued" or "sent" or 4 more` Current delivery status of a message - `"pending"` - `"queued"` - `"sent"` - `"delivered"` - `"received"` - `"read"` - `"failed"` - `is_read: boolean` DEPRECATED: Use `delivery_status == "read"` instead. Whether the message has been read. - `parts: array of TextPartResponse or MediaPartResponse or LinkPartResponse or object { app, layout, reactions, 3 more }` Message parts in order (text, media, and link) - `TextPartResponse object { reactions, type, value, text_decorations }` A text message part - `reactions: array of Reaction` Reactions on this message part - `handle: ChatHandle` - `id: string` Unique identifier for this handle - `handle: string` Phone number (E.164) or email address of the participant - `joined_at: string` When this participant joined the chat - `service: ServiceType` Messaging service type - `is_me: optional boolean` Whether this handle belongs to the sender (your phone number) - `left_at: optional string` When they left (if applicable) - `status: optional "active" or "left" or "removed"` Participant status - `is_me: boolean` Whether this reaction is from the current user - `type: ReactionType` Type of reaction. Standard iMessage tapbacks are love, like, dislike, laugh, emphasize, question. Custom emoji reactions have type "custom" with the actual emoji in the custom_emoji field. Sticker reactions have type "sticker" with sticker attachment details in the sticker field. - `"love"` - `"like"` - `"dislike"` - `"laugh"` - `"emphasize"` - `"question"` - `"custom"` - `"sticker"` - `custom_emoji: optional string` Custom emoji if type is "custom", null otherwise - `sticker: optional object { file_name, height, mime_type, 2 more }` Sticker attachment details when reaction_type is "sticker". Null for non-sticker reactions. - `file_name: optional string` Filename of the sticker - `height: optional number` Sticker image height in pixels - `mime_type: optional string` MIME type of the sticker image - `url: optional string` Presigned URL for downloading the sticker image (expires in 1 hour). - `width: optional number` Sticker image width in pixels - `type: "text"` Indicates this is a text message part - `"text"` - `value: string` The text content - `text_decorations: optional array of TextDecoration` Text decorations applied to character ranges in the value - `range: array of number` Character range `[start, end)` in the `value` string where the decoration applies. `start` is inclusive, `end` is exclusive. *Characters are measured as UTF-16 code units. Most characters count as 1; some emoji count as 2.* - `animation: optional "big" or "small" or "shake" or 5 more` Animated text effect to apply. Mutually exclusive with `style`. - `"big"` - `"small"` - `"shake"` - `"nod"` - `"explode"` - `"ripple"` - `"bloom"` - `"jitter"` - `style: optional "bold" or "italic" or "strikethrough" or "underline"` Text style to apply. Mutually exclusive with `animation`. - `"bold"` - `"italic"` - `"strikethrough"` - `"underline"` - `MediaPartResponse object { id, filename, mime_type, 4 more }` A media attachment part - `id: string` Unique attachment identifier - `filename: string` Original filename - `mime_type: string` MIME type of the file - `reactions: array of Reaction` Reactions on this message part - `handle: ChatHandle` - `is_me: boolean` Whether this reaction is from the current user - `type: ReactionType` Type of reaction. Standard iMessage tapbacks are love, like, dislike, laugh, emphasize, question. Custom emoji reactions have type "custom" with the actual emoji in the custom_emoji field. Sticker reactions have type "sticker" with sticker attachment details in the sticker field. - `custom_emoji: optional string` Custom emoji if type is "custom", null otherwise - `sticker: optional object { file_name, height, mime_type, 2 more }` Sticker attachment details when reaction_type is "sticker". Null for non-sticker reactions. - `size_bytes: number` File size in bytes - `type: "media"` Indicates this is a media attachment part - `"media"` - `url: string` Presigned URL for downloading the attachment (expires in 1 hour). - `LinkPartResponse object { reactions, type, value }` A rich link preview part - `reactions: array of Reaction` Reactions on this message part - `handle: ChatHandle` - `is_me: boolean` Whether this reaction is from the current user - `type: ReactionType` Type of reaction. Standard iMessage tapbacks are love, like, dislike, laugh, emphasize, question. Custom emoji reactions have type "custom" with the actual emoji in the custom_emoji field. Sticker reactions have type "sticker" with sticker attachment details in the sticker field. - `custom_emoji: optional string` Custom emoji if type is "custom", null otherwise - `sticker: optional object { file_name, height, mime_type, 2 more }` Sticker attachment details when reaction_type is "sticker". Null for non-sticker reactions. - `type: "link"` Indicates this is a rich link preview part - `"link"` - `value: string` The URL - `IMessageAppPartResponse object { app, layout, reactions, 3 more }` An iMessage app card part. - `app: object { bundle_id, name, team_id, app_store_id }` Identifies the iMessage app (Messages app extension) that backs the card. - `bundle_id: string` Bundle identifier of the Messages app extension. Must not contain `:`. - `name: string` Display name of the app, shown by Messages' fallback UI. - `team_id: string` The app's 10-character uppercase alphanumeric team identifier. - `app_store_id: