fix: handle view-once send/recv on linked devices

- messages-send.ts: for view-once messages, send DSM only to device=0
  (primary phone). Companion devices (device>0) are omitted from
  participants — the WA server generates <unavailable type="view_once"/>
  for them automatically. Sending explicit <unavailable> from a companion
  is rejected by the server and breaks delivery.
  phash is recalculated to match the actual participants sent.

- messages-recv.ts: add early return for <unavailable type="view_once"/>
  stanzas received by the companion (API). When the primary phone sends
  a view-once, linked companions receive this node with no enc content.
  Previously the code tried to decrypt it and crashed with a 500 error.

Co-Authored-By: Renato Alcara

src/Socket/messages-recv.ts

@@ -2258,6 +2258,17 @@ export const makeMessagesRecvSocket = (config: SocketConfig) => {
 			return
 		}
 
+		// Handle view-once unavailable sync from primary device.
+		// When the primary device sends a view-once, linked companions receive
+		// <unavailable type="view_once"/> — no enc content, just a sync signal.
+		// Acknowledge and skip decryption (nothing to decrypt).
+		const unavailableNode = getBinaryNodeChild(node, 'unavailable')
+		if (unavailableNode?.attrs?.type === 'view_once') {
+			logger.debug({ id: node.attrs.id, from: node.attrs.from }, 'received view_once unavailable sync from primary device')
+			await sendMessageAck(node)
+			return
+		}
+
 		const {
 			fullMessage: msg,
 			category,

src/Socket/messages-send.ts

@@ -1279,19 +1279,35 @@ export const makeMessagesSocket = (config: SocketConfig) => {
 
 				await assertSessions(effectiveAllRecipients)
 
+				// For view-once: only send DSM to primary phone (device=0).
+				// Companion devices (device>0) are omitted — WA server generates
+				// <unavailable type="view_once"/> for them automatically.
+				// Sending explicit <unavailable> from a companion is rejected by the server.
+				const isViewOnceMsg = !!(
+					message.viewOnceMessageV2 ||
+					message.viewOnceMessage ||
+					message.viewOnceMessageV2Extension
+				)
+				const viewOnceMeRecipients = isViewOnceMsg
+					? effectiveMeRecipients.filter(jid => !jidDecode(jid)?.device)
+					: effectiveMeRecipients
+
 				const [
 					{ nodes: meNodes, shouldIncludeDeviceIdentity: s1 },
 					{ nodes: otherNodes, shouldIncludeDeviceIdentity: s2 }
 				] = await Promise.all([
 					// For own devices: use DSM (deviceSentMessage) wrapper
-					createParticipantNodes(effectiveMeRecipients, meMsg || message, extraAttrs),
+					createParticipantNodes(viewOnceMeRecipients, meMsg || message, extraAttrs),
 					createParticipantNodes(effectiveOtherRecipients, message, extraAttrs)
 				])
 				participants.push(...meNodes)
 				participants.push(...otherNodes)
 
-				if (effectiveMeRecipients.length > 0 || effectiveOtherRecipients.length > 0) {
-					extraAttrs['phash'] = generateParticipantHashV2(effectiveAllRecipients)
+				const phashRecipients = isViewOnceMsg
+					? [...viewOnceMeRecipients, ...effectiveOtherRecipients]
+					: effectiveAllRecipients
+				if (phashRecipients.length > 0) {
+					extraAttrs['phash'] = generateParticipantHashV2(phashRecipients)
 				}
 
 				shouldIncludeDeviceIdentity = shouldIncludeDeviceIdentity || s1 || s2