diff --git a/packages/types/src/chunk.ts b/packages/types/src/chunk.ts
new file mode 100644
index 000000000..6acddb06b
--- /dev/null
+++ b/packages/types/src/chunk.ts
@@ -0,0 +1,106 @@
+/**
+ * Base interface for streaming message chunks.
+ * https://docs.slack.dev/messaging/sending-and-scheduling-messages#text-streaming
+ */
+export interface Chunk {
+  type: string;
+}
+
+/**
+ * Used for streaming text content with markdown formatting support.
+ * https://docs.slack.dev/messaging/sending-and-scheduling-messages#text-streaming
+ */
+export interface MarkdownTextChunk extends Chunk {
+  type: 'markdown_text';
+  text: string;
+}
+
+/**
+ * URL source for task update chunks.
+ */
+export interface URLSource {
+  type: 'url';
+  url: string;
+  text: string;
+  icon_url?: string;
+}
+
+/**
+ * An updated title of plans for task and tool calls.
+ * https://docs.slack.dev/messaging/sending-and-scheduling-messages#text-streaming
+ */
+export interface PlanUpdateChunk extends Chunk {
+  type: 'plan_update';
+  title: string;
+}
+
+/**
+ * Used for displaying tool execution progress in a timeline-style UI.
+ * https://docs.slack.dev/messaging/sending-and-scheduling-messages#text-streaming
+ */
+export interface TaskUpdateChunk extends Chunk {
+  type: 'task_update';
+  id: string;
+  title: string;
+  status: 'pending' | 'in_progress' | 'complete' | 'error';
+  details?: string;
+  output?: string;
+  sources?: URLSource[];
+}
+
+/**
+ * Union type of all possible chunk types
+ */
+export type AnyChunk = MarkdownTextChunk | PlanUpdateChunk | TaskUpdateChunk;
+
+/**
+ * Parse a chunk object and return the appropriate typed chunk.
+ * Returns null if the chunk is invalid or unknown.
+ */
+export function parseChunk(chunk: unknown): AnyChunk | null {
+  if (!chunk || typeof chunk !== 'object') {
+    return null;
+  }
+
+  const chunkObj = chunk as Record<string, unknown>;
+
+  if (!('type' in chunkObj) || typeof chunkObj.type !== 'string') {
+    console.warn('Unknown chunk detected and skipped (missing type)', chunk);
+    return null;
+  }
+
+  const { type } = chunkObj;
+
+  if (type === 'markdown_text') {
+    if (typeof chunkObj.text === 'string') {
+      return chunkObj as unknown as MarkdownTextChunk;
+    }
+    console.warn('Invalid MarkdownTextChunk (missing text property)', chunk);
+    return null;
+  }
+
+  if(type === 'plan_update') {
+    if (typeof chunkObj.title === 'string') {
+      return chunkObj as unknown as PlanUpdateChunk;
+    }
+    console.warn('Invalid PlanUpdateChunk (missing title property)', chunk);
+    return null;
+  }
+
+  if (type === 'task_update') {
+    const taskChunk = chunkObj as Partial<TaskUpdateChunk>;
+    if (
+      typeof taskChunk.id === 'string' &&
+      typeof taskChunk.title === 'string' &&
+      typeof taskChunk.status === 'string' &&
+      ['pending', 'in_progress', 'complete', 'error'].includes(taskChunk.status)
+    ) {
+      return chunkObj as unknown as TaskUpdateChunk;
+    }
+    console.warn('Invalid TaskUpdateChunk (missing required properties)', chunk);
+    return null;
+  }
+
+  console.warn(`Unknown chunk type detected and skipped: ${type}`, chunk);
+  return null;
+}
diff --git a/packages/types/src/index.ts b/packages/types/src/index.ts
index 9992536de..2740a2290 100644
--- a/packages/types/src/index.ts
+++ b/packages/types/src/index.ts
@@ -3,6 +3,7 @@ export * from './block-kit/blocks';
 export * from './block-kit/composition-objects';
 export * from './block-kit/extensions';
 export * from './calls';
+export * from './chunk';
 export * from './dialog';
 export * from './events';
 export * from './message-attachments';
diff --git a/packages/web-api/package.json b/packages/web-api/package.json
index 36ffc23bf..c41da4903 100644
--- a/packages/web-api/package.json
+++ b/packages/web-api/package.json
@@ -49,7 +49,7 @@
   },
   "dependencies": {
     "@slack/logger": "^4.0.0",
-    "@slack/types": "^2.18.0",
+    "@slack/types": "^2.19.0",
     "@types/node": ">=18.0.0",
     "@types/retry": "0.12.0",
     "axios": "^1.11.0",
diff --git a/packages/web-api/src/types/request/chat.ts b/packages/web-api/src/types/request/chat.ts
index 7734d7a7f..9c5c2292c 100644
--- a/packages/web-api/src/types/request/chat.ts
+++ b/packages/web-api/src/types/request/chat.ts
@@ -1,4 +1,5 @@
 import type {
+  AnyChunk,
   Block, // TODO: these will be combined into one in a new types release
   EntityMetadata,
   KnownBlock,
@@ -168,7 +169,13 @@ export interface Unfurls {
   unfurl_media?: boolean;
 }
 
