fix(heartbeat): bound responsePrefix strip for ack detection

CHANGELOG.md

@@ -50,6 +50,7 @@ Docs: https://docs.openclaw.ai
 - Security/Sessions: create new session transcript JSONL files with user-only (`0o600`) permissions and extend `openclaw security audit --fix` to remediate existing transcript file permissions.
 - Infra/Fetch: ensure foreign abort-signal listener cleanup never masks original fetch successes/failures, while still preventing detached-finally unhandled rejection noise in `wrapFetchWithAbortSignal`. Thanks @Jackten.
 - Heartbeat: allow suppressing tool error warning payloads during heartbeat runs via a new heartbeat config flag. (#18497) Thanks @thewilloftheshadow.
+- Heartbeat/Telegram: strip configured `responsePrefix` before heartbeat ack detection (with boundary-safe matching) so prefixed `HEARTBEAT_OK` replies are correctly suppressed instead of leaking into DMs. (#18602)
 
 ## 2026.2.15
 

src/infra/heartbeat-runner.respects-ackmaxchars-heartbeat-acks.test.ts

@@ -201,7 +201,7 @@ describe("resolveHeartbeatIntervalMs", () => {
     });
   });
 
-  it("strips responsePrefix before detecting HEARTBEAT_OK and skips telegram delivery", async () => {
+  it("strips responsePrefix before HEARTBEAT_OK detection and suppresses short ack text", async () => {
     await withTempTelegramHeartbeatSandbox(async ({ tmpDir, storePath, replySpy }) => {
       const cfg = createHeartbeatConfig({
         tmpDir,
@@ -226,7 +226,7 @@ describe("resolveHeartbeatIntervalMs", () => {
         lastTo: "12345",
       });
 
-      replySpy.mockResolvedValue({ text: "[openclaw] HEARTBEAT_OK" });
+      replySpy.mockResolvedValue({ text: "[openclaw] HEARTBEAT_OK all good" });
       const sendTelegram = vi.fn().mockResolvedValue({
         messageId: "m1",
         toJid: "jid",
@@ -241,6 +241,51 @@ describe("resolveHeartbeatIntervalMs", () => {
     });
   });
 
+  it("does not strip alphanumeric responsePrefix from larger words", async () => {
+    await withTempTelegramHeartbeatSandbox(async ({ tmpDir, storePath, replySpy }) => {
+      const cfg = createHeartbeatConfig({
+        tmpDir,
+        storePath,
+        heartbeat: {
+          every: "5m",
+          target: "telegram",
+        },
+        channels: {
+          telegram: {
+            token: "test-token",
+            allowFrom: ["*"],
+            heartbeat: { showOk: false },
+          },
+        },
+        messages: { responsePrefix: "Hi" },
+      });
+
+      await seedMainSession(storePath, cfg, {
+        lastChannel: "telegram",
+        lastProvider: "telegram",
+        lastTo: "12345",
+      });
+
+      replySpy.mockResolvedValue({ text: "History check complete" });
+      const sendTelegram = vi.fn().mockResolvedValue({
+        messageId: "m1",
+        toJid: "jid",
+      });
+
+      await runHeartbeatOnce({
+        cfg,
+        deps: makeTelegramDeps({ sendTelegram }),
+      });
+
+      expect(sendTelegram).toHaveBeenCalledTimes(1);
+      expect(sendTelegram).toHaveBeenCalledWith(
+        "12345",
+        "History check complete",
+        expect.any(Object),
+      );
+    });
+  });
+
   it("skips heartbeat LLM calls when visibility disables all output", async () => {
     await withTempHeartbeatSandbox(async ({ tmpDir, storePath, replySpy }) => {
       const cfg = createHeartbeatConfig({

src/infra/heartbeat-runner.ts

@@ -430,17 +430,31 @@ async function captureTranscriptState(params: {
   }
 }
 
+function stripLeadingHeartbeatResponsePrefix(
+  text: string,
+  responsePrefix: string | undefined,
+): string {
+  const normalizedPrefix = responsePrefix?.trim();
+  if (!normalizedPrefix) {
+    return text;
+  }
+
+  // Require a boundary after the configured prefix so short prefixes like "Hi"
+  // do not strip the beginning of normal words like "History".
+  const prefixPattern = new RegExp(
+    `^${escapeRegExp(normalizedPrefix)}(?=$|\\s|[\\p{P}\\p{S}])\\s*`,
+    "iu",
+  );
+  return text.replace(prefixPattern, "");
+}
+
 function normalizeHeartbeatReply(
   payload: ReplyPayload,
   responsePrefix: string | undefined,
   ackMaxChars: number,
 ) {
   const rawText = typeof payload.text === "string" ? payload.text : "";
-
-  const prefixPattern = responsePrefix?.trim()
-    ? new RegExp(`^${escapeRegExp(responsePrefix.trim())}\\s*`, "i")
-    : null;
-  const textForStrip = prefixPattern ? rawText.replace(prefixPattern, "") : rawText;
+  const textForStrip = stripLeadingHeartbeatResponsePrefix(rawText, responsePrefix);
   const stripped = stripHeartbeatToken(textForStrip, {
     mode: "heartbeat",
     maxAckChars: ackMaxChars,