diff --git a/CHANGELOG.md b/CHANGELOG.md
index a2e976281e1..366c5af34e2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -58,6 +58,7 @@ Docs: https://docs.openclaw.ai
 - Telegram/topics: auto-rename DM forum topics on first message with LLM-generated labels, with per-account and per-DM `autoTopicLabel` overrides. (#51502) Thanks @Lukavyi.
 - Docs/plugins: add the community wecom plugin listing to the docs catalog. (#29905) Thanks @sliverp.
 - Models/GitHub Copilot: allow forward-compat dynamic model ids without code updates, while preserving configured provider and per-model overrides for those synthetic models. (#51325) Thanks @fuller-stack-dev.
+- Agents/compaction: notify users when followup auto-compaction starts and finishes, keeping those notices out of TTS and preserving reply threading for the real assistant reply. (#38805) Thanks @zidongdesign.
 
 ### Fixes
 
diff --git a/src/auto-reply/reply/agent-runner-execution.ts b/src/auto-reply/reply/agent-runner-execution.ts
index c25342e4a28..7e6a4cfa6bc 100644
--- a/src/auto-reply/reply/agent-runner-execution.ts
+++ b/src/auto-reply/reply/agent-runner-execution.ts
@@ -199,6 +199,23 @@ export async function runAgentTurnWithFallback(params: {
         return text;
       };
       const blockReplyPipeline = params.blockReplyPipeline;
+      // Build the delivery handler once so both onAgentEvent (compaction start
+      // notice) and the onBlockReply field share the same instance.  This
+      // ensures replyToId threading (replyToMode=all|first) is applied to
+      // compaction notices just like every other block reply.
+      const blockReplyHandler = params.opts?.onBlockReply
+        ? createBlockReplyDeliveryHandler({
+            onBlockReply: params.opts.onBlockReply,
+            currentMessageId: params.sessionCtx.MessageSidFull ?? params.sessionCtx.MessageSid,
+            normalizeStreamingText,
+            applyReplyToMode: params.applyReplyToMode,
+            normalizeMediaPaths: normalizeReplyMediaPaths,
+            typingSignals: params.typingSignals,
+            blockStreamingEnabled: params.blockStreamingEnabled,
+            blockReplyPipeline,
+            directlySentBlockKeys,
+          })
+        : undefined;
       const onToolResult = params.opts?.onToolResult;
       const fallbackResult = await runWithModelFallback({
         ...resolveModelFallbackOptions(params.followupRun.run),
@@ -394,11 +411,34 @@ export async function runAgentTurnWithFallback(params: {
                       await params.opts?.onToolStart?.({ name, phase });
                     }
                   }
-                  // Track auto-compaction completion and notify UI layer.
+                  // Track auto-compaction and notify higher layers.
                   if (evt.stream === "compaction") {
                     const phase = typeof evt.data.phase === "string" ? evt.data.phase : "";
                     if (phase === "start") {
-                      await params.opts?.onCompactionStart?.();
+                      if (params.opts?.onCompactionStart) {
+                        await params.opts.onCompactionStart();
+                      } else if (params.opts?.onBlockReply) {
+                        // Send directly via opts.onBlockReply (bypassing the
+                        // pipeline) so the notice does not cause final payloads
+                        // to be discarded on non-streaming model paths.
+                        const currentMessageId =
+                          params.sessionCtx.MessageSidFull ?? params.sessionCtx.MessageSid;
+                        const noticePayload = params.applyReplyToMode({
+                          text: "🧹 Compacting context...",
+                          replyToId: currentMessageId,
+                          replyToCurrent: true,
+                          isCompactionNotice: true,
+                        });
+                        try {
+                          await params.opts.onBlockReply(noticePayload);
+                        } catch (err) {
+                          // Non-critical notice delivery failure should not
+                          // bubble out of the fire-and-forget event handler.
+                          logVerbose(
+                            `compaction start notice delivery failed (non-fatal): ${String(err)}`,
+                          );
+                        }
+                      }
                     }
                     const completed = evt.data?.completed === true;
                     if (phase === "end" && completed) {
@@ -410,20 +450,7 @@ export async function runAgentTurnWithFallback(params: {
                 // Always pass onBlockReply so flushBlockReplyBuffer works before tool execution,
                 // even when regular block streaming is disabled. The handler sends directly
                 // via opts.onBlockReply when the pipeline isn't available.
-                onBlockReply: params.opts?.onBlockReply
-                  ? createBlockReplyDeliveryHandler({
-                      onBlockReply: params.opts.onBlockReply,
-                      currentMessageId:
-                        params.sessionCtx.MessageSidFull ?? params.sessionCtx.MessageSid,
-                      normalizeStreamingText,
-                      applyReplyToMode: params.applyReplyToMode,
-                      normalizeMediaPaths: normalizeReplyMediaPaths,
-                      typingSignals: params.typingSignals,
-                      blockStreamingEnabled: params.blockStreamingEnabled,
-                      blockReplyPipeline,
-                      directlySentBlockKeys,
-                    })
-                  : undefined,
+                onBlockReply: blockReplyHandler,
                 onBlockReplyFlush:
                   params.blockStreamingEnabled && blockReplyPipeline
                     ? async () => {
diff --git a/src/auto-reply/reply/agent-runner.ts b/src/auto-reply/reply/agent-runner.ts
index fbdad1be160..7499657d6d4 100644
--- a/src/auto-reply/reply/agent-runner.ts
+++ b/src/auto-reply/reply/agent-runner.ts
@@ -418,6 +418,11 @@ export async function runReplyAgent(params: {
       await blockReplyPipeline.flush({ force: true });
       blockReplyPipeline.stop();
     }
+
+    // NOTE: The compaction completion notice for block-streaming mode is sent
+    // further below — after incrementRunCompactionCount — so it can include
+    // the `(count N)` suffix.  Sending it here (before the count is known)
+    // would omit that information.
     if (pendingToolTasks.size > 0) {
       await Promise.allSettled(pendingToolTasks);
     }
@@ -697,9 +702,48 @@ export async function runReplyAgent(params: {
           });
       }
 
