diff --git a/src/agents/subagent-announce.ts b/src/agents/subagent-announce.ts
index 27176029fc4..c0c981e8e3f 100644
--- a/src/agents/subagent-announce.ts
+++ b/src/agents/subagent-announce.ts
@@ -21,7 +21,7 @@ import {
   mergeDeliveryContext,
   normalizeDeliveryContext,
 } from "../utils/delivery-context.js";
-import { isDeliverableMessageChannel } from "../utils/message-channel.js";
+import { isDeliverableMessageChannel, isInternalMessageChannel } from "../utils/message-channel.js";
 import {
   buildAnnounceIdFromChildRun,
   buildAnnounceIdempotencyKey,
@@ -350,9 +350,12 @@ function resolveAnnounceOrigin(
 ): DeliveryContext | undefined {
   const normalizedRequester = normalizeDeliveryContext(requesterOrigin);
   const normalizedEntry = deliveryContextFromSession(entry);
-  if (normalizedRequester?.channel && !isDeliverableMessageChannel(normalizedRequester.channel)) {
-    // Ignore internal/non-deliverable channel hints (for example webchat)
-    // so a valid persisted route can still be used for outbound delivery.
+  if (normalizedRequester?.channel && isInternalMessageChannel(normalizedRequester.channel)) {
+    // Ignore internal channel hints (webchat) so a valid persisted route
+    // can still be used for outbound delivery. Non-standard channels that
+    // are not in the deliverable list should NOT be stripped here — doing
+    // so causes the session entry's stale lastChannel (often WhatsApp) to
+    // override the actual requester origin, leading to delivery failures.
     return mergeDeliveryContext(
       {
         accountId: normalizedRequester.accountId,