diff --git a/extensions/mattermost/src/mattermost/monitor-helpers.test.ts b/extensions/mattermost/src/mattermost/monitor-helpers.test.ts
index e064d78aa3aa..aa6b03dbda63 100644
--- a/extensions/mattermost/src/mattermost/monitor-helpers.test.ts
+++ b/extensions/mattermost/src/mattermost/monitor-helpers.test.ts
@@ -1,6 +1,6 @@
 // Mattermost tests cover monitor helpers plugin behavior.
 import { describe, expect, it } from "vitest";
-import { normalizeMention } from "./monitor-helpers.js";
+import { normalizeMention, shouldDropEmptyMattermostBody } from "./monitor-helpers.js";
 
 describe("normalizeMention", () => {
   it("returns trimmed text when no mention provided", () => {
@@ -81,3 +81,106 @@ describe("normalizeMention", () => {
     expect(result).toBe("    code line 1\n    code line 2");
   });
 });
+
+describe("shouldDropEmptyMattermostBody", () => {
+  it("drops a non-mention message that normalizes to an empty body", () => {
+    expect(
+      shouldDropEmptyMattermostBody({
+        bodyText: "",
+        rawText: "   ",
+        botUsername: "openclaw",
+      }),
+    ).toBe(true);
+  });
+
+  it("keeps a message that still has body text", () => {
+    expect(
+      shouldDropEmptyMattermostBody({
+        bodyText: "hello",
+        rawText: "hello",
+        botUsername: "openclaw",
+      }),
+    ).toBe(false);
+  });
+
+  it("keeps a bare mention in a group", () => {
+    expect(
+      shouldDropEmptyMattermostBody({
+        bodyText: "",
+        rawText: "@openclaw",
+        botUsername: "openclaw",
+      }),
+    ).toBe(false);
+  });
+
+  it("keeps a bare mention in a direct message", () => {
+    expect(
+      shouldDropEmptyMattermostBody({
+        bodyText: "",
+        rawText: "@OpenClaw",
+        botUsername: "openclaw",
+      }),
+    ).toBe(false);
+  });
+
+  it("drops an empty body when the bot username is unknown", () => {
+    expect(
+      shouldDropEmptyMattermostBody({
+        bodyText: "",
+        rawText: "@someoneelse",
+        botUsername: undefined,
+      }),
+    ).toBe(true);
+  });
+
+  it("drops a blank post even when a generic mention pattern matched it", () => {
+    expect(
+      shouldDropEmptyMattermostBody({
+        bodyText: "",
+        rawText: "",
+        botUsername: "openclaw",
+      }),
+    ).toBe(true);
+  });
+
+  it("drops a bot mention with only a Unicode control residual", () => {
+    expect(
+      shouldDropEmptyMattermostBody({
+        bodyText: "\u0085",
+        rawText: "@openclaw\u0085",
+        botUsername: "openclaw",
+      }),
+    ).toBe(true);
+  });
+
+  it("drops a bot mention with only a combining-mark residual", () => {
+    expect(
+      shouldDropEmptyMattermostBody({
+        bodyText: "\ufe0f",
+        rawText: "@openclaw\ufe0f",
+        botUsername: "openclaw",
+      }),
+    ).toBe(true);
+  });
+
+  it.each([
+    "@openclaw @openclaw",
+    "@openclaw\n@openclaw",
+    "@openclaw\n",
+    "\n@openclaw",
+    "@openclaw\r\n",
+    "@openclaw\u2028",
+    "@openclaw\u2029",
+    "\v@openclaw\f",
+    "@openclaw\u00a0",
+    "\u2003@openclaw",
+  ])("drops an invalid empty-body candidate: %j", (rawText) => {
+    expect(
+      shouldDropEmptyMattermostBody({
+        bodyText: "",
+        rawText,
+        botUsername: "openclaw",
+      }),
+    ).toBe(true);
+  });
+});
diff --git a/extensions/mattermost/src/mattermost/monitor-helpers.ts b/extensions/mattermost/src/mattermost/monitor-helpers.ts
index 443973c22fd9..2892a58939ca 100644
--- a/extensions/mattermost/src/mattermost/monitor-helpers.ts
+++ b/extensions/mattermost/src/mattermost/monitor-helpers.ts
@@ -1,6 +1,7 @@
 // Mattermost helper module supports monitor helpers behavior.
 import { formatInboundFromLabel as formatInboundFromLabelShared } from "openclaw/plugin-sdk/channel-inbound";
 import { resolveThreadSessionKeys as resolveThreadSessionKeysShared } from "openclaw/plugin-sdk/routing";
+import { normalizeLowercaseStringOrEmpty } from "openclaw/plugin-sdk/string-coerce-runtime";
 import { rawDataToString } from "openclaw/plugin-sdk/webhook-ingress";
 
 export { rawDataToString };
@@ -53,3 +54,16 @@ export function normalizeMention(text: string, mention: string | undefined): str
 
