chat: route AI customization list through item sources

src/vs/sessions/AI_CUSTOMIZATIONS.md

@@ -15,6 +15,8 @@ src/vs/workbench/contrib/chat/browser/aiCustomization/
 ├── aiCustomizationManagementEditor.ts          # SplitView list/editor
 ├── aiCustomizationManagementEditorInput.ts     # Singleton input
 ├── aiCustomizationListWidget.ts                # Search + grouped list + harness toggle
+├── aiCustomizationItemSource.ts                # Item pipeline: ICustomizationItem → IAICustomizationListItem view model
+├── promptsServiceCustomizationItemProvider.ts  # Adapts IPromptsService → ICustomizationItemProvider
 ├── aiCustomizationListWidgetUtils.ts           # List item helpers (truncation, etc.)
 ├── aiCustomizationDebugPanel.ts                # Debug diagnostics panel
 ├── aiCustomizationWorkspaceService.ts          # Core VS Code workspace service impl
@@ -29,7 +31,7 @@ src/vs/workbench/contrib/chat/browser/aiCustomization/
 
 src/vs/workbench/contrib/chat/common/
 ├── aiCustomizationWorkspaceService.ts          # IAICustomizationWorkspaceService + IStorageSourceFilter + BUILTIN_STORAGE
-└── customizationHarnessService.ts              # ICustomizationHarnessService + ISectionOverride + helpers
+└── customizationHarnessService.ts              # ICustomizationHarnessService + ICustomizationItem + ICustomizationItemProvider + helpers
 ```
 
 The tree view and overview live in `vs/sessions` (agent sessions window only):
@@ -98,6 +100,8 @@ Key properties on the harness descriptor:
 
 | Property | Purpose |
 |----------|--------|
+| `itemProvider` | `ICustomizationItemProvider` supplying items; when absent, falls back to `PromptsServiceCustomizationItemProvider` |
+| `syncProvider` | `ICustomizationSyncProvider` enabling local→remote sync checkboxes |
 | `hiddenSections` | Sidebar sections to hide (e.g. Claude: `[Prompts, Plugins]`) |
 | `workspaceSubpaths` | Restrict file creation/display to directories (e.g. Claude: `['.claude']`) |
 | `hideGenerateButton` | Replace "Generate X" sparkle button with "New X" |
@@ -157,16 +161,38 @@ Claude additionally applies:
 
 In core VS Code, customization items contributed by the default chat extension (`productService.defaultChatAgent.chatExtensionId`, typically `GitHub.copilot-chat`) are grouped under the "Built-in" header in the management editor list widget, separate from third-party "Extensions".
 
-This follows the same pattern as the MCP list widget, which determines grouping at the UI layer by inspecting collection sources. The list widget uses `IProductService` to identify the chat extension and sets `groupKey: BUILTIN_STORAGE` on matching items:
+`PromptsServiceCustomizationItemProvider` handles this via `applyBuiltinGroupKeys()`: it builds a URI→extension-ID lookup from prompt file metadata, then sets `groupKey: BUILTIN_STORAGE` on items whose extension matches the chat extension ID (checked via the shared `isChatExtensionItem()` utility). The underlying `storage` remains `PromptsStorage.extension` — the grouping is a `groupKey` override that keeps `applyStorageSourceFilter` working while visually distinguishing chat-extension items from third-party extension items.
 
-- **Agents**: checks `agent.source.extensionId` against the chat extension ID
-- **Skills**: builds a URI→ExtensionIdentifier lookup from `listPromptFiles(PromptsType.skill)`, then checks each skill's URI
-- **Prompts**: checks `command.promptPath.extension?.identifier`
-- **Instructions/Hooks**: checks `item.extension?.identifier` via `IPromptPath`
+`BUILTIN_STORAGE` is defined in `aiCustomizationWorkspaceService.ts` (common layer) and re-exported by both `aiCustomizationManagement.ts` (browser) and `builtinPromptsStorage.ts` (sessions) for backward compatibility.
 
-The underlying `storage` remains `PromptsStorage.extension` — the grouping is a UI-level override via `groupKey` that keeps `applyStorageSourceFilter` working with existing storage types while visually distinguishing chat-extension items from third-party extension items.
