diff --git a/extensions/discord/src/outbound-adapter.sendpayload.test.ts b/extensions/discord/src/outbound-adapter.sendpayload.test.ts
deleted file mode 100644
index ae5d86f8700..00000000000
--- a/extensions/discord/src/outbound-adapter.sendpayload.test.ts
+++ /dev/null
@@ -1,37 +0,0 @@
-import { describe, vi } from "vitest";
-import type { ReplyPayload } from "../../../src/auto-reply/types.js";
-import {
-  installSendPayloadContractSuite,
-  primeSendMock,
-} from "../../../src/test-utils/send-payload-contract.js";
-import { discordOutbound } from "./outbound-adapter.js";
-
-function createHarness(params: {
-  payload: ReplyPayload;
-  sendResults?: Array<{ messageId: string }>;
-}) {
-  const sendDiscord = vi.fn();
-  primeSendMock(sendDiscord, { messageId: "dc-1", channelId: "123456" }, params.sendResults);
-  const ctx = {
-    cfg: {},
-    to: "channel:123456",
-    text: "",
-    payload: params.payload,
-    deps: {
-      sendDiscord,
-    },
-  };
-  return {
-    run: async () => await discordOutbound.sendPayload!(ctx),
-    sendMock: sendDiscord,
-    to: ctx.to,
-  };
-}
-
-describe("discordOutbound sendPayload", () => {
-  installSendPayloadContractSuite({
-    channel: "discord",
-    chunking: { mode: "passthrough", longTextLength: 3000 },
-    createHarness,
-  });
-});
diff --git a/extensions/whatsapp/src/outbound-adapter.sendpayload.test.ts b/extensions/whatsapp/src/outbound-adapter.sendpayload.test.ts
index 81f30ea1c71..52b44de49e7 100644
--- a/extensions/whatsapp/src/outbound-adapter.sendpayload.test.ts
+++ b/extensions/whatsapp/src/outbound-adapter.sendpayload.test.ts
@@ -1,40 +1,7 @@
 import { describe, expect, it, vi } from "vitest";
-import type { ReplyPayload } from "../../../src/auto-reply/types.js";
-import {
-  installSendPayloadContractSuite,
-  primeSendMock,
-} from "../../../src/test-utils/send-payload-contract.js";
 import { whatsappOutbound } from "./outbound-adapter.js";
 
-function createHarness(params: {
-  payload: ReplyPayload;
-  sendResults?: Array<{ messageId: string }>;
-}) {
-  const sendWhatsApp = vi.fn();
-  primeSendMock(sendWhatsApp, { messageId: "wa-1" }, params.sendResults);
-  const ctx = {
-    cfg: {},
-    to: "5511999999999@c.us",
-    text: "",
-    payload: params.payload,
-    deps: {
-      sendWhatsApp,
-    },
-  };
-  return {
-    run: async () => await whatsappOutbound.sendPayload!(ctx),
-    sendMock: sendWhatsApp,
-    to: ctx.to,
-  };
-}
-
 describe("whatsappOutbound sendPayload", () => {
-  installSendPayloadContractSuite({
-    channel: "whatsapp",
-    chunking: { mode: "split", longTextLength: 5000, maxChunkLength: 4000 },
-    createHarness,
-  });
-
   it("trims leading whitespace for direct text sends", async () => {
     const sendWhatsApp = vi.fn(async () => ({ messageId: "wa-1", toJid: "jid" }));
 
diff --git a/extensions/zalo/src/channel.sendpayload.test.ts b/extensions/zalo/src/channel.sendpayload.test.ts
deleted file mode 100644
index 27acb737f9f..00000000000
--- a/extensions/zalo/src/channel.sendpayload.test.ts
+++ /dev/null
@@ -1,44 +0,0 @@
-import type { ReplyPayload } from "openclaw/plugin-sdk/zalo";
-import { beforeEach, describe, expect, it, vi } from "vitest";
-import {
-  installSendPayloadContractSuite,
-  primeSendMock,
-} from "../../../src/test-utils/send-payload-contract.js";
-import { zaloPlugin } from "./channel.js";
-
-vi.mock("./send.js", () => ({
-  sendMessageZalo: vi.fn().mockResolvedValue({ ok: true, messageId: "zl-1" }),
