feat: add harness filtering layer to Chat Customizations

src/vs/sessions/AI_CUSTOMIZATIONS.md

@@ -14,17 +14,19 @@ src/vs/workbench/contrib/chat/browser/aiCustomization/
 ├── aiCustomizationManagement.ts                # IDs + context keys
 ├── aiCustomizationManagementEditor.ts          # SplitView list/editor
 ├── aiCustomizationManagementEditorInput.ts     # Singleton input
-├── aiCustomizationListWidget.ts                # Search + grouped list
+├── aiCustomizationListWidget.ts                # Search + grouped list + harness toggle
 ├── aiCustomizationDebugPanel.ts                # Debug diagnostics panel
 ├── aiCustomizationWorkspaceService.ts          # Core VS Code workspace service impl
+├── customizationHarnessService.ts              # Core harness service impl (VS Code harness)
 ├── customizationCreatorService.ts              # AI-guided creation flow
 ├── mcpListWidget.ts                            # MCP servers section
 ├── aiCustomizationIcons.ts                     # Icons
 └── media/
     └── aiCustomizationManagement.css
 
 src/vs/workbench/contrib/chat/common/
-└── aiCustomizationWorkspaceService.ts          # IAICustomizationWorkspaceService + IStorageSourceFilter
+├── aiCustomizationWorkspaceService.ts          # IAICustomizationWorkspaceService + IStorageSourceFilter
+└── customizationHarnessService.ts              # ICustomizationHarnessService + CustomizationHarness enum
 ```
 
 The tree view and overview live in `vs/sessions` (sessions window only):
@@ -44,6 +46,7 @@ Sessions-specific overrides:
 ```
 src/vs/sessions/contrib/chat/browser/
 ├── aiCustomizationWorkspaceService.ts          # Sessions workspace service override
+├── customizationHarnessService.ts              # Sessions harness service (CLI + Claude harnesses)
 └── promptsService.ts                           # AgenticPromptsService (CLI user roots)
 src/vs/sessions/contrib/sessions/browser/
 ├── customizationCounts.ts                      # Source count utilities (type-aware)
@@ -57,10 +60,31 @@ The `IAICustomizationWorkspaceService` interface controls per-window behavior:
 | Property / Method | Core VS Code | Sessions Window |
 |----------|-------------|----------|
 | `managementSections` | All sections except Models | Same minus MCP |
-| `getStorageSourceFilter(type)` | All sources, no user root filter | Per-type (see below) |
+| `getStorageSourceFilter(type)` | Delegates to `ICustomizationHarnessService` | Delegates to `ICustomizationHarnessService` |
 | `isSessionsWindow` | `false` | `true` |
 | `activeProjectRoot` | First workspace folder | Active session worktree |
 
+### ICustomizationHarnessService
+
+A harness represents the AI execution environment that consumes customizations.
+Storage answers "where did this come from?"; harness answers "who consumes it?".
+
+The service is defined in `common/customizationHarnessService.ts` which also provides:
+- **`CustomizationHarnessServiceBase`** — reusable base class handling active-harness state, the observable list, and `getStorageSourceFilter` dispatch.
+- **Factory functions** — `createVSCodeHarnessDescriptor`, `createCliHarnessDescriptor`, `createClaudeHarnessDescriptor` — parameterized by an `extras` array (the additional storage sources beyond `local`, `user`, `plugin`). Core passes `[PromptsStorage.extension]`; sessions passes `[BUILTIN_STORAGE]`.
+- **Well-known root helpers** — `getCliUserRoots(userHome)` and `getClaudeUserRoots(userHome)` centralize the `~/.copilot`, `~/.claude`, `~/.agents` path knowledge so it isn't duplicated.
+
+Available harnesses:
+
+| Harness | Label | Description |
+|---------|-------|-------------|
+| `vscode` | VS Code | Shows all storage sources (default in core) |
+| `cli` | Copilot CLI | Restricts user roots to `~/.copilot`, `~/.claude`, `~/.agents` |
+| `claude` | Claude | Restricts user roots to `~/.claude` |
+
+In core VS Code, all three harnesses are registered; VS Code is the default.
+In sessions, `cli` and `claude` harnesses are registered with a toggle bar above the list.
+
 ### IStorageSourceFilter
 
 A unified per-type filter controlling which storage sources and user file roots are visible.
@@ -75,13 +99,23 @@ interface IStorageSourceFilter {
 
 The shared `applyStorageSourceFilter()` helper applies this filter to any `{uri, storage}` array.
 
