diff --git a/CHANGELOG.md b/CHANGELOG.md
index d8f15ff26a7..15aa0bb6590 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,7 @@ Docs: https://docs.openclaw.ai
 ### Fixes
 
 - Models/UI: hide unauthenticated providers from the default Web chat, `/models`, and model setup pickers while keeping explicit full-catalog browse paths through `view: "all"`, `/models <provider> all`, and `models list --all`. Fixes #74423. Thanks @guarismo and @SymbolStar.
+- Slack/reactions: treat duplicate `already_reacted` responses as idempotent success so repeated agent reaction adds no longer surface as tool failures. Fixes #69005. Thanks @shipitsteven and @martingarramon.
 - Slack/tools: expose `fileId` in the shared message tool schema so `download-file` can receive Slack attachment IDs from inbound placeholders. Fixes #45574. Thanks @chadvegas.
 - Exec: reject invalid per-call `host` values instead of silently falling back to the default target, so hostname-like values fail before commands run. Fixes #74426. Thanks @scr00ge-00 and @vyctorbrzezowski.
 - Google/Gemini: send non-empty placeholder content when a Gemini run is triggered with empty or filtered user content, avoiding `contents is not specified` API errors. Thanks @CaoYuhaoCarl.
diff --git a/extensions/slack/src/action-runtime.test.ts b/extensions/slack/src/action-runtime.test.ts
index 0f4ae86f3f0..29ad2a610e5 100644
--- a/extensions/slack/src/action-runtime.test.ts
+++ b/extensions/slack/src/action-runtime.test.ts
@@ -115,7 +115,7 @@ describe("handleSlackAction", () => {
     { name: "raw channel id", channelId: "C1" },
     { name: "channel: prefixed id", channelId: "channel:C1" },
   ])("adds reactions for $name", async ({ channelId }) => {
-    await handleSlackAction(
+    const result = await handleSlackAction(
       {
         action: "react",
         channelId,
@@ -130,6 +130,10 @@ describe("handleSlackAction", () => {
       "✅",
       expect.objectContaining({ cfg: expect.any(Object) }),
     );
+    expect(JSON.parse((result.content?.[0] as { type: "text"; text: string }).text)).toEqual({
+      ok: true,
+      added: "✅",
+    });
   });
 
   it("removes reactions on empty emoji", async () => {
diff --git a/extensions/slack/src/actions.reactions.test.ts b/extensions/slack/src/actions.reactions.test.ts
new file mode 100644
index 00000000000..4d885cc675b
--- /dev/null
+++ b/extensions/slack/src/actions.reactions.test.ts
@@ -0,0 +1,60 @@
+import type { WebClient } from "@slack/web-api";
+import { describe, expect, it, vi } from "vitest";
+import { reactSlackMessage } from "./actions.js";
+
+function createClient() {
+  return {
+    reactions: {
+      add: vi.fn(async () => ({})),
+    },
+  } as unknown as WebClient & {
+    reactions: {
+      add: ReturnType<typeof vi.fn>;
+    };
+  };
+}
+
+function slackPlatformError(error: string) {
+  return Object.assign(new Error(`An API error occurred: ${error}`), {
+    data: {
+      ok: false,
+      error,
+    },
+  });
+}
+
+describe("reactSlackMessage", () => {
+  it("treats already_reacted as idempotent success", async () => {
+    const client = createClient();
+    client.reactions.add.mockRejectedValueOnce(slackPlatformError("already_reacted"));
+
+    await expect(
+      reactSlackMessage("C1", "123.456", ":white_check_mark:", {
+        client,
+        token: "xoxb-test",
+      }),
+    ).resolves.toBeUndefined();
+
+    expect(client.reactions.add).toHaveBeenCalledWith({
+      channel: "C1",
+      timestamp: "123.456",
+      name: "white_check_mark",
+    });
+  });
+
+  it("propagates unrelated reaction add errors", async () => {
+    const client = createClient();
+    client.reactions.add.mockRejectedValueOnce(slackPlatformError("invalid_name"));
+
+    await expect(
+      reactSlackMessage("C1", "123.456", "not-an-emoji", {
+        client,
+        token: "xoxb-test",
+      }),
+    ).rejects.toMatchObject({
+      data: {
+        error: "invalid_name",
+      },
+    });
+  });
+});
diff --git a/extensions/slack/src/actions.ts b/extensions/slack/src/actions.ts
index ca11ea3c4eb..2bfc4247ec2 100644
--- a/extensions/slack/src/actions.ts
+++ b/extensions/slack/src/actions.ts
@@ -77,6 +77,17 @@ function normalizeEmoji(raw: string) {
   return trimmed.replace(/^:+|:+$/g, "");
 }
 
+function hasSlackPlatformError(err: unknown, code: string): boolean {
+  if (!err || typeof err !== "object") {
+    return false;
+  }
+  const data = (err as { data?: unknown }).data;
+  if (!data || typeof data !== "object") {
+    return false;
+  }
+  return (data as { error?: unknown }).error === code;
+}
+
 async function getClient(opts: SlackActionClientOpts = {}, mode: "read" | "write" = "read") {
   if (opts.client) {
     return opts.client;
@@ -100,11 +111,18 @@ export async function reactSlackMessage(
   opts: SlackActionClientOpts = {},
 ) {
   const client = await getClient(opts, "write");
-  await client.reactions.add({
-    channel: channelId,
-    timestamp: messageId,
-    name: normalizeEmoji(emoji),
-  });
+  try {
+    await client.reactions.add({
+      channel: channelId,
+      timestamp: messageId,
+      name: normalizeEmoji(emoji),
+    });
+  } catch (err) {
+    if (hasSlackPlatformError(err, "already_reacted")) {
+      return;
+    }
+    throw err;
+  }
 }
 
 export async function removeSlackReaction(