-}));
-
-function baseCtx(payload: ReplyPayload) {
-  return {
-    cfg: {},
-    to: "123456789",
-    text: "",
-    payload,
-  };
-}
-
-describe("zaloPlugin outbound sendPayload", () => {
-  let mockedSend: ReturnType<typeof vi.mocked<(typeof import("./send.js"))["sendMessageZalo"]>>;
-
-  beforeEach(async () => {
-    const mod = await import("./send.js");
-    mockedSend = vi.mocked(mod.sendMessageZalo);
-    mockedSend.mockClear();
-    mockedSend.mockResolvedValue({ ok: true, messageId: "zl-1" });
-  });
-
-  installSendPayloadContractSuite({
-    channel: "zalo",
-    chunking: { mode: "split", longTextLength: 3000, maxChunkLength: 2000 },
-    createHarness: ({ payload, sendResults }) => {
-      primeSendMock(mockedSend, { ok: true, messageId: "zl-1" }, sendResults);
-      return {
-        run: async () => await zaloPlugin.outbound!.sendPayload!(baseCtx(payload)),
-        sendMock: mockedSend,
-        to: "123456789",
-      };
-    },
-  });
-});
diff --git a/extensions/zalouser/src/channel.sendpayload.test.ts b/extensions/zalouser/src/channel.sendpayload.test.ts
index 27a8adf2c0d..2c9d5240ba9 100644
--- a/extensions/zalouser/src/channel.sendpayload.test.ts
+++ b/extensions/zalouser/src/channel.sendpayload.test.ts
@@ -1,10 +1,7 @@
 import type { ReplyPayload } from "openclaw/plugin-sdk/zalouser";
 import { beforeEach, describe, expect, it, vi } from "vitest";
 import "./accounts.test-mocks.js";
-import {
-  installSendPayloadContractSuite,
-  primeSendMock,
-} from "../../../src/test-utils/send-payload-contract.js";
+import { primeChannelOutboundSendMock } from "../../../src/channels/plugins/contracts/suites.js";
 import { zalouserPlugin } from "./channel.js";
 import { setZalouserRuntime } from "./runtime.js";
 
@@ -36,8 +33,7 @@ describe("zalouserPlugin outbound sendPayload", () => {
     } as never);
     const mod = await import("./send.js");
     mockedSend = vi.mocked(mod.sendMessageZalouser);
-    mockedSend.mockClear();
-    mockedSend.mockResolvedValue({ ok: true, messageId: "zlu-1" });
+    primeChannelOutboundSendMock(mockedSend, { ok: true, messageId: "zlu-1" });
   });
 
   it("group target delegates with isGroup=true and stripped threadId", async () => {
@@ -110,19 +106,6 @@ describe("zalouserPlugin outbound sendPayload", () => {
     );
     expect(result).toMatchObject({ channel: "zalouser", messageId: "zlu-code" });
   });
-
-  installSendPayloadContractSuite({
-    channel: "zalouser",
-    chunking: { mode: "passthrough", longTextLength: 3000 },
-    createHarness: ({ payload, sendResults }) => {
-      primeSendMock(mockedSend, { ok: true, messageId: "zlu-1" }, sendResults);
-      return {
-        run: async () => await zalouserPlugin.outbound!.sendPayload!(baseCtx(payload)),
-        sendMock: mockedSend,
-        to: "987654321",
-      };
-    },
-  });
 });
 
 describe("zalouserPlugin messaging target normalization", () => {
diff --git a/src/channels/plugins/contracts/outbound-payload.contract.test.ts b/src/channels/plugins/contracts/outbound-payload.contract.test.ts
new file mode 100644
index 00000000000..5faa47893cb
--- /dev/null
+++ b/src/channels/plugins/contracts/outbound-payload.contract.test.ts
@@ -0,0 +1,209 @@
+import { describe, vi } from "vitest";
+import { discordOutbound } from "../../../../extensions/discord/src/outbound-adapter.js";
+import { whatsappOutbound } from "../../../../extensions/whatsapp/src/outbound-adapter.js";
