diff --git a/src/vs/workbench/api/browser/mainThreadChatAgents2.ts b/src/vs/workbench/api/browser/mainThreadChatAgents2.ts
index 57f98dd25bf..385f5ac4e93 100644
--- a/src/vs/workbench/api/browser/mainThreadChatAgents2.ts
+++ b/src/vs/workbench/api/browser/mainThreadChatAgents2.ts
@@ -18,7 +18,7 @@ import { ILanguageFeaturesService } from 'vs/editor/common/services/languageFeat
 import { ExtensionIdentifier } from 'vs/platform/extensions/common/extensions';
 import { IInstantiationService } from 'vs/platform/instantiation/common/instantiation';
 import { ILogService } from 'vs/platform/log/common/log';
-import { ExtHostChatAgentsShape2, ExtHostContext, IChatProgressDto, IExtensionChatAgentMetadata, MainContext, MainThreadChatAgentsShape2 } from 'vs/workbench/api/common/extHost.protocol';
+import { ExtHostChatAgentsShape2, ExtHostContext, IChatProgressDto, IDynamicChatAgentProps, IExtensionChatAgentMetadata, MainContext, MainThreadChatAgentsShape2 } from 'vs/workbench/api/common/extHost.protocol';
 import { IChatWidgetService } from 'vs/workbench/contrib/chat/browser/chat';
 import { ChatInputPart } from 'vs/workbench/contrib/chat/browser/chatInputPart';
 import { AddDynamicVariableAction, IAddDynamicVariableContext } from 'vs/workbench/contrib/chat/browser/contrib/chatDynamicVariables';
@@ -96,7 +96,7 @@ export class MainThreadChatAgents2 extends Disposable implements MainThreadChatA
 		this._chatService.transferChatSession({ sessionId, inputValue }, URI.revive(toWorkspace));
 	}
 
-	$registerAgent(handle: number, extension: ExtensionIdentifier, id: string, metadata: IExtensionChatAgentMetadata, dynamicProps: { name: string; description: string; publisherDisplayName: string } | undefined): void {
+	$registerAgent(handle: number, extension: ExtensionIdentifier, id: string, metadata: IExtensionChatAgentMetadata, dynamicProps: IDynamicChatAgentProps | undefined): void {
 		const staticAgentRegistration = this._chatAgentService.getAgent(id);
 		if (!staticAgentRegistration && !dynamicProps) {
 			if (this._chatAgentService.getAgentsByName(id).length) {
@@ -143,7 +143,8 @@ export class MainThreadChatAgents2 extends Disposable implements MainThreadChatA
 					extensionId: extension,
 					extensionDisplayName: extensionDescription?.displayName ?? extension.value,
 					extensionPublisherId: extensionDescription?.publisher ?? '',
-					publisherDisplayName: dynamicProps.publisherDisplayName,
+					publisherDisplayName: dynamicProps.publisherName,
+					fullName: dynamicProps.fullName,
 					metadata: revive(metadata),
 					slashCommands: [],
 					locations: [ChatAgentLocation.Panel] // TODO all dynamic participants are panel only?
diff --git a/src/vs/workbench/api/common/extHost.api.impl.ts b/src/vs/workbench/api/common/extHost.api.impl.ts
index 0a622e4d95a..186d496596b 100644
--- a/src/vs/workbench/api/common/extHost.api.impl.ts
+++ b/src/vs/workbench/api/common/extHost.api.impl.ts
@@ -1420,9 +1420,9 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 				checkProposedApiEnabled(extension, 'chatParticipant');
 				return extHostChatAgents2.createChatAgent(extension, id, handler);
 			},
-			createDynamicChatParticipant(id: string, name: string, publisherName: string, description: string, handler: vscode.ChatExtendedRequestHandler): vscode.ChatParticipant {
+			createDynamicChatParticipant(id: string, dynamicProps: vscode.DynamicChatParticipantProps, handler: vscode.ChatExtendedRequestHandler): vscode.ChatParticipant {
 				checkProposedApiEnabled(extension, 'chatParticipantAdditions');
-				return extHostChatAgents2.createDynamicChatAgent(extension, id, name, publisherName, description, handler);
+				return extHostChatAgents2.createDynamicChatAgent(extension, id, dynamicProps, handler);
 			}
 		};
 
diff --git a/src/vs/workbench/api/common/extHost.protocol.ts b/src/vs/workbench/api/common/extHost.protocol.ts
index 190e7c4b45e..a8750532975 100644
--- a/src/vs/workbench/api/common/extHost.protocol.ts
+++ b/src/vs/workbench/api/common/extHost.protocol.ts
@@ -1232,8 +1232,15 @@ export interface IExtensionChatAgentMetadata extends Dto<IChatAgentMetadata> {
 	hasFollowups?: boolean;
 }
 
