sessions: enable customizations UI for all session types with deep-link navigation (#312398)

Previously the customizations sidebar only worked for copilotcli sessions. This change extends support to any session type that has a registered content provider, making it work for claude-code and other AHP harnesses. - Remove hardcoded copilotcli gate in mainThreadChatAgents2; now any session type with a registered content provider schema is accepted - Wire ICustomizationHarnessService into count widgets so they use the active harness's itemProvider when available (avoids count mismatches for remote item providers) - Add getActiveItemProvider() utility and update getCustomizationTotalCount() to accept an optional itemProvider for harness-backed sessions - Each sidebar customization link now deep-links to its section in the management editor via selectSectionById - Use reader.store pattern instead of MutableDisposable + manual rebind for itemProvider change subscriptions - Add tests for getActiveItemProvider and getCustomizationTotalCount with itemProvider; add ICustomizationHarnessService mock to widget fixture - Update AI_CUSTOMIZATIONS.md to reflect the new multi-harness sessions behavior
2026-05-31 00:10:04 +08:00 · 2026-04-24 10:29:55 -07:00
parent 4651bee042
commit 439c85ab2d
7 changed files with 250 additions and 26 deletions
--- a/src/vs/sessions/AI_CUSTOMIZATIONS.md
+++ b/src/vs/sessions/AI_CUSTOMIZATIONS.md
@@ -51,7 +51,7 @@ Sessions-specific overrides:
 ```
 src/vs/sessions/contrib/chat/browser/
 ├── aiCustomizationWorkspaceService.ts          # Sessions workspace service override
-├── customizationHarnessService.ts              # Sessions harness service (CLI harness only)
+├── customizationHarnessService.ts              # Sessions harness service (accepts any content-provider-backed session type)
 └── promptsService.ts                           # AgenticPromptsService (CLI user roots)
 src/vs/sessions/contrib/sessions/browser/
 ├── aiCustomizationShortcutsWidget.ts           # Shortcuts widget
@@ -92,7 +92,7 @@ Available harnesses:
 | `claude` | Claude | Restricts user roots to `~/.claude`; hides Prompts + Plugins sections |

 In core VS Code, all three harnesses are registered but CLI and Claude only appear when their respective agents are registered (`requiredAgentId` checked via `IChatAgentService`). VS Code is the default.
-In sessions, only CLI is registered (single harness, toggle bar hidden).
+In sessions, harnesses are accepted for any session type that has a registered content provider (checked via `IChatSessionsService.getContentProviderSchemes()`). AHP remote servers register directly via `registerExternalHarness`.

 ### IHarnessDescriptor

@@ -220,7 +220,7 @@ Skills that are directly invoked by UI elements (toolbar buttons, menu items) ar

 ### Count Consistency

-`customizationCounts.ts` uses the **same data sources** as the list widget. Both go through the active harness's `ICustomizationItemProvider` (or the `PromptsServiceCustomizationItemProvider` fallback), ensuring counts match what the list displays.
+`customizationCounts.ts` uses the **same data sources** as the list widget. When a harness with an `itemProvider` is active (determined by `getActiveItemProvider()`), counts come from that provider's `provideChatSessionCustomizations()`. Otherwise, both counts and the list go through the `PromptsServiceCustomizationItemProvider` fallback, ensuring counts match what the list displays.

