diff --git a/src/vs/workbench/api/browser/mainThreadChatAgents2.ts b/src/vs/workbench/api/browser/mainThreadChatAgents2.ts
index 216ed63768a..4be5c86b6d4 100644
--- a/src/vs/workbench/api/browser/mainThreadChatAgents2.ts
+++ b/src/vs/workbench/api/browser/mainThreadChatAgents2.ts
@@ -29,7 +29,7 @@ import { IChatAgentHistoryEntry, IChatAgentImplementation, IChatAgentRequest, IC
 import { IChatEditingService, IChatRelatedFileProviderMetadata } from '../../contrib/chat/common/chatEditingService.js';
 import { ChatRequestAgentPart } from '../../contrib/chat/common/chatParserTypes.js';
 import { ChatRequestParser } from '../../contrib/chat/common/chatRequestParser.js';
-import { IChatContentInlineReference, IChatContentReference, IChatFollowup, IChatNotebookEdit, IChatProgress, IChatService, IChatTask, IChatWarningMessage } from '../../contrib/chat/common/chatService.js';
+import { IChatContentInlineReference, IChatContentReference, IChatFollowup, IChatNotebookEdit, IChatProgress, IChatService, IChatTask, IChatTaskSerialized, IChatWarningMessage } from '../../contrib/chat/common/chatService.js';
 import { ChatAgentLocation, ChatMode } from '../../contrib/chat/common/constants.js';
 import { IExtHostContext, extHostNamedCustomer } from '../../services/extensions/common/extHostCustomers.js';
 import { IExtensionService } from '../../services/extensions/common/extensions.js';
@@ -72,6 +72,14 @@ export class MainThreadChatTask implements IChatTask {
 		this.progress.push(progress);
 		this._onDidAddProgress.fire(progress);
 	}
+
+	toJSON(): IChatTaskSerialized {
+		return {
+			kind: 'progressTaskSerialized',
+			content: this.content,
+			progress: this.progress
+		};
+	}
 }
 
 @extHostNamedCustomer(MainContext.MainThreadChatAgents2)
diff --git a/src/vs/workbench/contrib/chat/browser/chatContentParts/chatProgressContentPart.ts b/src/vs/workbench/contrib/chat/browser/chatContentParts/chatProgressContentPart.ts
index 6c5c13e045e..35057aaff35 100644
--- a/src/vs/workbench/contrib/chat/browser/chatContentParts/chatProgressContentPart.ts
+++ b/src/vs/workbench/contrib/chat/browser/chatContentParts/chatProgressContentPart.ts
@@ -13,7 +13,7 @@ import { URI } from '../../../../../base/common/uri.js';
 import { MarkdownRenderer } from '../../../../../editor/browser/widget/markdownRenderer/browser/markdownRenderer.js';
 import { localize } from '../../../../../nls.js';
 import { IInstantiationService } from '../../../../../platform/instantiation/common/instantiation.js';
-import { IChatProgressMessage, IChatTask } from '../../common/chatService.js';
+import { IChatProgressMessage, IChatTask, IChatTaskSerialized } from '../../common/chatService.js';
 import { IChatRendererContent, IChatWorkingProgress, isResponseVM } from '../../common/chatViewModel.js';
 import { ChatTreeItem } from '../chat.js';
 import { InlineAnchorWidget } from '../chatInlineAnchorWidget.js';
@@ -27,7 +27,7 @@ export class ChatProgressContentPart extends Disposable implements IChatContentP
 	private readonly isHidden: boolean;
 
 	constructor(
-		progress: IChatProgressMessage | IChatTask,
+		progress: IChatProgressMessage | IChatTask | IChatTaskSerialized,
 		renderer: MarkdownRenderer,
 		context: IChatContentPartRenderContext,
 		forceShowSpinner: boolean | undefined,
diff --git a/src/vs/workbench/contrib/chat/browser/chatContentParts/chatTaskContentPart.ts b/src/vs/workbench/contrib/chat/browser/chatContentParts/chatTaskContentPart.ts
index 310130ec951..8ce898d086e 100644
--- a/src/vs/workbench/contrib/chat/browser/chatContentParts/chatTaskContentPart.ts
+++ b/src/vs/workbench/contrib/chat/browser/chatContentParts/chatTaskContentPart.ts
@@ -9,7 +9,7 @@ import { Disposable, IDisposable } from '../../../../../base/common/lifecycle.js
 import { MarkdownRenderer } from '../../../../../editor/browser/widget/markdownRenderer/browser/markdownRenderer.js';
 import { IInstantiationService } from '../../../../../platform/instantiation/common/instantiation.js';
 import { IChatProgressRenderableResponseContent } from '../../common/chatModel.js';
-import { IChatTask } from '../../common/chatService.js';
+import { IChatTask, IChatTaskSerialized } from '../../common/chatService.js';
 import { IChatContentPart, IChatContentPartRenderContext } from './chatContentParts.js';
 import { ChatProgressContentPart } from './chatProgressContentPart.js';
 import { ChatCollapsibleListContentPart, CollapsibleListPool } from './chatReferencesContentPart.js';
@@ -21,7 +21,7 @@ export class ChatTaskContentPart extends Disposable implements IChatContentPart
 	private isSettled: boolean;
 
