diff --git a/packages/types/src/block-kit/block-elements.ts b/packages/types/src/block-kit/block-elements.ts
index 806561d7d..9525ab752 100644
--- a/packages/types/src/block-kit/block-elements.ts
+++ b/packages/types/src/block-kit/block-elements.ts
@@ -702,6 +702,33 @@ export interface URLInput extends Actionable, Dispatchable, Focusable, Placehold
   initial_value?: string;
 }
 
+/**
+ *  @description A URL source element to reference in a task card block.
+ *  @see {@link https://docs.slack.dev/reference/block-kit/block-elements/url-source-element}
+ */
+
+export interface URLSourceElement {
+  /**
+   * @description The type of element. In this case `type` is always `url`.
+   */
+  type: 'url';
+
+  /**
+   * @description The URL type source.
+   */
+  url: string;
+
+  /**
+   * @description Display text for the URL.
+   */
+  text: string;
+
+  /**
+   * @description Icon URL to display with the source.
+   */
+  icon_url?: string[];
+}
+
 /**
  * @description Allows users to run a {@link https://docs.slack.dev/tools/deno-slack-sdk/guides/creating-link-triggers/#workflow_buttons link trigger} with customizable inputs.
  * @see {@link https://docs.slack.dev/reference/block-kit/block-elements/workflow-button-element Workflow button element reference}.
diff --git a/packages/types/src/block-kit/blocks.ts b/packages/types/src/block-kit/blocks.ts
index 17d710acb..99b464683 100644
--- a/packages/types/src/block-kit/blocks.ts
+++ b/packages/types/src/block-kit/blocks.ts
@@ -22,6 +22,7 @@ import type {
   Select,
   Timepicker,
   URLInput,
+  URLSourceElement,
   WorkflowButton,
 } from './block-elements';
 import type {
@@ -64,6 +65,8 @@ export type KnownBlock =
   | RichTextBlock
   | SectionBlock
   | TableBlock
+  | TaskCardBlock
+  | PlanUpdateBlock
   | VideoBlock;
 
 /**
@@ -402,6 +405,73 @@ interface TableBlockColumnSettings {
   is_wrapped?: boolean;
 }
 
+/** 
+ * @description A discrete action or tool call.
+ * @see https://docs.slack.dev/reference/block-kit/blocks/task-card-block/
+*/
+export interface TaskCardBlock extends Block {
+  /**
+   * @description The type of element. In this case `type` is always `task_card`.
+   */
+  type: 'task_card';
+
+  /**
+   * @description ID for the task.
+   */
+  task_id: string;
+
+  /**
+   * @description Title of the task in plain text.
+   */
+  title: string;
+
+  /**
+   * @description Details of the task in the form of a single `rich_text` block.
+   */
+  details?: RichTextBlock | Record<string, unknown>;
+
+  /**
+   * @description Output of the task in the form of a single "rich_text" entity.
+   */
+  output?: RichTextBlock | Record<string, unknown>;
+
+  /**
+   * @description List of sources used to generate a response.
+   */
+  sources?: (URLSourceElement | Record<string, unknown>)[]
+
+  /**
+   * @description The state of a task. Either `pending`, `in_progress`, `complete`, or `error`.
+   */
+  status: 'pending' | 'in_progress' | 'complete' | 'error';
+}
+
+/**
+ * @description A collection of related tasks.
+ * @see https://docs.slack.dev/reference/block-kit/blocks/plan-block/
+ */
+export interface PlanUpdateBlock extends Block {
+  /**
+   * @description The type of block. In this case `type` is always `plan`.
+   */
+  type: 'plan';
+
+  /**
+   * @description ID for the plan.
+   */
+  plan_id: string;
+
+  /**
+   * @description Title of the plan in plain text.
+   */
+  title: string;
+
+  /**
+   * @description An array of tasks associated with this plan.
+   */
+  tasks?: (TaskCardBlock | Record<string, unknown>)[];
+}
+
 /**
  * @description Displays an embedded video player. A video block is designed to embed videos in all app surfaces (e.g.
  * link unfurls, messages, modals, App Home) — anywhere you can put blocks! To use the video block within your app, you
diff --git a/packages/types/src/chunk.ts b/packages/types/src/chunk.ts
new file mode 100644
index 000000000..a60007a33
--- /dev/null
+++ b/packages/types/src/chunk.ts
@@ -0,0 +1,97 @@
+import { URLSourceElement } from "./block-kit/block-elements";
+/**
+ * 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;
+}
+
+/**
+ * Used for updating the title of a plan.
+ * 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?: URLSourceElement[];
+}
+
+/**
+ * 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/chat-stream.ts b/packages/web-api/src/chat-stream.ts
index 695100b14..4db44b6a6 100644
--- a/packages/web-api/src/chat-stream.ts
+++ b/packages/web-api/src/chat-stream.ts
@@ -89,7 +89,14 @@ export class ChatStreamer {
     if (args.token) {
       this.token = args.token;
     }
-    this.buffer += args.markdown_text;
+  
+    if (args.chunks) {
+      return await this.flushBuffer(args);
+    }
+  
+    if (args.markdown_text) {
+      this.buffer += args.markdown_text;
+    }
     if (this.buffer.length >= this.options.buffer_size) {
       return await this.flushBuffer(args);
     }
@@ -144,12 +151,13 @@ export class ChatStreamer {
       this.streamTs = response.ts;
       this.state = 'in_progress';
     }
+    const finalArgs = args?.chunks ? args : { ...args, markdown_text: this.buffer };
+
     const response = await this.client.chat.stopStream({
       token: this.token,
       channel: this.streamArgs.channel,
       ts: this.streamTs,
-      ...args,
-      markdown_text: this.buffer,
+      ...finalArgs,
     });
     this.state = 'completed';
     return response;
@@ -158,12 +166,14 @@ export class ChatStreamer {
   private async flushBuffer(
     args: Omit<ChatStartStreamArguments | ChatAppendStreamArguments, 'channel' | 'ts'>,
   ): Promise<ChatStartStreamResponse | ChatAppendStreamResponse> {
+
+    const finalArgs = args.chunks ? args : { ...args, markdown_text: this.buffer };
+
     if (!this.streamTs) {
       const response = await this.client.chat.startStream({
         ...this.streamArgs,
         token: this.token,
-        ...args,
-        markdown_text: this.buffer,
+        ...finalArgs,
       });
       this.buffer = '';
       this.streamTs = response.ts;
@@ -174,8 +184,7 @@ export class ChatStreamer {
       token: this.token,
       channel: this.streamArgs.channel,
       ts: this.streamTs,
-      ...args,
-      markdown_text: this.buffer,
+      ...finalArgs,
     });
     this.buffer = '';
     return response;
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..5755f951c 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: 'Hello world',
+      },
+      {
+        type: 'task_update',
+        id: 'task-1',
+        title: 'Processing request',
+        status: 'in_progress',
+        details: 'Working on it...',
+      },
+    ],
+  },
+]);
 
