diff --git a/packages/web-api/src/WebClient.spec.ts b/packages/web-api/src/WebClient.spec.ts
index 15dcb3fbe..c0c326297 100644
--- a/packages/web-api/src/WebClient.spec.ts
+++ b/packages/web-api/src/WebClient.spec.ts
@@ -1228,7 +1228,11 @@ describe('WebClient', () => {
           ok: true,
           ts: '123.123',
         })
-        .post('/api/chat.stopStream', { channel: 'C0123456789', ts: '123.123', markdown_text: 'nice!' })
+        .post('/api/chat.stopStream', {
+          channel: 'C0123456789',
+          ts: '123.123',
+          chunks: JSON.stringify([{ type: 'markdown_text', text: 'nice!' }]),
+        })
         .reply(200, {
           ok: true,
         });
@@ -1279,7 +1283,7 @@ describe('WebClient', () => {
       const scope = nock('https://slack.com')
         .post('/api/chat.startStream', {
           channel: 'C0123456789',
-          markdown_text: '**this messag',
+          chunks: JSON.stringify([{ type: 'markdown_text', text: '**this messag' }]),
           recipient_team_id: 'T0123456789',
           recipient_user_id: 'U0123456789',
           thread_ts: '123.000',
@@ -1290,7 +1294,7 @@ describe('WebClient', () => {
         })
         .post('/api/chat.appendStream', {
           channel: 'C0123456789',
-          markdown_text: 'e is bold!',
+          chunks: JSON.stringify([{ type: 'markdown_text', text: 'e is bold!' }]),
           token: 'xoxb-updated-1',
           ts: '123.123',
         })
@@ -1300,7 +1304,7 @@ describe('WebClient', () => {
         .post('/api/chat.stopStream', {
           blocks: JSON.stringify([contextActionsBlock]),
           channel: 'C0123456789',
-          markdown_text: '**',
+          chunks: JSON.stringify([{ type: 'markdown_text', text: '**' }]),
           token: 'xoxb-updated-2',
           ts: '123.123',
         })
@@ -1370,7 +1374,11 @@ describe('WebClient', () => {
           ok: true,
           ts: '123.123',
         })
-        .post('/api/chat.stopStream', { channel: 'C0123456789', ts: '123.123', markdown_text: 'nice!' })
+        .post('/api/chat.stopStream', {
+          channel: 'C0123456789',
+          ts: '123.123',
+          chunks: JSON.stringify([{ type: 'markdown_text', text: 'nice!' }]),
+        })
         .reply(200, {
           ok: true,
         });
diff --git a/packages/web-api/src/chat-stream.ts b/packages/web-api/src/chat-stream.ts
index 695100b14..779aee80d 100644
--- a/packages/web-api/src/chat-stream.ts
+++ b/packages/web-api/src/chat-stream.ts
@@ -1,4 +1,5 @@
 import type { Logger } from '@slack/logger';
+import type { AnyChunk } from '@slack/types';
 import type { ChatAppendStreamArguments, ChatStartStreamArguments, ChatStopStreamArguments } from './types/request';
 import type { ChatAppendStreamResponse, ChatStartStreamResponse, ChatStopStreamResponse } from './types/response';
 import type WebClient from './WebClient';
@@ -89,8 +90,11 @@ export class ChatStreamer {
     if (args.token) {
       this.token = args.token;
     }
-    this.buffer += args.markdown_text;
-    if (this.buffer.length >= this.options.buffer_size) {
+    if (args?.markdown_text) {
+      this.buffer += args.markdown_text;
+      args.markdown_text = undefined;
+    }
+    if (this.buffer.length >= this.options.buffer_size || args?.chunks) {
       return await this.flushBuffer(args);
     }
     const details = {
@@ -132,6 +136,7 @@ export class ChatStreamer {
     }
     if (args?.markdown_text) {
       this.buffer += args.markdown_text;
+      args.markdown_text = undefined;
     }
     if (!this.streamTs) {
       const response = await this.client.chat.startStream({
@@ -144,12 +149,25 @@ export class ChatStreamer {
       this.streamTs = response.ts;
       this.state = 'in_progress';
     }
+
+    const flushings: AnyChunk[] = [];
+
+    if (this.buffer.length > 0) {
+      flushings.push({
+        type: 'markdown_text',
+        text: this.buffer,
+      });
+    }
+    if (args?.chunks) {
+      flushings.push(...args.chunks);
+    }
+
     const response = await this.client.chat.stopStream({
       token: this.token,
       channel: this.streamArgs.channel,
       ts: this.streamTs,
+      chunks: flushings,
       ...args,
-      markdown_text: this.buffer,
     });
     this.state = 'completed';
     return response;
@@ -158,12 +176,24 @@ export class ChatStreamer {
   private async flushBuffer(
     args: Omit<ChatStartStreamArguments | ChatAppendStreamArguments, 'channel' | 'ts'>,
   ): Promise<ChatStartStreamResponse | ChatAppendStreamResponse> {
+    const flushings: AnyChunk[] = [];
+
+    if (this.buffer.length > 0) {
+      flushings.push({
+        type: 'markdown_text',
+        text: this.buffer,
+      });
+    }
+    if (args?.chunks) {
+      flushings.push(...args.chunks);
+    }
+
     if (!this.streamTs) {
       const response = await this.client.chat.startStream({
         ...this.streamArgs,
         token: this.token,
+        chunks: flushings,
         ...args,
-        markdown_text: this.buffer,
       });
       this.buffer = '';
       this.streamTs = response.ts;
@@ -174,8 +204,8 @@ export class ChatStreamer {
       token: this.token,
       channel: this.streamArgs.channel,
       ts: this.streamTs,
+      chunks: flushings,
       ...args,
-      markdown_text: this.buffer,
     });
     this.buffer = '';
     return response;
diff --git a/packages/web-api/test/types/methods/chat.test-d.ts b/packages/web-api/test/types/methods/chat.test-d.ts
index 419ec7486..a73e40249 100644
--- a/packages/web-api/test/types/methods/chat.test-d.ts
+++ b/packages/web-api/test/types/methods/chat.test-d.ts
@@ -676,7 +676,23 @@ expectAssignable<Parameters<typeof web.chat.startStream>>([
   {
     channel: 'C1234',
     thread_ts: '1234.56',
-    markdown_text: 'hello',
+    chunks: [
+      {
+        type: 'markdown_text',
+        text: 'Hello world',
+      },
+      {
+        type: 'plan_update',
+        title: 'Analyzing request',
+      },
+      {
+        type: 'task_update',
+        id: 'task-1',
+        title: 'Processing request',
+        status: 'in_progress',
+        details: 'Working on it...',
+      },
+    ],
     recipient_team_id: 'T1234',
     recipient_user_id: 'U1234',
   },