diff --git a/extensions/zalouser/src/channel.sendpayload.test.ts b/extensions/zalouser/src/channel.sendpayload.test.ts
index 0cef65f8c05..d388773e2e6 100644
--- a/extensions/zalouser/src/channel.sendpayload.test.ts
+++ b/extensions/zalouser/src/channel.sendpayload.test.ts
@@ -5,6 +5,7 @@ import {
   primeSendMock,
 } from "../../../src/test-utils/send-payload-contract.js";
 import { zalouserPlugin } from "./channel.js";
+import { setZalouserRuntime } from "./runtime.js";
 
 vi.mock("./send.js", () => ({
   sendMessageZalouser: vi.fn().mockResolvedValue({ ok: true, messageId: "zlu-1" }),
@@ -38,6 +39,14 @@ describe("zalouserPlugin outbound sendPayload", () => {
   let mockedSend: ReturnType<typeof vi.mocked<(typeof import("./send.js"))["sendMessageZalouser"]>>;
 
   beforeEach(async () => {
+    setZalouserRuntime({
+      channel: {
+        text: {
+          resolveChunkMode: vi.fn(() => "length"),
+          resolveTextChunkLimit: vi.fn(() => 1200),
+        },
+      },
+    } as never);
     const mod = await import("./send.js");
     mockedSend = vi.mocked(mod.sendMessageZalouser);
     mockedSend.mockClear();
@@ -55,7 +64,7 @@ describe("zalouserPlugin outbound sendPayload", () => {
     expect(mockedSend).toHaveBeenCalledWith(
       "1471383327500481391",
       "hello group",
-      expect.objectContaining({ isGroup: true }),
+      expect.objectContaining({ isGroup: true, textMode: "markdown" }),
     );
     expect(result).toMatchObject({ channel: "zalouser", messageId: "zlu-g1" });
   });
@@ -71,7 +80,7 @@ describe("zalouserPlugin outbound sendPayload", () => {
     expect(mockedSend).toHaveBeenCalledWith(
       "987654321",
       "hello",
-      expect.objectContaining({ isGroup: false }),
+      expect.objectContaining({ isGroup: false, textMode: "markdown" }),
     );
     expect(result).toMatchObject({ channel: "zalouser", messageId: "zlu-d1" });
   });
@@ -87,14 +96,37 @@ describe("zalouserPlugin outbound sendPayload", () => {
     expect(mockedSend).toHaveBeenCalledWith(
       "g-1471383327500481391",
       "hello native group",
-      expect.objectContaining({ isGroup: true }),
+      expect.objectContaining({ isGroup: true, textMode: "markdown" }),
     );
     expect(result).toMatchObject({ channel: "zalouser", messageId: "zlu-g-native" });
   });
 
+  it("passes long markdown through once so formatting happens before chunking", async () => {
+    const text = `**${"a".repeat(2501)}**`;
+    mockedSend.mockResolvedValue({ ok: true, messageId: "zlu-code" });
+
+    const result = await zalouserPlugin.outbound!.sendPayload!({
+      ...baseCtx({ text }),
+      to: "987654321",
+    });
+
+    expect(mockedSend).toHaveBeenCalledTimes(1);
+    expect(mockedSend).toHaveBeenCalledWith(
+      "987654321",
+      text,
+      expect.objectContaining({
+        isGroup: false,
+        textMode: "markdown",
+        textChunkMode: "length",
+        textChunkLimit: 1200,
+      }),
+    );
+    expect(result).toMatchObject({ channel: "zalouser", messageId: "zlu-code" });
+  });
+
   installSendPayloadContractSuite({
     channel: "zalouser",
-    chunking: { mode: "split", longTextLength: 3000, maxChunkLength: 2000 },
+    chunking: { mode: "passthrough", longTextLength: 3000 },
     createHarness: ({ payload, sendResults }) => {
       primeSendMock(mockedSend, { ok: true, messageId: "zlu-1" }, sendResults);
       return {
diff --git a/extensions/zalouser/src/channel.test.ts b/extensions/zalouser/src/channel.test.ts
index 231bcc8b2d3..5580ddfb2e1 100644
--- a/extensions/zalouser/src/channel.test.ts
+++ b/extensions/zalouser/src/channel.test.ts
@@ -1,5 +1,7 @@
 import { beforeEach, describe, expect, it, vi } from "vitest";
+import { chunkMarkdownText } from "../../../src/auto-reply/chunk.js";
 import { zalouserPlugin } from "./channel.js";
+import { setZalouserRuntime } from "./runtime.js";
 import { sendReactionZalouser } from "./send.js";
 
 vi.mock("./send.js", async (importOriginal) => {
@@ -13,6 +15,16 @@ vi.mock("./send.js", async (importOriginal) => {
 const mockSendReaction = vi.mocked(sendReactionZalouser);
 
 describe("zalouser outbound chunker", () => {
+  beforeEach(() => {
+    setZalouserRuntime({
+      channel: {
+        text: {
+          chunkMarkdownText,
+        },
+      },
+    } as never);
+  });
+
   it("chunks without empty strings and respects limit", () => {
     const chunker = zalouserPlugin.outbound?.chunker;
     expect(chunker).toBeTypeOf("function");
diff --git a/extensions/zalouser/src/channel.ts b/extensions/zalouser/src/channel.ts
index 2091124be6e..a2e3435f75c 100644
--- a/extensions/zalouser/src/channel.ts
+++ b/extensions/zalouser/src/channel.ts
@@ -20,7 +20,6 @@ import {
   buildBaseAccountStatusSnapshot,
   buildChannelConfigSchema,
   DEFAULT_ACCOUNT_ID,
-  chunkTextForOutbound,
   deleteAccountFromConfigSection,
   formatAllowFromLowercase,
   isNumericTargetId,
@@ -43,6 +42,7 @@ import { resolveZalouserReactionMessageIds } from "./message-sid.js";
 import { zalouserOnboardingAdapter } from "./onboarding.js";
 import { probeZalouser } from "./probe.js";
 import { writeQrDataUrlToTempFile } from "./qr-temp-file.js";
+import { getZalouserRuntime } from "./runtime.js";
 import { sendMessageZalouser, sendReactionZalouser } from "./send.js";
 import { collectZalouserStatusIssues } from "./status-issues.js";
 import {
@@ -166,6 +166,16 @@ function resolveZalouserQrProfile(accountId?: string | null): string {
   return normalized;
 }
 
+function resolveZalouserOutboundChunkMode(cfg: OpenClawConfig, accountId?: string) {
+  return getZalouserRuntime().channel.text.resolveChunkMode(cfg, "zalouser", accountId);
+}
+
+function resolveZalouserOutboundTextChunkLimit(cfg: OpenClawConfig, accountId?: string) {
+  return getZalouserRuntime().channel.text.resolveTextChunkLimit(cfg, "zalouser", accountId, {
+    fallbackLimit: zalouserDock.outbound?.textChunkLimit ?? 2000,
+  });
+}
+
 function mapUser(params: {
   id: string;
   name?: string | null;
@@ -595,14 +605,9 @@ export const zalouserPlugin: ChannelPlugin<ResolvedZalouserAccount> = {
   },
   outbound: {
     deliveryMode: "direct",
-    chunker: chunkTextForOutbound,
-    chunkerMode: "text",
-    textChunkLimit: 2000,
     sendPayload: async (ctx) =>
       await sendPayloadWithChunkedTextAndMedia({
         ctx,
-        textChunkLimit: zalouserPlugin.outbound!.textChunkLimit,
-        chunker: zalouserPlugin.outbound!.chunker,
         sendText: (nextCtx) => zalouserPlugin.outbound!.sendText!(nextCtx),
         sendMedia: (nextCtx) => zalouserPlugin.outbound!.sendMedia!(nextCtx),
         emptyResult: { channel: "zalouser", messageId: "" },
@@ -613,6 +618,9 @@ export const zalouserPlugin: ChannelPlugin<ResolvedZalouserAccount> = {
       const result = await sendMessageZalouser(target.threadId, text, {
         profile: account.profile,
         isGroup: target.isGroup,
+        textMode: "markdown",
+        textChunkMode: resolveZalouserOutboundChunkMode(cfg, account.accountId),
+        textChunkLimit: resolveZalouserOutboundTextChunkLimit(cfg, account.accountId),
       });
       return buildChannelSendResult("zalouser", result);
     },
@@ -624,6 +632,9 @@ export const zalouserPlugin: ChannelPlugin<ResolvedZalouserAccount> = {
         isGroup: target.isGroup,
         mediaUrl,
         mediaLocalRoots,
+        textMode: "markdown",
+        textChunkMode: resolveZalouserOutboundChunkMode(cfg, account.accountId),
+        textChunkLimit: resolveZalouserOutboundTextChunkLimit(cfg, account.accountId),
       });
       return buildChannelSendResult("zalouser", result);
     },
diff --git a/extensions/zalouser/src/monitor.group-gating.test.ts b/extensions/zalouser/src/monitor.group-gating.test.ts
index b3e38efecd6..49593f07072 100644
--- a/extensions/zalouser/src/monitor.group-gating.test.ts
+++ b/extensions/zalouser/src/monitor.group-gating.test.ts
@@ -51,6 +51,7 @@ function createRuntimeEnv(): RuntimeEnv {
 