 ### Item Badges

--- a/src/vs/sessions/contrib/sessions/browser/aiCustomizationShortcutsWidget.ts
+++ b/src/vs/sessions/contrib/sessions/browser/aiCustomizationShortcutsWidget.ts
@@ -21,8 +21,10 @@ import { IPromptsService } from '../../../../workbench/contrib/chat/common/promp
 import { IMcpService } from '../../../../workbench/contrib/mcp/common/mcpTypes.js';
 import { IAICustomizationWorkspaceService } from '../../../../workbench/contrib/chat/common/aiCustomizationWorkspaceService.js';
 import { Menus } from '../../../browser/menus.js';
-import { getCustomizationTotalCount } from './customizationCounts.js';
+import { getCustomizationTotalCount, getActiveItemProvider } from './customizationCounts.js';
 import { IAgentPluginService } from '../../../../workbench/contrib/chat/common/plugins/agentPluginService.js';
+import { ICustomizationHarnessService } from '../../../../workbench/contrib/chat/common/customizationHarnessService.js';
+import { ISessionsManagementService } from '../../../services/sessions/common/sessionsManagement.js';

 const $ = DOM.$;

@@ -46,6 +48,8 @@ export class AICustomizationShortcutsWidget extends Disposable {
 		@IWorkspaceContextService private readonly workspaceContextService: IWorkspaceContextService,
 		@IAICustomizationWorkspaceService private readonly workspaceService: IAICustomizationWorkspaceService,
 		@IAgentPluginService private readonly agentPluginService: IAgentPluginService,
+		@ICustomizationHarnessService private readonly harnessService: ICustomizationHarnessService,
+		@ISessionsManagementService private readonly sessionsManagementService: ISessionsManagementService,
 	) {
 		super();

@@ -101,9 +105,10 @@ export class AICustomizationShortcutsWidget extends Disposable {
 		}));

 		let updateCountRequestId = 0;
+
 		const updateHeaderTotalCount = async () => {
 			const requestId = ++updateCountRequestId;
-			const totalCount = await getCustomizationTotalCount(this.promptsService, this.mcpService, this.workspaceService, this.workspaceContextService, this.agentPluginService);
+			const totalCount = await getCustomizationTotalCount(this.promptsService, this.mcpService, this.workspaceService, this.workspaceContextService, this.agentPluginService, getActiveItemProvider(this.sessionsManagementService, this.harnessService));
 			if (requestId !== updateCountRequestId) {
 				return;
 			}
@@ -123,6 +128,15 @@ export class AICustomizationShortcutsWidget extends Disposable {
 			this.workspaceService.activeProjectRoot.read(reader);
 			updateHeaderTotalCount();
 		}));
+		this._register(autorun(reader => {
+			this.sessionsManagementService.activeSession.read(reader);
+			this.harnessService.availableHarnesses.read(reader);
+			const provider = getActiveItemProvider(this.sessionsManagementService, this.harnessService);
+			if (provider) {
+				reader.store.add(provider.onDidChange(() => updateHeaderTotalCount()));
+			}
+			updateHeaderTotalCount();
+		}));
 		updateHeaderTotalCount();

 		// Toggle collapse on header click
--- a/src/vs/sessions/contrib/sessions/browser/customizationCounts.ts
+++ b/src/vs/sessions/contrib/sessions/browser/customizationCounts.ts
@@ -15,7 +15,9 @@ import { IMcpService } from '../../../../workbench/contrib/mcp/common/mcpTypes.j
 import { IAICustomizationWorkspaceService, applyStorageSourceFilter, IStorageSourceFilter } from '../../../../workbench/contrib/chat/common/aiCustomizationWorkspaceService.js';
 import { parseHooksFromFile } from '../../../../workbench/contrib/chat/common/promptSyntax/hookCompatibility.js';
 import { IAgentPluginService } from '../../../../workbench/contrib/chat/common/plugins/agentPluginService.js';
+import { ICustomizationHarnessService, ICustomizationItemProvider } from '../../../../workbench/contrib/chat/common/customizationHarnessService.js';
 import { parse as parseJSONC } from '../../../../base/common/jsonc.js';
+import { ISessionsManagementService } from '../../../services/sessions/common/sessionsManagement.js';

 export interface ISourceCounts {
 	readonly workspace: number;
@@ -136,19 +138,41 @@ export async function getSourceCounts(
 	};
 }

+const PROMPT_TYPES: PromptsType[] = [PromptsType.agent, PromptsType.skill, PromptsType.instructions, PromptsType.hook];
+const PROMPT_TYPE_SET = new Set<string>(PROMPT_TYPES);
+