+import { zaloPlugin } from "../../../../extensions/zalo/src/channel.js";
+import { sendMessageZalo } from "../../../../extensions/zalo/src/send.js";
+import "./../../../../extensions/zalouser/src/accounts.test-mocks.js";
+import { zalouserPlugin } from "../../../../extensions/zalouser/src/channel.js";
+import { setZalouserRuntime } from "../../../../extensions/zalouser/src/runtime.js";
+import { sendMessageZalouser } from "../../../../extensions/zalouser/src/send.js";
+import { slackOutbound } from "../../../../test/channel-outbounds.js";
+import type { ReplyPayload } from "../../../auto-reply/types.js";
+import { createDirectTextMediaOutbound } from "../outbound/direct-text-media.js";
+import {
+  installChannelOutboundPayloadContractSuite,
+  primeChannelOutboundSendMock,
+} from "./suites.js";
+
+vi.mock("../../../../extensions/zalo/src/send.js", () => ({
+  sendMessageZalo: vi.fn().mockResolvedValue({ ok: true, messageId: "zl-1" }),
+}));
+
+vi.mock("../../../../extensions/zalouser/src/send.js", () => ({
+  sendMessageZalouser: vi.fn().mockResolvedValue({ ok: true, messageId: "zlu-1" }),
+  sendReactionZalouser: vi.fn().mockResolvedValue({ ok: true }),
+}));
+
+type PayloadHarnessParams = {
+  payload: ReplyPayload;
+  sendResults?: Array<{ messageId: string }>;
+};
+
+const mockedSendZalo = vi.mocked(sendMessageZalo);
+const mockedSendZalouser = vi.mocked(sendMessageZalouser);
+
+function createSlackHarness(params: PayloadHarnessParams) {
+  const sendSlack = vi.fn();
+  primeChannelOutboundSendMock(
+    sendSlack,
+    { messageId: "sl-1", channelId: "C12345", ts: "1234.5678" },
+    params.sendResults,
+  );
+  const ctx = {
+    cfg: {},
+    to: "C12345",
+    text: "",
+    payload: params.payload,
+    deps: {
+      sendSlack,
+    },
+  };
+  return {
+    run: async () => await slackOutbound.sendPayload!(ctx),
+    sendMock: sendSlack,
+    to: ctx.to,
+  };
+}
+
+function createDiscordHarness(params: PayloadHarnessParams) {
+  const sendDiscord = vi.fn();
+  primeChannelOutboundSendMock(
+    sendDiscord,
+    { messageId: "dc-1", channelId: "123456" },
+    params.sendResults,
+  );
+  const ctx = {
+    cfg: {},
+    to: "channel:123456",
+    text: "",
+    payload: params.payload,
+    deps: {
+      sendDiscord,
+    },
+  };
+  return {
+    run: async () => await discordOutbound.sendPayload!(ctx),
+    sendMock: sendDiscord,
+    to: ctx.to,
+  };
+}
+
+function createWhatsAppHarness(params: PayloadHarnessParams) {
+  const sendWhatsApp = vi.fn();
+  primeChannelOutboundSendMock(sendWhatsApp, { messageId: "wa-1" }, params.sendResults);
+  const ctx = {
+    cfg: {},
+    to: "5511999999999@c.us",
+    text: "",
+    payload: params.payload,
+    deps: {
+      sendWhatsApp,
+    },
+  };
+  return {
+    run: async () => await whatsappOutbound.sendPayload!(ctx),
+    sendMock: sendWhatsApp,
+    to: ctx.to,
+  };
+}
+
+function createDirectTextMediaHarness(params: PayloadHarnessParams) {
+  const sendFn = vi.fn();
+  primeChannelOutboundSendMock(sendFn, { messageId: "m1" }, params.sendResults);
+  const outbound = createDirectTextMediaOutbound({
+    channel: "imessage",
+    resolveSender: () => sendFn,
+    resolveMaxBytes: () => undefined,
+    buildTextOptions: (opts) => opts as never,
+    buildMediaOptions: (opts) => opts as never,
+  });
+  const ctx = {
+    cfg: {},
+    to: "user1",
+    text: "",
+    payload: params.payload,
+  };
+  return {
