Display model name in subagent session

src/vs/workbench/contrib/chat/browser/widget/chatContentParts/chatCollapsibleContentPart.ts

@@ -143,7 +143,7 @@ export abstract class ChatCollapsibleContentPart extends Disposable implements I
 
 	abstract hasSameContent(other: IChatRendererContent, followingContent: IChatRendererContent[], element: ChatTreeItem): boolean;
 
-	private updateAriaLabel(element: HTMLElement, label: string, expanded?: boolean): void {
+	protected updateAriaLabel(element: HTMLElement, label: string, expanded?: boolean): void {
 		element.ariaLabel = label;
 		element.ariaExpanded = String(expanded);
 	}

src/vs/workbench/contrib/chat/browser/widget/chatContentParts/chatSubagentContentPart.ts

@@ -103,10 +103,11 @@ export class ChatSubagentContentPart extends ChatCollapsibleContentPart implemen
 	// Current tool message for collapsed title (persists even after tool completes)
 	private currentRunningToolMessage: string | undefined;
 
-	// Model name used by this subagent for hover tooltip
+	// Model name used by this subagent
 	private modelName: string | undefined;
 	private _isDefaultDescription: boolean;
 	private readonly _hoverDisposable = this._register(new MutableDisposable());
+	private titleModelSpan: HTMLElement | undefined;
 
 	// Confirmation auto-expand tracking
 	private toolsWaitingForConfirmation: number = 0;
@@ -283,6 +284,7 @@ export class ChatSubagentContentPart extends ChatCollapsibleContentPart implemen
 
 		// Set up hover tooltip with model name if available
 		this.updateHover();
+		this.updateTitle();
 
 		// Render the prompt section at the start if available (must be after wrapper is initialized)
 		this.renderPromptSection();
@@ -490,6 +492,7 @@ export class ChatSubagentContentPart extends ChatCollapsibleContentPart implemen
 		if (!this.isActive) {
 			labelElement.textContent = '';
 			this.titleShimmerSpan = undefined;
+			this.titleModelSpan = undefined;
 
 			this._titleDetailRendered.clear();
 			this._titleFileWidgetStore.clear();
@@ -503,7 +506,13 @@ export class ChatSubagentContentPart extends ChatCollapsibleContentPart implemen
 			descSpan.textContent = ` ${this.description}`;
 			labelElement.appendChild(descSpan);
 
-			this._collapseButton.element.ariaLabel = shimmerText;
+			if (this.modelName) {
+				this.titleModelSpan = $('span.chat-subagent-model-label');
+				this.titleModelSpan.textContent = ` \u2014 ${this.modelName}`;
+				labelElement.appendChild(this.titleModelSpan);
+			}
+
+			this._collapseButton.element.ariaLabel = this.getTitleAriaLabel();
 			this._collapseButton.element.ariaExpanded = String(this.isExpanded());
 			return;
 		}
@@ -513,9 +522,25 @@ export class ChatSubagentContentPart extends ChatCollapsibleContentPart implemen
 			labelElement.textContent = '';
 			this.titleShimmerSpan = $('span.chat-thinking-title-shimmer');
 			labelElement.appendChild(this.titleShimmerSpan);
+			this.titleModelSpan = undefined;
+			this.titleDetailContainer = undefined;
 		}
 		this.titleShimmerSpan.textContent = shimmerText;
 
+		// Show model name inline during active state if available
+		if (this.modelName) {
+			if (this.titleModelSpan) {
+				this.titleModelSpan.textContent = ` \u2014 ${this.modelName}`;
+			} else {
+				this.titleModelSpan = $('span.chat-subagent-model-label');
+				this.titleModelSpan.textContent = ` \u2014 ${this.modelName}`;
+				this.titleShimmerSpan.after(this.titleModelSpan);
+			}
+		} else if (this.titleModelSpan) {
+			this.titleModelSpan.remove();
+			this.titleModelSpan = undefined;
+		}
+
 		// Dispose previous detail rendering
 		this._titleDetailRendered.clear();
 		this._titleFileWidgetStore.clear();
@@ -539,13 +564,31 @@ export class ChatSubagentContentPart extends ChatCollapsibleContentPart implemen
 			this.titleDetailContainer = result.element;
 		}
 