+export interface IDynamicChatAgentProps {
+	name: string;
+	publisherName: string;
+	description?: string;
+	fullName?: string;
+}
+
 export interface MainThreadChatAgentsShape2 extends IDisposable {
-	$registerAgent(handle: number, extension: ExtensionIdentifier, id: string, metadata: IExtensionChatAgentMetadata, dynamicProps: { name: string; description: string; publisherDisplayName: string } | undefined): void;
+	$registerAgent(handle: number, extension: ExtensionIdentifier, id: string, metadata: IExtensionChatAgentMetadata, dynamicProps: IDynamicChatAgentProps | undefined): void;
 	$registerAgentCompletionsProvider(handle: number, triggerCharacters: string[]): void;
 	$unregisterAgentCompletionsProvider(handle: number): void;
 	$updateAgent(handle: number, metadataUpdate: IExtensionChatAgentMetadata): void;
diff --git a/src/vs/workbench/api/common/extHostChatAgents2.ts b/src/vs/workbench/api/common/extHostChatAgents2.ts
index 78a4076d962..11fcd8875c6 100644
--- a/src/vs/workbench/api/common/extHostChatAgents2.ts
+++ b/src/vs/workbench/api/common/extHostChatAgents2.ts
@@ -258,12 +258,12 @@ export class ExtHostChatAgents2 extends Disposable implements ExtHostChatAgentsS
 		return agent.apiAgent;
 	}
 
-	createDynamicChatAgent(extension: IExtensionDescription, id: string, name: string, publisherName: string, description: string, handler: vscode.ChatExtendedRequestHandler): vscode.ChatParticipant {
+	createDynamicChatAgent(extension: IExtensionDescription, id: string, dynamicProps: vscode.DynamicChatParticipantProps, handler: vscode.ChatExtendedRequestHandler): vscode.ChatParticipant {
 		const handle = ExtHostChatAgents2._idPool++;
 		const agent = new ExtHostChatAgent(extension, id, this._proxy, handle, handler);
 		this._agents.set(handle, agent);
 
-		this._proxy.$registerAgent(handle, extension.identifier, id, { isSticky: true } satisfies IExtensionChatAgentMetadata, { name, description, publisherDisplayName: publisherName });
+		this._proxy.$registerAgent(handle, extension.identifier, id, { isSticky: true } satisfies IExtensionChatAgentMetadata, dynamicProps);
 		return agent.apiAgent;
 	}
 
@@ -439,7 +439,6 @@ export class ExtHostChatAgents2 extends Disposable implements ExtHostChatAgentsS
 class ExtHostChatAgent {
 