 function installRuntime(params: {
   commandAuthorized?: boolean;
+  replyPayload?: { text?: string; mediaUrl?: string; mediaUrls?: string[] };
   resolveCommandAuthorizedFromAuthorizers?: (params: {
     useAccessGroups: boolean;
     authorizers: Array<{ configured: boolean; allowed: boolean }>;
@@ -58,6 +59,9 @@ function installRuntime(params: {
 }) {
   const dispatchReplyWithBufferedBlockDispatcher = vi.fn(async ({ dispatcherOptions, ctx }) => {
     await dispatcherOptions.typingCallbacks?.onReplyStart?.();
+    if (params.replyPayload) {
+      await dispatcherOptions.deliver(params.replyPayload);
+    }
     return { queuedFinal: false, counts: { tool: 0, block: 0, final: 0 }, ctx };
   });
   const resolveCommandAuthorizedFromAuthorizers = vi.fn(
@@ -166,7 +170,8 @@ function installRuntime(params: {
       text: {
         resolveMarkdownTableMode: vi.fn(() => "code"),
         convertMarkdownTables: vi.fn((text: string) => text),
-        resolveChunkMode: vi.fn(() => "line"),
+        resolveChunkMode: vi.fn(() => "length"),
+        resolveTextChunkLimit: vi.fn(() => 1200),
         chunkMarkdownTextWithMode: vi.fn((text: string) => [text]),
       },
     },
@@ -304,6 +309,42 @@ describe("zalouser monitor group mention gating", () => {
     expect(callArg?.ctx?.WasMentioned).toBe(true);
   });
 
+  it("passes long markdown replies through once so formatting happens before chunking", async () => {
+    const replyText = `**${"a".repeat(2501)}**`;
+    installRuntime({
+      commandAuthorized: false,
+      replyPayload: { text: replyText },
+    });
+
+    await __testing.processMessage({
+      message: createDmMessage({
+        content: "hello",
+      }),
+      account: {
+        ...createAccount(),
+        config: {
+          ...createAccount().config,
+          dmPolicy: "open",
+        },
+      },
+      config: createConfig(),
+      runtime: createRuntimeEnv(),
+    });
+
+    expect(sendMessageZalouserMock).toHaveBeenCalledTimes(1);
+    expect(sendMessageZalouserMock).toHaveBeenCalledWith(
+      "u-1",
+      replyText,
+      expect.objectContaining({
+        isGroup: false,
+        profile: "default",
+        textMode: "markdown",
+        textChunkMode: "length",
+        textChunkLimit: 1200,
+      }),
+    );
+  });
+
   it("uses commandContent for mention-prefixed control commands", async () => {
     const { dispatchReplyWithBufferedBlockDispatcher } = installRuntime({
       commandAuthorized: true,
diff --git a/extensions/zalouser/src/monitor.ts b/extensions/zalouser/src/monitor.ts
index 6590082e830..5329b22fa68 100644
--- a/extensions/zalouser/src/monitor.ts
+++ b/extensions/zalouser/src/monitor.ts
@@ -703,6 +703,10 @@ async function deliverZalouserReply(params: {
     params;
   const tableMode = params.tableMode ?? "code";
   const text = core.channel.text.convertMarkdownTables(payload.text ?? "", tableMode);
+  const chunkMode = core.channel.text.resolveChunkMode(config, "zalouser", accountId);
+  const textChunkLimit = core.channel.text.resolveTextChunkLimit(config, "zalouser", accountId, {
+    fallbackLimit: ZALOUSER_TEXT_LIMIT,
+  });
 
   const sentMedia = await sendMediaWithLeadingCaption({
     mediaUrls: resolveOutboundMediaUrls(payload),
@@ -713,6 +717,9 @@ async function deliverZalouserReply(params: {
         profile,
         mediaUrl,
         isGroup,
+        textMode: "markdown",
+        textChunkMode: chunkMode,
+        textChunkLimit,
       });
       statusSink?.({ lastOutboundAt: Date.now() });
     },
@@ -725,20 +732,17 @@ async function deliverZalouserReply(params: {
   }
 
   if (text) {
-    const chunkMode = core.channel.text.resolveChunkMode(config, "zalouser", accountId);
-    const chunks = core.channel.text.chunkMarkdownTextWithMode(
-      text,
-      ZALOUSER_TEXT_LIMIT,
-      chunkMode,
-    );
-    logVerbose(core, runtime, `Sending ${chunks.length} text chunk(s) to ${chatId}`);
-    for (const chunk of chunks) {
-      try {
-        await sendMessageZalouser(chatId, chunk, { profile, isGroup });
-        statusSink?.({ lastOutboundAt: Date.now() });
-      } catch (err) {
-        runtime.error(`Zalouser message send failed: ${String(err)}`);
-      }
+    try {
+      await sendMessageZalouser(chatId, text, {
+        profile,
+        isGroup,
+        textMode: "markdown",
+        textChunkMode: chunkMode,
+        textChunkLimit,
+      });
+      statusSink?.({ lastOutboundAt: Date.now() });
+    } catch (err) {
+      runtime.error(`Zalouser message send failed: ${String(err)}`);
     }
   }
 }
diff --git a/extensions/zalouser/src/send.test.ts b/extensions/zalouser/src/send.test.ts
index 92b3cec25f2..cc920e6be7e 100644
--- a/extensions/zalouser/src/send.test.ts
+++ b/extensions/zalouser/src/send.test.ts
@@ -8,6 +8,7 @@ import {
   sendSeenZalouser,
   sendTypingZalouser,
 } from "./send.js";
+import { parseZalouserTextStyles } from "./text-styles.js";
 import {
   sendZaloDeliveredEvent,
   sendZaloLink,
@@ -16,6 +17,7 @@ import {
   sendZaloTextMessage,
   sendZaloTypingEvent,
 } from "./zalo-js.js";
+import { TextStyle } from "./zca-client.js";
 
 vi.mock("./zalo-js.js", () => ({
   sendZaloTextMessage: vi.fn(),
@@ -43,36 +45,272 @@ describe("zalouser send helpers", () => {
     mockSendSeen.mockReset();
   });
 
-  it("delegates text send to JS transport", async () => {
+  it("keeps plain text literal by default", async () => {
     mockSendText.mockResolvedValueOnce({ ok: true, messageId: "mid-1" });
 
-    const result = await sendMessageZalouser("thread-1", "hello", {
+    const result = await sendMessageZalouser("thread-1", "**hello**", {
       profile: "default",
       isGroup: true,
     });
 
-    expect(mockSendText).toHaveBeenCalledWith("thread-1", "hello", {
-      profile: "default",
-      isGroup: true,
-    });
+    expect(mockSendText).toHaveBeenCalledWith(
+      "thread-1",
+      "**hello**",
+      expect.objectContaining({
+        profile: "default",
+        isGroup: true,
+      }),
+    );
     expect(result).toEqual({ ok: true, messageId: "mid-1" });
   });
 