-      if (verboseEnabled) {
-        const suffix = typeof count === "number" ? ` (count ${count})` : "";
-        verboseNotices.push({ text: `🧹 Auto-compaction complete${suffix}.` });
+      // Always notify the user when compaction completes — not just in verbose
+      // mode. The "🧹 Compacting context..." notice was already sent at start,
+      // so the completion message closes the loop for every user regardless of
+      // their verbose setting.
+      const suffix = typeof count === "number" ? ` (count ${count})` : "";
+      const completionText = verboseEnabled
+        ? `🧹 Auto-compaction complete${suffix}.`
+        : `✅ Context compacted${suffix}.`;
+
+      if (blockReplyPipeline && opts?.onBlockReply) {
+        // In block-streaming mode, send the completion notice via
+        // fire-and-forget *after* the pipeline has flushed (so it does not set
+        // didStream()=true and cause buildReplyPayloads to discard the real
+        // assistant reply).  Now that the count is known we can include it.
+        const currentMessageId = sessionCtx.MessageSidFull ?? sessionCtx.MessageSid;
+        const noticePayload = applyReplyToMode({
+          text: completionText,
+          replyToId: currentMessageId,
+          replyToCurrent: true,
+          isCompactionNotice: true,
+        });
+        void Promise.race([
+          opts.onBlockReply(noticePayload),
+          new Promise<void>((_, reject) =>
+            setTimeout(() => reject(new Error("compaction notice timeout")), blockReplyTimeoutMs),
+          ),
+        ]).catch(() => {
+          // Intentionally swallowed — the notice is informational only.
+        });
+      } else {
+        // Non-streaming: push into verboseNotices with full compaction metadata
+        // so threading exemptions apply and replyToMode=first does not thread
+        // the notice instead of the real assistant reply.
+        const currentMessageId = sessionCtx.MessageSidFull ?? sessionCtx.MessageSid;
+        verboseNotices.push(
+          applyReplyToMode({
+            text: completionText,
+            replyToId: currentMessageId,
+            replyToCurrent: true,
+            isCompactionNotice: true,
+          }),
+        );
       }
     }
     if (verboseNotices.length > 0) {
diff --git a/src/auto-reply/reply/dispatch-from-config.ts b/src/auto-reply/reply/dispatch-from-config.ts
index 9df6ef2bc63..9f603b30863 100644
--- a/src/auto-reply/reply/dispatch-from-config.ts
+++ b/src/auto-reply/reply/dispatch-from-config.ts
@@ -582,8 +582,10 @@ export async function dispatchReplyFromConfig(params: {
             if (shouldSuppressReasoningPayload(payload)) {
               return;
             }
-            // Accumulate block text for TTS generation after streaming
-            if (payload.text) {
+            // Accumulate block text for TTS generation after streaming.
+            // Exclude compaction status notices — they are informational UI
+            // signals and must not be synthesised into the spoken reply.
+            if (payload.text && !payload.isCompactionNotice) {
               if (accumulatedBlockText.length > 0) {
                 accumulatedBlockText += "\n";
               }
diff --git a/src/auto-reply/reply/followup-runner.test.ts b/src/auto-reply/reply/followup-runner.test.ts
index 0e93ab156a8..33fd8b9fb89 100644
--- a/src/auto-reply/reply/followup-runner.test.ts
+++ b/src/auto-reply/reply/followup-runner.test.ts
@@ -70,6 +70,10 @@ function mockCompactionRun(params: {
     async (args: {
       onAgentEvent?: (evt: { stream: string; data: Record<string, unknown> }) => void;
     }) => {
+      args.onAgentEvent?.({
+        stream: "compaction",
+        data: { phase: "start" },
+      });
       args.onAgentEvent?.({
         stream: "compaction",
         data: { phase: "end", willRetry: params.willRetry, completed: true },
@@ -84,7 +88,7 @@ function createAsyncReplySpy() {
 }
 