optional number` The owning app's App Store id (optional). When set, recipients without the iMessage app installed see a "Get the app" affordance. - `layout: object { caption, subcaption, trailing_caption, trailing_subcaption }` Visible layout of the card. At least one of `caption`, `subcaption`, `trailing_caption`, or `trailing_subcaption` must be set, otherwise the card renders as an empty bubble. These four caption fields are the complete set of layout properties. The `image`, `mediaFileURL`, `imageTitle`, and `imageSubtitle` fields belong to your app's own Messages extension, not this API: they only render when an app composes the message on-device, and cannot be set here (a sender-supplied image, even delivered as an attachment, does not render). The small icon beside the caption is likewise the app's own icon, not a settable field. - `caption: optional string` Primary label, top-left and bold. - `subcaption: optional string` Secondary label, below `caption` on the left. - `trailing_caption: optional string` Label shown top-right. - `trailing_subcaption: optional string` Label shown below `trailing_caption`, on the right. - `reactions: array of Reaction` Reactions on this message part - `handle: ChatHandle` - `is_me: boolean` Whether this reaction is from the current user - `type: ReactionType` Type of reaction. Standard iMessage tapbacks are love, like, dislike, laugh, emphasize, question. Custom emoji reactions have type "custom" with the actual emoji in the custom_emoji field. Sticker reactions have type "sticker" with sticker attachment details in the sticker field. - `custom_emoji: optional string` Custom emoji if type is "custom", null otherwise - `sticker: optional object { file_name, height, mime_type, 2 more }` Sticker attachment details when reaction_type is "sticker". Null for non-sticker reactions. - `type: "imessage_app"` Indicates this is an iMessage app card part. - `"imessage_app"` - `url: string` The URL delivered to the iMessage app on tap. - `fallback_text: optional string` Fallback text for surfaces that cannot render the card. - `sent_at: string` When the message was actually sent (null if still queued) - `delivered_at: optional string` When the message was delivered - `effect: optional MessageEffect` iMessage effect applied to a message (screen or bubble effect) - `name: optional string` Name of the effect. Common values: - Screen effects: confetti, fireworks, lasers, sparkles, celebration, hearts, love, balloons, happy_birthday, echo, spotlight - Bubble effects: slam, loud, gentle, invisible - `type: optional "screen" or "bubble"` Type of effect - `"screen"` - `"bubble"` - `from_handle: optional ChatHandle` The sender of this message as a full handle object - `preferred_service: optional ServiceType` Messaging service type - `reply_to: optional ReplyTo` Indicates this message is a threaded reply to another message - `message_id: string` The ID of the message to reply to - `part_index: optional number` The specific message part to reply to (0-based index). Defaults to 0 (first part) if not provided. Use this when replying to a specific part of a multipart message. - `service: optional ServiceType` Messaging service type - `service: ServiceType` Messaging service type - `previous_chat_id: optional string` Set ONLY on `failover_flagged`: the abandoned flagged chat that was NOT sent into. Null otherwise. ### Example ```http curl https://api.linqapp.com/api/partner/v3/messages \ -H 'Content-Type: application/json' \ -H "Authorization: Bearer $LINQ_API_V3_API_KEY" \ -d '{ "message": { "parts": [ { "type": "text", "value": "Hi! Thanks for reaching out — how can we help?" } ] }, "to": [ "+14155559876" ] }' ``` #### Response ```json { "chat_id": "94c6bf33-31d9-40e3-a0e9-f94250ecedb9", "created_new_chat": false, "from": "+12052535597", "from_selection": { "reason": "reused_active_chat", "reused_existing_chat": true }, "handles": [ { "id": "550e8400-e29b-41d4-a716-446655440000", "handle": "+15551234567", "joined_at": "2025-05-21T15:30:00.000-05:00", "service": "iMessage", "is_me": false, "left_at": "2019-12-27T18:11:19.117Z", "status": "active" } ], "is_group": false, "message": { "id": "69a37c7d-af4f-4b5e-af42-e28e98ce873a", "created_at": "2025-10-23T13:07:55.019-05:00", "delivery_status": "pending", "is_read": false, "parts": [ { "reactions": [ { "handle": { "id": "69a37c7d-af4f-4b5e-af42-e28e98ce873a", "handle": "+15551234567", "joined_at": "2025-05-21T15:30:00.000-05:00", "service": "iMessage", "is_me": false, "left_at": "2019-12-27T18:11:19.117Z", "status": "active" }, "is_me": false, "type": "love", "custom_emoji": null, "sticker": { "file_name": "sticker.png", "height": 420, "mime_type": "image/png", "url": "https://cdn.linqapp.com/attachments/a1b2c3d4/sticker.png?signature=...", "width": 420 } } ], "type": "text", "value": "Hello!", "text_decorations": [ { "range": [ 0, 5 ], "animation": "shake", "style": "bold" } ] } ], "sent_at": null, "delivered_at": null, "effect": { "name": "confetti", "type": "screen" }, "from_handle": { "id": "550e8400-e29b-41d4-a716-446655440000", "handle": "+15551234567", "joined_at": "2025-05-21T15:30:00.000-05:00", "service": "iMessage", "is_me": false, "left_at": "2019-12-27T18:11:19.117Z", "status": "active" }, "preferred_service": "iMessage", "reply_to": { "message_id": "550e8400-e29b-41d4-a716-446655440000", "part_index": 0 }, "service": "iMessage" }, "service": "iMessage", "previous_chat_id": null } ```