-  it("maps image helper to media send", async () => {
+  it("formats markdown text when markdown mode is enabled", async () => {
+    mockSendText.mockResolvedValueOnce({ ok: true, messageId: "mid-1b" });
+
+    await sendMessageZalouser("thread-1", "**hello**", {
+      profile: "default",
+      isGroup: true,
+      textMode: "markdown",
+    });
+
+    expect(mockSendText).toHaveBeenCalledWith(
+      "thread-1",
+      "hello",
+      expect.objectContaining({
+        profile: "default",
+        isGroup: true,
+        textMode: "markdown",
+        textStyles: [{ start: 0, len: 5, st: TextStyle.Bold }],
+      }),
+    );
+  });
+
+  it("formats image captions in markdown mode", async () => {
     mockSendText.mockResolvedValueOnce({ ok: true, messageId: "mid-2" });
 
     await sendImageZalouser("thread-2", "https://example.com/a.png", {
       profile: "p2",
-      caption: "cap",
+      caption: "_cap_",
       isGroup: false,
+      textMode: "markdown",
     });
 
-    expect(mockSendText).toHaveBeenCalledWith("thread-2", "cap", {
+    expect(mockSendText).toHaveBeenCalledWith(
+      "thread-2",
+      "cap",
+      expect.objectContaining({
+        profile: "p2",
+        caption: undefined,
+        isGroup: false,
+        mediaUrl: "https://example.com/a.png",
+        textMode: "markdown",
+        textStyles: [{ start: 0, len: 3, st: TextStyle.Italic }],
+      }),
+    );
+  });
+
+  it("does not keep the raw markdown caption as a media fallback after formatting", async () => {
+    mockSendText.mockResolvedValueOnce({ ok: true, messageId: "mid-2b" });
+
+    await sendImageZalouser("thread-2", "https://example.com/a.png", {
       profile: "p2",
-      caption: "cap",
+      caption: "```\n```",
       isGroup: false,
-      mediaUrl: "https://example.com/a.png",
+      textMode: "markdown",
     });
+
+    expect(mockSendText).toHaveBeenCalledWith(
+      "thread-2",
+      "",
+      expect.objectContaining({
+        profile: "p2",
+        caption: undefined,
+        isGroup: false,
+        mediaUrl: "https://example.com/a.png",
+        textMode: "markdown",
+        textStyles: undefined,
+      }),
+    );
+  });
+
+  it("rechunks normalized markdown text before sending to avoid transport truncation", async () => {
+    const text = "\t".repeat(500) + "a".repeat(1500);
+    const formatted = parseZalouserTextStyles(text);
+    mockSendText
+      .mockResolvedValueOnce({ ok: true, messageId: "mid-2c-1" })
+      .mockResolvedValueOnce({ ok: true, messageId: "mid-2c-2" });
+
+    const result = await sendMessageZalouser("thread-2c", text, {
+      profile: "p2c",
+      isGroup: false,
+      textMode: "markdown",
+    });
+
+    expect(formatted.text.length).toBeGreaterThan(2000);
+    expect(mockSendText).toHaveBeenCalledTimes(2);
+    expect(mockSendText.mock.calls.map((call) => call[1]).join("")).toBe(formatted.text);
+    expect(mockSendText.mock.calls.every((call) => (call[1] as string).length <= 2000)).toBe(true);
+    expect(result).toEqual({ ok: true, messageId: "mid-2c-2" });
+  });
+
+  it("preserves text styles when splitting long formatted markdown", async () => {
+    const text = `**${"a".repeat(2501)}**`;
+    mockSendText
+      .mockResolvedValueOnce({ ok: true, messageId: "mid-2d-1" })
+      .mockResolvedValueOnce({ ok: true, messageId: "mid-2d-2" });
+
+    const result = await sendMessageZalouser("thread-2d", text, {
+      profile: "p2d",
+      isGroup: false,
+      textMode: "markdown",
+    });
+
+    expect(mockSendText).toHaveBeenNthCalledWith(
+      1,
+      "thread-2d",
+      "a".repeat(2000),
+      expect.objectContaining({
+        profile: "p2d",
+        isGroup: false,
+        textMode: "markdown",
+        textStyles: [{ start: 0, len: 2000, st: TextStyle.Bold }],
+      }),
+    );
+    expect(mockSendText).toHaveBeenNthCalledWith(
+      2,
+      "thread-2d",
+      "a".repeat(501),
+      expect.objectContaining({
+        profile: "p2d",
+        isGroup: false,
+        textMode: "markdown",
+        textStyles: [{ start: 0, len: 501, st: TextStyle.Bold }],
+      }),
+    );
+    expect(result).toEqual({ ok: true, messageId: "mid-2d-2" });
+  });
+
+  it("preserves formatted text and styles when newline chunk mode splits after parsing", async () => {
+    const text = `**${"a".repeat(1995)}**\n\nsecond paragraph`;
+    const formatted = parseZalouserTextStyles(text);
+    mockSendText
+      .mockResolvedValueOnce({ ok: true, messageId: "mid-2d-3" })
+      .mockResolvedValueOnce({ ok: true, messageId: "mid-2d-4" });
+
+    const result = await sendMessageZalouser("thread-2d-2", text, {
+      profile: "p2d-2",
+      isGroup: false,
+      textMode: "markdown",
+      textChunkMode: "newline",
+    });
+
+    expect(mockSendText).toHaveBeenCalledTimes(2);
+    expect(mockSendText.mock.calls.map((call) => call[1]).join("")).toBe(formatted.text);
+    expect(mockSendText).toHaveBeenNthCalledWith(
+      1,
+      "thread-2d-2",
+      `${"a".repeat(1995)}\n\n`,
+      expect.objectContaining({
+        profile: "p2d-2",
+        isGroup: false,
+        textMode: "markdown",
+        textChunkMode: "newline",
+        textStyles: [{ start: 0, len: 1995, st: TextStyle.Bold }],
+      }),
+    );
+    expect(mockSendText).toHaveBeenNthCalledWith(
+      2,
+      "thread-2d-2",
+      "second paragraph",
+      expect.objectContaining({
+        profile: "p2d-2",
+        isGroup: false,
+        textMode: "markdown",
+        textChunkMode: "newline",
+        textStyles: undefined,
+      }),
+    );
+    expect(result).toEqual({ ok: true, messageId: "mid-2d-4" });
+  });
+
+  it("respects an explicit text chunk limit when splitting formatted markdown", async () => {
+    const text = `**${"a".repeat(1501)}**`;
+    mockSendText
+      .mockResolvedValueOnce({ ok: true, messageId: "mid-2d-5" })
+      .mockResolvedValueOnce({ ok: true, messageId: "mid-2d-6" });
+
+    const result = await sendMessageZalouser("thread-2d-3", text, {
+      profile: "p2d-3",
+      isGroup: false,
+      textMode: "markdown",
+      textChunkLimit: 1200,
+    } as never);
+
+    expect(mockSendText).toHaveBeenCalledTimes(2);
+    expect(mockSendText).toHaveBeenNthCalledWith(
+      1,
+      "thread-2d-3",
+      "a".repeat(1200),
+      expect.objectContaining({
+        profile: "p2d-3",
+        isGroup: false,
+        textMode: "markdown",
+        textChunkLimit: 1200,
+        textStyles: [{ start: 0, len: 1200, st: TextStyle.Bold }],
+      }),
+    );
+    expect(mockSendText).toHaveBeenNthCalledWith(
+      2,
+      "thread-2d-3",
+      "a".repeat(301),
+      expect.objectContaining({
+        profile: "p2d-3",
+        isGroup: false,
+        textMode: "markdown",
+        textChunkLimit: 1200,
+        textStyles: [{ start: 0, len: 301, st: TextStyle.Bold }],
+      }),
+    );
+    expect(result).toEqual({ ok: true, messageId: "mid-2d-6" });
+  });
+
+  it("sends overflow markdown captions as follow-up text after the media message", async () => {
+    const caption = "\t".repeat(500) + "a".repeat(1500);
+    const formatted = parseZalouserTextStyles(caption);
+    mockSendText
+      .mockResolvedValueOnce({ ok: true, messageId: "mid-2e-1" })
+      .mockResolvedValueOnce({ ok: true, messageId: "mid-2e-2" });
+
+    const result = await sendImageZalouser("thread-2e", "https://example.com/long.png", {
+      profile: "p2e",
+      caption,
+      isGroup: false,
+      textMode: "markdown",
+    });
+
+    expect(mockSendText).toHaveBeenCalledTimes(2);
+    expect(mockSendText.mock.calls.map((call) => call[1]).join("")).toBe(formatted.text);
+    expect(mockSendText).toHaveBeenNthCalledWith(
+      1,
+      "thread-2e",
+      expect.any(String),
+      expect.objectContaining({
+        profile: "p2e",
+        caption: undefined,
+        isGroup: false,
+        mediaUrl: "https://example.com/long.png",
+        textMode: "markdown",
+      }),
+    );
+    expect(mockSendText).toHaveBeenNthCalledWith(
+      2,
+      "thread-2e",
+      expect.any(String),
+      expect.not.objectContaining({
+        mediaUrl: "https://example.com/long.png",
+      }),
+    );
+    expect(result).toEqual({ ok: true, messageId: "mid-2e-2" });
   });
 