 describe("createFollowupRunner compaction", () => {
-  it("adds verbose auto-compaction notice and tracks count", async () => {
+  it("adds compaction notices and tracks count in verbose mode", async () => {
     const storePath = path.join(
       await fs.mkdtemp(path.join(tmpdir(), "openclaw-compaction-")),
       "sessions.json",
@@ -122,9 +126,15 @@ describe("createFollowupRunner compaction", () => {
 
     await runner(queued);
 
-    expect(onBlockReply).toHaveBeenCalled();
-    const firstCall = (onBlockReply.mock.calls as unknown as Array<Array<{ text?: string }>>)[0];
-    expect(firstCall?.[0]?.text).toContain("Auto-compaction complete");
+    expect(onBlockReply).toHaveBeenCalledTimes(3);
+    const calls = onBlockReply.mock.calls as unknown as Array<
+      Array<{ text?: string; isCompactionNotice?: boolean }>
+    >;
+    expect(calls[0]?.[0]?.text).toBe("🧹 Compacting context...");
+    expect(calls[0]?.[0]?.isCompactionNotice).toBe(true);
+    expect(calls[1]?.[0]?.text).toContain("Auto-compaction complete");
+    expect(calls[1]?.[0]?.isCompactionNotice).toBe(true);
+    expect(calls[2]?.[0]?.text).toBe("final");
     expect(sessionStore.main.compactionCount).toBe(1);
   });
 
@@ -171,12 +181,84 @@ describe("createFollowupRunner compaction", () => {
 
     await runner(queued);
 