+    run: async () => await outbound.sendPayload!(ctx),
+    sendMock: sendFn,
+    to: ctx.to,
+  };
+}
+
+describe("channel outbound payload contract", () => {
+  describe("slack", () => {
+    installChannelOutboundPayloadContractSuite({
+      channel: "slack",
+      chunking: { mode: "passthrough", longTextLength: 5000 },
+      createHarness: createSlackHarness,
+    });
+  });
+
+  describe("discord", () => {
+    installChannelOutboundPayloadContractSuite({
+      channel: "discord",
+      chunking: { mode: "passthrough", longTextLength: 3000 },
+      createHarness: createDiscordHarness,
+    });
+  });
+
+  describe("whatsapp", () => {
+    installChannelOutboundPayloadContractSuite({
+      channel: "whatsapp",
+      chunking: { mode: "split", longTextLength: 5000, maxChunkLength: 4000 },
+      createHarness: createWhatsAppHarness,
+    });
+  });
+
+  describe("zalo", () => {
+    installChannelOutboundPayloadContractSuite({
+      channel: "zalo",
+      chunking: { mode: "split", longTextLength: 3000, maxChunkLength: 2000 },
+      createHarness: ({ payload, sendResults }) => {
+        primeChannelOutboundSendMock(mockedSendZalo, { ok: true, messageId: "zl-1" }, sendResults);
+        return {
+          run: async () =>
+            await zaloPlugin.outbound!.sendPayload!({
+              cfg: {},
+              to: "123456789",
+              text: "",
+              payload,
+            }),
+          sendMock: mockedSendZalo,
+          to: "123456789",
+        };
+      },
+    });
+  });
+
+  describe("zalouser", () => {
+    installChannelOutboundPayloadContractSuite({
+      channel: "zalouser",
+      chunking: { mode: "passthrough", longTextLength: 3000 },
+      createHarness: ({ payload, sendResults }) => {
+        setZalouserRuntime({
+          channel: {
+            text: {
+              resolveChunkMode: vi.fn(() => "length"),
+              resolveTextChunkLimit: vi.fn(() => 1200),
+            },
+          },
+        } as never);
+        primeChannelOutboundSendMock(
+          mockedSendZalouser,
+          { ok: true, messageId: "zlu-1" },
+          sendResults,
+        );
+        return {
+          run: async () =>
+            await zalouserPlugin.outbound!.sendPayload!({
+              cfg: {},
+              to: "user:987654321",
+              text: "",
+              payload,
+            }),
+          sendMock: mockedSendZalouser,
+          to: "987654321",
+        };
+      },
+    });
+  });
+
+  describe("direct-text-media", () => {
+    installChannelOutboundPayloadContractSuite({
+      channel: "imessage",
+      chunking: { mode: "split", longTextLength: 5000, maxChunkLength: 4000 },
+      createHarness: createDirectTextMediaHarness,
+    });
+  });
+});
diff --git a/src/channels/plugins/outbound/direct-text-media.sendpayload.test.ts b/src/channels/plugins/outbound/direct-text-media.sendpayload.test.ts
deleted file mode 100644
index 42971f1e89c..00000000000
--- a/src/channels/plugins/outbound/direct-text-media.sendpayload.test.ts
+++ /dev/null
@@ -1,47 +0,0 @@
-import { describe, vi } from "vitest";
-import type { ReplyPayload } from "../../../auto-reply/types.js";
-import {
-  installSendPayloadContractSuite,
-  primeSendMock,
-} from "../../../test-utils/send-payload-contract.js";
-import { createDirectTextMediaOutbound } from "./direct-text-media.js";
-
-function createDirectHarness(params: {
-  payload: ReplyPayload;