-**Sessions filter behavior by type:**
+**Sessions filter behavior by harness and type:**
+
+CLI harness:
+
+| Type | sources | includedUserFileRoots |
+|------|---------|----------------------|
+| Hooks | `[local, plugin]` | N/A |
+| Prompts | `[local, user, plugin, builtin]` | `undefined` (all roots) |
+| Agents, Skills, Instructions | `[local, user, plugin, builtin]` | `[~/.copilot, ~/.claude, ~/.agents]` |
+
+Claude harness:
 
 | Type | sources | includedUserFileRoots |
 |------|---------|----------------------|
-| Hooks | `[local]` | N/A |
-| Prompts | `[local, user]` | `undefined` (all roots) |
-| Agents, Skills, Instructions | `[local, user]` | `[~/.copilot, ~/.claude, ~/.agents]` |
+| Hooks | `[local, plugin]` | N/A |
+| Prompts | `[local, user, plugin, builtin]` | `undefined` (all roots) |
+| Agents, Skills, Instructions | `[local, user, plugin, builtin]` | `[~/.claude]` |
 
 **Core VS Code:** All types use `[local, user, extension, plugin]` with no user root filter.
 

src/vs/sessions/contrib/chat/browser/aiCustomizationWorkspaceService.ts

@@ -4,17 +4,16 @@
  *--------------------------------------------------------------------------------------------*/
 
 import { derived, IObservable, observableValue, ISettableObservable } from '../../../../base/common/observable.js';
-import { joinPath, relativePath } from '../../../../base/common/resources.js';
+import { relativePath } from '../../../../base/common/resources.js';
 import { URI } from '../../../../base/common/uri.js';
 import { CancellationToken } from '../../../../base/common/cancellation.js';
 import { IAICustomizationWorkspaceService, AICustomizationManagementSection, IStorageSourceFilter, applyStorageSourceFilter } from '../../../../workbench/contrib/chat/common/aiCustomizationWorkspaceService.js';
-import { IChatPromptSlashCommand, IPromptsService, PromptsStorage } from '../../../../workbench/contrib/chat/common/promptSyntax/service/promptsService.js';
-import { BUILTIN_STORAGE } from '../../chat/common/builtinPromptsStorage.js';
+import { IChatPromptSlashCommand, IPromptsService } from '../../../../workbench/contrib/chat/common/promptSyntax/service/promptsService.js';
+import { ICustomizationHarnessService } from '../../../../workbench/contrib/chat/common/customizationHarnessService.js';
 import { ISessionsManagementService } from '../../sessions/browser/sessionsManagementService.js';
 import { IInstantiationService } from '../../../../platform/instantiation/common/instantiation.js';
 import { CustomizationCreatorService } from '../../../../workbench/contrib/chat/browser/aiCustomization/customizationCreatorService.js';
 import { PromptsType } from '../../../../workbench/contrib/chat/common/promptSyntax/promptTypes.js';
-import { IPathService } from '../../../../workbench/services/path/common/pathService.js';
 import { ICommandService } from '../../../../platform/commands/common/commands.js';
 import { ILogService } from '../../../../platform/log/common/log.js';
 import { IFileService } from '../../../../platform/files/common/files.js';
@@ -43,37 +42,16 @@ export class SessionsAICustomizationWorkspaceService implements IAICustomization
 	 */
 	private readonly _overrideRoot: ISettableObservable<URI | undefined>;
 
-	/**
-	 * CLI-accessible user directories for customization file filtering and creation.
-	 */
-	private readonly _cliUserRoots: readonly URI[];
-
-	/**
-	 * Pre-built filter for types that should only show CLI-accessible user roots.
-	 */
-	private readonly _cliUserFilter: IStorageSourceFilter;
-
 	constructor(
 		@ISessionsManagementService private readonly sessionsService: ISessionsManagementService,
 		@IInstantiationService private readonly instantiationService: IInstantiationService,
 		@IPromptsService private readonly promptsService: IPromptsService,
-		@IPathService pathService: IPathService,
+		@ICustomizationHarnessService private readonly harnessService: ICustomizationHarnessService,
 		@ICommandService private readonly commandService: ICommandService,
 		@ILogService private readonly logService: ILogService,
 		@IFileService private readonly fileService: IFileService,
 		@INotificationService private readonly notificationService: INotificationService,
 	) {
-		const userHome = pathService.userHome({ preferLocal: true });
-		this._cliUserRoots = [
-			joinPath(userHome, '.copilot'),
-			joinPath(userHome, '.claude'),
-			joinPath(userHome, '.agents'),
-		];
-		this._cliUserFilter = {
-			sources: [PromptsStorage.local, PromptsStorage.user, PromptsStorage.plugin, BUILTIN_STORAGE],
-			includedUserFileRoots: this._cliUserRoots,
-		};
-
 		this._overrideRoot = observableValue(this, undefined);
 
 		this.activeProjectRoot = derived(reader => {
@@ -117,24 +95,8 @@ export class SessionsAICustomizationWorkspaceService implements IAICustomization
 		AICustomizationManagementSection.Plugins,
 	];
 