-		const fullLabel = `${shimmerText}${toolCallText}`;
-		this._collapseButton.element.ariaLabel = fullLabel;
+		this._collapseButton.element.ariaLabel = this.getTitleAriaLabel();
 		this._collapseButton.element.ariaExpanded = String(this.isExpanded());
 	}
 
+	protected override updateAriaLabel(element: HTMLElement, _label: string, expanded?: boolean): void {
+		element.ariaLabel = this.getTitleAriaLabel();
+		element.ariaExpanded = String(expanded);
+	}
+
+	private getTitleAriaLabel(): string {
+		const rawName = this.agentName || localize('chat.subagent.prefix', 'Subagent');
+		const prefix = rawName.charAt(0).toUpperCase() + rawName.slice(1);
+		const modelFragment = this.modelName ? localize('chat.subagent.ariaLabel.modelFragment', " \u2014 {0}", this.modelName) : '';
+		const toolFragment = (this.currentRunningToolMessage && this.isActive) ? localize('chat.subagent.ariaLabel.toolFragment', " \u2014 {0}", this.currentRunningToolMessage) : '';
+
+		return localize('chat.subagent.ariaLabel', "{0}: {1}{2}{3}", prefix, this.description, modelFragment, toolFragment);
+	}
+
 	private updateHover(): void {
-		if (!this.modelName || !this._collapseButton) {
+		if (!this._collapseButton) {
+			return;
+		}
+
+		if (!this.modelName) {
+			this._hoverDisposable.clear();
 			return;
 		}
 
@@ -754,17 +797,22 @@ export class ChatSubagentContentPart extends ChatCollapsibleContentPart implemen
 					// after the part was first constructed in PendingConfirmation).
 					// Re-read metadata and update the title if real values are
 					// now available that we didn't have before.
-					const { description, isDefaultDescription, agentName } = ChatSubagentContentPart.extractSubagentInfo(toolInvocation);
+					const { description, isDefaultDescription, agentName, modelName } = ChatSubagentContentPart.extractSubagentInfo(toolInvocation);
 					const descriptionChanged = this._isDefaultDescription && !isDefaultDescription;
 					const agentNameChanged = !!agentName && agentName !== this.agentName;
-					if (descriptionChanged || agentNameChanged) {
+					const modelNameChanged = modelName !== this.modelName;
+					if (descriptionChanged || agentNameChanged || modelNameChanged) {
 						if (descriptionChanged) {
 							this.description = description;
 							this._isDefaultDescription = isDefaultDescription;
 						}
 						if (agentNameChanged) {
 							this.agentName = agentName;
 						}
+						if (modelNameChanged) {
+							this.modelName = modelName;
+							this.updateHover();
+						}
 						this.updateTitle();
 					}
 				}

src/vs/workbench/contrib/chat/browser/widget/chatContentParts/media/chatSubagentContent.css

@@ -19,6 +19,12 @@
 		overflow: visible;
 	}
 
+	/* Model label shown in subagent title */
+	.chat-subagent-model-label {
+		color: var(--vscode-descriptionForeground);
+		font-weight: normal;
+	}
+
 	/* Prompt and result section styling */
 	.chat-subagent-section {
 		padding: 4px 12px 4px 18px;

src/vs/workbench/contrib/chat/test/browser/widget/chatContentParts/chatSubagentContentPart.test.ts