   it("delegates link helper to JS transport", async () => {
diff --git a/extensions/zalouser/src/send.ts b/extensions/zalouser/src/send.ts
index 07ae1408bff..55ff17df636 100644
--- a/extensions/zalouser/src/send.ts
+++ b/extensions/zalouser/src/send.ts
@@ -1,3 +1,4 @@
+import { parseZalouserTextStyles } from "./text-styles.js";
 import type { ZaloEventMessage, ZaloSendOptions, ZaloSendResult } from "./types.js";
 import {
   sendZaloDeliveredEvent,
@@ -7,16 +8,58 @@ import {
   sendZaloTextMessage,
   sendZaloTypingEvent,
 } from "./zalo-js.js";
+import { TextStyle } from "./zca-client.js";
 
 export type ZalouserSendOptions = ZaloSendOptions;
 export type ZalouserSendResult = ZaloSendResult;
 
+const ZALO_TEXT_LIMIT = 2000;
+const DEFAULT_TEXT_CHUNK_MODE = "length";
+
+type StyledTextChunk = {
+  text: string;
+  styles?: ZaloSendOptions["textStyles"];
+};
+
+type TextChunkMode = NonNullable<ZaloSendOptions["textChunkMode"]>;
+
 export async function sendMessageZalouser(
   threadId: string,
   text: string,
   options: ZalouserSendOptions = {},
 ): Promise<ZalouserSendResult> {
-  return await sendZaloTextMessage(threadId, text, options);
+  const prepared =
+    options.textMode === "markdown"
+      ? parseZalouserTextStyles(text)
+      : { text, styles: options.textStyles };
+  const textChunkLimit = options.textChunkLimit ?? ZALO_TEXT_LIMIT;
+  const chunks = splitStyledText(
+    prepared.text,
+    (prepared.styles?.length ?? 0) > 0 ? prepared.styles : undefined,
+    textChunkLimit,
+    options.textChunkMode,
+  );
+
+  let lastResult: ZalouserSendResult | null = null;
+  for (const [index, chunk] of chunks.entries()) {
+    const chunkOptions =
+      index === 0
+        ? { ...options, textStyles: chunk.styles }
+        : {
+            ...options,
+            caption: undefined,
+            mediaLocalRoots: undefined,
+            mediaUrl: undefined,
+            textStyles: chunk.styles,
+          };
+    const result = await sendZaloTextMessage(threadId, chunk.text, chunkOptions);
+    if (!result.ok) {
+      return result;
+    }
+    lastResult = result;
+  }
+
+  return lastResult ?? { ok: false, error: "No message content provided" };
 }
 
