fix: make markdown text optional and add missing chunk type

Author: srtaalej

packages/types/src/chunk.ts

@@ -25,6 +25,15 @@ export interface URLSource {
   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
@@ -42,7 +51,7 @@ export interface TaskUpdateChunk extends Chunk {
 /**
  * Union type of all possible chunk types
  */
-export type AnyChunk = MarkdownTextChunk | TaskUpdateChunk;
+export type AnyChunk = MarkdownTextChunk | PlanUpdateChunk | TaskUpdateChunk;
 
 /**
  * Parse a chunk object and return the appropriate typed chunk.
@@ -70,6 +79,14 @@ export function parseChunk(chunk: unknown): AnyChunk | null {
     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 (

packages/web-api/src/types/request/chat.ts

@@ -169,7 +169,7 @@ 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.