@@ -1615,5 +1615,227 @@ suite('ChatSubagentContentPart', () => {
 			const modelHover = setupDelayedHoverCalls.find(c => c.content.includes('Claude Sonnet 4'));
 			assert.ok(modelHover, 'Should set up hover with model name after completion');
 		});
+
+		test('should show model name in title for serialized invocations', () => {
+			const serializedInvocation = createMockSerializedToolInvocation({
+				toolSpecificData: {
+					kind: 'subagent',
+					description: 'Completed task',
+					agentName: 'TestAgent',
+					prompt: 'Do the thing',
+					result: 'Done',
+					modelName: 'GPT-4o'
+				}
+			});
+			const context = createMockRenderContext(true);
+
+			const part = createPart(serializedInvocation, context);
+			const button = getCollapseButton(part);
+			assert.ok(button, 'Should have collapse button');
+
+			const label = getCollapseButtonLabel(button);
+			assert.ok(label, 'Should have label');
+
+			const modelLabel = label.querySelector('.chat-subagent-model-label');
+			assert.ok(modelLabel, 'Should have model label element in title');
+			assert.ok(modelLabel.textContent?.includes('GPT-4o'), 'Model label should contain model name');
+		});
+
+		test('should not show model name in title when no model name is available', () => {
+			const serializedInvocation = createMockSerializedToolInvocation({
+				toolSpecificData: {
+					kind: 'subagent',
+					description: 'Completed task',
+					agentName: 'TestAgent',
+					prompt: 'Do the thing',
+					result: 'Done',
+					// no modelName
+				}
+			});
+			const context = createMockRenderContext(true);
+
+			const part = createPart(serializedInvocation, context);
+			const button = getCollapseButton(part);
+			assert.ok(button, 'Should have collapse button');
+
+			const label = getCollapseButtonLabel(button);
+			assert.ok(label, 'Should have label');
+
+			const modelLabel = label.querySelector('.chat-subagent-model-label');
+			assert.strictEqual(modelLabel, null, 'Should not have model label when no model name');
+		});
+
+		test('should show model name in title after tool completion', () => {
+			const toolSpecificData: IChatSubagentToolInvocationData = {
+				kind: 'subagent',
+				description: 'Working on task',
+				agentName: 'TestAgent',
+				prompt: 'Do stuff',
+			};
+
+			const toolInvocation = createMockToolInvocation({
+				toolSpecificData,
+				stateType: IChatToolInvocation.StateKind.Executing,
+			});
+			const context = createMockRenderContext(false);
+
+			const part = createPart(toolInvocation, context);
+			const button = getCollapseButton(part);
+			assert.ok(button, 'Should have collapse button');
+
+			// Simulate invoke() setting modelName on toolSpecificData
+			toolSpecificData.modelName = 'Claude Sonnet 4';
+
+			// Simulate tool completion
+			const state = toolInvocation.state as ReturnType<typeof observableValue<IChatToolInvocation.State>>;
+			state.set(createState(IChatToolInvocation.StateKind.Completed), undefined);
+
+			const label = getCollapseButtonLabel(button);
+			assert.ok(label, 'Should have label');
+
+			const modelLabel = label.querySelector('.chat-subagent-model-label');
+			assert.ok(modelLabel, 'Should have model label element after completion');
+			assert.ok(modelLabel.textContent?.includes('Claude Sonnet 4'), 'Model label should contain resolved model name');
+		});
+
+		test('should include model name in aria-label for completed subagents', () => {
+			const serializedInvocation = createMockSerializedToolInvocation({
+				toolSpecificData: {
+					kind: 'subagent',
+					description: 'Completed task',
+					agentName: 'TestAgent',
+					prompt: 'Do the thing',
+					result: 'Done',
+					modelName: 'GPT-4o'
+				}
+			});
+			const context = createMockRenderContext(true);
+
+			const part = createPart(serializedInvocation, context);
+			const button = getCollapseButton(part);
+			assert.ok(button, 'Should have collapse button');
+
+			const ariaLabel = button.getAttribute('aria-label') ?? '';
+			assert.ok(ariaLabel.includes('GPT-4o'), 'aria-label should include model name for completed subagent');
+		});
+
+		test('should not duplicate model label on repeated updateTitle calls', () => {
+			const toolSpecificData: IChatSubagentToolInvocationData = {
+				kind: 'subagent',
+				description: 'Working on task',
+				agentName: 'TestAgent',
+				prompt: 'Do stuff',
+				modelName: 'Claude Sonnet 4',
+			};
+