 export async function getCustomizationTotalCount(
 	promptsService: IPromptsService,
 	mcpService: IMcpService,
 	workspaceService: IAICustomizationWorkspaceService,
 	workspaceContextService: IWorkspaceContextService,
 	agentPluginService?: IAgentPluginService,
+	itemProvider?: ICustomizationItemProvider,
 ): Promise<number> {
-	const types: PromptsType[] = [PromptsType.agent, PromptsType.skill, PromptsType.instructions, PromptsType.hook];
-	const results = await Promise.all(types.map(type => {
-		const filter = workspaceService.getStorageSourceFilter(type);
-		return getSourceCounts(promptsService, type, filter, workspaceContextService, workspaceService)
-			.then(counts => getSourceCountsTotal(counts, filter));
-	}));
+	let promptTotal: number;
+	if (itemProvider) {
+		const allItems = await itemProvider.provideChatSessionCustomizations(CancellationToken.None);
+		promptTotal = allItems?.filter(item => PROMPT_TYPE_SET.has(item.type)).length ?? 0;
+	} else {
+		const results = await Promise.all(PROMPT_TYPES.map(type => {
+			const filter = workspaceService.getStorageSourceFilter(type);
+			return getSourceCounts(promptsService, type, filter, workspaceContextService, workspaceService)
+				.then(counts => getSourceCountsTotal(counts, filter));
+		}));
+		promptTotal = results.reduce((sum, n) => sum + n, 0);
+	}
+
 	const pluginCount = agentPluginService?.plugins.get().length ?? 0;
-	return results.reduce((sum, n) => sum + n, 0) + mcpService.servers.get().length + pluginCount;
+	return promptTotal + mcpService.servers.get().length + pluginCount;
+}
+
+export function getActiveItemProvider(
+	sessionsManagementService: ISessionsManagementService,
+	harnessService: ICustomizationHarnessService,
+): ICustomizationItemProvider | undefined {
+	const sessionType = sessionsManagementService.activeSession.get()?.sessionType;
+	if (sessionType) {
+		return harnessService.findHarnessById(sessionType)?.itemProvider;
+	}
+	return undefined;
 }
--- a/src/vs/sessions/contrib/sessions/browser/customizationsToolbar.contribution.ts
+++ b/src/vs/sessions/contrib/sessions/browser/customizationsToolbar.contribution.ts
@@ -5,6 +5,7 @@

 import '../../../browser/media/sidebarActionButton.css';
 import './media/customizationsToolbar.css';
+import { CancellationToken } from '../../../../base/common/cancellation.js';
 import { Disposable, DisposableStore } from '../../../../base/common/lifecycle.js';
 import { ThemeIcon } from '../../../../base/common/themables.js';
 import { localize, localize2 } from '../../../../nls.js';
@@ -12,6 +13,7 @@ import { Action2, registerAction2 } from '../../../../platform/actions/common/ac
 import { IActionViewItemService } from '../../../../platform/actions/browser/actionViewItemService.js';
 import { IInstantiationService, ServicesAccessor } from '../../../../platform/instantiation/common/instantiation.js';
 import { IWorkbenchContribution, registerWorkbenchContribution2, WorkbenchPhase } from '../../../../workbench/common/contributions.js';
+import { AICustomizationManagementEditor } from '../../../../workbench/contrib/chat/browser/aiCustomization/aiCustomizationManagementEditor.js';
 import { AICustomizationManagementEditorInput } from '../../../../workbench/contrib/chat/browser/aiCustomization/aiCustomizationManagementEditorInput.js';
 import { IPromptsService } from '../../../../workbench/contrib/chat/common/promptSyntax/service/promptsService.js';
 import { PromptsType } from '../../../../workbench/contrib/chat/common/promptSyntax/promptTypes.js';
@@ -27,16 +29,18 @@ import { IWorkspaceContextService } from '../../../../platform/workspace/common/
 import { IFileService } from '../../../../platform/files/common/files.js';
 import { Button } from '../../../../base/browser/ui/button/button.js';
 import { defaultButtonStyles } from '../../../../platform/theme/browser/defaultStyles.js';
-import { getSourceCounts, getSourceCountsTotal } from './customizationCounts.js';
+import { getSourceCounts, getSourceCountsTotal, getActiveItemProvider } from './customizationCounts.js';
 import { IEditorService } from '../../../../workbench/services/editor/common/editorService.js';
-import { IAICustomizationWorkspaceService } from '../../../../workbench/contrib/chat/common/aiCustomizationWorkspaceService.js';
