fix(mattermost): suppress reasoning-only replies

extensions/mattermost/src/mattermost/reply-delivery.test.ts

@@ -38,6 +38,78 @@ function createReplyDeliveryCore(): DeliverMattermostReplyPayloadParams["core"]
 }
 
 describe("deliverMattermostReplyPayload", () => {
+  it("suppresses payloads flagged as reasoning", async () => {
+    const sendMessage = vi.fn(async () => undefined);
+    const cfg = {} satisfies OpenClawConfig;
+    const core = createReplyDeliveryCore();
+
+    await deliverMattermostReplyPayload({
+      core,
+      cfg,
+      payload: { text: "Reasoning:\n_hidden_", isReasoning: true },
+      to: "channel:town-square",
+      accountId: "default",
+      agentId: "agent-1",
+      replyToId: "root-post",
+      textLimit: 4000,
+      tableMode: "off",
+      sendMessage,
+    });
+
+    expect(sendMessage).not.toHaveBeenCalled();
+  });
+
+  it("suppresses reasoning-prefixed payloads even without an explicit flag", async () => {
+    const sendMessage = vi.fn(async () => undefined);
+    const cfg = {} satisfies OpenClawConfig;
+    const core = createReplyDeliveryCore();
+
+    await deliverMattermostReplyPayload({
+      core,
+      cfg,
+      payload: { text: "  \n Reasoning:\n_hidden_" },
+      to: "channel:town-square",
+      accountId: "default",
+      agentId: "agent-1",
+      replyToId: "root-post",
+      textLimit: 4000,
+      tableMode: "off",
+      sendMessage,
+    });
+
+    expect(sendMessage).not.toHaveBeenCalled();
+  });
+
+  it("does not suppress messages that mention Reasoning: mid-text", async () => {
+    const sendMessage = vi.fn(async () => undefined);
+    const cfg = {} satisfies OpenClawConfig;
+    const core = createReplyDeliveryCore();
+
+    await deliverMattermostReplyPayload({
+      core,
+      cfg,
+      payload: { text: "Intro line\nReasoning: appears in content but is not a prefix" },
+      to: "channel:town-square",
+      accountId: "default",
+      agentId: "agent-1",
+      replyToId: "root-post",
+      textLimit: 4000,
+      tableMode: "off",
+      sendMessage,
+    });
+
+    expect(sendMessage).toHaveBeenCalledTimes(1);
+    expect(sendMessage).toHaveBeenCalledWith(
+      "channel:town-square",
+      "Intro line\nReasoning: appears in content but is not a prefix",
+      expect.objectContaining({
+        cfg,
+        accountId: "default",
+        replyToId: "root-post",
+      }),
+    );
+  });
+
   it("passes agent-scoped mediaLocalRoots when sending media paths", async () => {
     const previousStateDir = process.env.OPENCLAW_STATE_DIR;
     const stateDir = await fs.mkdtemp(path.join(os.tmpdir(), "openclaw-mm-state-"));

extensions/mattermost/src/mattermost/reply-delivery.ts

@@ -2,6 +2,7 @@ import {
   deliverTextOrMediaReply,
   resolveSendableOutboundReplyParts,
 } from "openclaw/plugin-sdk/reply-payload";
+import { normalizeLowercaseStringOrEmpty } from "openclaw/plugin-sdk/text-runtime";
 import {
   getAgentScopedMediaLocalRoots,
   type OpenClawConfig,
@@ -23,6 +24,19 @@ type SendMattermostMessage = (
   },
 ) => Promise<unknown>;
 
+const REASONING_PREFIX = "reasoning:";
+
+function shouldSuppressReasoningReply(payload: ReplyPayload): boolean {
+  if (payload.isReasoning === true) {
+    return true;
+  }
+  const text = payload.text;
+  if (typeof text !== "string") {
+    return false;
+  }
+  return normalizeLowercaseStringOrEmpty(text.trimStart()).startsWith(REASONING_PREFIX);
+}
+
 export async function deliverMattermostReplyPayload(params: {
   core: PluginRuntime;
   cfg: OpenClawConfig;
@@ -35,6 +49,9 @@ export async function deliverMattermostReplyPayload(params: {
   tableMode: MarkdownTableMode;
   sendMessage: SendMattermostMessage;
 }): Promise<void> {
+  if (shouldSuppressReasoningReply(params.payload)) {
+    return;
+  }
   const reply = resolveSendableOutboundReplyParts(params.payload, {
     text: params.core.channel.text.convertMarkdownTables(
       params.payload.text ?? "",