diff --git a/docs/channels/whatsapp.md b/docs/channels/whatsapp.md
index b6ae260ce..5d9653c16 100644
--- a/docs/channels/whatsapp.md
+++ b/docs/channels/whatsapp.md
@@ -239,6 +239,18 @@ WhatsApp can automatically send emoji reactions to incoming messages immediately
   - `"mentions"`: React only when bot is @mentioned
   - `"never"`: Never react in groups
 
+**Per-session override:**
+The global and per-account configurations can be overridden for specific sessions (DMs or Groups) using session configuration (in `sessions.json`).
+- `ackReaction`: `"always" | "mentions" | "never"`
+  - `"always"`: Enables reactions (overrides global off/never).
+  - `"never"`: Disables reactions (overrides global on/always/mentions).
+  - `"mentions"`: Enforces **strict** mention-only reactions (requires actual @mention, ignores group activation state).
+  - Useful for disabling reactions in specific DMs (`"never"`) or forcing them in specific groups.
+
+> **Note:** Setting `"mentions"` on a DM session effectively disables reactions for that DM, since direct messages don't have @mentions. Use `"always"` or `"never"` for DMs.
+>
+> **Note:** Unlike the global `group: "mentions"` setting which respects group activation state, the session-level `"mentions"` override is strict and always requires an actual @mention.
+
 **Per-account override:**
 ```json
 {
diff --git a/src/channels/ack-reactions.test.ts b/src/channels/ack-reactions.test.ts
index ed018ba5a..b0cb70acb 100644
--- a/src/channels/ack-reactions.test.ts
+++ b/src/channels/ack-reactions.test.ts
@@ -225,6 +225,77 @@ describe("shouldAckReactionForWhatsApp", () => {
       }),
     ).toBe(false);
   });
+  it("honors session overrides", () => {
+    // Session: NEVER overrides Global: ALWAYS
+    expect(
+      shouldAckReactionForWhatsApp({
+        emoji: "👀",
+        isDirect: false,
+        isGroup: true,
+        directEnabled: true,
+        groupMode: "always",
+        wasMentioned: false,
+        groupActivated: false,
+        sessionMode: "never",
+      }),
+    ).toBe(false);
+
+    // Session: ALWAYS overrides Global: NEVER
+    expect(
+      shouldAckReactionForWhatsApp({
+        emoji: "👀",
+        isDirect: false,
+        isGroup: true,
+        directEnabled: true,
+        groupMode: "never",
+        wasMentioned: false,
+        groupActivated: false,
+        sessionMode: "always",
+      }),
+    ).toBe(true);
+
+    // Session: MENTIONS in DM (effectively OFF unless mentioned, which is false)
+    expect(
+      shouldAckReactionForWhatsApp({
+        emoji: "👀",
+        isDirect: true,
+        isGroup: false,
+        directEnabled: true, // Globally enabled
+        groupMode: "mentions",
+        wasMentioned: false,
+        groupActivated: false,
+        sessionMode: "mentions", // Override to strict mentions
+      }),
+    ).toBe(false);
+
+    // Session: MENTIONS in Group (works if mentioned)
+    expect(
+      shouldAckReactionForWhatsApp({
+        emoji: "👀",
+        isDirect: false,
+        isGroup: true,
+        directEnabled: true,
+        groupMode: "never", // Global OFF
+        wasMentioned: true, // But mentioned
+        groupActivated: false,
+        sessionMode: "mentions", // Session override ON (if mentioned)
+      }),
+    ).toBe(true);
+
+    // Session: MENTIONS is strict - does NOT bypass via groupActivated
+    expect(
+      shouldAckReactionForWhatsApp({
+        emoji: "👀",
+        isDirect: false,
+        isGroup: true,
+        directEnabled: true,
+        groupMode: "always",
+        wasMentioned: false, // Not mentioned