+### Management Editor Item Pipeline
 
-`BUILTIN_STORAGE` is defined in `aiCustomizationWorkspaceService.ts` (common layer) and re-exported by both `aiCustomizationManagement.ts` (browser) and `builtinPromptsStorage.ts` (sessions) for backward compatibility.
+All customization sources — `IPromptsService`, extension-contributed providers, and AHP remote servers — produce items conforming to the same `ICustomizationItem` contract (defined in `customizationHarnessService.ts`). This contract carries `uri`, `type`, `name`, `description`, optional `storage`, `groupKey`, `badge`, and status fields.
+
+```
+promptsService ──→ PromptsServiceCustomizationItemProvider ──→ ICustomizationItem[]
+                                                                       │
+Extension Provider ───────────────────────────────────────→ ICustomizationItem[]
+                                                                       │
+AHP Remote Server ────────────────────────────────────────→ ICustomizationItem[]
+                                                                       │
+                                                                       ▼
+                                              CustomizationItemSource (aiCustomizationItemSource.ts)
+                                              ├── normalizes → IAICustomizationListItem[]
+                                              ├── expands hooks from file content
+                                              └── blends sync overlays when syncProvider present
+                                                                       │
+                                                                       ▼
+                                                              List Widget renders
+```
+
+**Key files:**
+
+- **`aiCustomizationItemSource.ts`** — The browser-side pipeline: `IAICustomizationListItem` (view model), `IAICustomizationItemSource` (data contract), `AICustomizationItemNormalizer` (maps `ICustomizationItem` → view model, inferring storage/grouping from URIs when the provider doesn't supply them), `ProviderCustomizationItemSource` (orchestrates provider + sync + normalizer), and shared utilities (`expandHookFileItems`, `getFriendlyName`, `isChatExtensionItem`).
+
+- **`promptsServiceCustomizationItemProvider.ts`** — Adapts `IPromptsService` to `ICustomizationItemProvider`. Reads agents, skills, instructions, hooks, and prompts from the core service, expands instruction categories and hook entries, applies harness-specific filters (storage sources, workspace subpaths, instruction file patterns), and returns `ICustomizationItem[]` with `storage` set from the authoritative promptsService metadata. Used as the default item provider for harnesses that don't supply their own.
+
+- **`customizationHarnessService.ts`** (common layer) — Defines `ICustomizationItem`, `ICustomizationItemProvider`, `ICustomizationSyncProvider`, and `IHarnessDescriptor`. A harness descriptor optionally carries an `itemProvider`; when absent, the widget falls back to `PromptsServiceCustomizationItemProvider`.
 
 ### AgenticPromptsService (Sessions)
 
@@ -194,26 +220,18 @@ 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's `loadItems()`:
-
-| Type | Data Source | Notes |
-|------|-------------|-------|
-| Agents | `getCustomAgents()` | Parsed agents, not raw files |
-| Skills | `findAgentSkills()` | Parsed skills with frontmatter |
-| Prompts | `getPromptSlashCommands()` | Filters out skill-type commands |
-| Instructions | `listPromptFiles()` + `listAgentInstructions()` | Includes AGENTS.md, CLAUDE.md etc. |
-| Hooks | `listPromptFiles()` | Individual hooks parsed via `parseHooksFromFile()` |
+`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.
 
 ### Item Badges
 
 `IAICustomizationListItem.badge` is an optional string that renders as a small inline tag next to the item name (same visual style as the MCP "Bridged" badge). For context instructions, this badge shows the raw `applyTo` pattern (e.g. a glob like `**/*.ts`), while the tooltip (`badgeTooltip`) explains the behavior. For skills with UI integrations, the badge reads "UI Integration" with a tooltip describing which UI surface invokes the skill. The badge text is also included in search filtering.