-  sendResults?: Array<{ messageId: string }>;
-}) {
-  const sendFn = vi.fn();
-  primeSendMock(sendFn, { messageId: "m1" }, params.sendResults);
-  const outbound = createDirectTextMediaOutbound({
-    channel: "imessage",
-    resolveSender: () => sendFn,
-    resolveMaxBytes: () => undefined,
-    buildTextOptions: (opts) => opts as never,
-    buildMediaOptions: (opts) => opts as never,
-  });
-  return { outbound, sendFn };
-}
-
-function baseCtx(payload: ReplyPayload) {
-  return {
-    cfg: {},
-    to: "user1",
-    text: "",
-    payload,
-  };
-}
-
-describe("createDirectTextMediaOutbound sendPayload", () => {
-  installSendPayloadContractSuite({
-    channel: "imessage",
-    chunking: { mode: "split", longTextLength: 5000, maxChunkLength: 4000 },
-    createHarness: ({ payload, sendResults }) => {
-      const { outbound, sendFn } = createDirectHarness({ payload, sendResults });
-      return {
-        run: async () => await outbound.sendPayload!(baseCtx(payload)),
-        sendMock: sendFn,
-        to: "user1",
-      };
-    },
-  });
-});
diff --git a/src/channels/plugins/outbound/slack.sendpayload.test.ts b/src/channels/plugins/outbound/slack.sendpayload.test.ts
index e1175023858..a78916c1336 100644
--- a/src/channels/plugins/outbound/slack.sendpayload.test.ts
+++ b/src/channels/plugins/outbound/slack.sendpayload.test.ts
@@ -1,17 +1,14 @@
 import { describe, expect, it, vi } from "vitest";
 import { slackOutbound } from "../../../../test/channel-outbounds.js";
 import type { ReplyPayload } from "../../../auto-reply/types.js";
-import {
-  installSendPayloadContractSuite,
-  primeSendMock,
-} from "../../../test-utils/send-payload-contract.js";
+import { primeChannelOutboundSendMock } from "../contracts/suites.js";
 
 function createHarness(params: {
   payload: ReplyPayload;
   sendResults?: Array<{ messageId: string }>;
 }) {
   const sendSlack = vi.fn();
-  primeSendMock(
+  primeChannelOutboundSendMock(
     sendSlack,
     { messageId: "sl-1", channelId: "C12345", ts: "1234.5678" },
     params.sendResults,
@@ -33,12 +30,6 @@ function createHarness(params: {
 }
 
 describe("slackOutbound sendPayload", () => {
-  installSendPayloadContractSuite({
-    channel: "slack",
-    chunking: { mode: "passthrough", longTextLength: 5000 },
-    createHarness,
-  });
-
   it("forwards Slack blocks from channelData", async () => {
     const { run, sendMock, to } = createHarness({
       payload: {
diff --git a/src/test-utils/send-payload-contract.ts b/src/test-utils/send-payload-contract.ts
deleted file mode 100644
index 5e78e406a74..00000000000
--- a/src/test-utils/send-payload-contract.ts
+++ /dev/null
@@ -1,138 +0,0 @@
-import { expect, it, type Mock } from "vitest";
-
-type PayloadLike = {
-  mediaUrl?: string;
-  mediaUrls?: string[];
-  text?: string;
-};
-
-type SendResultLike = {
-  messageId: string;
-  [key: string]: unknown;
-};
-
-type ChunkingMode =
-  | {
-      longTextLength: number;
-      maxChunkLength: number;
-      mode: "split";
-    }
-  | {
-      longTextLength: number;
-      mode: "passthrough";
-    };
-
-export function installSendPayloadContractSuite(params: {
-  channel: string;
-  chunking: ChunkingMode;
-  createHarness: (params: { payload: PayloadLike; sendResults?: SendResultLike[] }) => {
-    run: () => Promise<Record<string, unknown>>;
-    sendMock: Mock;
-    to: string;
-  };
-}) {
-  it("text-only delegates to sendText", async () => {
