diff --git a/src/vs/workbench/api/browser/mainThreadChatSessions.ts b/src/vs/workbench/api/browser/mainThreadChatSessions.ts
index ff23264d592..50a510c6c0d 100644
--- a/src/vs/workbench/api/browser/mainThreadChatSessions.ts
+++ b/src/vs/workbench/api/browser/mainThreadChatSessions.ts
@@ -16,6 +16,7 @@ import { URI, UriComponents } from '../../../base/common/uri.js';
 import { localize } from '../../../nls.js';
 import { IDialogService } from '../../../platform/dialogs/common/dialogs.js';
 import { ILogService } from '../../../platform/log/common/log.js';
+import { hasValidDiff, IAgentSession } from '../../contrib/chat/browser/agentSessions/agentSessionsModel.js';
 import { ChatViewPaneTarget, IChatWidgetService, isIChatViewViewContext } from '../../contrib/chat/browser/chat.js';
 import { IChatEditorOptions } from '../../contrib/chat/browser/chatEditor.js';
 import { ChatEditorInput } from '../../contrib/chat/browser/chatEditorInput.js';
@@ -474,12 +475,14 @@ export class MainThreadChatSessions extends Disposable implements MainThreadChat
 				// We can still get stats if there is no model or if fetching from model failed
 				if (!session.changes || !model) {
 					const stats = (await this._chatService.getMetadataForSession(uri))?.stats;
-					if (stats) {
-						session.changes = {
-							files: stats.fileCount,
-							insertions: stats.added,
-							deletions: stats.removed
-						};
+					// TODO: we shouldn't be converting this, the types should match
+					const diffs: IAgentSession['changes'] = {
+						files: stats?.fileCount || 0,
+						insertions: stats?.added || 0,
+						deletions: stats?.removed || 0
+					};
+					if (hasValidDiff(diffs)) {
+						session.changes = diffs;
 					}
 				}
 
diff --git a/src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsActions.ts b/src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsActions.ts
index 8c09e5602ee..727e7103553 100644
--- a/src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsActions.ts
+++ b/src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsActions.ts
@@ -5,7 +5,7 @@
 
 import './media/agentsessionsactions.css';
 import { localize, localize2 } from '../../../../../nls.js';
-import { getAgentChangesSummary, IAgentSession } from './agentSessionsModel.js';
+import { IAgentSession, getAgentChangesSummary } from './agentSessionsModel.js';
 import { Action, IAction } from '../../../../../base/common/actions.js';
 import { ActionViewItem, IActionViewItemOptions } from '../../../../../base/browser/ui/actionbar/actionViewItems.js';
 import { CommandsRegistry, ICommandService } from '../../../../../platform/commands/common/commands.js';
diff --git a/src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsModel.ts b/src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsModel.ts
index 637e35728ee..2060d4aed82 100644
--- a/src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsModel.ts
+++ b/src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsModel.ts
@@ -64,6 +64,24 @@ interface IAgentSessionData {
 	};
 }
 
+/**
+ * Checks if the provided changes object represents valid diff information.
+ */
+export function hasValidDiff(changes: IAgentSession['changes']): boolean {
+	if (!changes) {
+		return false;
+	}
+
+	if (changes instanceof Array) {
+		return changes.length > 0;
+	}
+
+	return changes.files > 0 || changes.insertions > 0 || changes.deletions > 0;
+}
+
+/**
+ * Gets a summary of agent session changes, converting from array format to object format if needed.
+ */
 export function getAgentChangesSummary(changes: IAgentSession['changes']) {
 	if (!changes) {
 		return;
diff --git a/src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsViewer.ts b/src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsViewer.ts
index b25ccb3e2a1..1d77ae313b2 100644
--- a/src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsViewer.ts
+++ b/src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsViewer.ts
@@ -13,7 +13,7 @@ import { ICompressedTreeNode } from '../../../../../base/browser/ui/tree/compres
 import { ICompressibleKeyboardNavigationLabelProvider, ICompressibleTreeRenderer } from '../../../../../base/browser/ui/tree/objectTree.js';
 import { ITreeNode, ITreeElementRenderDetails, IAsyncDataSource, ITreeSorter, ITreeDragAndDrop, ITreeDragOverReaction } from '../../../../../base/browser/ui/tree/tree.js';
 import { Disposable, DisposableStore, IDisposable } from '../../../../../base/common/lifecycle.js';
-import { IAgentSession, IAgentSessionsModel, isAgentSession, isAgentSessionsModel } from './agentSessionsModel.js';
+import { IAgentSession, IAgentSessionsModel, isAgentSession, isAgentSessionsModel, hasValidDiff } from './agentSessionsModel.js';
 import { IconLabel } from '../../../../../base/browser/ui/iconLabel/iconLabel.js';
 import { ThemeIcon } from '../../../../../base/common/themables.js';
 import { Codicon } from '../../../../../base/common/codicons.js';
@@ -162,11 +162,9 @@ export class AgentSessionRenderer implements ICompressibleTreeRenderer<IAgentSes
 
 		// Details Actions
 		const { changes: diff } = session.element;
-		if (session.element.status !== ChatSessionStatus.InProgress && diff && this.hasValidDiff(diff)) {
-			if (diff instanceof Array ? diff.length > 0 : (diff.files > 0 || diff.insertions > 0 || diff.deletions > 0)) {
-				const diffAction = template.elementDisposable.add(new AgentSessionShowDiffAction(session.element));
-				template.detailsToolbar.push([diffAction], { icon: false, label: true });
-			}
+		if (session.element.status !== ChatSessionStatus.InProgress && diff && hasValidDiff(diff)) {
+			const diffAction = template.elementDisposable.add(new AgentSessionShowDiffAction(session.element));
+			template.detailsToolbar.push([diffAction], { icon: false, label: true });
 		}
 
 		// Description otherwise
@@ -181,17 +179,7 @@ export class AgentSessionRenderer implements ICompressibleTreeRenderer<IAgentSes
 		this.renderHover(session, template);
 	}
 
-	private hasValidDiff(diff: IAgentSession['changes']): boolean {
-		if (!diff) {
-			return false;
-		}
 
-		if (diff instanceof Array) {
-			return diff.length > 0;
-		}
-
-		return diff.files > 0 || diff.insertions > 0 || diff.deletions > 0;
-	}
 
 	private getIcon(session: IAgentSession): ThemeIcon {
 		if (session.status === ChatSessionStatus.InProgress) {