 export async function sendImageZalouser(
@@ -24,8 +67,9 @@ export async function sendImageZalouser(
   imageUrl: string,
   options: ZalouserSendOptions = {},
 ): Promise<ZalouserSendResult> {
-  return await sendZaloTextMessage(threadId, options.caption ?? "", {
+  return await sendMessageZalouser(threadId, options.caption ?? "", {
     ...options,
+    caption: undefined,
     mediaUrl: imageUrl,
   });
 }
@@ -85,3 +129,144 @@ export async function sendSeenZalouser(params: {
 }): Promise<void> {
   await sendZaloSeenEvent(params);
 }
+
+function splitStyledText(
+  text: string,
+  styles: ZaloSendOptions["textStyles"],
+  limit: number,
+  mode: ZaloSendOptions["textChunkMode"],
+): StyledTextChunk[] {
+  if (text.length === 0) {
+    return [{ text, styles: undefined }];
+  }
+
+  const chunks: StyledTextChunk[] = [];
+  for (const range of splitTextRanges(text, limit, mode ?? DEFAULT_TEXT_CHUNK_MODE)) {
+    const { start, end } = range;
+    chunks.push({
+      text: text.slice(start, end),
+      styles: sliceTextStyles(styles, start, end),
+    });
+  }
+  return chunks;
+}
+
+function sliceTextStyles(
+  styles: ZaloSendOptions["textStyles"],
+  start: number,
+  end: number,
+): ZaloSendOptions["textStyles"] {
+  if (!styles || styles.length === 0) {
+    return undefined;
+  }
+
+  const chunkStyles = styles
+    .map((style) => {
+      const overlapStart = Math.max(style.start, start);
+      const overlapEnd = Math.min(style.start + style.len, end);
+      if (overlapEnd <= overlapStart) {
+        return null;
+      }
+
+      if (style.st === TextStyle.Indent) {
+        return {
+          start: overlapStart - start,
+          len: overlapEnd - overlapStart,
+          st: style.st,
+          indentSize: style.indentSize,
+        };
+      }
+
+      return {
+        start: overlapStart - start,
+        len: overlapEnd - overlapStart,
+        st: style.st,
+      };
+    })
+    .filter((style): style is NonNullable<typeof style> => style !== null);
+
+  return chunkStyles.length > 0 ? chunkStyles : undefined;
+}
+
+function splitTextRanges(
+  text: string,
+  limit: number,
+  mode: TextChunkMode,
+): Array<{ start: number; end: number }> {
+  if (mode === "newline") {
+    return splitTextRangesByPreferredBreaks(text, limit);
+  }
+
+  const ranges: Array<{ start: number; end: number }> = [];
+  for (let start = 0; start < text.length; start += limit) {
+    ranges.push({
+      start,
+      end: Math.min(text.length, start + limit),
+    });
+  }
+  return ranges;
+}
+
+function splitTextRangesByPreferredBreaks(
+  text: string,
+  limit: number,
+): Array<{ start: number; end: number }> {
+  const ranges: Array<{ start: number; end: number }> = [];
+  let start = 0;
+
+  while (start < text.length) {
+    const maxEnd = Math.min(text.length, start + limit);
+    let end = maxEnd;
+    if (maxEnd < text.length) {
+      end =
+        findParagraphBreak(text, start, maxEnd) ??
+        findLastBreak(text, "\n", start, maxEnd) ??
+        findLastWhitespaceBreak(text, start, maxEnd) ??
+        maxEnd;
+    }
+
+    if (end <= start) {
+      end = maxEnd;
+    }
+
+    ranges.push({ start, end });
+    start = end;
+  }
+
+  return ranges;
+}
+
+function findParagraphBreak(text: string, start: number, end: number): number | undefined {
+  const slice = text.slice(start, end);
+  const matches = slice.matchAll(/\n[\t ]*\n+/g);
+  let lastMatch: RegExpMatchArray | undefined;
+  for (const match of matches) {
+    lastMatch = match;
+  }
+  if (!lastMatch || lastMatch.index === undefined) {
+    return undefined;
+  }
+  return start + lastMatch.index + lastMatch[0].length;
+}
+
+function findLastBreak(
+  text: string,
+  marker: string,
+  start: number,
+  end: number,
+): number | undefined {
+  const index = text.lastIndexOf(marker, end - 1);
+  if (index < start) {
+    return undefined;
+  }
+  return index + marker.length;
+}
+
+function findLastWhitespaceBreak(text: string, start: number, end: number): number | undefined {
+  for (let index = end - 1; index > start; index -= 1) {
+    if (/\s/.test(text[index])) {
+      return index + 1;
+    }
+  }
+  return undefined;
+}
diff --git a/extensions/zalouser/src/text-styles.test.ts b/extensions/zalouser/src/text-styles.test.ts
new file mode 100644
index 00000000000..01e6c2da86b
--- /dev/null
+++ b/extensions/zalouser/src/text-styles.test.ts
@@ -0,0 +1,203 @@
+import { describe, expect, it } from "vitest";
+import { parseZalouserTextStyles } from "./text-styles.js";
+import { TextStyle } from "./zca-client.js";
+
+describe("parseZalouserTextStyles", () => {
+  it("renders inline markdown emphasis as Zalo style ranges", () => {
+    expect(parseZalouserTextStyles("**bold** *italic* ~~strike~~")).toEqual({
+      text: "bold italic strike",
+      styles: [
+        { start: 0, len: 4, st: TextStyle.Bold },
+        { start: 5, len: 6, st: TextStyle.Italic },
+        { start: 12, len: 6, st: TextStyle.StrikeThrough },
+      ],
+    });
+  });
+
+  it("keeps inline code and plain math markers literal", () => {
+    expect(parseZalouserTextStyles("before `inline *code*` after\n2 * 3 * 4")).toEqual({
+      text: "before `inline *code*` after\n2 * 3 * 4",
+      styles: [],
+    });
+  });
+
+  it("preserves backslash escapes inside code spans and fenced code blocks", () => {
+    expect(parseZalouserTextStyles("before `\\*` after\n```ts\n\\*\\_\\\\\n```")).toEqual({
+      text: "before `\\*` after\n\\*\\_\\\\",
+      styles: [],
+    });
+  });
+
+  it("closes fenced code blocks when the input uses CRLF newlines", () => {
+    expect(parseZalouserTextStyles("```\r\n*code*\r\n```\r\n**after**")).toEqual({
+      text: "*code*\nafter",
+      styles: [{ start: 7, len: 5, st: TextStyle.Bold }],
+    });
+  });
+
+  it("maps headings, block quotes, and lists into line styles", () => {
+    expect(parseZalouserTextStyles(["# Title", "> quoted", "  - nested"].join("\n"))).toEqual({
+      text: "Title\nquoted\nnested",
+      styles: [
+        { start: 0, len: 5, st: TextStyle.Bold },
+        { start: 0, len: 5, st: TextStyle.Big },
+        { start: 6, len: 6, st: TextStyle.Indent, indentSize: 1 },
+        { start: 13, len: 6, st: TextStyle.UnorderedList },
+      ],
+    });
+  });
+
+  it("treats 1-3 leading spaces as markdown padding for headings and lists", () => {
+    expect(parseZalouserTextStyles("  # Title\n   1. item\n  - bullet")).toEqual({
+      text: "Title\nitem\nbullet",
+      styles: [
+        { start: 0, len: 5, st: TextStyle.Bold },
+        { start: 0, len: 5, st: TextStyle.Big },
+        { start: 6, len: 4, st: TextStyle.OrderedList },
+        { start: 11, len: 6, st: TextStyle.UnorderedList },
+      ],
+    });
+  });
+
+  it("strips fenced code markers and preserves leading indentation with nbsp", () => {
+    expect(parseZalouserTextStyles("```ts\n  const x = 1\n\treturn x\n```")).toEqual({
+      text: "\u00A0\u00A0const x = 1\n\u00A0\u00A0\u00A0\u00A0return x",
+      styles: [],
+    });
+  });
+
+  it("treats tilde fences as literal code blocks", () => {
+    expect(parseZalouserTextStyles("~~~bash\n*cmd*\n~~~")).toEqual({
+      text: "*cmd*",
+      styles: [],
+    });
+  });
+
+  it("treats fences indented under list items as literal code blocks", () => {
+    expect(parseZalouserTextStyles("  ```\n*cmd*\n  ```")).toEqual({
+      text: "*cmd*",
+      styles: [],
+    });
+  });
+
+  it("treats quoted backtick fences as literal code blocks", () => {
+    expect(parseZalouserTextStyles("> ```js\n> *cmd*\n> ```")).toEqual({
+      text: "*cmd*",
+      styles: [],
+    });
+  });
+
+  it("treats quoted tilde fences as literal code blocks", () => {
+    expect(parseZalouserTextStyles("> ~~~\n> *cmd*\n> ~~~")).toEqual({
+      text: "*cmd*",
+      styles: [],
+    });
+  });
+
+  it("preserves quote-prefixed lines inside normal fenced code blocks", () => {
+    expect(parseZalouserTextStyles("```\n> prompt\n```")).toEqual({
+      text: "> prompt",
+      styles: [],
+    });
+  });
+
+  it("does not treat quote-prefixed fence text inside code as a closing fence", () => {
+    expect(parseZalouserTextStyles("```\n> ```\n*still code*\n```")).toEqual({
+      text: "> ```\n*still code*",
+      styles: [],
+    });
+  });
+
+  it("treats indented blockquotes as quoted lines", () => {
+    expect(parseZalouserTextStyles("  > quoted")).toEqual({
+      text: "quoted",
+      styles: [{ start: 0, len: 6, st: TextStyle.Indent, indentSize: 1 }],
+    });
+  });
+
+  it("treats spaced nested blockquotes as deeper quoted lines", () => {
+    expect(parseZalouserTextStyles("> > quoted")).toEqual({
+      text: "quoted",
+      styles: [{ start: 0, len: 6, st: TextStyle.Indent, indentSize: 2 }],
+    });
+  });
+
+  it("treats indented quoted fences as literal code blocks", () => {
+    expect(parseZalouserTextStyles("  > ```\n  > *cmd*\n  > ```")).toEqual({
+      text: "*cmd*",
+      styles: [],
+    });
+  });
+
+  it("treats spaced nested quoted fences as literal code blocks", () => {
+    expect(parseZalouserTextStyles("> > ```\n> > code\n> > ```")).toEqual({
+      text: "code",
+      styles: [],
+    });
+  });
+
+  it("preserves inner quote markers inside quoted fenced code blocks", () => {
+    expect(parseZalouserTextStyles("> ```\n>> prompt\n> ```")).toEqual({
+      text: "> prompt",
+      styles: [],
+    });
+  });
+
+  it("keeps quote indentation on heading lines", () => {
+    expect(parseZalouserTextStyles("> # Title")).toEqual({
+      text: "Title",
+      styles: [
+        { start: 0, len: 5, st: TextStyle.Bold },
+        { start: 0, len: 5, st: TextStyle.Big },
+        { start: 0, len: 5, st: TextStyle.Indent, indentSize: 1 },
+      ],
+    });
+  });
+
+  it("keeps unmatched fences literal", () => {
+    expect(parseZalouserTextStyles("```python")).toEqual({
+      text: "```python",
+      styles: [],
+    });
+  });
+
+  it("keeps unclosed fenced blocks literal until eof", () => {
+    expect(parseZalouserTextStyles("```python\n\\*not italic*\n_next_")).toEqual({
+      text: "```python\n\\*not italic*\n_next_",
+      styles: [],
+    });
+  });
+
+  it("supports nested markdown and tag styles regardless of order", () => {
+    expect(parseZalouserTextStyles("**{red}x{/red}** {red}**y**{/red}")).toEqual({
+      text: "x y",
+      styles: [
+        { start: 0, len: 1, st: TextStyle.Bold },
+        { start: 0, len: 1, st: TextStyle.Red },
+        { start: 2, len: 1, st: TextStyle.Red },
+        { start: 2, len: 1, st: TextStyle.Bold },
+      ],
+    });
+  });
+
+  it("treats small text tags as normal text", () => {
+    expect(parseZalouserTextStyles("{small}tiny{/small}")).toEqual({
+      text: "tiny",
+      styles: [],
+    });
+  });
+
+  it("keeps escaped markers literal", () => {
+    expect(parseZalouserTextStyles("\\*literal\\* \\{underline}tag{/underline}")).toEqual({
+      text: "*literal* {underline}tag{/underline}",
+      styles: [],
+    });
+  });
+
+  it("keeps indented code blocks literal", () => {
+    expect(parseZalouserTextStyles("    *cmd*")).toEqual({
+      text: "\u00A0\u00A0\u00A0\u00A0*cmd*",
+      styles: [],
+    });
+  });
+});
diff --git a/extensions/zalouser/src/text-styles.ts b/extensions/zalouser/src/text-styles.ts
new file mode 100644
index 00000000000..cdfe8b492b5
--- /dev/null
+++ b/extensions/zalouser/src/text-styles.ts
@@ -0,0 +1,537 @@
+import { TextStyle, type Style } from "./zca-client.js";
+
+type InlineStyle = (typeof TextStyle)[keyof typeof TextStyle];
+
+type LineStyle = {
+  lineIndex: number;
+  style: InlineStyle;
+  indentSize?: number;
+};
+
+type Segment = {
+  text: string;
+  styles: InlineStyle[];
+};
+
+type InlineMarker = {
+  pattern: RegExp;
+  extractText: (match: RegExpExecArray) => string;
+  resolveStyles?: (match: RegExpExecArray) => InlineStyle[];
+  literal?: boolean;
+};
+
+type ResolvedInlineMatch = {
+  match: RegExpExecArray;
+  marker: InlineMarker;
+  styles: InlineStyle[];
+  text: string;
+  priority: number;
+};
+
+type FenceMarker = {
+  char: "`" | "~";
+  length: number;
+  indent: number;
+};
+
+type ActiveFence = FenceMarker & {
+  quoteIndent: number;
+};
+
+const TAG_STYLE_MAP: Record<string, InlineStyle | null> = {
+  red: TextStyle.Red,
+  orange: TextStyle.Orange,
+  yellow: TextStyle.Yellow,
+  green: TextStyle.Green,
+  small: null,
+  big: TextStyle.Big,
+  underline: TextStyle.Underline,
+};
+
+const INLINE_MARKERS: InlineMarker[] = [
+  {
+    pattern: /`([^`\n]+)`/g,
+    extractText: (match) => match[0],
+    literal: true,
+  },
+  {
+    pattern: /\\([*_~#\\{}>+\-`])/g,
+    extractText: (match) => match[1],
+    literal: true,
+  },
+  {
+    pattern: new RegExp(`\\{(${Object.keys(TAG_STYLE_MAP).join("|")})\\}(.+?)\\{/\\1\\}`, "g"),
+    extractText: (match) => match[2],
+    resolveStyles: (match) => {
+      const style = TAG_STYLE_MAP[match[1]];
+      return style ? [style] : [];
+    },
+  },
+  {
+    pattern: /(?<!\*)\*\*\*(?=\S)([^\n]*?\S)(?<!\*)\*\*\*(?!\*)/g,
+    extractText: (match) => match[1],
+    resolveStyles: () => [TextStyle.Bold, TextStyle.Italic],
+  },
+  {
+    pattern: /(?<!\*)\*\*(?![\s*])([^\n]*?\S)(?<!\*)\*\*(?!\*)/g,
+    extractText: (match) => match[1],
+    resolveStyles: () => [TextStyle.Bold],
+  },
+  {
+    pattern: /(?<![\w_])__(?![\s_])([^\n]*?\S)(?<!_)__(?![\w_])/g,
+    extractText: (match) => match[1],
+    resolveStyles: () => [TextStyle.Bold],
+  },
+  {