+import { AICustomizationManagementSection, IAICustomizationWorkspaceService } from '../../../../workbench/contrib/chat/common/aiCustomizationWorkspaceService.js';
 import { IAgentPluginService } from '../../../../workbench/contrib/chat/common/plugins/agentPluginService.js';
+import { ICustomizationHarnessService } from '../../../../workbench/contrib/chat/common/customizationHarnessService.js';
 import { ISessionsManagementService } from '../../../services/sessions/common/sessionsManagement.js';

 export interface ICustomizationItemConfig {
 	readonly id: string;
 	readonly label: string;
 	readonly icon: ThemeIcon;
+	readonly section: typeof AICustomizationManagementSection[keyof typeof AICustomizationManagementSection];
 	readonly promptType?: PromptsType;
 	readonly isMcp?: boolean;
 	readonly isPlugins?: boolean;
@@ -47,36 +51,42 @@ export const CUSTOMIZATION_ITEMS: ICustomizationItemConfig[] = [
 		id: 'sessions.customization.agents',
 		label: localize('agents', "Agents"),
 		icon: agentIcon,
+		section: AICustomizationManagementSection.Agents,
 		promptType: PromptsType.agent,
 	},
 	{
 		id: 'sessions.customization.skills',
 		label: localize('skills', "Skills"),
 		icon: skillIcon,
+		section: AICustomizationManagementSection.Skills,
 		promptType: PromptsType.skill,
 	},
 	{
 		id: 'sessions.customization.instructions',
 		label: localize('instructions', "Instructions"),
 		icon: instructionsIcon,
+		section: AICustomizationManagementSection.Instructions,
 		promptType: PromptsType.instructions,
 	},
 	{
 		id: 'sessions.customization.hooks',
 		label: localize('hooks', "Hooks"),
 		icon: hookIcon,
+		section: AICustomizationManagementSection.Hooks,
 		promptType: PromptsType.hook,
 	},
 	{
 		id: 'sessions.customization.mcpServers',
 		label: localize('mcpServers', "MCP Servers"),
 		icon: mcpServerIcon,
+		section: AICustomizationManagementSection.McpServers,
 		isMcp: true,
 	},
 	{
 		id: 'sessions.customization.plugins',
 		label: localize('plugins', "Plugins"),
 		icon: pluginIcon,
+		section: AICustomizationManagementSection.Plugins,
 		isPlugins: true,
 	},
 ];
@@ -103,6 +113,7 @@ export class CustomizationLinkViewItem extends ActionViewItem {
 		@IAICustomizationWorkspaceService private readonly _workspaceService: IAICustomizationWorkspaceService,
 		@IFileService private readonly _fileService: IFileService,
 		@IAgentPluginService private readonly _agentPluginService: IAgentPluginService,
+		@ICustomizationHarnessService private readonly _harnessService: ICustomizationHarnessService,
 	) {
 		super(undefined, action, { ...options, icon: false, label: false });
 		this._viewItemDisposables = this._register(new DisposableStore());
@@ -153,6 +164,11 @@ export class CustomizationLinkViewItem extends ActionViewItem {
 		this._viewItemDisposables.add(this._workspaceContextService.onDidChangeWorkspaceFolders(() => this._updateCounts()));
 		this._viewItemDisposables.add(autorun(reader => {
 			this._activeSessionService.activeSession.read(reader);
+			this._harnessService.availableHarnesses.read(reader);
+			const provider = getActiveItemProvider(this._activeSessionService, this._harnessService);
+			if (provider) {
+				reader.store.add(provider.onDidChange(() => this._updateCounts()));
+			}
 			this._updateCounts();
 		}));

@@ -168,16 +184,26 @@ export class CustomizationLinkViewItem extends ActionViewItem {
 		}

 		const requestId = ++this._updateCountsRequestId;
+		const itemProvider = getActiveItemProvider(this._activeSessionService, this._harnessService);

 		if (this._config.promptType) {
-			const type = this._config.promptType;
-			const filter = this._workspaceService.getStorageSourceFilter(type);
-			const counts = await getSourceCounts(this._promptsService, type, filter, this._workspaceContextService, this._workspaceService, this._fileService);
-			if (requestId !== this._updateCountsRequestId) {
-				return;
+			if (itemProvider) {
+				const allItems = await itemProvider.provideChatSessionCustomizations(CancellationToken.None);
+				if (requestId !== this._updateCountsRequestId) {
+					return;
+				}
+				const total = allItems?.filter(item => item.type === this._config.promptType).length ?? 0;
+				this._renderTotalCount(this._countContainer, total);
+			} else {
+				const type = this._config.promptType;
+				const filter = this._workspaceService.getStorageSourceFilter(type);
