diff --git a/CHANGELOG.md b/CHANGELOG.md
index 449d81b3ede..c868ccc18c0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -318,6 +318,7 @@ Docs: https://docs.openclaw.ai
 - Plugins/runtime state: share plugin-facing infra singleton state across duplicate module graphs and keep session-binding adapter ownership stable until the active owner unregisters. (#50725) thanks @huntharo.
 - Discord/pickers: keep `/codex_resume --browse-projects` picker callbacks alive in Discord by sharing component callback state across duplicate module graphs, preserving callback fallbacks, and acknowledging matched plugin interactions before dispatch. (#51260) Thanks @huntharo.
 - Memory/core tools: register `memory_search` and `memory_get` independently so one unavailable memory tool no longer suppresses the other in new sessions. (#50198) Thanks @artwalker.
+- Telegram/Mattermost message tool: keep plugin button schemas optional in isolated and cron sessions so plain sends do not fail validation when no current channel is active. (#52589) Thanks @tylerliu612.
 
 ## 2026.3.13
 
diff --git a/extensions/mattermost/src/channel.test.ts b/extensions/mattermost/src/channel.test.ts
index 5c015b9546d..5c600649d27 100644
--- a/extensions/mattermost/src/channel.test.ts
+++ b/extensions/mattermost/src/channel.test.ts
@@ -1,3 +1,4 @@
+import { Type } from "@sinclair/typebox";
 import { beforeEach, describe, expect, it, vi } from "vitest";
 import type { OpenClawConfig } from "../runtime-api.js";
 import { createChannelReplyPipeline } from "../runtime-api.js";
@@ -181,6 +182,26 @@ describe("mattermostPlugin", () => {
       expect(actions).toEqual([]);
     });
 
+    it("keeps buttons optional in message tool schema", () => {
+      const cfg: OpenClawConfig = {
+        channels: {
+          mattermost: {
+            enabled: true,
+            botToken: "test-token",
+            baseUrl: "https://chat.example.com",
+          },
+        },
+      };
+
+      const discovery = mattermostPlugin.actions?.describeMessageTool?.({ cfg });
+      const schema = discovery?.schema;
+      if (!schema || Array.isArray(schema)) {
+        throw new Error("expected mattermost message-tool schema");
+      }
+
+      expect(Type.Object(schema.properties).required).toBeUndefined();
+    });
+
     it("hides react when actions.reactions is false", () => {
       const cfg: OpenClawConfig = {
         channels: {
diff --git a/extensions/mattermost/src/channel.ts b/extensions/mattermost/src/channel.ts
index b91f1c995a3..3827f328464 100644
--- a/extensions/mattermost/src/channel.ts
+++ b/extensions/mattermost/src/channel.ts
@@ -1,3 +1,4 @@
+import { Type } from "@sinclair/typebox";
 import { describeAccountSnapshot } from "openclaw/plugin-sdk/account-helpers";
 import { formatNormalizedAllowFromEntries } from "openclaw/plugin-sdk/allow-from";
 import { createMessageToolButtonsSchema } from "openclaw/plugin-sdk/channel-actions";
@@ -97,7 +98,7 @@ function describeMattermostMessageTool({
       enabledAccounts.length > 0
         ? {
             properties: {
-              buttons: createMessageToolButtonsSchema(),
+              buttons: Type.Optional(createMessageToolButtonsSchema()),
             },
           }
         : null,