-    expect(onBlockReply).toHaveBeenCalled();
-    const firstCall = (onBlockReply.mock.calls as unknown as Array<Array<{ text?: string }>>)[0];
-    expect(firstCall?.[0]?.text).toContain("Auto-compaction complete");
+    expect(onBlockReply).toHaveBeenCalledTimes(2);
+    const calls = onBlockReply.mock.calls as unknown as Array<
+      Array<{ text?: string; isCompactionNotice?: boolean }>
+    >;
+    expect(calls[0]?.[0]?.text).toContain("Auto-compaction complete");
+    expect(calls[0]?.[0]?.isCompactionNotice).toBe(true);
+    expect(calls[1]?.[0]?.text).toBe("final");
     expect(sessionStore.main.compactionCount).toBe(2);
   });
 
+  it("threads followup compaction notices without consuming the first reply slot", async () => {
+    const storePath = path.join(
+      await fs.mkdtemp(path.join(tmpdir(), "openclaw-compaction-threading-")),
+      "sessions.json",
+    );
+    const sessionEntry: SessionEntry = {
+      sessionId: "session",
+      updatedAt: Date.now(),
+    };
+    const sessionStore: Record<string, SessionEntry> = {
+      main: sessionEntry,
+    };
+    const onBlockReply = vi.fn(async () => {});
+
+    mockCompactionRun({
+      willRetry: true,
+      result: { payloads: [{ text: "final" }], meta: {} },
+    });
+
+    const runner = createFollowupRunner({
+      opts: { onBlockReply },
+      typing: createMockTypingController(),
+      typingMode: "instant",
+      sessionEntry,
+      sessionStore,
+      sessionKey: "main",
+      storePath,
+      defaultModel: "anthropic/claude-opus-4-5",
+    });
+
+    const queued = createQueuedRun({
+      messageId: "msg-42",
+      run: {
+        messageProvider: "discord",
+        config: {
+          channels: {
+            discord: {
+              replyToMode: "first",
+            },
+          },
+        },
+        verboseLevel: "off",
+      },
+    });
+
+    await runner(queued);
+
+    expect(onBlockReply).toHaveBeenCalledTimes(3);
+    const calls = onBlockReply.mock.calls as unknown as Array<
+      Array<{ text?: string; replyToId?: string; isCompactionNotice?: boolean }>
+    >;
+    expect(calls[0]?.[0]).toMatchObject({
+      text: "🧹 Compacting context...",
+      replyToId: "msg-42",
+      isCompactionNotice: true,
+    });
+    expect(calls[1]?.[0]).toMatchObject({
+      text: "✅ Context compacted (count 1).",
+      replyToId: "msg-42",
+      isCompactionNotice: true,
+    });
+    expect(calls[2]?.[0]).toMatchObject({
+      text: "final",
+      replyToId: "msg-42",
+    });
+    expect(calls[2]?.[0]?.isCompactionNotice).toBeUndefined();
+  });
+
   it("does not count failed compaction end events in followup runs", async () => {
     const storePath = path.join(
       await fs.mkdtemp(path.join(tmpdir(), "openclaw-compaction-failed-")),
diff --git a/src/auto-reply/reply/followup-runner.ts b/src/auto-reply/reply/followup-runner.ts
index 2fd21607095..ee69187d9df 100644
--- a/src/auto-reply/reply/followup-runner.ts
+++ b/src/auto-reply/reply/followup-runner.ts
@@ -148,6 +148,43 @@ export function createFollowupRunner(params: {
           isControlUiVisible: shouldSurfaceToControlUi,
         });
       }
+      const replyToChannel = resolveOriginMessageProvider({
+        originatingChannel: queued.originatingChannel,
+        provider: queued.run.messageProvider,
+      }) as OriginatingChannelType | undefined;
+      const replyToMode = resolveReplyToMode(
+        queued.run.config,
+        replyToChannel,
+        queued.originatingAccountId,
+        queued.originatingChatType,
+      );
+      const currentMessageId = queued.messageId?.trim() || undefined;
+      const applyFollowupReplyThreading = (payloads: ReplyPayload[]) =>
+        applyReplyThreading({
+          payloads,
+          replyToMode,
+          replyToChannel,
+          currentMessageId,
+        });
+      const sendCompactionNotice = async (text: string) => {
+        const noticePayloads = applyFollowupReplyThreading([
+          {
+            text,
+            replyToCurrent: true,
+            isCompactionNotice: true,
+          },
+        ]);
+        if (noticePayloads.length === 0) {
+          return;
+        }
+        try {
+          await sendFollowupPayloads(noticePayloads, queued);
+        } catch (err) {
+          logVerbose(
+            `followup queue: compaction notice delivery failed (non-fatal): ${String(err)}`,
+          );
+        }
+      };
       let autoCompactionCount = 0;
       let runResult: Awaited<ReturnType<typeof runEmbeddedPiAgent>>;
       let fallbackProvider = queued.run.provider;
@@ -229,6 +266,9 @@ export function createFollowupRunner(params: {
                     return;
                   }
                   const phase = typeof evt.data.phase === "string" ? evt.data.phase : "";
+                  if (phase === "start") {
+                    void sendCompactionNotice("🧹 Compacting context...");
+                  }
                   const completed = evt.data?.completed === true;
                   if (phase === "end" && completed) {
                     attemptCompactionCount += 1;
@@ -284,9 +324,6 @@ export function createFollowupRunner(params: {
       }
 