-    const { run, sendMock, to } = params.createHarness({
-      payload: { text: "hello" },
-    });
-    const result = await run();
-
-    expect(sendMock).toHaveBeenCalledTimes(1);
-    expect(sendMock).toHaveBeenCalledWith(to, "hello", expect.any(Object));
-    expect(result).toMatchObject({ channel: params.channel });
-  });
-
-  it("single media delegates to sendMedia", async () => {
-    const { run, sendMock, to } = params.createHarness({
-      payload: { text: "cap", mediaUrl: "https://example.com/a.jpg" },
-    });
-    const result = await run();
-
-    expect(sendMock).toHaveBeenCalledTimes(1);
-    expect(sendMock).toHaveBeenCalledWith(
-      to,
-      "cap",
-      expect.objectContaining({ mediaUrl: "https://example.com/a.jpg" }),
-    );
-    expect(result).toMatchObject({ channel: params.channel });
-  });
-
-  it("multi-media iterates URLs with caption on first", async () => {
-    const { run, sendMock, to } = params.createHarness({
-      payload: {
-        text: "caption",
-        mediaUrls: ["https://example.com/1.jpg", "https://example.com/2.jpg"],
-      },
-      sendResults: [{ messageId: "m-1" }, { messageId: "m-2" }],
-    });
-    const result = await run();
-
-    expect(sendMock).toHaveBeenCalledTimes(2);
-    expect(sendMock).toHaveBeenNthCalledWith(
-      1,
-      to,
-      "caption",
-      expect.objectContaining({ mediaUrl: "https://example.com/1.jpg" }),
-    );
-    expect(sendMock).toHaveBeenNthCalledWith(
-      2,
-      to,
-      "",
-      expect.objectContaining({ mediaUrl: "https://example.com/2.jpg" }),
-    );
-    expect(result).toMatchObject({ channel: params.channel, messageId: "m-2" });
-  });
-
-  it("empty payload returns no-op", async () => {
-    const { run, sendMock } = params.createHarness({ payload: {} });
-    const result = await run();
-
-    expect(sendMock).not.toHaveBeenCalled();
-    expect(result).toEqual({ channel: params.channel, messageId: "" });
-  });
-
-  if (params.chunking.mode === "passthrough") {
-    it("text exceeding chunk limit is sent as-is when chunker is null", async () => {
-      const text = "a".repeat(params.chunking.longTextLength);
-      const { run, sendMock, to } = params.createHarness({ payload: { text } });
-      const result = await run();
-
-      expect(sendMock).toHaveBeenCalledTimes(1);
-      expect(sendMock).toHaveBeenCalledWith(to, text, expect.any(Object));
-      expect(result).toMatchObject({ channel: params.channel });
-    });
-    return;
-  }
-
-  const chunking = params.chunking;
-
-  it("chunking splits long text", async () => {
-    const text = "a".repeat(chunking.longTextLength);
-    const { run, sendMock } = params.createHarness({
-      payload: { text },
-      sendResults: [{ messageId: "c-1" }, { messageId: "c-2" }],
-    });
-    const result = await run();
-
-    expect(sendMock.mock.calls.length).toBeGreaterThanOrEqual(2);
-    for (const call of sendMock.mock.calls) {
-      expect((call[1] as string).length).toBeLessThanOrEqual(chunking.maxChunkLength);
-    }
-    expect(result).toMatchObject({ channel: params.channel });
-  });
-}
-
-export function primeSendMock(
-  sendMock: Mock,
-  fallbackResult: Record<string, unknown>,
-  sendResults: SendResultLike[] = [],
-) {
-  sendMock.mockReset();
-  if (sendResults.length === 0) {
-    sendMock.mockResolvedValue(fallbackResult);
-    return;
-  }
-  for (const result of sendResults) {
-    sendMock.mockResolvedValueOnce(result);
-  }
-}