 	private _followupProvider: vscode.ChatFollowupProvider | undefined;
-	private _fullName: string | undefined;
 	private _iconPath: vscode.Uri | { light: vscode.Uri; dark: vscode.Uri } | vscode.ThemeIcon | undefined;
 	private _isDefault: boolean | undefined;
 	private _helpTextPrefix: string | vscode.MarkdownString | undefined;
@@ -535,7 +534,6 @@ class ExtHostChatAgent {
 			updateScheduled = true;
 			queueMicrotask(() => {
 				this._proxy.$updateAgent(this._handle, {
-					fullName: this._fullName,
 					icon: !this._iconPath ? undefined :
 						this._iconPath instanceof URI ? this._iconPath :
 							'light' in this._iconPath ? this._iconPath.light :
@@ -561,15 +559,6 @@ class ExtHostChatAgent {
 			get id() {
 				return that.id;
 			},
-			get fullName() {
-				checkProposedApiEnabled(that.extension, 'defaultChatParticipant');
-				return that._fullName ?? that.extension.displayName ?? that.extension.name;
-			},
-			set fullName(v) {
-				checkProposedApiEnabled(that.extension, 'defaultChatParticipant');
-				that._fullName = v;
-				updateMetadataSoon();
-			},
 			get iconPath() {
 				return that._iconPath;
 			},
diff --git a/src/vs/workbench/contrib/chat/browser/chatListRenderer.ts b/src/vs/workbench/contrib/chat/browser/chatListRenderer.ts
index ca31e35b677..e4d158b307f 100644
--- a/src/vs/workbench/contrib/chat/browser/chatListRenderer.ts
+++ b/src/vs/workbench/contrib/chat/browser/chatListRenderer.ts
@@ -16,7 +16,6 @@ import { ICompressibleTreeRenderer } from 'vs/base/browser/ui/tree/objectTree';
 import { IAsyncDataSource, ITreeNode, ITreeRenderer } from 'vs/base/browser/ui/tree/tree';
 import { IAction } from 'vs/base/common/actions';
 import { distinct } from 'vs/base/common/arrays';
-import { disposableTimeout } from 'vs/base/common/async';
 import { CancellationTokenSource } from 'vs/base/common/cancellation';
 import { Codicon } from 'vs/base/common/codicons';
 import { Emitter, Event } from 'vs/base/common/event';
@@ -26,12 +25,11 @@ import { Disposable, DisposableStore, IDisposable, toDisposable } from 'vs/base/
 import { ResourceMap } from 'vs/base/common/map';
 import { FileAccess, Schemas, matchesSomeScheme } from 'vs/base/common/network';
 import { clamp } from 'vs/base/common/numbers';
-import { IObservable, autorun, constObservable } from 'vs/base/common/observable';
+import { autorun } from 'vs/base/common/observable';
 import { basename } from 'vs/base/common/path';
 import { basenameOrAuthority } from 'vs/base/common/resources';
 import { equalsIgnoreCase } from 'vs/base/common/strings';
 import { ThemeIcon } from 'vs/base/common/themables';
-import { isUndefined } from 'vs/base/common/types';
 import { URI } from 'vs/base/common/uri';
 import { generateUuid } from 'vs/base/common/uuid';
 import { IMarkdownRenderResult, MarkdownRenderer } from 'vs/editor/browser/widget/markdownRenderer/browser/markdownRenderer';
@@ -66,10 +64,10 @@ import { ChatFollowups } from 'vs/workbench/contrib/chat/browser/chatFollowups';
 import { ChatMarkdownDecorationsRenderer } from 'vs/workbench/contrib/chat/browser/chatMarkdownDecorationsRenderer';
 import { ChatEditorOptions } from 'vs/workbench/contrib/chat/browser/chatOptions';
 import { ChatCodeBlockContentProvider, CodeBlockPart, CodeCompareBlockPart, ICodeBlockData, ICodeCompareBlockData, ICodeCompareBlockDiffData, localFileLanguageId, parseLocalFileData } from 'vs/workbench/contrib/chat/browser/codeBlockPart';
-import { ChatAgentLocation, IChatAgentMetadata, IChatAgentNameService } from 'vs/workbench/contrib/chat/common/chatAgents';
+import { ChatAgentLocation, IChatAgentMetadata } from 'vs/workbench/contrib/chat/common/chatAgents';
 import { CONTEXT_CHAT_RESPONSE_SUPPORT_ISSUE_REPORTING, CONTEXT_REQUEST, CONTEXT_RESPONSE, CONTEXT_RESPONSE_DETECTED_AGENT_COMMAND, CONTEXT_RESPONSE_FILTERED, CONTEXT_RESPONSE_VOTE } from 'vs/workbench/contrib/chat/common/chatContextKeys';
 import { IChatProgressRenderableResponseContent, IChatTextEditGroup } from 'vs/workbench/contrib/chat/common/chatModel';
-import { chatAgentLeader, chatSubcommandLeader } from 'vs/workbench/contrib/chat/common/chatParserTypes';
+import { chatSubcommandLeader } from 'vs/workbench/contrib/chat/common/chatParserTypes';
 import { IChatCommandButton, IChatConfirmation, IChatContentReference, IChatFollowup, IChatProgressMessage, IChatResponseProgressFileTreeData, IChatSendRequestOptions, IChatService, IChatTask, IChatWarningMessage, InteractiveSessionVoteDirection } from 'vs/workbench/contrib/chat/common/chatService';
 import { IChatVariablesService } from 'vs/workbench/contrib/chat/common/chatVariables';
 import { IChatProgressMessageRenderData, IChatRenderData, IChatResponseMarkdownRenderData, IChatResponseViewModel, IChatTaskRenderData, IChatWelcomeMessageViewModel, isRequestVM, isResponseVM, isWelcomeVM } from 'vs/workbench/contrib/chat/common/chatViewModel';
@@ -88,7 +86,6 @@ interface IChatListItemTemplate {
 	readonly rowContainer: HTMLElement;
 	readonly titleToolbar?: MenuWorkbenchToolBar;
 	readonly avatarContainer: HTMLElement;
-	readonly agentAvatarContainer: HTMLElement;
 	readonly username: HTMLElement;
 	readonly detail: HTMLElement;
 	readonly value: HTMLElement;
@@ -159,7 +156,6 @@ export class ChatListItemRenderer extends Disposable implements ITreeRenderer<Ch
 		@IModelService private readonly modelService: IModelService,
 		@ITrustedDomainService private readonly trustedDomainService: ITrustedDomainService,
 		@IHoverService private readonly hoverService: IHoverService,
-		@IChatAgentNameService private readonly chatAgentNameService: IChatAgentNameService,
 		@IChatService private readonly chatService: IChatService,
 	) {
 		super();
@@ -268,7 +264,6 @@ export class ChatListItemRenderer extends Disposable implements ITreeRenderer<Ch
 		const header = dom.append(rowContainer, $('.header'));
 		const user = dom.append(header, $('.user'));
 		const avatarContainer = dom.append(user, $('.avatar-container'));
-		const agentAvatarContainer = dom.append(user, $('.agent-avatar-container'));
 		const username = dom.append(user, $('h3.username'));
 		const detailContainer = dom.append(user, $('span.detail-container'));
 		const detail = dom.append(detailContainer, $('span.detail'));
@@ -310,7 +305,7 @@ export class ChatListItemRenderer extends Disposable implements ITreeRenderer<Ch
 			return undefined;
 		}));
 
