fix(regression): preserve mattermost reaction channel routing

extensions/mattermost/src/mattermost/monitor.test.ts

@@ -3,6 +3,7 @@ import type { OpenClawConfig } from "../../runtime-api.js";
 import { resolveMattermostAccount } from "./accounts.js";
 import {
   evaluateMattermostMentionGate,
+  resolveMattermostReactionChannelId,
   resolveMattermostEffectiveReplyToId,
   resolveMattermostReplyRootId,
   resolveMattermostThreadSessionContext,
@@ -274,3 +275,26 @@ describe("resolveMattermostThreadSessionContext", () => {
     });
   });
 });
+
+describe("resolveMattermostReactionChannelId", () => {
+  it("prefers broadcast channel_id when present", () => {
+    expect(
+      resolveMattermostReactionChannelId({
+        broadcast: { channel_id: "chan-broadcast" },
+        data: { channel_id: "chan-data" },
+      }),
+    ).toBe("chan-broadcast");
+  });
+
+  it("falls back to data.channel_id when broadcast channel_id is missing", () => {
+    expect(
+      resolveMattermostReactionChannelId({
+        data: { channel_id: "chan-data" },
+      }),
+    ).toBe("chan-data");
+  });
+
+  it("returns undefined when neither payload location includes channel_id", () => {
+    expect(resolveMattermostReactionChannelId({})).toBeUndefined();
+  });
+});

extensions/mattermost/src/mattermost/monitor.ts

@@ -212,6 +212,13 @@ export function resolveMattermostThreadSessionContext(params: {
     parentSessionKey: threadKeys.parentSessionKey,
   };
 }
+
+export function resolveMattermostReactionChannelId(
+  payload: Pick<MattermostEventPayload, "broadcast" | "data">,
+): string | undefined {
+  return payload.broadcast?.channel_id?.trim() || payload.data?.channel_id?.trim() || undefined;
+}
+
 function buildMattermostAttachmentPlaceholder(mediaList: MattermostMediaInfo[]): string {
   if (mediaList.length === 0) {
     return "";
@@ -1492,7 +1499,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
     const senderName = senderInfo?.username?.trim() || userId;
 
     // Resolve the channel from broadcast or post to route to the correct agent session
-    const channelId = payload.broadcast?.channel_id;
+    const channelId = resolveMattermostReactionChannelId(payload);
     if (!channelId) {
       // Without a channel id we cannot verify DM/group policies — drop to be safe
       logVerboseMessage(