diff --git a/src/web/auto-reply.ack-reaction.test.ts b/src/web/auto-reply.ack-reaction.test.ts
new file mode 100644
index 000000000..922c0b353
--- /dev/null
+++ b/src/web/auto-reply.ack-reaction.test.ts
@@ -0,0 +1,266 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import type { ClawdbotConfig } from "../config/types.js";
+
+describe("WhatsApp ack reaction", () => {
+  const mockSendReaction = vi.fn(async () => {});
+  const mockGetReply = vi.fn(async () => ({
+    payloads: [{ text: "test reply" }],
+    meta: {},
+  }));
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("should send ack reaction in direct chat when scope is 'all'", async () => {
+    const cfg: ClawdbotConfig = {
+      messages: {
+        ackReaction: "👀",
+        ackReactionScope: "all",
+      },
+    };
+
+    // Simulate the logic from auto-reply.ts
+    const msg = {
+      id: "msg123",
+      chatId: "123456789@s.whatsapp.net",
+      chatType: "direct" as const,
+      from: "+1234567890",
+      to: "+9876543210",
+      body: "hello",
+    };
+
+    const ackReaction = (cfg.messages?.ackReaction ?? "").trim();
+    const ackReactionScope = cfg.messages?.ackReactionScope ?? "group-mentions";
+    const didSendReply = true;
+
+    const shouldAckReaction = () => {
+      if (!ackReaction) return false;
+      if (!msg.id) return false;
+      if (!didSendReply) return false;
+      if (ackReactionScope === "all") return true;
+      if (ackReactionScope === "direct") return msg.chatType === "direct";
+      if (ackReactionScope === "group-all") return msg.chatType === "group";
+      if (ackReactionScope === "group-mentions") {
+        if (msg.chatType !== "group") return false;
+        return false; // Would check wasMentioned
+      }
+      return false;
+    };
+
+    expect(shouldAckReaction()).toBe(true);
+  });
+
+  it("should send ack reaction in direct chat when scope is 'direct'", async () => {
+    const cfg: ClawdbotConfig = {
+      messages: {
+        ackReaction: "👀",
+        ackReactionScope: "direct",
+      },
+    };
+
+    const msg = {
+      id: "msg123",
+      chatId: "123456789@s.whatsapp.net",
+      chatType: "direct" as const,
+      from: "+1234567890",
+      to: "+9876543210",
+      body: "hello",
+    };
+
+    const ackReaction = (cfg.messages?.ackReaction ?? "").trim();
+    const ackReactionScope = cfg.messages?.ackReactionScope ?? "group-mentions";
+    const didSendReply = true;
+
+    const shouldAckReaction = () => {
+      if (!ackReaction) return false;
+      if (!msg.id) return false;
+      if (!didSendReply) return false;
+      if (ackReactionScope === "all") return true;
+      if (ackReactionScope === "direct") return msg.chatType === "direct";
+      if (ackReactionScope === "group-all") return msg.chatType === "group";
+      return false;
+    };
+
+    expect(shouldAckReaction()).toBe(true);
+  });
+
+  it("should NOT send ack reaction in group when scope is 'direct'", async () => {
+    const cfg: ClawdbotConfig = {
+      messages: {
+        ackReaction: "👀",
+        ackReactionScope: "direct",
+      },
+    };
+
+    const msg = {
+      id: "msg123",
+      chatId: "123456789-group@g.us",
+      chatType: "group" as const,
+      from: "123456789-group@g.us",
+      to: "+9876543210",
+      body: "hello",
+      wasMentioned: true,
+    };
+
+    const ackReaction = (cfg.messages?.ackReaction ?? "").trim();
+    const ackReactionScope = cfg.messages?.ackReactionScope ?? "group-mentions";
+    const didSendReply = true;
+
+    const shouldAckReaction = () => {
+      if (!ackReaction) return false;
+      if (!msg.id) return false;
+      if (!didSendReply) return false;
+      if (ackReactionScope === "all") return true;
+      if (ackReactionScope === "direct") return msg.chatType === "direct";
+      if (ackReactionScope === "group-all") return msg.chatType === "group";
+      return false;
+    };
+
+    expect(shouldAckReaction()).toBe(false);
+  });
+
+  it("should send ack reaction in group when mentioned and scope is 'group-mentions'", async () => {
+    const cfg: ClawdbotConfig = {
+      messages: {
+        ackReaction: "👀",
+        ackReactionScope: "group-mentions",
+      },
+    };
+
+    const msg = {
+      id: "msg123",
+      chatId: "123456789-group@g.us",
+      chatType: "group" as const,
+      from: "123456789-group@g.us",
+      to: "+9876543210",
+      body: "hello @bot",
+      wasMentioned: true,
+    };
+
+    const ackReaction = (cfg.messages?.ackReaction ?? "").trim();
+    const ackReactionScope = cfg.messages?.ackReactionScope ?? "group-mentions";
+    const didSendReply = true;
+    const requireMention = true; // Simulated from activation check
+
+    const shouldAckReaction = () => {
+      if (!ackReaction) return false;
+      if (!msg.id) return false;
+      if (!didSendReply) return false;
+      if (ackReactionScope === "all") return true;
+      if (ackReactionScope === "direct") return msg.chatType === "direct";
+      if (ackReactionScope === "group-all") return msg.chatType === "group";
+      if (ackReactionScope === "group-mentions") {
+        if (msg.chatType !== "group") return false;
+        if (!requireMention) return false;
+        return msg.wasMentioned === true;
+      }
+      return false;
+    };
+
+    expect(shouldAckReaction()).toBe(true);