-		const template: IChatListItemTemplate = { avatarContainer, agentAvatarContainer, username, detail, referencesListContainer, value, rowContainer, elementDisposables, titleToolbar, templateDisposables, contextKeyService, agentHover };
+		const template: IChatListItemTemplate = { avatarContainer, username, detail, referencesListContainer, value, rowContainer, elementDisposables, titleToolbar, templateDisposables, contextKeyService, agentHover };
 		return template;
 	}
 
@@ -395,47 +390,20 @@ export class ChatListItemRenderer extends Disposable implements ITreeRenderer<Ch
 	}
 
 	private renderDetail(element: IChatResponseViewModel, templateData: IChatListItemTemplate): void {
-		let agentName: IObservable<string | undefined> = constObservable(undefined);
-
-		if (element.agent && !element.agent.isDefault) {
-			const name = element.agent.name;
-			agentName = this.chatAgentNameService.getAgentNameRestriction(element.agent)
-				.map(allowed => allowed ? name : name); // TODO
-		}
-
 		templateData.elementDisposables.add(autorun(reader => {
-			this._renderDetail(element, agentName.read(reader), templateData);
+			this._renderDetail(element, templateData);
 		}));
 	}
 
-	private _renderDetail(element: IChatResponseViewModel, agentName: string | undefined, templateData: IChatListItemTemplate): void {
+	private _renderDetail(element: IChatResponseViewModel, templateData: IChatListItemTemplate): void {
 		let progressMsg: string = '';
-		if (!isUndefined(agentName)) {
-			let usingMsg = chatAgentLeader + agentName;
-			if (element.slashCommand) {
-				usingMsg += ` ${chatSubcommandLeader}${element.slashCommand.name}`;
-			}
-
+		if (element.slashCommand && element.agentOrSlashCommandDetected) {
+			const usingMsg = `${chatSubcommandLeader}${element.slashCommand.name}`;
 			if (element.isComplete) {
 				progressMsg = localize('usedAgent', "used {0}", usingMsg);
 			} else {
 				progressMsg = localize('usingAgent', "using {0}", usingMsg);
 			}
-		} else if (element.agentOrSlashCommandDetected) {
-			const usingMsg: string[] = [];
-			if (!isUndefined(agentName)) {
-				usingMsg.push(chatAgentLeader + agentName);
-			}
-			if (element.slashCommand) {
-				usingMsg.push(chatSubcommandLeader + element.slashCommand.name);
-			}
-			if (usingMsg.length) {
-				if (element.isComplete) {
-					progressMsg = localize('usedAgent', "used {0}", usingMsg.join(' '));
-				} else {
-					progressMsg = localize('usingAgent', "using {0}", usingMsg.join(' '));
-				}
-			}
 		} else if (!element.isComplete) {
 			progressMsg = GeneratingPhrase;
 		}
@@ -444,53 +412,28 @@ export class ChatListItemRenderer extends Disposable implements ITreeRenderer<Ch
 	}
 