-	private static readonly _hooksFilter: IStorageSourceFilter = {
-		sources: [PromptsStorage.local, PromptsStorage.plugin],
-	};
-
-	private static readonly _allUserRootsFilter: IStorageSourceFilter = {
-		sources: [PromptsStorage.local, PromptsStorage.user, PromptsStorage.plugin, BUILTIN_STORAGE],
-	};
-
 	getStorageSourceFilter(type: PromptsType): IStorageSourceFilter {
-		if (type === PromptsType.hook) {
-			return SessionsAICustomizationWorkspaceService._hooksFilter;
-		}
-		if (type === PromptsType.prompt) {
-			// Prompts are shown from all user roots (including VS Code profile)
-			return SessionsAICustomizationWorkspaceService._allUserRootsFilter;
-		}
-		// Other types only show user files from CLI-accessible roots (~/.copilot, ~/.claude, ~/.agents)
-		return this._cliUserFilter;
+		return this.harnessService.getStorageSourceFilter(type);
 	}
 
 	readonly isSessionsWindow = true;

src/vs/sessions/contrib/chat/browser/chat.contribution.ts

@@ -28,7 +28,9 @@ import { AgenticPromptsService } from './promptsService.js';
 import { IPromptsService } from '../../../../workbench/contrib/chat/common/promptSyntax/service/promptsService.js';
 import { ISessionsConfigurationService, SessionsConfigurationService } from './sessionsConfigurationService.js';
 import { IAICustomizationWorkspaceService } from '../../../../workbench/contrib/chat/common/aiCustomizationWorkspaceService.js';
+import { ICustomizationHarnessService } from '../../../../workbench/contrib/chat/common/customizationHarnessService.js';
 import { SessionsAICustomizationWorkspaceService } from './aiCustomizationWorkspaceService.js';
+import { SessionsCustomizationHarnessService } from './customizationHarnessService.js';
 import { ChatViewContainerId, ChatViewId } from '../../../../workbench/contrib/chat/browser/chat.js';
 import { CHAT_CATEGORY } from '../../../../workbench/contrib/chat/browser/actions/chatActions.js';
 import { NewChatViewPane, SessionsViewId } from './newChatViewPane.js';
@@ -195,3 +197,4 @@ registerWorkbenchContribution2(RunScriptContribution.ID, RunScriptContribution,
 registerSingleton(IPromptsService, AgenticPromptsService, InstantiationType.Delayed);
 registerSingleton(ISessionsConfigurationService, SessionsConfigurationService, InstantiationType.Delayed);
 registerSingleton(IAICustomizationWorkspaceService, SessionsAICustomizationWorkspaceService, InstantiationType.Delayed);
+registerSingleton(ICustomizationHarnessService, SessionsCustomizationHarnessService, InstantiationType.Delayed);

src/vs/sessions/contrib/chat/browser/customizationHarnessService.ts

@@ -0,0 +1,32 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import {
+	CustomizationHarness,
+	CustomizationHarnessServiceBase,
+	createCliHarnessDescriptor,
+	getCliUserRoots,
+} from '../../../../workbench/contrib/chat/common/customizationHarnessService.js';
+import { IPathService } from '../../../../workbench/services/path/common/pathService.js';
+import { BUILTIN_STORAGE } from '../common/builtinPromptsStorage.js';
+
+/**
+ * Sessions-window override of the customization harness service.
+ *
+ * Only the CLI harness is registered because sessions always run via
+ * the Copilot CLI. With a single harness the toggle bar is hidden.
+ */
+export class SessionsCustomizationHarnessService extends CustomizationHarnessServiceBase {
+	constructor(
+		@IPathService pathService: IPathService,
+	) {
+		const userHome = pathService.userHome({ preferLocal: true });
+		const extras = [BUILTIN_STORAGE];
+		super(
+			[createCliHarnessDescriptor(getCliUserRoots(userHome), extras)],
+			CustomizationHarness.CLI,
+		);
+	}
+}

src/vs/workbench/contrib/chat/browser/aiCustomization/aiCustomizationListWidget.ts