 
 ### Debug Panel
 
-Toggle via Command Palette: "Toggle Customizations Debug Panel". Shows a 4-stage pipeline view:
+Toggle via Command Palette: "Toggle Customizations Debug Panel". Shows a diagnostic view of the item pipeline:
 
-1. **Raw PromptsService data** — per-storage file lists + type-specific extras
-2. **After applyStorageSourceFilter** — what was removed and why
+1. **Provider data** — items returned by the active `ICustomizationItemProvider`
+2. **After filtering** — what was removed by storage source and workspace subpath filters
 3. **Widget state** — allItems vs displayEntries with group counts
 4. **Source/resolved folders** — creation targets and discovery order
 

src/vs/sessions/contrib/remoteAgentHost/browser/remoteAgentHostCustomizationHarness.ts

@@ -12,7 +12,7 @@ import { CancellationToken } from '../../../../base/common/cancellation.js';
 import { AICustomizationManagementSection, type IStorageSourceFilter } from '../../../../workbench/contrib/chat/common/aiCustomizationWorkspaceService.js';
 import { PromptsStorage } from '../../../../workbench/contrib/chat/common/promptSyntax/service/promptsService.js';
 import { PromptsType } from '../../../../workbench/contrib/chat/common/promptSyntax/promptTypes.js';
-import { type IHarnessDescriptor, type IExternalCustomizationItem, type IExternalCustomizationItemProvider } from '../../../../workbench/contrib/chat/common/customizationHarnessService.js';
+import { type IHarnessDescriptor, type ICustomizationItem, type ICustomizationItemProvider } from '../../../../workbench/contrib/chat/common/customizationHarnessService.js';
 import type { IAgentConnection } from '../../../../platform/agentHost/common/agentService.js';
 import { ActionType } from '../../../../platform/agentHost/common/state/sessionActions.js';
 import { type IAgentInfo, type ICustomizationRef, type ISessionCustomization, CustomizationStatus } from '../../../../platform/agentHost/common/state/sessionState.js';
@@ -23,7 +23,7 @@ export { AgentCustomizationSyncProvider as RemoteAgentSyncProvider } from '../..
 
 /**
  * Maps a {@link CustomizationStatus} enum value to the string literal
- * expected by {@link IExternalCustomizationItem.status}.
+ * expected by {@link ICustomizationItem.status}.
  */
 function toStatusString(status: CustomizationStatus | undefined): 'loading' | 'loaded' | 'degraded' | 'error' | undefined {
 	switch (status) {
@@ -37,14 +37,14 @@ function toStatusString(status: CustomizationStatus | undefined): 'loading' | 'l
 
 /**
  * Provider that exposes a remote agent's customizations as
- * {@link IExternalCustomizationItem} entries for the list widget.
+ * {@link ICustomizationItem} entries for the list widget.
  *
  * Baseline items come from {@link IAgentInfo.customizations} (available
  * without an active session). When a session is active, the provider
  * overlays {@link ISessionCustomization} data, which includes loading
  * status and enabled state.
  */
-export class RemoteAgentCustomizationItemProvider extends Disposable implements IExternalCustomizationItemProvider {
+export class RemoteAgentCustomizationItemProvider extends Disposable implements ICustomizationItemProvider {
 	private readonly _onDidChange = this._register(new Emitter<void>());
 	readonly onDidChange: Event<void> = this._onDidChange.event;
 
@@ -79,7 +79,7 @@ export class RemoteAgentCustomizationItemProvider extends Disposable implements
 		this._onDidChange.fire();
 	}
 
-	async provideChatSessionCustomizations(_token: CancellationToken): Promise<IExternalCustomizationItem[]> {
+	async provideChatSessionCustomizations(_token: CancellationToken): Promise<ICustomizationItem[]> {
 		// When a session is active, prefer session-level data (includes status)
 		if (this._sessionCustomizations) {
 			return this._sessionCustomizations.map(sc => ({
@@ -108,7 +108,7 @@ export class RemoteAgentCustomizationItemProvider extends Disposable implements
  * the agent host protocol.
  *
  * The descriptor exposes the agent's server-provided customizations through
- * an {@link IExternalCustomizationItemProvider} and allows the user to
+ * an {@link ICustomizationItemProvider} and allows the user to
  * select local customizations for syncing via an {@link ICustomizationSyncProvider}.