 	private renderAvatar(element: ChatTreeItem, templateData: IChatListItemTemplate): void {
-		if (URI.isUri(element.avatarIcon)) {
-			const avatarImgIcon = dom.$<HTMLImageElement>('img.icon');
-			avatarImgIcon.src = FileAccess.uriToBrowserUri(element.avatarIcon).toString(true);
-			templateData.avatarContainer.replaceChildren(dom.$('.avatar', undefined, avatarImgIcon));
+		const icon = isResponseVM(element) ?
+			this.getAgentIcon(element.agent?.metadata) :
+			(element.avatarIcon ?? Codicon.account);
+		if (icon instanceof URI) {
+			const avatarIcon = dom.$<HTMLImageElement>('img.icon');
+			avatarIcon.src = FileAccess.uriToBrowserUri(icon).toString(true);
+			templateData.avatarContainer.replaceChildren(dom.$('.avatar', undefined, avatarIcon));
 		} else {
-			const defaultIcon = isRequestVM(element) ? Codicon.account : Codicon.copilot;
-			const icon = element.avatarIcon ?? defaultIcon;
 			const avatarIcon = dom.$(ThemeIcon.asCSSSelector(icon));
 			templateData.avatarContainer.replaceChildren(dom.$('.avatar.codicon-avatar', undefined, avatarIcon));
 		}
-
-		if (isResponseVM(element) && element.agent && !element.agent.isDefault) {
-			dom.show(templateData.agentAvatarContainer);
-			const icon = this.getAgentIcon(element.agent.metadata);
-			if (icon instanceof URI) {
-				const avatarIcon = dom.$<HTMLImageElement>('img.icon');
-				avatarIcon.src = FileAccess.uriToBrowserUri(icon).toString(true);
-				templateData.agentAvatarContainer.replaceChildren(dom.$('.avatar', undefined, avatarIcon));
-			} else if (icon) {
-				const avatarIcon = dom.$(ThemeIcon.asCSSSelector(icon));
-				templateData.agentAvatarContainer.replaceChildren(dom.$('.avatar.codicon-avatar', undefined, avatarIcon));
-			} else {
-				dom.hide(templateData.agentAvatarContainer);
-				return;
-			}
-
-			templateData.agentAvatarContainer.classList.toggle('complete', element.isComplete);
-			if (!element.agentAvatarHasBeenRendered && !element.isComplete) {
-				element.agentAvatarHasBeenRendered = true;
-				templateData.agentAvatarContainer.classList.remove('loading');
-				templateData.elementDisposables.add(disposableTimeout(() => {
-					templateData.agentAvatarContainer.classList.toggle('loading', !element.isComplete);
-				}, 100));
-			} else {
-				templateData.agentAvatarContainer.classList.toggle('loading', !element.isComplete);
-			}
-		} else {
-			dom.hide(templateData.agentAvatarContainer);
-		}
 	}
 
-	private getAgentIcon(agent: IChatAgentMetadata): URI | ThemeIcon | undefined {
-		if (agent.themeIcon) {
+	private getAgentIcon(agent: IChatAgentMetadata | undefined): URI | ThemeIcon {
+		if (agent?.themeIcon) {
 			return agent.themeIcon;
+		} else if (agent?.iconDark && this.themeService.getColorTheme().type === ColorScheme.DARK) {
+			return agent.iconDark;
+		} else if (agent?.icon) {
+			return agent.icon;
 		} else {
-			return this.themeService.getColorTheme().type === ColorScheme.DARK && agent.iconDark ? agent.iconDark :
-				agent.icon;
+			return Codicon.copilot;
 		}
 	}
 
diff --git a/src/vs/workbench/contrib/chat/browser/chatParticipantContributions.ts b/src/vs/workbench/contrib/chat/browser/chatParticipantContributions.ts
index c50724ba6d1..f5132a7ab55 100644
--- a/src/vs/workbench/contrib/chat/browser/chatParticipantContributions.ts
+++ b/src/vs/workbench/contrib/chat/browser/chatParticipantContributions.ts
@@ -39,7 +39,12 @@ const chatParticipantExtensionPoint = extensionsRegistry.ExtensionsRegistry.regi
 					type: 'string'
 				},
 				name: {
-					description: localize('chatParticipantName', "User-facing display name for this chat participant. The user will use '@' with this name to invoke the participant."),
+					description: localize('chatParticipantName', "User-facing name for this chat participant. The user will use '@' with this name to invoke the participant."),
+					type: 'string',
+					pattern: '^[\w0-9_-]+$'
+				},
+				fullName: {
+					markdownDescription: localize('chatParticipantFullName', "The full name of this chat participant, which is shown as the label for responses coming from this participant. If not provided, {0} is used.", '`name`'),
 					type: 'string'
 				},
 				description: {
@@ -216,6 +221,7 @@ export class ChatExtensionPointHandler implements IWorkbenchContribution {
 								sampleRequest: providerDescriptor.sampleRequest,
 							},
 							name: providerDescriptor.name,
+							fullName: providerDescriptor.fullName,
 							isDefault: providerDescriptor.isDefault,
 							defaultImplicitVariables: providerDescriptor.defaultImplicitVariables,
 							locations: isNonEmptyArray(providerDescriptor.locations) ?
diff --git a/src/vs/workbench/contrib/chat/browser/media/chat.css b/src/vs/workbench/contrib/chat/browser/media/chat.css
index 15de8a3352b..b6c75bca71e 100644
--- a/src/vs/workbench/contrib/chat/browser/media/chat.css
+++ b/src/vs/workbench/contrib/chat/browser/media/chat.css
@@ -124,23 +124,6 @@
 	font-size: 14px;
 }
 