+				const counts = await getSourceCounts(this._promptsService, type, filter, this._workspaceContextService, this._workspaceService, this._fileService);
+				if (requestId !== this._updateCountsRequestId) {
+					return;
+				}
+				const total = getSourceCountsTotal(counts, filter);
+				this._renderTotalCount(this._countContainer, total);
 			}
-			const total = getSourceCountsTotal(counts, filter);
-			this._renderTotalCount(this._countContainer, total);
 		} else if (this._config.isMcp) {
 			const total = this._mcpService.servers.get().length;
 			this._renderTotalCount(this._countContainer, total);
@@ -231,8 +257,17 @@ export class CustomizationsToolbarContribution extends Disposable implements IWo
 				}
 				async run(accessor: ServicesAccessor): Promise<void> {
 					const editorService = accessor.get(IEditorService);
+					const harnessService = accessor.get(ICustomizationHarnessService);
+					const sessionsManagementService = accessor.get(ISessionsManagementService);
+					const activeSessionType = sessionsManagementService.activeSession.get()?.sessionType;
+					if (activeSessionType && harnessService.findHarnessById(activeSessionType)) {
+						harnessService.setActiveHarness(activeSessionType);
+					}
 					const input = AICustomizationManagementEditorInput.getOrCreate();
-					await editorService.openEditor(input, { pinned: true });
+					const pane = await editorService.openEditor(input, { pinned: true });
+					if (pane instanceof AICustomizationManagementEditor) {
+						pane.selectSectionById(config.section);
+					}
 				}
 			}));
 		}
--- a/src/vs/sessions/contrib/sessions/test/browser/aiCustomizationShortcutsWidget.fixture.ts
+++ b/src/vs/sessions/contrib/sessions/test/browser/aiCustomizationShortcutsWidget.fixture.ts
@@ -21,6 +21,7 @@ import { ILanguageModelsService } from '../../../../../workbench/contrib/chat/co
 import { IMcpServer, IMcpService } from '../../../../../workbench/contrib/mcp/common/mcpTypes.js';
 import { IAICustomizationWorkspaceService, IStorageSourceFilter } from '../../../../../workbench/contrib/chat/common/aiCustomizationWorkspaceService.js';
 import { IAgentPluginService } from '../../../../../workbench/contrib/chat/common/plugins/agentPluginService.js';
+import { ICustomizationHarnessService } from '../../../../../workbench/contrib/chat/common/customizationHarnessService.js';
 import { ComponentFixtureContext, createEditorServices, defineComponentFixture, defineThemedFixtureGroup, registerWorkbenchServices } from '../../../../../workbench/test/browser/componentFixtures/fixtureUtils.js';
 import { AICustomizationShortcutsWidget } from '../../browser/aiCustomizationShortcutsWidget.js';
 import { CUSTOMIZATION_ITEMS, CustomizationLinkViewItem } from '../../browser/customizationsToolbar.contribution.js';
@@ -204,6 +205,10 @@ function renderWidget(ctx: ComponentFixtureContext, options?: { mcpServerCount?:
 			reg.defineInstance(ISessionsManagementService, new class extends mock<ISessionsManagementService>() {
 				override readonly activeSession = observableValue<IActiveSession | undefined>('activeSession', undefined);
 			}());
+			reg.defineInstance(ICustomizationHarnessService, new class extends mock<ICustomizationHarnessService>() {
+				override readonly availableHarnesses = observableValue<readonly never[]>('availableHarnesses', []);
+				override findHarnessById() { return undefined; }
+			}());
 			reg.defineInstance(IFileService, new class extends mock<IFileService>() {
 				override readonly onDidFilesChange = Event.None;
 			}());
--- a/src/vs/sessions/contrib/sessions/test/browser/customizationCounts.test.ts
+++ b/src/vs/sessions/contrib/sessions/test/browser/customizationCounts.test.ts
@@ -10,10 +10,14 @@ import { PromptsType } from '../../../../../workbench/contrib/chat/common/prompt
 import { IPromptsService, PromptsStorage, IPromptPath, ILocalPromptPath, IUserPromptPath, IExtensionPromptPath, IAgentInstructionFile, AgentInstructionFileType } from '../../../../../workbench/contrib/chat/common/promptSyntax/service/promptsService.js';
 import { IAICustomizationWorkspaceService, IStorageSourceFilter } from '../../../../../workbench/contrib/chat/common/aiCustomizationWorkspaceService.js';