+    pattern: /(?<!~)~~(?=\S)([^\n]*?\S)(?<!~)~~(?!~)/g,
+    extractText: (match) => match[1],
+    resolveStyles: () => [TextStyle.StrikeThrough],
+  },
+  {
+    pattern: /(?<!\*)\*(?![\s*])([^\n]*?\S)(?<!\*)\*(?!\*)/g,
+    extractText: (match) => match[1],
+    resolveStyles: () => [TextStyle.Italic],
+  },
+  {
+    pattern: /(?<![\w_])_(?![\s_])([^\n]*?\S)(?<!_)_(?![\w_])/g,
+    extractText: (match) => match[1],
+    resolveStyles: () => [TextStyle.Italic],
+  },
+];
+
+export function parseZalouserTextStyles(input: string): { text: string; styles: Style[] } {
+  const allStyles: Style[] = [];
+
+  const escapeMap: string[] = [];
+  const lines = input.replace(/\r\n?/g, "\n").split("\n");
+  const lineStyles: LineStyle[] = [];
+  const processedLines: string[] = [];
+  let activeFence: ActiveFence | null = null;
+
+  for (let lineIndex = 0; lineIndex < lines.length; lineIndex += 1) {
+    const rawLine = lines[lineIndex];
+    const { text: unquotedLine, indent: baseIndent } = stripQuotePrefix(rawLine);
+
+    if (activeFence) {
+      const codeLine =
+        activeFence.quoteIndent > 0
+          ? stripQuotePrefix(rawLine, activeFence.quoteIndent).text
+          : rawLine;
+      if (isClosingFence(codeLine, activeFence)) {
+        activeFence = null;
+        continue;
+      }
+      processedLines.push(
+        escapeLiteralText(
+          normalizeCodeBlockLeadingWhitespace(stripCodeFenceIndent(codeLine, activeFence.indent)),
+          escapeMap,
+        ),
+      );
+      continue;
+    }
+
+    let line = unquotedLine;
+    const openingFence = resolveOpeningFence(rawLine);
+    if (openingFence) {
+      const fenceLine = openingFence.quoteIndent > 0 ? unquotedLine : rawLine;
+      if (!hasClosingFence(lines, lineIndex + 1, openingFence)) {
+        processedLines.push(escapeLiteralText(fenceLine, escapeMap));
+        activeFence = openingFence;
+        continue;
+      }
+      activeFence = openingFence;
+      continue;
+    }
+
+    const outputLineIndex = processedLines.length;
+    if (isIndentedCodeBlockLine(line)) {
+      if (baseIndent > 0) {
+        lineStyles.push({
+          lineIndex: outputLineIndex,
+          style: TextStyle.Indent,
+          indentSize: baseIndent,
+        });
+      }
+      processedLines.push(escapeLiteralText(normalizeCodeBlockLeadingWhitespace(line), escapeMap));
+      continue;
+    }
+
+    const { text: markdownLine, size: markdownPadding } = stripOptionalMarkdownPadding(line);
+
+    const headingMatch = markdownLine.match(/^(#{1,4})\s(.*)$/);
+    if (headingMatch) {
+      const depth = headingMatch[1].length;
+      lineStyles.push({ lineIndex: outputLineIndex, style: TextStyle.Bold });
+      if (depth === 1) {
+        lineStyles.push({ lineIndex: outputLineIndex, style: TextStyle.Big });
+      }
+      if (baseIndent > 0) {
+        lineStyles.push({
+          lineIndex: outputLineIndex,
+          style: TextStyle.Indent,
+          indentSize: baseIndent,
+        });
+      }
+      processedLines.push(headingMatch[2]);
+      continue;
+    }
+
+    const indentMatch = markdownLine.match(/^(\s+)(.*)$/);
+    let indentLevel = 0;
+    let content = markdownLine;
+    if (indentMatch) {
+      indentLevel = clampIndent(indentMatch[1].length);
+      content = indentMatch[2];
+    }
+    const totalIndent = Math.min(5, baseIndent + indentLevel);
+
+    if (/^[-*+]\s\[[ xX]\]\s/.test(content)) {
+      if (totalIndent > 0) {
+        lineStyles.push({
+          lineIndex: outputLineIndex,
+          style: TextStyle.Indent,
+          indentSize: totalIndent,
+        });
+      }
+      processedLines.push(content);
+      continue;
+    }
+
+    const orderedListMatch = content.match(/^(\d+)\.\s(.*)$/);
+    if (orderedListMatch) {
+      if (totalIndent > 0) {
+        lineStyles.push({
+          lineIndex: outputLineIndex,
+          style: TextStyle.Indent,
+          indentSize: totalIndent,
+        });
+      }
+      lineStyles.push({ lineIndex: outputLineIndex, style: TextStyle.OrderedList });
+      processedLines.push(orderedListMatch[2]);
+      continue;
+    }
+
+    const unorderedListMatch = content.match(/^[-*+]\s(.*)$/);
+    if (unorderedListMatch) {
+      if (totalIndent > 0) {
+        lineStyles.push({
+          lineIndex: outputLineIndex,
+          style: TextStyle.Indent,
+          indentSize: totalIndent,
+        });
+      }
+      lineStyles.push({ lineIndex: outputLineIndex, style: TextStyle.UnorderedList });
+      processedLines.push(unorderedListMatch[1]);
+      continue;
+    }
+
+    if (markdownPadding > 0) {
+      if (baseIndent > 0) {
+        lineStyles.push({
+          lineIndex: outputLineIndex,
+          style: TextStyle.Indent,
+          indentSize: baseIndent,
+        });
+      }
+      processedLines.push(line);
+      continue;
+    }
+
+    if (totalIndent > 0) {
+      lineStyles.push({
+        lineIndex: outputLineIndex,
+        style: TextStyle.Indent,
+        indentSize: totalIndent,
+      });
+      processedLines.push(content);
+      continue;
+    }
+
+    processedLines.push(line);
+  }
+
+  const segments = parseInlineSegments(processedLines.join("\n"));
+
+  let plainText = "";
+  for (const segment of segments) {
+    const start = plainText.length;
+    plainText += segment.text;
+    for (const style of segment.styles) {
+      allStyles.push({ start, len: segment.text.length, st: style } as Style);
+    }
+  }
+
+  if (escapeMap.length > 0) {
+    const escapeRegex = /\x01(\d+)\x02/g;
+    const shifts: Array<{ pos: number; delta: number }> = [];
+    let cumulativeDelta = 0;
+
+    for (const match of plainText.matchAll(escapeRegex)) {
+      const escapeIndex = Number.parseInt(match[1], 10);
+      cumulativeDelta += match[0].length - escapeMap[escapeIndex].length;
+      shifts.push({ pos: (match.index ?? 0) + match[0].length, delta: cumulativeDelta });
+    }
+
+    for (const style of allStyles) {
+      let startDelta = 0;
+      let endDelta = 0;
+      const end = style.start + style.len;
+      for (const shift of shifts) {
+        if (shift.pos <= style.start) {
+          startDelta = shift.delta;
+        }
+        if (shift.pos <= end) {
+          endDelta = shift.delta;
+        }
+      }
+      style.start -= startDelta;
+      style.len -= endDelta - startDelta;
+    }
+
+    plainText = plainText.replace(
+      escapeRegex,
+      (_match, index) => escapeMap[Number.parseInt(index, 10)],
+    );
+  }
+
+  const finalLines = plainText.split("\n");
+  let offset = 0;
+  for (let lineIndex = 0; lineIndex < finalLines.length; lineIndex += 1) {
+    const lineLength = finalLines[lineIndex].length;
+    if (lineLength > 0) {
+      for (const lineStyle of lineStyles) {
+        if (lineStyle.lineIndex !== lineIndex) {
+          continue;
+        }
+
+        if (lineStyle.style === TextStyle.Indent) {
+          allStyles.push({
+            start: offset,
+            len: lineLength,
+            st: TextStyle.Indent,
+            indentSize: lineStyle.indentSize,
+          });
+        } else {
+          allStyles.push({ start: offset, len: lineLength, st: lineStyle.style } as Style);
+        }
+      }
+    }
+    offset += lineLength + 1;
+  }
+
+  return { text: plainText, styles: allStyles };
+}
+
+function clampIndent(spaceCount: number): number {
+  return Math.min(5, Math.max(1, Math.floor(spaceCount / 2)));
+}
+
+function stripOptionalMarkdownPadding(line: string): { text: string; size: number } {
+  const match = line.match(/^( {1,3})(?=\S)/);
+  if (!match) {
+    return { text: line, size: 0 };
+  }
+  return {
+    text: line.slice(match[1].length),
+    size: match[1].length,
+  };
+}
+
+function hasClosingFence(lines: string[], startIndex: number, fence: ActiveFence): boolean {
+  for (let index = startIndex; index < lines.length; index += 1) {
+    const candidate =
+      fence.quoteIndent > 0 ? stripQuotePrefix(lines[index], fence.quoteIndent).text : lines[index];
+    if (isClosingFence(candidate, fence)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+function resolveOpeningFence(line: string): ActiveFence | null {
+  const directFence = parseFenceMarker(line);
+  if (directFence) {
+    return { ...directFence, quoteIndent: 0 };
+  }
+
+  const quoted = stripQuotePrefix(line);
+  if (quoted.indent === 0) {
+    return null;
+  }
+
+  const quotedFence = parseFenceMarker(quoted.text);
+  if (!quotedFence) {
+    return null;
+  }
+
+  return {
+    ...quotedFence,
+    quoteIndent: quoted.indent,
+  };
+}
+
+function stripQuotePrefix(
+  line: string,
+  maxDepth = Number.POSITIVE_INFINITY,
+): { text: string; indent: number } {
+  let cursor = 0;
+  while (cursor < line.length && cursor < 3 && line[cursor] === " ") {
+    cursor += 1;
+  }
+
+  let removedDepth = 0;
+  let consumedCursor = cursor;
+  while (removedDepth < maxDepth && consumedCursor < line.length && line[consumedCursor] === ">") {
+    removedDepth += 1;
+    consumedCursor += 1;
+    if (line[consumedCursor] === " ") {
+      consumedCursor += 1;
+    }
+  }
+
+  if (removedDepth === 0) {
+    return { text: line, indent: 0 };
+  }
+
+  return {
+    text: line.slice(consumedCursor),
+    indent: Math.min(5, removedDepth),
+  };
+}
+
+function parseFenceMarker(line: string): FenceMarker | null {
+  const match = line.match(/^([ ]{0,3})(`{3,}|~{3,})(.*)$/);
+  if (!match) {
+    return null;
+  }
+
+  const marker = match[2];
+  const char = marker[0];
+  if (char !== "`" && char !== "~") {
+    return null;
+  }
+
+  return {
+    char,
+    length: marker.length,
+    indent: match[1].length,
+  };
+}
+
+function isClosingFence(line: string, fence: FenceMarker): boolean {
+  const match = line.match(/^([ ]{0,3})(`{3,}|~{3,})[ \t]*$/);
+  if (!match) {
+    return false;
+  }
+  return match[2][0] === fence.char && match[2].length >= fence.length;
+}
+
+function escapeLiteralText(input: string, escapeMap: string[]): string {
+  return input.replace(/[\\*_~{}`]/g, (ch) => {
+    const index = escapeMap.length;
+    escapeMap.push(ch);
+    return `\x01${index}\x02`;
+  });
+}
+
+function parseInlineSegments(text: string, inheritedStyles: InlineStyle[] = []): Segment[] {
+  const segments: Segment[] = [];
+  let cursor = 0;
+
+  while (cursor < text.length) {
+    const nextMatch = findNextInlineMatch(text, cursor);
+    if (!nextMatch) {
+      pushSegment(segments, text.slice(cursor), inheritedStyles);
+      break;
+    }
+
+    if (nextMatch.match.index > cursor) {
+      pushSegment(segments, text.slice(cursor, nextMatch.match.index), inheritedStyles);
+    }
+
+    const combinedStyles = [...inheritedStyles, ...nextMatch.styles];
+    if (nextMatch.marker.literal) {
+      pushSegment(segments, nextMatch.text, combinedStyles);
+    } else {
+      segments.push(...parseInlineSegments(nextMatch.text, combinedStyles));
+    }
+
+    cursor = nextMatch.match.index + nextMatch.match[0].length;
+  }
+
+  return segments;
+}
+
+function findNextInlineMatch(text: string, startIndex: number): ResolvedInlineMatch | null {
+  let bestMatch: ResolvedInlineMatch | null = null;
+
+  for (const [priority, marker] of INLINE_MARKERS.entries()) {
+    const regex = new RegExp(marker.pattern.source, marker.pattern.flags);
+    regex.lastIndex = startIndex;
+    const match = regex.exec(text);
+    if (!match) {
+      continue;
+    }
+
+    if (
+      bestMatch &&
+      (match.index > bestMatch.match.index ||
+        (match.index === bestMatch.match.index && priority > bestMatch.priority))
+    ) {
+      continue;
+    }
+
+    bestMatch = {
+      match,
+      marker,
+      text: marker.extractText(match),
+      styles: marker.resolveStyles?.(match) ?? [],
+      priority,
+    };
+  }
+
+  return bestMatch;
+}
+
+function pushSegment(segments: Segment[], text: string, styles: InlineStyle[]): void {
+  if (!text) {
+    return;
+  }
+
+  const lastSegment = segments.at(-1);
+  if (lastSegment && sameStyles(lastSegment.styles, styles)) {
+    lastSegment.text += text;
+    return;
+  }
+
+  segments.push({
+    text,
+    styles: [...styles],
+  });
+}
+
+function sameStyles(left: InlineStyle[], right: InlineStyle[]): boolean {
+  return left.length === right.length && left.every((style, index) => style === right[index]);
+}
+
+function normalizeCodeBlockLeadingWhitespace(line: string): string {
+  return line.replace(/^[ \t]+/, (leadingWhitespace) =>
+    leadingWhitespace.replace(/\t/g, "\u00A0\u00A0\u00A0\u00A0").replace(/ /g, "\u00A0"),
+  );
+}
+
+function isIndentedCodeBlockLine(line: string): boolean {
+  return /^(?: {4,}|\t)/.test(line);
+}
+
+function stripCodeFenceIndent(line: string, indent: number): string {
+  let consumed = 0;
+  let cursor = 0;
+
+  while (cursor < line.length && consumed < indent && line[cursor] === " ") {
+    cursor += 1;
+    consumed += 1;
+  }
+
+  return line.slice(cursor);
+}
diff --git a/extensions/zalouser/src/types.ts b/extensions/zalouser/src/types.ts
index d704a1b3f78..e6343b1f6bd 100644
--- a/extensions/zalouser/src/types.ts
+++ b/extensions/zalouser/src/types.ts
@@ -1,3 +1,5 @@
+import type { Style } from "./zca-client.js";
+
 export type ZcaFriend = {
   userId: string;
   displayName: string;
@@ -59,6 +61,10 @@ export type ZaloSendOptions = {
   caption?: string;
   isGroup?: boolean;
   mediaLocalRoots?: readonly string[];
+  textMode?: "markdown" | "plain";
+  textChunkMode?: "length" | "newline";
+  textChunkLimit?: number;
+  textStyles?: Style[];
 };
 