-.interactive-item-container .header .agent-avatar-container {
-	margin-left: -30px;
-	transition: margin 0.15s ease-out;
-	transition-delay: 0.5s;
-	z-index: -1;
-}
-
-.interactive-item-container .header .agent-avatar-container.loading {
-	margin-left: 0px;
-	z-index: 1;
-}
-
-.interactive-item-container .header .agent-avatar-container.complete {
-	margin-left: -12px;
-	z-index: 1;
-}
-
 .monaco-list-row:not(.focused) .interactive-item-container:not(:hover) .header .monaco-toolbar,
 .monaco-list:not(:focus-within) .monaco-list-row .interactive-item-container:not(:hover) .header .monaco-toolbar,
 .monaco-list-row:not(.focused) .interactive-item-container:not(:hover) .header .monaco-toolbar .action-label,
diff --git a/src/vs/workbench/contrib/chat/common/chatAgents.ts b/src/vs/workbench/contrib/chat/common/chatAgents.ts
index 9bf43b3db5c..2fd60cfb727 100644
--- a/src/vs/workbench/contrib/chat/common/chatAgents.ts
+++ b/src/vs/workbench/contrib/chat/common/chatAgents.ts
@@ -57,6 +57,7 @@ export namespace ChatAgentLocation {
 export interface IChatAgentData {
 	id: string;
 	name: string;
+	fullName?: string;
 	description?: string;
 	extensionId: ExtensionIdentifier;
 	extensionPublisherId: string;
@@ -100,7 +101,6 @@ export interface IChatAgentMetadata {
 	helpTextVariablesPrefix?: string | IMarkdownString;
 	helpTextPostfix?: string | IMarkdownString;
 	isSecondary?: boolean; // Invoked by ctrl/cmd+enter
-	fullName?: string;
 	icon?: URI;
 	iconDark?: URI;
 	themeIcon?: ThemeIcon;
diff --git a/src/vs/workbench/contrib/chat/common/chatModel.ts b/src/vs/workbench/contrib/chat/common/chatModel.ts
index 31fb8e81f3f..d4649b0acd7 100644
--- a/src/vs/workbench/contrib/chat/common/chatModel.ts
+++ b/src/vs/workbench/contrib/chat/common/chatModel.ts
@@ -580,7 +580,7 @@ export class ChatModel extends Disposable implements IChatModel {
 
 	get responderUsername(): string {
 		return (this._defaultAgent ?
-			this._defaultAgent.metadata.fullName :
+			this._defaultAgent.fullName :
 			this.initialData?.responderUsername) ?? '';
 	}
 
@@ -956,7 +956,7 @@ export class ChatWelcomeMessageModel implements IChatWelcomeMessageModel {
 	}
 
 	public get username(): string {
-		return this.chatAgentService.getDefaultAgent(ChatAgentLocation.Panel)?.metadata.fullName ?? '';
+		return this.chatAgentService.getDefaultAgent(ChatAgentLocation.Panel)?.fullName ?? '';
 	}
 
 	public get avatarIcon(): ThemeIcon | undefined {
diff --git a/src/vs/workbench/contrib/chat/common/chatParticipantContribTypes.ts b/src/vs/workbench/contrib/chat/common/chatParticipantContribTypes.ts
index 4c4449bbaf9..e6d695c3824 100644
--- a/src/vs/workbench/contrib/chat/common/chatParticipantContribTypes.ts
+++ b/src/vs/workbench/contrib/chat/common/chatParticipantContribTypes.ts
@@ -17,6 +17,7 @@ export type RawChatParticipantLocation = 'panel' | 'terminal' | 'notebook';
 export interface IRawChatParticipantContribution {
 	id: string;
 	name: string;
+	fullName: string;
 	description?: string;
 	isDefault?: boolean;
 	isSticky?: boolean;
diff --git a/src/vs/workbench/contrib/chat/common/chatViewModel.ts b/src/vs/workbench/contrib/chat/common/chatViewModel.ts
index 3f34f8f239d..96b4ef6d464 100644
--- a/src/vs/workbench/contrib/chat/common/chatViewModel.ts
+++ b/src/vs/workbench/contrib/chat/common/chatViewModel.ts
@@ -137,7 +137,6 @@ export interface IChatResponseViewModel {
 	readonly result?: IChatAgentResult;
 	readonly contentUpdateTimings?: IChatLiveUpdateData;
 	renderData?: IChatResponseRenderData;
-	agentAvatarHasBeenRendered?: boolean;
 	currentRenderedHeight: number | undefined;
 	setVote(vote: InteractiveSessionVoteDirection): void;
 	usedReferencesExpanded?: boolean;
@@ -375,7 +374,9 @@ export class ChatResponseViewModel extends Disposable implements IChatResponseVi
 	}
 