 // chat.delete
 // -- sad path
@@ -475,6 +499,131 @@ function wideBooleanTest(b: boolean) {
 wideBooleanTest(true);
 wideBooleanTest(false);
 
+// TaskCardBlock with all properties
+expectAssignable<Parameters<typeof web.chat.postMessage>>([
+  {
+    channel: 'C1234',
+    text: 'fallback',
+    blocks: [
+      {
+        type: 'task_card',
+        task_id: '000',
+        title: 'Living life well...',
+        status: 'error',
+        details: {
+          type: 'rich_text',
+          elements: [
+            {
+              type: 'rich_text_section',
+              elements: [
+                {
+                  type: 'text',
+                  text: 'Dreamt of touching grass',
+                },
+              ],
+            },
+          ],
+        },
+        sources: [
+          {
+            type: 'url',
+            text: 'An online encyclopedia',
+            url: 'https://wikipedia.org',
+          },
+        ],
+        output: {
+          type: 'rich_text',
+          elements: [
+            {
+              type: 'rich_text_section',
+              elements: [
+                {
+                  type: 'text',
+                  text: 'Good things once happened',
+                },
+              ],
+            },
+          ],
+        },
+      },
+    ],
+  },
+]);
+
+// TaskCardBlock with minimal required properties
+expectAssignable<Parameters<typeof web.chat.postMessage>>([
+  {
+    channel: 'C1234',
+    text: 'fallback',
+    blocks: [
+      {
+        type: 'task_card',
+        task_id: 'task-123',
+        title: 'Simple task',
+        status: 'pending',
+      },
+    ],
+  },
+]);
+
+// PlanUpdateBlock with nested TaskCardBlocks
+expectAssignable<Parameters<typeof web.chat.postMessage>>([
+  {
+    channel: 'C1234',
+    text: 'fallback',
+    blocks: [
+      {
+        type: 'plan',
+        plan_id: 'plan-001',
+        title: 'My execution plan',
+        tasks: [
+          {
+            type: 'task_card',
+            task_id: 'task-1',
+            title: 'First task',
+            status: 'complete',
+          },
+          {
+            type: 'task_card',
+            task_id: 'task-2',
+            title: 'Second task',
+            status: 'in_progress',
+            details: {
+              type: 'rich_text',
+              elements: [
+                {
+                  type: 'rich_text_section',
+                  elements: [
+                    {
+                      type: 'text',
+                      text: 'Working on this...',
+                    },
+                  ],
+                },
+              ],
+            },
+          },
+        ],
+      },
+    ],
+  },
+]);
+
+// PlanUpdateBlock with minimal required properties
+expectAssignable<Parameters<typeof web.chat.postMessage>>([
+  {
+    channel: 'C1234',
+    text: 'fallback',
+    blocks: [
+      {
+        type: 'plan',
+        plan_id: 'plan-minimal',
+        title: 'Empty plan',
+      },
+    ],
+  },
+]);
+
 // chat.scheduleMessage
 // -- sad path
 expectError(web.chat.scheduleMessage()); // lacking argument
@@ -635,7 +784,46 @@ 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: 'Hello world',
+      },
+      {
+        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',
+    chunks: [
+      {
+        type: 'markdown_text',
+        text: 'Hello world',
+      },
+      {
+        type: 'plan_update',
+        title: 'Hello world',
+      },
+      {
+        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 +858,30 @@ 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: 'Hello world',
+      },
+      {
+        type: 'task_update',
+        id: 'task-1',
+        title: 'Processing request',
+        status: 'in_progress',
+        details: 'Working on it...',
+      },
+    ],
+    blocks: [],
+  },
+]);
 
 // chat.unfurl
 // -- sad path