       const payloadArray = runResult.payloads ?? [];
-      if (payloadArray.length === 0) {
-        return;
-      }
       const sanitizedPayloads = payloadArray.flatMap((payload) => {
         const text = payload.text;
         if (!text || !text.includes("HEARTBEAT_OK")) {
@@ -299,22 +336,7 @@ export function createFollowupRunner(params: {
         }
         return [{ ...payload, text: stripped.text }];
       });
-      const replyToChannel = resolveOriginMessageProvider({
-        originatingChannel: queued.originatingChannel,
-        provider: queued.run.messageProvider,
-      }) as OriginatingChannelType | undefined;
-      const replyToMode = resolveReplyToMode(
-        queued.run.config,
-        replyToChannel,
-        queued.originatingAccountId,
-        queued.originatingChatType,
-      );
-
-      const replyTaggedPayloads: ReplyPayload[] = applyReplyThreading({
-        payloads: sanitizedPayloads,
-        replyToMode,
-        replyToChannel,
-      });
+      const replyTaggedPayloads = applyFollowupReplyThreading(sanitizedPayloads);
 
       const dedupedPayloads = filterMessagingToolDuplicates({
         payloads: replyTaggedPayloads,
@@ -338,11 +360,7 @@ export function createFollowupRunner(params: {
           accountId: queued.run.agentAccountId,
         }),
       });
-      const finalPayloads = suppressMessagingToolReplies ? [] : mediaFilteredPayloads;
-
-      if (finalPayloads.length === 0) {
-        return;
-      }
+      let finalPayloads = suppressMessagingToolReplies ? [] : mediaFilteredPayloads;
 
       if (autoCompactionCount > 0) {
         const count = await incrementRunCompactionCount({
@@ -354,12 +372,25 @@ export function createFollowupRunner(params: {
           lastCallUsage: runResult.meta?.agentMeta?.lastCallUsage,
           contextTokensUsed,
         });
-        if (queued.run.verboseLevel && queued.run.verboseLevel !== "off") {
-          const suffix = typeof count === "number" ? ` (count ${count})` : "";
-          finalPayloads.unshift({
-            text: `🧹 Auto-compaction complete${suffix}.`,
-          });
-        }
+        const suffix = typeof count === "number" ? ` (count ${count})` : "";
+        const completionText =
+          queued.run.verboseLevel && queued.run.verboseLevel !== "off"
+            ? `🧹 Auto-compaction complete${suffix}.`
+            : `✅ Context compacted${suffix}.`;
+        finalPayloads = [
+          ...applyFollowupReplyThreading([
+            {
+              text: completionText,
+              replyToCurrent: true,
+              isCompactionNotice: true,
+            },
+          ]),
+          ...finalPayloads,
+        ];
+      }
+
+      if (finalPayloads.length === 0) {
+        return;
       }
 