 	get username() {
-		return this._model.username;
+		return this.agent ?
+			(this.agent.fullName || this.agent.name) :
+			this._model.username;
 	}
 
 	get avatarIcon() {
@@ -443,7 +444,6 @@ export class ChatResponseViewModel extends Disposable implements IChatResponseVi
 	}
 
 	renderData: IChatResponseRenderData | undefined = undefined;
-	agentAvatarHasBeenRendered?: boolean;
 	currentRenderedHeight: number | undefined;
 
 	private _usedReferencesExpanded: boolean | undefined;
diff --git a/src/vs/workbench/contrib/chat/test/common/__snapshots__/ChatService_can_deserialize.0.snap b/src/vs/workbench/contrib/chat/test/common/__snapshots__/ChatService_can_deserialize.0.snap
index 83ff5c45284..383288306cb 100644
--- a/src/vs/workbench/contrib/chat/test/common/__snapshots__/ChatService_can_deserialize.0.snap
+++ b/src/vs/workbench/contrib/chat/test/common/__snapshots__/ChatService_can_deserialize.0.snap
@@ -1,7 +1,7 @@
 {
   requesterUsername: "test",
   requesterAvatarIconUri: undefined,
-  responderUsername: "test",
+  responderUsername: "",
   responderAvatarIconUri: undefined,
   initialLocation: "panel",
   welcomeMessage: undefined,
diff --git a/src/vs/workbench/contrib/chat/test/common/__snapshots__/ChatService_can_serialize.0.snap b/src/vs/workbench/contrib/chat/test/common/__snapshots__/ChatService_can_serialize.0.snap
index 75fe21b2b15..a0e87754398 100644
--- a/src/vs/workbench/contrib/chat/test/common/__snapshots__/ChatService_can_serialize.0.snap
+++ b/src/vs/workbench/contrib/chat/test/common/__snapshots__/ChatService_can_serialize.0.snap
@@ -1,7 +1,7 @@
 {
   requesterUsername: "test",
   requesterAvatarIconUri: undefined,
-  responderUsername: "test",
+  responderUsername: "",
   responderAvatarIconUri: undefined,
   initialLocation: "panel",
   welcomeMessage: undefined,
diff --git a/src/vs/workbench/contrib/chat/test/common/__snapshots__/ChatService_can_serialize.1.snap b/src/vs/workbench/contrib/chat/test/common/__snapshots__/ChatService_can_serialize.1.snap
index c4e365a2a54..cf9cc42dfc6 100644
--- a/src/vs/workbench/contrib/chat/test/common/__snapshots__/ChatService_can_serialize.1.snap
+++ b/src/vs/workbench/contrib/chat/test/common/__snapshots__/ChatService_can_serialize.1.snap
@@ -1,7 +1,7 @@
 {
   requesterUsername: "test",
   requesterAvatarIconUri: undefined,
-  responderUsername: "test",
+  responderUsername: "",
   responderAvatarIconUri: undefined,
   initialLocation: "panel",
   welcomeMessage: undefined,
@@ -31,10 +31,7 @@
               publisherDisplayName: "",
               extensionDisplayName: "",
               locations: [ "panel" ],
-              metadata: {
-                requester: { name: "test" },
-                fullName: "test"
-              },
+              metadata: { requester: { name: "test" } },
               slashCommands: [  ]
             },
             kind: "agent"
@@ -73,10 +70,7 @@
         publisherDisplayName: "",
         extensionDisplayName: "",
         locations: [ "panel" ],
-        metadata: {
-          requester: { name: "test" },
-          fullName: "test"
-        },
+        metadata: { requester: { name: "test" } },
         slashCommands: [  ]
       },
       slashCommand: undefined,
diff --git a/src/vs/workbench/contrib/chat/test/common/chatService.test.ts b/src/vs/workbench/contrib/chat/test/common/chatService.test.ts
index bcca1f9bc98..513f786bb59 100644
--- a/src/vs/workbench/contrib/chat/test/common/chatService.test.ts
+++ b/src/vs/workbench/contrib/chat/test/common/chatService.test.ts
@@ -95,7 +95,7 @@ suite('ChatService', () => {
 		testDisposables.add(chatAgentService.registerAgent('testAgent', { name: 'testAgent', id: 'testAgent', isDefault: true, extensionId: nullExtensionDescription.identifier, extensionPublisherId: '', publisherDisplayName: '', extensionDisplayName: '', locations: [ChatAgentLocation.Panel], metadata: {}, slashCommands: [] }));
 		testDisposables.add(chatAgentService.registerAgent(chatAgentWithUsedContextId, { name: chatAgentWithUsedContextId, id: chatAgentWithUsedContextId, extensionId: nullExtensionDescription.identifier, extensionPublisherId: '', publisherDisplayName: '', extensionDisplayName: '', locations: [ChatAgentLocation.Panel], metadata: {}, slashCommands: [] }));
 		testDisposables.add(chatAgentService.registerAgentImplementation('testAgent', agent));
-		chatAgentService.updateAgent('testAgent', { requester: { name: 'test' }, fullName: 'test' });
+		chatAgentService.updateAgent('testAgent', { requester: { name: 'test' } });
 	});
 