   return normalizedLines.map((line) => line.text).join("\n");
 }
+
+export function shouldDropEmptyMattermostBody(params: {
+  bodyText: string;
+  rawText: string;
+  botUsername?: string | null;
+}): boolean {
+  if (/[^\p{White_Space}\p{Cc}\p{Cf}\p{M}]/u.test(params.bodyText)) {
+    return false;
+  }
+  const botUsername = normalizeLowercaseStringOrEmpty(params.botUsername ?? "");
+  const bareMention = params.rawText.match(/^[ \t]*(@\S+)[ \t]*$/u)?.[1];
+  return !botUsername || normalizeLowercaseStringOrEmpty(bareMention ?? "") !== `@${botUsername}`;
+}
diff --git a/extensions/mattermost/src/mattermost/monitor.inbound-system-event.test.ts b/extensions/mattermost/src/mattermost/monitor.inbound-system-event.test.ts
index 51bd71d043e8..30aa01b5061a 100644
--- a/extensions/mattermost/src/mattermost/monitor.inbound-system-event.test.ts
+++ b/extensions/mattermost/src/mattermost/monitor.inbound-system-event.test.ts
@@ -445,6 +445,54 @@ describe("mattermost inbound user posts", () => {
     expect(ctx?.Provider).toBe("mattermost");
   });
 
+  it("dispatches a bare bot mention whose body is empty after normalization as a wake event", async () => {
+    const socket = new FakeWebSocket();
+    const abortController = new AbortController();
+    mockState.abortController = abortController;
+
+    const monitor = monitorMattermostProvider({
+      config: testConfig,
+      runtime: testRuntime(),
+      abortSignal: abortController.signal,
+      webSocketFactory: () => socket,
+    });
+
+    await vi.waitFor(() => {
+      expect(socket.openListenerCount).toBeGreaterThan(0);
+    });
+    socket.emitOpen();
+
+    await socket.emitMessage({
+      event: "posted",
+      data: {
+        channel_id: "chan-1",
+        channel_name: "town-square",
+        channel_display_name: "Town Square",
+        sender_name: "alice",
+        post: JSON.stringify({
+          id: "post-bare-mention",
+          channel_id: "chan-1",
+          user_id: "user-1",
+          message: "@openclaw",
+          create_at: 1_714_000_000_001,
+        }),
+      },
+      broadcast: {
+        channel_id: "chan-1",
+        user_id: "user-1",
+      },
+    });
+    socket.emitClose(1000);
+    await monitor;
+
+    expect(mockState.dispatchReplyFromConfig).toHaveBeenCalledTimes(1);
+    const ctx = mockState.dispatchReplyFromConfig.mock.calls.at(0)?.[0].ctx;
+    expect(ctx?.BodyForAgent).toBe("@openclaw");
+    expect(ctx?.MessageSid).toBe("post-bare-mention");
+    expect(ctx?.OriginatingChannel).toBe("mattermost");
+    expect(ctx?.Provider).toBe("mattermost");
+  });
+
   it("merges Mattermost progress preview updates and clears after message-tool delivery", async () => {
     const socket = new FakeWebSocket();
     const abortController = new AbortController();
diff --git a/extensions/mattermost/src/mattermost/monitor.ts b/extensions/mattermost/src/mattermost/monitor.ts
index 4990678e84e9..28f25852449b 100644
--- a/extensions/mattermost/src/mattermost/monitor.ts
+++ b/extensions/mattermost/src/mattermost/monitor.ts
@@ -69,6 +69,7 @@ import {
   formatInboundFromLabel,
   normalizeMention,
   resolveThreadSessionKeys,
+  shouldDropEmptyMattermostBody,
 } from "./monitor-helpers.js";
 import { resolveOncharPrefixes, stripOncharPrefix } from "./monitor-onchar.js";
 import { createMattermostMonitorResources, type MattermostMediaInfo } from "./monitor-resources.js";
@@ -1332,7 +1333,8 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
           normalizeOptionalString(payload.data?.sender_name) ??
           normalizeOptionalString((await resolveUserInfo(senderId))?.username) ??
           senderId;
-        const rawText = normalizeOptionalString(post.message) ?? "";
+        const rawPostText = typeof post.message === "string" ? post.message : "";
+        const rawText = normalizeOptionalString(rawPostText) ?? "";
         const allowTextCommands = core.channel.commands.shouldHandleTextCommands({
           cfg,
           surface: "mattermost",
@@ -1526,12 +1528,15 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
         const bodySource = oncharTriggered ? oncharResult.stripped : rawText;
         const baseText = [bodySource, mediaPlaceholder].filter(Boolean).join("\n").trim();
         const bodyText = normalizeMention(baseText, botUsername);
-        if (!bodyText) {
+        if (shouldDropEmptyMattermostBody({ bodyText, rawText: rawPostText, botUsername })) {
           logVerboseMessage(
-            `mattermost: drop group message (empty body after normalization channel=${channelId} sender=${senderId})`,
+            `mattermost: drop message (empty body after normalization channel=${channelId} sender=${senderId} wasMentioned=${wasMentioned})`,
           );
           return;
         }
+        // Mention-only turns need non-empty agent text; the shared reply runner rejects empty
+        // bodies before model invocation. The guard above ensures this fallback is a bot mention.
+        const bodyForAgent = bodyText || rawText.trim();
 
         core.channel.activity.record({
           channel: "mattermost",
@@ -1590,7 +1595,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
             : undefined;
         const ctxPayload = core.channel.reply.finalizeInboundContext({
           Body: combinedBody,
-          BodyForAgent: bodyText,
+          BodyForAgent: bodyForAgent,
           InboundHistory: inboundHistory,
           RawBody: bodyText,
           CommandBody: commandBody,