diff --git a/CHANGELOG.md b/CHANGELOG.md
index 91563fbaf..cdcc1eda9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -49,6 +49,7 @@
 - CLI/Gateway: clarify that `clawdbot gateway status` reports RPC health (connect + RPC) and shows RPC failures separately from connect failures.
 - CLI/Update: gate progress spinner on stdout TTY and align clean-check step label. (#701) — thanks @bjesuiter.
 - Telegram: add `/whoami` + `/id` commands to reveal sender id for allowlists; allow `@username` and prefixed ids in `allowFrom` prompts (with stability warning).
+- Heartbeat: strip markup-wrapped `HEARTBEAT_OK` so acks don’t leak to external providers (e.g., Telegram).
 - Control UI: stop auto-writing `telegram.groups["*"]` and warn/confirm before enabling wildcard groups.
 - WhatsApp: send ack reactions only for handled messages and ignore legacy `messages.ackReaction` (doctor copies to `whatsapp.ackReaction`). (#629) — thanks @pasogott.
 - Sandbox/Skills: mirror skills into sandbox workspaces for read-only mounts so SKILL.md stays accessible.
diff --git a/src/auto-reply/heartbeat.test.ts b/src/auto-reply/heartbeat.test.ts
index 9cf47e276..60fa83521 100644
--- a/src/auto-reply/heartbeat.test.ts
+++ b/src/auto-reply/heartbeat.test.ts
@@ -90,4 +90,36 @@ describe("stripHeartbeatToken", () => {
       didStrip: false,
     });
   });
+
+  it("strips HTML-wrapped heartbeat tokens", () => {
+    expect(
+      stripHeartbeatToken(`<b>${HEARTBEAT_TOKEN}</b>`, { mode: "heartbeat" }),
+    ).toEqual({
+      shouldSkip: true,
+      text: "",
+      didStrip: true,
+    });
+  });
+
+  it("strips markdown-wrapped heartbeat tokens", () => {
+    expect(
+      stripHeartbeatToken(`**${HEARTBEAT_TOKEN}**`, { mode: "heartbeat" }),
+    ).toEqual({
+      shouldSkip: true,
+      text: "",
+      didStrip: true,
+    });
+  });
+
+  it("removes markup-wrapped token and keeps trailing content", () => {
+    expect(
+      stripHeartbeatToken(`<code>${HEARTBEAT_TOKEN}</code> all good`, {
+        mode: "message",
+      }),
+    ).toEqual({
+      shouldSkip: false,
+      text: "all good",
+      didStrip: true,
+    });
+  });
 });
diff --git a/src/auto-reply/heartbeat.ts b/src/auto-reply/heartbeat.ts
index d76994df5..c5d02576d 100644
--- a/src/auto-reply/heartbeat.ts
+++ b/src/auto-reply/heartbeat.ts
@@ -52,30 +52,58 @@ export function stripHeartbeatToken(
   if (!trimmed) return { shouldSkip: true, text: "", didStrip: false };
 
   const mode: StripHeartbeatMode = opts.mode ?? "message";
+  const maxAckCharsRaw = opts.maxAckChars;
+  const parsedAckChars =
+    typeof maxAckCharsRaw === "string"
+      ? Number(maxAckCharsRaw)
+      : maxAckCharsRaw;
   const maxAckChars = Math.max(
     0,
-    opts.maxAckChars ?? DEFAULT_HEARTBEAT_ACK_MAX_CHARS,
+    Number.isFinite(parsedAckChars)
+      ? parsedAckChars
+      : DEFAULT_HEARTBEAT_ACK_MAX_CHARS,
   );
 
-  if (!trimmed.includes(HEARTBEAT_TOKEN)) {
+  // Normalize lightweight markup so HEARTBEAT_OK wrapped in HTML/Markdown
+  // (e.g., <b>HEARTBEAT_OK</b> or **HEARTBEAT_OK**) still strips.
+  const stripMarkup = (text: string) =>
+    text
+      // Drop HTML tags.
+      .replace(/<[^>]*>/g, " ")
+      // Decode common nbsp variant.
+      .replace(/&nbsp;/gi, " ")
+      // Remove markdown-ish wrappers at the edges.
+      .replace(/^[*`~_]+/, "")
+      .replace(/[*`~_]+$/, "");
+
+  const trimmedNormalized = stripMarkup(trimmed);
+  const hasToken =
+    trimmed.includes(HEARTBEAT_TOKEN) ||
+    trimmedNormalized.includes(HEARTBEAT_TOKEN);
+  if (!hasToken) {
     return { shouldSkip: false, text: trimmed, didStrip: false };
   }
 