+        groupActivated: true, // But group is activated
+        sessionMode: "mentions", // Explicit mentions = strict, no bypass
+      }),
+    ).toBe(false);
+  });
 });
 
 describe("removeAckReactionAfterReply", () => {
diff --git a/src/channels/ack-reactions.ts b/src/channels/ack-reactions.ts
index f35ae76d8..00734c5e4 100644
--- a/src/channels/ack-reactions.ts
+++ b/src/channels/ack-reactions.ts
@@ -36,8 +36,28 @@ export function shouldAckReactionForWhatsApp(params: {
   groupMode: WhatsAppAckReactionMode;
   wasMentioned: boolean;
   groupActivated: boolean;
+  sessionMode?: "always" | "mentions" | "never";
 }): boolean {
   if (!params.emoji) return false;
+
+  // Session override
+  if (params.sessionMode === "never") return false;
+  if (params.sessionMode === "always") return true;
+  if (params.sessionMode === "mentions") {
+    // Strict mention-only: explicit session override should not bypass via activation
+    return shouldAckReaction({
+      scope: "group-mentions",
+      isDirect: params.isDirect,
+      isGroup: params.isGroup,
+      isMentionableGroup: true,
+      requireMention: true,
+      canDetectMention: true,
+      effectiveWasMentioned: params.wasMentioned,
+      // Note: intentionally not passing shouldBypassMention here
+    });
+  }
+
+  // Config fallback
   if (params.isDirect) return params.directEnabled;
   if (!params.isGroup) return false;
   if (params.groupMode === "never") return false;
diff --git a/src/config/sessions/types.ts b/src/config/sessions/types.ts
index 48ce428c1..9efbfd00f 100644
--- a/src/config/sessions/types.ts
+++ b/src/config/sessions/types.ts
@@ -54,6 +54,7 @@ export type SessionEntry = {
   authProfileOverride?: string;
   authProfileOverrideSource?: "auto" | "user";
   authProfileOverrideCompactionCount?: number;
+  ackReaction?: "always" | "mentions" | "never";
   groupActivation?: "mention" | "always";
   groupActivationNeedsSystemIntro?: boolean;
   sendPolicy?: "allow" | "deny";
diff --git a/src/web/auto-reply/monitor/ack-reaction.ts b/src/web/auto-reply/monitor/ack-reaction.ts
index 6a99da312..6a589bc88 100644
--- a/src/web/auto-reply/monitor/ack-reaction.ts
+++ b/src/web/auto-reply/monitor/ack-reaction.ts
@@ -1,4 +1,5 @@
 import type { loadConfig } from "../../../config/config.js";
+import { loadSessionStore, resolveStorePath } from "../../../config/sessions.js";
 import { logVerbose } from "../../../globals.js";
 import { shouldAckReactionForWhatsApp } from "../../../channels/ack-reactions.js";
 import { sendReactionWhatsApp } from "../../outbound.js";
@@ -25,6 +26,16 @@ export function maybeSendAckReaction(params: {
   const groupMode = ackConfig?.group ?? "mentions";
   const conversationIdForCheck = params.msg.conversationId ?? params.msg.from;
 
+  // Load session to check for per-session ackReaction override.
+  // Note: loadSessionStore uses an in-memory cache (45s TTL) so this is not
+  // doing disk I/O on every message in typical usage patterns.
+  const storePath = resolveStorePath(params.cfg.session?.store, {
+    agentId: params.agentId,
+  });
+  const store = loadSessionStore(storePath);
+  const sessionEntry = store[params.sessionKey];
+  const sessionMode = sessionEntry?.ackReaction;
+
   const activation =
     params.msg.chatType === "group"
       ? resolveGroupActivationFor({
@@ -41,6 +52,7 @@ export function maybeSendAckReaction(params: {
       isGroup: params.msg.chatType === "group",
       directEnabled,
       groupMode,
+      sessionMode,
       wasMentioned: params.msg.wasMentioned === true,
       groupActivated: activation === "always",
     });