 	constructor(
-		private readonly task: IChatTask,
+		private readonly task: IChatTask | IChatTaskSerialized,
 		contentReferencesListPool: CollapsibleListPool,
 		renderer: MarkdownRenderer,
 		context: IChatContentPartRenderContext,
@@ -36,8 +36,9 @@ export class ChatTaskContentPart extends Disposable implements IChatContentPart
 			this.domNode.appendChild(refsPart.domNode);
 			this.onDidChangeHeight = refsPart.onDidChangeHeight;
 		} else {
-			// #217645
-			const isSettled = task.isSettled?.() ?? true;
+			const isSettled = task.kind === 'progressTask' ?
+				task.isSettled() :
+				true;
 			this.isSettled = isSettled;
 			const showSpinner = !isSettled && !context.element.isComplete;
 			const progressPart = this._register(instantiationService.createInstance(ChatProgressContentPart, task, renderer, context, showSpinner, true, undefined));
@@ -47,9 +48,16 @@ export class ChatTaskContentPart extends Disposable implements IChatContentPart
 	}
 
 	hasSameContent(other: IChatProgressRenderableResponseContent): boolean {
-		return other.kind === 'progressTask'
-			&& other.progress.length === this.task.progress.length
-			&& other.isSettled() === this.isSettled;
+		if (
+			other.kind === 'progressTask' &&
+			this.task.kind === 'progressTask' &&
+			other.isSettled() !== this.isSettled
+		) {
+			return false;
+		}
+
+		return other.kind === this.task.kind &&
+			other.progress.length === this.task.progress.length;
 	}
 
 	addDisposable(disposable: IDisposable): void {
diff --git a/src/vs/workbench/contrib/chat/browser/chatListRenderer.ts b/src/vs/workbench/contrib/chat/browser/chatListRenderer.ts
index eec6156d468..053797cfae4 100644
--- a/src/vs/workbench/contrib/chat/browser/chatListRenderer.ts
+++ b/src/vs/workbench/contrib/chat/browser/chatListRenderer.ts
@@ -48,7 +48,7 @@ import { IChatAgentMetadata } from '../common/chatAgents.js';
 import { ChatContextKeys } from '../common/chatContextKeys.js';
 import { IChatRequestVariableEntry, IChatTextEditGroup } from '../common/chatModel.js';
 import { chatSubcommandLeader } from '../common/chatParserTypes.js';
-import { ChatAgentVoteDirection, ChatAgentVoteDownReason, ChatErrorLevel, IChatConfirmation, IChatContentReference, IChatExtensionsContent, IChatFollowup, IChatMarkdownContent, IChatTask, IChatToolInvocation, IChatToolInvocationSerialized, IChatTreeData, IChatUndoStop } from '../common/chatService.js';
+import { ChatAgentVoteDirection, ChatAgentVoteDownReason, ChatErrorLevel, IChatConfirmation, IChatContentReference, IChatExtensionsContent, IChatFollowup, IChatMarkdownContent, IChatTask, IChatTaskSerialized, IChatToolInvocation, IChatToolInvocationSerialized, IChatTreeData, IChatUndoStop } from '../common/chatService.js';
 import { IChatCodeCitations, IChatReferences, IChatRendererContent, IChatRequestViewModel, IChatResponseViewModel, IChatWorkingProgress, isRequestVM, isResponseVM } from '../common/chatViewModel.js';
 import { getNWords } from '../common/chatWordCounter.js';
 import { CodeBlockModelCollection } from '../common/codeBlockModelCollection.js';
@@ -905,7 +905,7 @@ export class ChatListItemRenderer extends Disposable implements ITreeRenderer<Ch
 			return this.renderTreeData(content, templateData, context);
 		} else if (content.kind === 'progressMessage') {
 			return this.instantiationService.createInstance(ChatProgressContentPart, content, this.renderer, context, undefined, undefined, undefined);
-		} else if (content.kind === 'progressTask') {
+		} else if (content.kind === 'progressTask' || content.kind === 'progressTaskSerialized') {
 			return this.renderProgressTask(content, templateData, context);
 		} else if (content.kind === 'command') {
 			return this.instantiationService.createInstance(ChatCommandButtonContentPart, content, context);
@@ -1051,7 +1051,7 @@ export class ChatListItemRenderer extends Disposable implements ITreeRenderer<Ch
 		return part;
 	}
 