-  const stripped = stripTokenAtEdges(trimmed);
-  if (!stripped.didStrip) {
+  const strippedOriginal = stripTokenAtEdges(trimmed);
+  const strippedNormalized = stripTokenAtEdges(trimmedNormalized);
+  const picked =
+    strippedOriginal.didStrip && strippedOriginal.text
+      ? strippedOriginal
+      : strippedNormalized;
+  if (!picked.didStrip) {
     return { shouldSkip: false, text: trimmed, didStrip: false };
   }
 
-  if (!stripped.text) {
+  if (!picked.text) {
     return { shouldSkip: true, text: "", didStrip: true };
   }
 
+  const rest = picked.text.trim();
   if (mode === "heartbeat") {
-    const rest = stripped.text.trim();
     if (rest.length <= maxAckChars) {
       return { shouldSkip: true, text: "", didStrip: true };
     }
   }
 
-  return { shouldSkip: false, text: stripped.text, didStrip: true };
+  return { shouldSkip: false, text: rest, didStrip: true };
 }
diff --git a/src/infra/heartbeat-runner.test.ts b/src/infra/heartbeat-runner.test.ts
index a33d4a43d..33bd24159 100644
--- a/src/infra/heartbeat-runner.test.ts
+++ b/src/infra/heartbeat-runner.test.ts
@@ -2,6 +2,9 @@ import fs from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
 import { describe, expect, it, vi } from "vitest";
+
+// Avoid pulling optional runtime deps during isolated runs.
+vi.mock("jiti", () => ({ createJiti: () => () => ({}) }));
 import { HEARTBEAT_PROMPT } from "../auto-reply/heartbeat.js";
 import * as replyModule from "../auto-reply/reply.js";
 import type { ClawdbotConfig } from "../config/config.js";
@@ -518,6 +521,65 @@ describe("runHeartbeatOnce", () => {
     }
   });
 
+  it("skips delivery for markup-wrapped HEARTBEAT_OK", async () => {
+    const tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "clawdbot-hb-"));
+    const storePath = path.join(tmpDir, "sessions.json");
+    const replySpy = vi.spyOn(replyModule, "getReplyFromConfig");
+    try {
+      await fs.writeFile(
+        storePath,
+        JSON.stringify(
+          {
+            main: {
+              sessionId: "sid",
+              updatedAt: Date.now(),
+              lastProvider: "whatsapp",
+              lastTo: "+1555",
+            },
+          },
+          null,
+          2,
+        ),
+      );
+
+      const cfg: ClawdbotConfig = {
+        agents: {
+          defaults: {
+            heartbeat: {
+              every: "5m",
+              target: "whatsapp",
+              to: "+1555",
+            },
+          },
+        },
+        whatsapp: { allowFrom: ["*"] },
+        session: { store: storePath },
+      };
+
+      replySpy.mockResolvedValue({ text: "<b>HEARTBEAT_OK</b>" });
+      const sendWhatsApp = vi.fn().mockResolvedValue({
+        messageId: "m1",
+        toJid: "jid",
+      });
+
+      await runHeartbeatOnce({
+        cfg,
+        deps: {
+          sendWhatsApp,
+          getQueueSize: () => 0,
+          nowMs: () => 0,
+          webAuthExists: async () => true,
+          hasActiveWebListener: () => true,
+        },
+      });
+
+      expect(sendWhatsApp).not.toHaveBeenCalled();
+    } finally {
+      replySpy.mockRestore();
+      await fs.rm(tmpDir, { recursive: true, force: true });
+    }
+  });
+
   it("skips WhatsApp delivery when not linked or running", async () => {
     const tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "clawdbot-hb-"));
     const storePath = path.join(tmpDir, "sessions.json");