 import { IWorkspaceContextService, IWorkspace, IWorkspaceFolder, WorkbenchState } from '../../../../../platform/workspace/common/workspace.js';
-import { getSourceCounts, getSourceCountsTotal, getCustomizationTotalCount } from '../../browser/customizationCounts.js';
+import { getSourceCounts, getSourceCountsTotal, getCustomizationTotalCount, getActiveItemProvider } from '../../browser/customizationCounts.js';
 import { IMcpService } from '../../../../../workbench/contrib/mcp/common/mcpTypes.js';
 import { Event } from '../../../../../base/common/event.js';
 import { observableValue } from '../../../../../base/common/observable.js';
+import { ICustomizationHarnessService, ICustomizationItem, ICustomizationItemProvider, IHarnessDescriptor } from '../../../../../workbench/contrib/chat/common/customizationHarnessService.js';
+import { IActiveSession, ISessionsManagementService } from '../../../../services/sessions/common/sessionsManagement.js';
+import { CancellationToken } from '../../../../../base/common/cancellation.js';
+import { IAgentPluginService } from '../../../../../workbench/contrib/chat/common/plugins/agentPluginService.js';

 function localFile(path: string): ILocalPromptPath {
 	return { uri: URI.file(path), storage: PromptsStorage.local, type: PromptsType.instructions };
@@ -691,6 +695,148 @@ suite('customizationCounts', () => {
 		});
 	});

+	suite('getActiveItemProvider', () => {
+		function createMockSessionsService(sessionType?: string): ISessionsManagementService {
+			const activeSession = observableValue<IActiveSession | undefined>(
+				'test',
+				sessionType ? { sessionType } as IActiveSession : undefined,
+			);
+			return { activeSession } as unknown as ISessionsManagementService;
+		}
+
+		function createMockHarnessService(harnesses: { id: string; itemProvider?: ICustomizationItemProvider }[]): ICustomizationHarnessService {
+			return {
+				findHarnessById: (sessionType: string) => {
+					const h = harnesses.find(h => h.id === sessionType);
+					return h ? { id: h.id, itemProvider: h.itemProvider } as IHarnessDescriptor : undefined;
+				},
+			} as unknown as ICustomizationHarnessService;
+		}
+
+		test('returns undefined when no active session', () => {
+			const sessionsService = createMockSessionsService(undefined);
+			const harnessService = createMockHarnessService([]);
+			assert.strictEqual(getActiveItemProvider(sessionsService, harnessService), undefined);
+		});
+
+		test('returns undefined when session type has no matching harness', () => {
+			const sessionsService = createMockSessionsService('unknown-type');
+			const harnessService = createMockHarnessService([{ id: 'copilotcli' }]);
+			assert.strictEqual(getActiveItemProvider(sessionsService, harnessService), undefined);
+		});
+
+		test('returns undefined when harness has no itemProvider', () => {
+			const sessionsService = createMockSessionsService('copilotcli');
+			const harnessService = createMockHarnessService([{ id: 'copilotcli', itemProvider: undefined }]);
+			assert.strictEqual(getActiveItemProvider(sessionsService, harnessService), undefined);
+		});
+
+		test('returns the itemProvider when harness exists with one', () => {
+			const mockProvider: ICustomizationItemProvider = {
+				onDidChange: Event.None,
+				provideChatSessionCustomizations: async () => [],
+			};
+			const sessionsService = createMockSessionsService('claude-code');
+			const harnessService = createMockHarnessService([{ id: 'claude-code', itemProvider: mockProvider }]);
+			assert.strictEqual(getActiveItemProvider(sessionsService, harnessService), mockProvider);
+		});
+	});
+
+	suite('getCustomizationTotalCount with itemProvider', () => {
+		function createItemProvider(items: ICustomizationItem[]): ICustomizationItemProvider {
+			return {
+				onDidChange: Event.None,
+				provideChatSessionCustomizations: async (_token: CancellationToken) => items,
+			};
+		}
+
+		function makeItem(type: string, name: string): ICustomizationItem {
+			return { uri: URI.file(`/mock/${name}`), type, name, extensionId: undefined, pluginUri: undefined };
+		}
+
+		test('uses itemProvider counts when provided', async () => {
+			const promptsService = createMockPromptsService({});
+			const mcpService = {
+				servers: observableValue('test', [{ id: 's1' }]),
+			} as unknown as IMcpService;