-	private renderProgressTask(task: IChatTask, templateData: IChatListItemTemplate, context: IChatContentPartRenderContext): IChatContentPart | undefined {
+	private renderProgressTask(task: IChatTask | IChatTaskSerialized, templateData: IChatListItemTemplate, context: IChatContentPartRenderContext): IChatContentPart | undefined {
 		if (!isResponseVM(context.element)) {
 			return;
 		}
diff --git a/src/vs/workbench/contrib/chat/common/chatModel.ts b/src/vs/workbench/contrib/chat/common/chatModel.ts
index 3a8f5cf7097..a713a2fb4c0 100644
--- a/src/vs/workbench/contrib/chat/common/chatModel.ts
+++ b/src/vs/workbench/contrib/chat/common/chatModel.ts
@@ -27,7 +27,7 @@ import { CellUri, ICellEditOperation } from '../../notebook/common/notebookCommo
 import { IChatAgentCommand, IChatAgentData, IChatAgentResult, IChatAgentService, reviveSerializedAgent } from './chatAgents.js';
 import { IChatEditingService, IChatEditingSession } from './chatEditingService.js';
 import { ChatRequestTextPart, IParsedChatRequest, reviveParsedChatRequest } from './chatParserTypes.js';
-import { ChatAgentVoteDirection, ChatAgentVoteDownReason, IChatAgentMarkdownContentWithVulnerability, IChatCodeCitation, IChatCommandButton, IChatConfirmation, IChatContentInlineReference, IChatContentReference, IChatEditingSessionAction, IChatExtensionsContent, IChatFollowup, IChatLocationData, IChatMarkdownContent, IChatNotebookEdit, IChatPrepareToolInvocationPart, IChatProgress, IChatProgressMessage, IChatResponseCodeblockUriPart, IChatResponseProgressFileTreeData, IChatTask, IChatTextEdit, IChatToolInvocation, IChatToolInvocationSerialized, IChatTreeData, IChatUndoStop, IChatUsedContext, IChatWarningMessage, isIUsedContext } from './chatService.js';
+import { ChatAgentVoteDirection, ChatAgentVoteDownReason, IChatAgentMarkdownContentWithVulnerability, IChatCodeCitation, IChatCommandButton, IChatConfirmation, IChatContentInlineReference, IChatContentReference, IChatEditingSessionAction, IChatExtensionsContent, IChatFollowup, IChatLocationData, IChatMarkdownContent, IChatNotebookEdit, IChatPrepareToolInvocationPart, IChatProgress, IChatProgressMessage, IChatResponseCodeblockUriPart, IChatResponseProgressFileTreeData, IChatTask, IChatTaskSerialized, IChatTextEdit, IChatToolInvocation, IChatToolInvocationSerialized, IChatTreeData, IChatUndoStop, IChatUsedContext, IChatWarningMessage, isIUsedContext } from './chatService.js';
 import { IChatRequestVariableValue } from './chatVariables.js';
 import { ChatAgentLocation, ChatMode } from './constants.js';
 
@@ -311,11 +311,11 @@ export type IChatProgressHistoryResponseContent =
 	| IChatCommandButton
 	| IChatWarningMessage
 	| IChatTask
+	| IChatTaskSerialized
 	| IChatTextEditGroup
 	| IChatNotebookEditGroup
 	| IChatConfirmation
-	| IChatExtensionsContent
-	| IChatPrepareToolInvocationPart;
+	| IChatExtensionsContent;
 
 /**
  * "Normal" progress kinds that are rendered as parts of the stream of content.
@@ -324,9 +324,10 @@ export type IChatProgressResponseContent =
 	| IChatProgressHistoryResponseContent
 	| IChatToolInvocation
 	| IChatToolInvocationSerialized
-	| IChatUndoStop;
+	| IChatUndoStop
+	| IChatPrepareToolInvocationPart;
 
-const nonHistoryKinds = new Set(['toolInvocation', 'toolInvocationSerialized']);
+const nonHistoryKinds = new Set(['toolInvocation', 'toolInvocationSerialized', 'undoStop', 'prepareToolInvocation']);
 function isChatProgressHistoryResponseContent(content: IChatProgressResponseContent): content is IChatProgressHistoryResponseContent {
 	return !nonHistoryKinds.has(content.kind);
 }
diff --git a/src/vs/workbench/contrib/chat/common/chatService.ts b/src/vs/workbench/contrib/chat/common/chatService.ts
index b43c25ac8a0..2dbb25323c2 100644
--- a/src/vs/workbench/contrib/chat/common/chatService.ts
+++ b/src/vs/workbench/contrib/chat/common/chatService.ts
@@ -152,6 +152,12 @@ export interface IChatTaskDto {
 	kind: 'progressTask';
 }
 
+export interface IChatTaskSerialized {
+	content: IMarkdownString;
+	progress: (IChatWarningMessage | IChatContentReference)[];
+	kind: 'progressTaskSerialized';
+}
+
 export interface IChatTaskResult {
 	content: IMarkdownString | void;
 	kind: 'progressTaskResult';
@@ -295,7 +301,8 @@ export type IChatProgress =
 	| IChatToolInvocationSerialized
 	| IChatExtensionsContent
 	| IChatUndoStop
-	| IChatPrepareToolInvocationPart;
+	| IChatPrepareToolInvocationPart
+	| IChatTaskSerialized;
 
 export interface IChatFollowup {
 	kind: 'reply';