       await sendFollowupPayloads(finalPayloads, queued);
diff --git a/src/auto-reply/reply/reply-threading.ts b/src/auto-reply/reply/reply-threading.ts
index 66871f226b7..5c0e1e423bc 100644
--- a/src/auto-reply/reply/reply-threading.ts
+++ b/src/auto-reply/reply/reply-threading.ts
@@ -33,7 +33,12 @@ export function createReplyToModeFilter(
     }
     if (mode === "off") {
       const isExplicit = Boolean(payload.replyToTag) || Boolean(payload.replyToCurrent);
-      if (opts.allowExplicitReplyTagsWhenOff && isExplicit) {
+      // Compaction notices must never be threaded when replyToMode=off — even
+      // if they carry explicit reply tags (replyToCurrent).  Honouring the
+      // explicit tag here would make status notices appear in-thread while
+      // normal assistant replies stay off-thread, contradicting the off-mode
+      // expectation.  Strip replyToId unconditionally for compaction payloads.
+      if (opts.allowExplicitReplyTagsWhenOff && isExplicit && !payload.isCompactionNotice) {
         return payload;
       }
       return { ...payload, replyToId: undefined };
@@ -42,9 +47,21 @@ export function createReplyToModeFilter(
       return payload;
     }
     if (hasThreaded) {
+      // Compaction notices are transient status messages that should always
+      // appear in-thread, even after the first assistant block has already
+      // consumed the "first" slot.  Let them keep their replyToId.
+      if (payload.isCompactionNotice) {
+        return payload;
+      }
       return { ...payload, replyToId: undefined };
     }
-    hasThreaded = true;
+    // Compaction notices are transient status messages — they should be
+    // threaded (so they appear in-context), but they must not consume the
+    // "first" slot of the replyToMode=first filter.  Skip advancing
+    // hasThreaded so the real assistant reply still gets replyToId.
+    if (!payload.isCompactionNotice) {
+      hasThreaded = true;
+    }
     return payload;
   };
 }
diff --git a/src/auto-reply/types.ts b/src/auto-reply/types.ts
index c424f43ab92..638dda42d8f 100644
--- a/src/auto-reply/types.ts
+++ b/src/auto-reply/types.ts
@@ -91,6 +91,10 @@ export type ReplyPayload = {
   /** Marks this payload as a reasoning/thinking block. Channels that do not
    *  have a dedicated reasoning lane (e.g. WhatsApp, web) should suppress it. */
   isReasoning?: boolean;
+  /** Marks this payload as a compaction status notice (start/end).
+   *  Should be excluded from TTS transcript accumulation so compaction
+   *  status lines are not synthesised into the spoken assistant reply. */
+  isCompactionNotice?: boolean;
   /** Channel-specific payload data (per-channel envelope). */
   channelData?: Record<string, unknown>;
 };
diff --git a/src/tts/tts.ts b/src/tts/tts.ts
index 17a7c2fc981..348ff94be91 100644
--- a/src/tts/tts.ts
+++ b/src/tts/tts.ts
@@ -825,6 +825,10 @@ export async function maybeApplyTtsToPayload(params: {
   inboundAudio?: boolean;
   ttsAuto?: string;
 }): Promise<ReplyPayload> {
+  // Compaction notices are informational UI signals — never synthesise them as speech.
+  if (params.payload.isCompactionNotice) {
+    return params.payload;
+  }
   const config = resolveTtsConfig(params.cfg);
   const prefsPath = resolveTtsPrefsPath(config);
   const autoMode = resolveTtsAutoMode({