 export type ZaloSendResult = {
diff --git a/extensions/zalouser/src/zalo-js.ts b/extensions/zalouser/src/zalo-js.ts
index 25d263b7d6a..0e2d744232f 100644
--- a/extensions/zalouser/src/zalo-js.ts
+++ b/extensions/zalouser/src/zalo-js.ts
@@ -20,6 +20,7 @@ import type {
 } from "./types.js";
 import {
   LoginQRCallbackEventType,
+  TextStyle,
   ThreadType,
   Zalo,
   type API,
@@ -136,6 +137,39 @@ function toErrorMessage(error: unknown): string {
   return String(error);
 }
 
+function clampTextStyles(
+  text: string,
+  styles?: ZaloSendOptions["textStyles"],
+): ZaloSendOptions["textStyles"] {
+  if (!styles || styles.length === 0) {
+    return undefined;
+  }
+  const maxLength = text.length;
+  const clamped = styles
+    .map((style) => {
+      const start = Math.max(0, Math.min(style.start, maxLength));
+      const end = Math.min(style.start + style.len, maxLength);
+      if (end <= start) {
+        return null;
+      }
+      if (style.st === TextStyle.Indent) {
+        return {
+          start,
+          len: end - start,
+          st: style.st,
+          indentSize: style.indentSize,
+        };
+      }
+      return {
+        start,
+        len: end - start,
+        st: style.st,
+      };
+    })
+    .filter((style): style is NonNullable<typeof style> => style !== null);
+  return clamped.length > 0 ? clamped : undefined;
+}
+
 function toNumberId(value: unknown): string {
   if (typeof value === "number" && Number.isFinite(value)) {
     return String(Math.trunc(value));
@@ -1018,11 +1052,16 @@ export async function sendZaloTextMessage(
         kind: media.kind,
       });
       const payloadText = (text || options.caption || "").slice(0, 2000);
+      const textStyles = clampTextStyles(payloadText, options.textStyles);
 
