diff --git a/CHANGELOG.md b/CHANGELOG.md
index c11df205000..8e13b3d144d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,8 @@ Docs: https://docs.openclaw.ai
 
 ### Fixes
 
+- Agents/cron: suppress the default heartbeat system prompt for cron-triggered embedded runs even when they target non-cron session keys, so cron tasks stop reading `HEARTBEAT.md` and polluting unrelated threads. (#53152) Thanks @Protocol-zero-0.
+
 ## 2026.3.23
 
 ### Breaking
diff --git a/src/infra/update-global.test.ts b/src/infra/update-global.test.ts
index e9007bf28d1..22100d270c1 100644
--- a/src/infra/update-global.test.ts
+++ b/src/infra/update-global.test.ts
@@ -5,6 +5,7 @@ import { afterEach, describe, expect, it } from "vitest";
 import { captureEnv } from "../test-utils/env.js";
 import {
   canResolveRegistryVersionForPackageTarget,
+  collectInstalledGlobalPackageErrors,
   cleanupGlobalRenameDirs,
   detectGlobalInstallManagerByPresence,
   detectGlobalInstallManagerForRoot,
@@ -185,4 +186,33 @@ describe("update global helpers", () => {
     await expect(fs.stat(path.join(root, "openclaw"))).resolves.toBeDefined();
     await expect(fs.stat(path.join(root, ".openclaw-file"))).resolves.toBeDefined();
   });
+
+  it("checks bundled runtime sidecars, including Matrix helper-api", async () => {
+    const packageRoot = await fs.mkdtemp(path.join(os.tmpdir(), "openclaw-update-global-pkg-"));
+    const sidecars = [
+      "dist/extensions/whatsapp/light-runtime-api.js",
+      "dist/extensions/whatsapp/runtime-api.js",
+      "dist/extensions/matrix/helper-api.js",
+      "dist/extensions/matrix/runtime-api.js",
+      "dist/extensions/matrix/thread-bindings-runtime.js",
+      "dist/extensions/msteams/runtime-api.js",
+    ] as const;
+    await fs.writeFile(
+      path.join(packageRoot, "package.json"),
+      JSON.stringify({ name: "openclaw", version: "1.0.0" }),
+      "utf-8",
+    );
+    for (const relativePath of sidecars) {
+      const absolutePath = path.join(packageRoot, relativePath);
+      await fs.mkdir(path.dirname(absolutePath), { recursive: true });
+      await fs.writeFile(absolutePath, "export {};\n", "utf-8");
+    }
+
+    await expect(collectInstalledGlobalPackageErrors({ packageRoot })).resolves.toEqual([]);
+
+    await fs.rm(path.join(packageRoot, "dist/extensions/matrix/helper-api.js"));
+    await expect(collectInstalledGlobalPackageErrors({ packageRoot })).resolves.toContain(
+      "missing bundled runtime sidecar dist/extensions/matrix/helper-api.js",
+    );
+  });
 });
diff --git a/src/plugin-sdk/channel-import-guardrails.test.ts b/src/plugin-sdk/channel-import-guardrails.test.ts
index c5b20b7bdc9..d8c3e481341 100644
--- a/src/plugin-sdk/channel-import-guardrails.test.ts
+++ b/src/plugin-sdk/channel-import-guardrails.test.ts
@@ -11,6 +11,7 @@ const ALLOWED_EXTENSION_PUBLIC_SURFACES = new Set([
   "allow-from.js",
   "api.js",
   "auth-presence.js",
+  "helper-api.js",
   "index.js",
   "light-runtime-api.js",
   "login-qr-api.js",
@@ -22,6 +23,7 @@ const ALLOWED_EXTENSION_PUBLIC_SURFACES = new Set([
   "setup-api.js",
   "setup-entry.js",
   "timeouts.js",
+  "thread-bindings-runtime.js",
 ]);
 const GUARDED_CHANNEL_EXTENSIONS = new Set([
   "bluebubbles",