+			const toolInvocation = createMockToolInvocation({
+				toolSpecificData,
+				stateType: IChatToolInvocation.StateKind.Executing,
+			});
+			const context = createMockRenderContext(false);
+
+			const part = createPart(toolInvocation, context);
+
+			// Force multiple title updates by tracking tool invocations
+			const childTool = createMockToolInvocation({
+				stateType: IChatToolInvocation.StateKind.Executing,
+				invocationMessage: 'Reading file',
+			});
+			part.trackToolState(childTool);
+
+			const childTool2 = createMockToolInvocation({
+				stateType: IChatToolInvocation.StateKind.Executing,
+				invocationMessage: 'Writing file',
+			});
+			part.trackToolState(childTool2);
+
+			const button = getCollapseButton(part);
+			assert.ok(button, 'Should have collapse button');
+			const label = getCollapseButtonLabel(button);
+			assert.ok(label, 'Should have label');
+
+			const modelLabels = label.querySelectorAll('.chat-subagent-model-label');
+			assert.strictEqual(modelLabels.length, 1, 'Should have exactly one model label after repeated updates');
+		});
+
+		test('should show model name in title for active invocations with initial modelName', () => {
+			const toolInvocation = createMockToolInvocation({
+				toolSpecificData: {
+					kind: 'subagent',
+					description: 'Working on task',
+					agentName: 'TestAgent',
+					prompt: 'Do stuff',
+					modelName: 'GPT-4o',
+				},
+				stateType: IChatToolInvocation.StateKind.Executing,
+			});
+			const context = createMockRenderContext(false);
+
+			const part = createPart(toolInvocation, context);
+			const button = getCollapseButton(part);
+			assert.ok(button, 'Should have collapse button');
+
+			const label = getCollapseButtonLabel(button);
+			assert.ok(label, 'Should have label');
+			const modelLabel = label.querySelector('.chat-subagent-model-label');
+			assert.ok(modelLabel, 'Should have model label element while active');
+			assert.ok(modelLabel.textContent?.includes('GPT-4o'), 'Model label should contain initial model name');
+
+			const ariaLabel = button.getAttribute('aria-label') ?? '';
+			assert.ok(ariaLabel.includes('GPT-4o'), 'aria-label should include model name while active');
+		});
+
+		test('should preserve model name in aria-label after expand and collapse', () => {
+			const serializedInvocation = createMockSerializedToolInvocation({
+				toolSpecificData: {
+					kind: 'subagent',
+					description: 'Completed task',
+					agentName: 'TestAgent',
+					prompt: 'Do the thing',
+					result: 'Done',
+					modelName: 'GPT-4o'
+				}
+			});
+			const context = createMockRenderContext(true);
+
+			const part = createPart(serializedInvocation, context);
+			const button = getCollapseButton(part);
+			assert.ok(button, 'Should have collapse button');
+
+			button.click();
+			assert.ok(button.getAttribute('aria-label')?.includes('GPT-4o'), 'aria-label should include model name after expand');
+
+			button.click();
+			assert.ok(button.getAttribute('aria-label')?.includes('GPT-4o'), 'aria-label should include model name after collapse');
+		});
+
+		test('should show model name when active metadata updates later', () => {
+			const toolSpecificData: IChatSubagentToolInvocationData = {
+				kind: 'subagent',
+				description: 'Working on task',
+				agentName: 'TestAgent',
+				prompt: 'Do stuff',
+			};
+			const toolInvocation = createMockToolInvocation({
+				toolSpecificData,
+				stateType: IChatToolInvocation.StateKind.Executing,
+			});
+			const context = createMockRenderContext(false);
+
+			const part = createPart(toolInvocation, context);
+			const button = getCollapseButton(part);
+			assert.ok(button, 'Should have collapse button');
+
+			toolSpecificData.modelName = 'Claude Sonnet 4';
+			const state = toolInvocation.state as ReturnType<typeof observableValue<IChatToolInvocation.State>>;
+			state.set(createState(IChatToolInvocation.StateKind.Executing), undefined);
+
+			const label = getCollapseButtonLabel(button);
+			assert.ok(label, 'Should have label');
+			const modelLabel = label.querySelector('.chat-subagent-model-label');
+			assert.ok(modelLabel, 'Should have model label element after metadata update');
+			assert.ok(modelLabel.textContent?.includes('Claude Sonnet 4'), 'Model label should contain late model name');
+			assert.ok(button.getAttribute('aria-label')?.includes('Claude Sonnet 4'), 'aria-label should include late model name');
+		});
 	});
 });