       if (media.kind === "audio") {
         let textMessageId: string | undefined;
         if (payloadText) {
-          const textResponse = await api.sendMessage(payloadText, trimmedThreadId, type);
+          const textResponse = await api.sendMessage(
+            textStyles ? { msg: payloadText, styles: textStyles } : payloadText,
+            trimmedThreadId,
+            type,
+          );
           textMessageId = extractSendMessageId(textResponse);
         }
 
@@ -1055,6 +1094,7 @@ export async function sendZaloTextMessage(
       const response = await api.sendMessage(
         {
           msg: payloadText,
+          ...(textStyles ? { styles: textStyles } : {}),
           attachments: [
             {
               data: media.buffer,
@@ -1071,7 +1111,13 @@ export async function sendZaloTextMessage(
       return { ok: true, messageId: extractSendMessageId(response) };
     }
 
-    const response = await api.sendMessage(text.slice(0, 2000), trimmedThreadId, type);
+    const payloadText = text.slice(0, 2000);
+    const textStyles = clampTextStyles(payloadText, options.textStyles);
+    const response = await api.sendMessage(
+      textStyles ? { msg: payloadText, styles: textStyles } : payloadText,
+      trimmedThreadId,
+      type,
+    );
     return { ok: true, messageId: extractSendMessageId(response) };
   } catch (error) {
     return { ok: false, error: toErrorMessage(error) };
diff --git a/extensions/zalouser/src/zca-client.ts b/extensions/zalouser/src/zca-client.ts
index 57172eef64d..00a1c8c1be0 100644
--- a/extensions/zalouser/src/zca-client.ts
+++ b/extensions/zalouser/src/zca-client.ts
@@ -28,6 +28,39 @@ export const Reactions = ReactionsRuntime as Record<string, string> & {
   NONE: string;
 };
 
+// Mirror zca-js sendMessage style constants locally because the package root
+// typing surface does not consistently expose TextStyle/Style to tsgo.
+export const TextStyle = {
+  Bold: "b",
+  Italic: "i",
+  Underline: "u",
+  StrikeThrough: "s",
+  Red: "c_db342e",
+  Orange: "c_f27806",
+  Yellow: "c_f7b503",
+  Green: "c_15a85f",
+  Small: "f_13",
+  Big: "f_18",
+  UnorderedList: "lst_1",
+  OrderedList: "lst_2",
+  Indent: "ind_$",
+} as const;
+
+type TextStyleValue = (typeof TextStyle)[keyof typeof TextStyle];
+
+export type Style =
+  | {
+      start: number;
+      len: number;
+      st: Exclude<TextStyleValue, typeof TextStyle.Indent>;
+    }
+  | {
+      start: number;
+      len: number;
+      st: typeof TextStyle.Indent;
+      indentSize?: number;
+    };
+
 export type Credentials = {
   imei: string;
   cookie: unknown;