+			const workspaceService = createMockWorkspaceService({ filter: { sources: [PromptsStorage.local] } });
+			const contextService = createMockWorkspaceContextService([]);
+
+			const provider = createItemProvider([
+				makeItem('agent', 'my-agent'),
+				makeItem('skill', 'my-skill'),
+				makeItem('instructions', 'my-instruction'),
+				makeItem('hook', 'my-hook'),
+			]);
+
+			const total = await getCustomizationTotalCount(promptsService, mcpService, workspaceService, contextService, undefined, provider);
+
+			// 4 from provider + 1 mcp = 5
+			assert.strictEqual(total, 5);
+		});
+
+		test('ignores non-prompt types from itemProvider', async () => {
+			const promptsService = createMockPromptsService({});
+			const mcpService = {
+				servers: observableValue('test', []),
+			} as unknown as IMcpService;
+			const workspaceService = createMockWorkspaceService({ filter: { sources: [PromptsStorage.local] } });
+			const contextService = createMockWorkspaceContextService([]);
+
+			const provider = createItemProvider([
+				makeItem('agent', 'a'),
+				makeItem('unknown-type', 'x'),
+				makeItem('prompt', 'p'),
+			]);
+
+			const total = await getCustomizationTotalCount(promptsService, mcpService, workspaceService, contextService, undefined, provider);
+
+			// Only 'agent' matches the prompt types (agent, skill, instructions, hook)
+			assert.strictEqual(total, 1);
+		});
+
+		test('itemProvider returning undefined counts as zero', async () => {
+			const promptsService = createMockPromptsService({});
+			const mcpService = {
+				servers: observableValue('test', [{ id: 's1' }, { id: 's2' }]),
+			} as unknown as IMcpService;
+			const workspaceService = createMockWorkspaceService({ filter: { sources: [PromptsStorage.local] } });
+			const contextService = createMockWorkspaceContextService([]);
+
+			const provider: ICustomizationItemProvider = {
+				onDidChange: Event.None,
+				provideChatSessionCustomizations: async () => undefined,
+			};
+
+			const total = await getCustomizationTotalCount(promptsService, mcpService, workspaceService, contextService, undefined, provider);
+
+			// 0 from provider + 2 mcp = 2
+			assert.strictEqual(total, 2);
+		});
+
+		test('sums itemProvider counts with plugins and mcp', async () => {
+			const promptsService = createMockPromptsService({});
+			const mcpService = {
+				servers: observableValue('test', [{ id: 's1' }]),
+			} as unknown as IMcpService;
+			const workspaceService = createMockWorkspaceService({ filter: { sources: [PromptsStorage.local] } });
+			const contextService = createMockWorkspaceContextService([]);
+
+			const provider = createItemProvider([
+				makeItem('agent', 'a'),
+				makeItem('skill', 's'),
+			]);
+			const agentPluginService = {
+				plugins: observableValue('test', [{ id: 'p1' }, { id: 'p2' }, { id: 'p3' }]),
+			} as unknown as IAgentPluginService;
+
+			const total = await getCustomizationTotalCount(promptsService, mcpService, workspaceService, contextService, agentPluginService, provider);
+
+			// 2 from provider + 1 mcp + 3 plugins = 6
+			assert.strictEqual(total, 6);
+		});
+	});
+
 	suite('data source consistency', () => {
 		// These tests verify that getSourceCounts uses the same data sources
 		// as the list widget's loadItems() — the root cause of the count mismatch bug.
--- a/src/vs/workbench/api/browser/mainThreadChatAgents2.ts
+++ b/src/vs/workbench/api/browser/mainThreadChatAgents2.ts
@@ -714,10 +714,10 @@ export class MainThreadChatAgents2 extends Disposable implements MainThreadChatA
 	}

 	async $registerChatSessionCustomizationProvider(handle: number, chatSessionType: string, metadata: IChatSessionCustomizationProviderMetadataDto, extensionId: ExtensionIdentifier): Promise<void> {
-		// In the sessions window, only the Copilot CLI harness is accepted via the
-		// extension API. Other harnesses (e.g. Claude) are not shown in sessions.
+		// In the sessions window, only accept harnesses for session types that
+		// have a registered content provider (i.e., can actually run sessions).
 		// AHP remote servers register directly via registerExternalHarness.
-		if (this._environmentService.isSessionsWindow && chatSessionType !== 'copilotcli') {
+		if (this._environmentService.isSessionsWindow && !this._chatSessionService.getContentProviderSchemes().includes(chatSessionType)) {
 			return;
 		}