 	test('retrieveSession', async () => {
@@ -132,7 +132,7 @@ suite('ChatService', () => {
 
 	test('can serialize', async () => {
 		testDisposables.add(chatAgentService.registerAgentImplementation(chatAgentWithUsedContextId, chatAgentWithUsedContext));
-		chatAgentService.updateAgent(chatAgentWithUsedContextId, { requester: { name: 'test' }, fullName: 'test' });
+		chatAgentService.updateAgent(chatAgentWithUsedContextId, { requester: { name: 'test' } });
 		const testService = testDisposables.add(instantiationService.createInstance(ChatService));
 
 		const model = testDisposables.add(testService.startSession(ChatAgentLocation.Panel, CancellationToken.None));
diff --git a/src/vs/workbench/contrib/quickaccess/browser/commandsQuickAccess.ts b/src/vs/workbench/contrib/quickaccess/browser/commandsQuickAccess.ts
index 59ec31d81d6..17b7b7ac490 100644
--- a/src/vs/workbench/contrib/quickaccess/browser/commandsQuickAccess.ts
+++ b/src/vs/workbench/contrib/quickaccess/browser/commandsQuickAccess.ts
@@ -176,7 +176,7 @@ export class CommandsQuickAccessProvider extends AbstractEditorCommandsQuickAcce
 		const defaultAgent = this.chatAgentService.getDefaultAgent(ChatAgentLocation.Panel);
 		if (defaultAgent) {
 			additionalPicks.push({
-				label: localize('askXInChat', "Ask {0}: {1}", defaultAgent.metadata.fullName, filter),
+				label: localize('askXInChat', "Ask {0}: {1}", defaultAgent.fullName, filter),
 				commandId: this.configuration.experimental.askChatLocation === 'quickChat' ? ASK_QUICK_QUESTION_ACTION_ID : CHAT_OPEN_ACTION_ID,
 				args: [filter]
 			});
diff --git a/src/vscode-dts/vscode.proposed.chatParticipantAdditions.d.ts b/src/vscode-dts/vscode.proposed.chatParticipantAdditions.d.ts
index d062407d47a..260c84c94a2 100644
--- a/src/vscode-dts/vscode.proposed.chatParticipantAdditions.d.ts
+++ b/src/vscode-dts/vscode.proposed.chatParticipantAdditions.d.ts
@@ -214,7 +214,17 @@ declare module 'vscode' {
 		 */
 		export function createChatParticipant(id: string, handler: ChatExtendedRequestHandler): ChatParticipant;
 
-		export function createDynamicChatParticipant(id: string, name: string, publisherName: string, description: string, handler: ChatExtendedRequestHandler): ChatParticipant;
+		export function createDynamicChatParticipant(id: string, dynamicProps: DynamicChatParticipantProps, handler: ChatExtendedRequestHandler): ChatParticipant;
+	}
+
+	/**
+	 * These don't get set on the ChatParticipant after creation, like other props, because they are typically defined in package.json and we want them at the time of creation.
+	 */
+	export interface DynamicChatParticipantProps {
+		name: string;
+		publisherName: string;
+		description?: string;
+		fullName?: string;
 	}
 
 	/*
diff --git a/src/vscode-dts/vscode.proposed.defaultChatParticipant.d.ts b/src/vscode-dts/vscode.proposed.defaultChatParticipant.d.ts
index d600adb0fee..f4261b5b6fb 100644
--- a/src/vscode-dts/vscode.proposed.defaultChatParticipant.d.ts
+++ b/src/vscode-dts/vscode.proposed.defaultChatParticipant.d.ts
@@ -27,11 +27,6 @@ declare module 'vscode' {
 		 */
 		isDefault?: boolean;
 
-		/**
-		 * The full name of this participant.
-		 */
-		fullName?: string;
-
 		/**
 		 * When true, this participant is invoked when the user submits their query using ctrl/cmd+enter
 		 * TODO@API name