@@ -51,6 +51,7 @@ import { parse as parseJSONC } from '../../../../../base/common/json.js';
 import { Schemas } from '../../../../../base/common/network.js';
 import { OS } from '../../../../../base/common/platform.js';
 import { ITelemetryService } from '../../../../../platform/telemetry/common/telemetry.js';
+import { ICustomizationHarnessService } from '../../common/customizationHarnessService.js';
 
 export { truncateToFirstSentence } from './aiCustomizationListWidgetUtils.js';
 
@@ -461,6 +462,7 @@ export class AICustomizationListWidget extends Disposable {
 		@IFileService private readonly fileService: IFileService,
 		@IPathService private readonly pathService: IPathService,
 		@ITelemetryService private readonly telemetryService: ITelemetryService,
+		@ICustomizationHarnessService private readonly harnessService: ICustomizationHarnessService,
 	) {
 		super();
 		this.element = $('.ai-customization-list-widget');
@@ -473,6 +475,13 @@ export class AICustomizationListWidget extends Disposable {
 			this.refresh();
 		}));
 
+		// Re-filter when the active harness changes
+		this._register(autorun(reader => {
+			this.harnessService.activeHarness.read(reader);
+			this.updateAddButton();
+			this.refresh();
+		}));
+
 	}
 
 	private create(): void {
@@ -766,6 +775,8 @@ export class AICustomizationListWidget extends Disposable {
 
 	/**
 	 * Gets the dropdown actions for the add button.
+	 * Respects the active harness filter — user-scoped creation is only
+	 * offered when the harness shows all user roots (i.e. "Local").
 	 */
 	private getDropdownActions(): Action[] {
 		this.dropdownActionDisposables.clear();
@@ -788,11 +799,22 @@ export class AICustomizationListWidget extends Disposable {
 			return actions;
 		}
 
+		// User-scoped creation: in core VS Code, only when the harness shows
+		// all user roots (no includedUserFileRoots restriction). Restricted
+		// harnesses like CLI/Claude filter user roots, so creating in the
+		// VS Code profile directory wouldn't be visible in the current view.
+		// In sessions, user creation always targets CLI-accessible paths
+		// (AgenticPromptsService routes to ~/.copilot/...) so it's always valid.
+		const filter = this.harnessService.getStorageSourceFilter(promptType);
+		const showUserCreate = this.workspaceService.isSessionsWindow || !filter.includedUserFileRoots;
+
 		if (this.workspaceService.isSessionsWindow) {
 			// Sessions: primary is workspace, dropdown has user
-			actions.push(this.dropdownActionDisposables.add(new Action('createUser', `$(${Codicon.account.id}) New ${typeLabel} (User)`, undefined, true, () => {
-				this._onDidRequestCreateManual.fire({ type: promptType, target: 'user' });
-			})));
+			if (showUserCreate) {
+				actions.push(this.dropdownActionDisposables.add(new Action('createUser', `$(${Codicon.account.id}) New ${typeLabel} (User)`, undefined, true, () => {
+					this._onDidRequestCreateManual.fire({ type: promptType, target: 'user' });
+				})));
+			}
 			// For instructions: offer AGENTS.md at workspace root
 			if (promptType === PromptsType.instructions && this.hasActiveWorkspace()) {
 				actions.push(this.dropdownActionDisposables.add(new Action('createAgentsMd', `$(${Codicon.file.id}) New ${AGENT_MD_FILENAME}`, undefined, true, () => {
@@ -806,9 +828,11 @@ export class AICustomizationListWidget extends Disposable {
 					this._onDidRequestCreateManual.fire({ type: promptType, target: 'workspace' });
 				})));
 			}
-			actions.push(this.dropdownActionDisposables.add(new Action('createUser', `$(${Codicon.account.id}) New ${typeLabel} (User)`, undefined, true, () => {
-				this._onDidRequestCreateManual.fire({ type: promptType, target: 'user' });
-			})));
+			if (showUserCreate) {
+				actions.push(this.dropdownActionDisposables.add(new Action('createUser', `$(${Codicon.account.id}) New ${typeLabel} (User)`, undefined, true, () => {
+					this._onDidRequestCreateManual.fire({ type: promptType, target: 'user' });
+				})));
+			}
 		}
 
 		return actions;