+  });
+
+  it("should NOT send ack reaction in group when NOT mentioned and scope is 'group-mentions'", async () => {
+    const cfg: ClawdbotConfig = {
+      messages: {
+        ackReaction: "👀",
+        ackReactionScope: "group-mentions",
+      },
+    };
+
+    const msg = {
+      id: "msg123",
+      chatId: "123456789-group@g.us",
+      chatType: "group" as const,
+      from: "123456789-group@g.us",
+      to: "+9876543210",
+      body: "hello",
+      wasMentioned: false,
+    };
+
+    const ackReaction = (cfg.messages?.ackReaction ?? "").trim();
+    const ackReactionScope = cfg.messages?.ackReactionScope ?? "group-mentions";
+    const didSendReply = true;
+    const requireMention = true;
+
+    const shouldAckReaction = () => {
+      if (!ackReaction) return false;
+      if (!msg.id) return false;
+      if (!didSendReply) return false;
+      if (ackReactionScope === "all") return true;
+      if (ackReactionScope === "direct") return msg.chatType === "direct";
+      if (ackReactionScope === "group-all") return msg.chatType === "group";
+      if (ackReactionScope === "group-mentions") {
+        if (msg.chatType !== "group") return false;
+        if (!requireMention) return false;
+        return msg.wasMentioned === true;
+      }
+      return false;
+    };
+
+    expect(shouldAckReaction()).toBe(false);
+  });
+
+  it("should NOT send ack reaction when no reply was sent", async () => {
+    const cfg: ClawdbotConfig = {
+      messages: {
+        ackReaction: "👀",
+        ackReactionScope: "all",
+      },
+    };
+
+    const msg = {
+      id: "msg123",
+      chatId: "123456789@s.whatsapp.net",
+      chatType: "direct" as const,
+      from: "+1234567890",
+      to: "+9876543210",
+      body: "hello",
+    };
+
+    const ackReaction = (cfg.messages?.ackReaction ?? "").trim();
+    const ackReactionScope = cfg.messages?.ackReactionScope ?? "group-mentions";
+    const didSendReply = false; // No reply sent
+
+    const shouldAckReaction = () => {
+      if (!ackReaction) return false;
+      if (!msg.id) return false;
+      if (!didSendReply) return false;
+      return true;
+    };
+
+    expect(shouldAckReaction()).toBe(false);
+  });
+
+  it("should NOT send ack reaction when ackReaction is empty", async () => {
+    const cfg: ClawdbotConfig = {
+      messages: {
+        ackReaction: "",
+        ackReactionScope: "all",
+      },
+    };
+
+    const msg = {
+      id: "msg123",
+      chatId: "123456789@s.whatsapp.net",
+      chatType: "direct" as const,
+      from: "+1234567890",
+      to: "+9876543210",
+      body: "hello",
+    };
+
+    const ackReaction = (cfg.messages?.ackReaction ?? "").trim();
+    const ackReactionScope = cfg.messages?.ackReactionScope ?? "group-mentions";
+    const didSendReply = true;
+
+    const shouldAckReaction = () => {
+      if (!ackReaction) return false;
+      if (!msg.id) return false;
+      if (!didSendReply) return false;
+      return true;
+    };
+
+    expect(shouldAckReaction()).toBe(false);
+  });
+});
diff --git a/src/web/auto-reply.ts b/src/web/auto-reply.ts
index c41f6de11..f3a77eed9 100644
--- a/src/web/auto-reply.ts
+++ b/src/web/auto-reply.ts
@@ -68,7 +68,7 @@ import { resolveWhatsAppAccount } from "./accounts.js";
 import { setActiveWebListener } from "./active-listener.js";
 import { monitorWebInbox } from "./inbound.js";
 import { loadWebMedia } from "./media.js";
-import { sendMessageWhatsApp } from "./outbound.js";
+import { sendMessageWhatsApp, sendReactionWhatsApp } from "./outbound.js";
 import {
   computeBackoff,
   newConnectionId,
@@ -1387,6 +1387,45 @@ export async function monitorWebProvider(
         groupHistories.set(groupHistoryKey, []);
       }
 
+      // Send ack reaction after successful reply
+      const ackReaction = (cfg.messages?.ackReaction ?? "").trim();
+      const ackReactionScope = cfg.messages?.ackReactionScope ?? "group-mentions";
+      const shouldAckReaction = () => {
+        if (!ackReaction) return false;
+        if (!msg.id) return false;
+        if (!didSendReply) return false;
+        if (ackReactionScope === "all") return true;
+        if (ackReactionScope === "direct") return msg.chatType === "direct";
+        if (ackReactionScope === "group-all") return msg.chatType === "group";
+        if (ackReactionScope === "group-mentions") {
+          if (msg.chatType !== "group") return false;
+          const activation = resolveGroupActivationFor({
+            agentId: route.agentId,
+            sessionKey: route.sessionKey,
+            conversationId,
+          });
+          const requireMention = activation !== "always";
+          if (!requireMention) return false;
+          return msg.wasMentioned === true;
+        }
+        return false;
+      };
+
+      if (shouldAckReaction() && msg.id) {
+        sendReactionWhatsApp(msg.chatId, msg.id, ackReaction, {
+          verbose,
+          fromMe: false,
+        }).catch((err) => {
+          replyLogger.warn(
+            { error: formatError(err), chatId: msg.chatId, messageId: msg.id },
+            "failed to send ack reaction",
+          );
+          logVerbose(
+            `WhatsApp ack reaction failed for chat ${msg.chatId}: ${formatError(err)}`,
+          );
+        });
+      }
+
       return didSendReply;
     };