-export interface ChatAppendStreamArguments extends TokenOverridable, ChannelAndTS, MarkdownText {}
+export interface ChatAppendStreamArguments extends TokenOverridable, ChannelAndTS, Partial<MarkdownText> {
+  /**
+   * @description An array of {@link https://docs.slack.dev/messaging/sending-and-scheduling-messages#text-streaming chunk objects} to append to the stream.
+   * Either `markdown_text` or `chunks` is required.
+   */
+  chunks?: AnyChunk[];
+}
 
 // https://docs.slack.dev/reference/methods/chat.delete
 export interface ChatDeleteArguments extends ChannelAndTS, AsUser, TokenOverridable {}
@@ -233,6 +240,11 @@ export type ChatScheduledMessagesListArguments = OptionalArgument<
 >;
 
 export interface ChatStartStreamArguments extends TokenOverridable, Channel, Partial<MarkdownText>, ThreadTS {
+  /**
+   * @description An array of {@link https://docs.slack.dev/messaging/sending-and-scheduling-messages#text-streaming chunk objects} to start the stream with.
+   * Either `markdown_text` or `chunks` is required.
+   */
+  chunks?: AnyChunk[];
   /**
    * @description The ID of the team that is associated with `recipient_user_id`.
    * This is required when starting a streaming conversation outside of a DM.
@@ -249,6 +261,10 @@ export type ChatStopStreamArguments = TokenOverridable &
   ChannelAndTS &
   Partial<MarkdownText> &
   Partial<Metadata> & {
+    /**
+     * @description An array of {@link https://docs.slack.dev/messaging/sending-and-scheduling-messages#text-streaming chunk objects} to finalize the stream with.
+     */
+    chunks?: AnyChunk[];
     /**
      * Block formatted elements will be appended to the end of the message.
      */
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 f1ec5f025..97ac7f59e 100644
--- a/packages/web-api/test/types/methods/chat.test-d.ts
+++ b/packages/web-api/test/types/methods/chat.test-d.ts
@@ -32,6 +32,30 @@ expectAssignable<Parameters<typeof web.chat.appendStream>>([
     markdown_text: 'hello',
   },
 ]);
+expectAssignable<Parameters<typeof web.chat.appendStream>>([
+  {
+    channel: 'C1234',
+    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...',
+      },
+    ],
+  },
+]);
 
 // chat.delete
 // -- sad path
@@ -631,11 +655,51 @@ expectAssignable<Parameters<typeof web.chat.startStream>>([
     markdown_text: 'hello',
   },
 ]);
+expectAssignable<Parameters<typeof web.chat.startStream>>([
+  {
+    channel: 'C1234',
+    thread_ts: '1234.56',
+    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...',
+      },
+    ],
+  },
+]);
 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',
   },
@@ -670,6 +734,30 @@ expectAssignable<Parameters<typeof web.chat.stopStream>>([
     blocks: [],
   },
 ]);
+expectAssignable<Parameters<typeof web.chat.stopStream>>([
+  {
+    channel: 'C1234',
+    ts: '1234.56',
+    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...',
+      },
+    ],
+    blocks: [],
+  },
+]);
 
 // chat.unfurl
 // -- sad path