diff --git a/slack_sdk/models/messages/chunk.py b/slack_sdk/models/messages/chunk.py
index 837714af..5f225bdc 100644
--- a/slack_sdk/models/messages/chunk.py
+++ b/slack_sdk/models/messages/chunk.py
@@ -34,6 +34,8 @@ def parse(cls, chunk: Union[Dict, "Chunk"]) -> Optional["Chunk"]:
                 type = chunk["type"]
                 if type == MarkdownTextChunk.type:
                     return MarkdownTextChunk(**chunk)
+                elif type == PlanUpdateChunk.type:
+                    return PlanUpdateChunk(**chunk)
                 elif type == TaskUpdateChunk.type:
                     return TaskUpdateChunk(**chunk)
                 else:
@@ -67,6 +69,29 @@ def __init__(
         self.text = text
 
 
+class PlanUpdateChunk(Chunk):
+    type = "plan_update"
+
+    @property
+    def attributes(self) -> Set[str]:  # type: ignore[override]
+        return super().attributes.union({"title"})
+
+    def __init__(
+        self,
+        *,
+        title: str,
+        **others: Dict,
+    ):
+        """An updated title of plans for task and tool calls.
+
+        https://docs.slack.dev/messaging/sending-and-scheduling-messages#text-streaming
+        """
+        super().__init__(type=self.type)
+        show_unknown_key_warning(self, others)
+
+        self.title = title
+
+
 class URLSource(JsonObject):
     type = "url"
 
diff --git a/tests/slack_sdk/models/test_chunks.py b/tests/slack_sdk/models/test_chunks.py
index 1b8b58c9..6d64bd17 100644
--- a/tests/slack_sdk/models/test_chunks.py
+++ b/tests/slack_sdk/models/test_chunks.py
@@ -1,6 +1,6 @@
 import unittest
 
-from slack_sdk.models.messages.chunk import MarkdownTextChunk, TaskUpdateChunk, URLSource
+from slack_sdk.models.messages.chunk import MarkdownTextChunk, PlanUpdateChunk, TaskUpdateChunk, URLSource
 
 
 class MarkdownTextChunkTests(unittest.TestCase):
@@ -14,6 +14,17 @@ def test_json(self):
         )
 
 
+class PlanUpdateChunkTests(unittest.TestCase):
+    def test_json(self):
+        self.assertDictEqual(
+            PlanUpdateChunk(title="Crunching numbers...").to_dict(),
+            {
+                "type": "plan_update",
+                "title": "Crunching numbers...",
+            },
+        )
+
+
 class TaskUpdateChunkTests(unittest.TestCase):
     def test_json(self):
         self.assertDictEqual(
diff --git a/tests/slack_sdk/web/test_internal_utils.py b/tests/slack_sdk/web/test_internal_utils.py
index fc6574aa..3e44f0c9 100644
--- a/tests/slack_sdk/web/test_internal_utils.py
+++ b/tests/slack_sdk/web/test_internal_utils.py
@@ -4,10 +4,9 @@
 from pathlib import Path
 from typing import Dict
 
-
 from slack_sdk.models.attachments import Attachment
 from slack_sdk.models.blocks import Block, DividerBlock
-from slack_sdk.models.messages.chunk import MarkdownTextChunk, TaskUpdateChunk
+from slack_sdk.models.messages.chunk import MarkdownTextChunk, PlanUpdateChunk, TaskUpdateChunk
 from slack_sdk.web.internal_utils import (
     _build_unexpected_body_error_message,
     _get_url,
@@ -59,9 +58,14 @@ def test_can_parse_sequence_of_attachments(self):
 
     def test_can_parse_sequence_of_chunks(self):
         for chunks in [
-            [MarkdownTextChunk(text="fiz"), TaskUpdateChunk(id="001", title="baz", status="complete")],  # list
+            [
+                MarkdownTextChunk(text="fiz"),
+                PlanUpdateChunk(title="fuz"),
+                TaskUpdateChunk(id="001", title="baz", status="complete"),
+            ],  # list
             (
                 MarkdownTextChunk(text="fiz"),
+                PlanUpdateChunk(title="fuz"),
                 TaskUpdateChunk(id="001", title="baz", status="complete"),
             ),  # tuple
         ]:
@@ -87,7 +91,11 @@ def test_can_parse_str_attachments(self):
 
     def test_can_parse_str_chunks(self):
         input = json.dumps(
-            [MarkdownTextChunk(text="fiz").to_dict(), TaskUpdateChunk(id="001", title="baz", status="complete").to_dict()]
+            [
+                MarkdownTextChunk(text="fiz").to_dict(),
+                PlanUpdateChunk(title="fuz").to_dict(),
+                TaskUpdateChunk(id="001", title="baz", status="complete").to_dict(),
+            ]
         )
         kwargs = {"chunks": input}
         _parse_web_class_objects(kwargs)