  */
 export function createRemoteAgentHarnessDescriptor(

src/vs/workbench/api/browser/mainThreadChatAgents2.ts

@@ -46,7 +46,7 @@ import { Dto } from '../../services/extensions/common/proxyIdentifier.js';
 import { ExtHostChatAgentsShape2, ExtHostContext, IChatAgentInvokeResult, IChatSessionCustomizationItemDto, IChatSessionCustomizationProviderMetadataDto, IChatNotebookEditDto, IChatParticipantMetadata, IChatProgressDto, IChatSessionContextDto, ICustomAgentDto, IDynamicChatAgentProps, IExtensionChatAgentMetadata, IHookDto, IInstructionDto, IPluginDto, ISkillDto, ISlashCommandDto, MainContext, MainThreadChatAgentsShape2 } from '../common/extHost.protocol.js';
 import { NotebookDto } from './mainThreadNotebookDto.js';
 import { isUntitledChatSession } from '../../contrib/chat/common/model/chatUri.js';
-import { ICustomizationHarnessService, IExternalCustomizationItem, IExternalCustomizationItemProvider, IHarnessDescriptor } from '../../contrib/chat/common/customizationHarnessService.js';
+import { ICustomizationHarnessService, ICustomizationItem, ICustomizationItemProvider, IHarnessDescriptor } from '../../contrib/chat/common/customizationHarnessService.js';
 import { AICustomizationManagementSection, BUILTIN_STORAGE } from '../../contrib/chat/common/aiCustomizationWorkspaceService.js';
 import { IAgentPluginService } from '../../contrib/chat/common/plugins/agentPluginService.js';
 import { IWorkbenchEnvironmentService } from '../../services/environment/common/environmentService.js';
@@ -762,14 +762,14 @@ export class MainThreadChatAgents2 extends Disposable implements MainThreadChatA
 		this._customizationProviderEmitters.set(handle, emitter);
 
 		// Build the item provider that calls back to the ExtHost
-		const itemProvider: IExternalCustomizationItemProvider = {
+		const itemProvider: ICustomizationItemProvider = {
 			onDidChange: emitter.event,
 			provideChatSessionCustomizations: async (token) => {
 				const items = await this._proxy.$provideChatSessionCustomizations(handle, token);
 				if (!items) {
 					return undefined;
 				}
-				return items.map((item: IChatSessionCustomizationItemDto): IExternalCustomizationItem => ({
+				return items.map((item: IChatSessionCustomizationItemDto): ICustomizationItem => ({
 					uri: URI.revive(item.uri),
 					type: item.type,
 					name: item.name,

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

@@ -9,7 +9,7 @@ import { IPromptsService, PromptsStorage, IPromptPath } from '../../common/promp
 import { PromptsType } from '../../common/promptSyntax/promptTypes.js';
 import { IAICustomizationWorkspaceService, applyStorageSourceFilter, IStorageSourceFilter } from '../../common/aiCustomizationWorkspaceService.js';
 import { AICustomizationManagementSection } from './aiCustomizationManagement.js';
-import { IExternalCustomizationItemProvider, IHarnessDescriptor } from '../../common/customizationHarnessService.js';
+import { ICustomizationItemProvider, IHarnessDescriptor } from '../../common/customizationHarnessService.js';
 
 /**
  * Maps section ID to prompt type. Duplicated from aiCustomizationListWidget
@@ -100,7 +100,7 @@ export async function generateCustomizationDebugReport(
 	return lines.join('\n');
 }
 
-async function appendExternalProviderData(lines: string[], provider: IExternalCustomizationItemProvider, promptType: PromptsType): Promise<void> {
+async function appendExternalProviderData(lines: string[], provider: ICustomizationItemProvider, promptType: PromptsType): Promise<void> {
 	lines.push('--- External Provider Data ---');
 
 	const allItems = await provider.provideChatSessionCustomizations(CancellationToken.None);

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

@@ -4,8 +4,10 @@
  *--------------------------------------------------------------------------------------------*/
 
 import { Codicon } from '../../../../../base/common/codicons.js';
+import { ThemeIcon } from '../../../../../base/common/themables.js';
 import { localize } from '../../../../../nls.js';
 import { registerIcon } from '../../../../../platform/theme/common/iconRegistry.js';
+import { PromptsStorage } from '../../common/promptSyntax/service/promptsService.js';
 
 /**
  * Icon for the AI Customization view container (sidebar).
@@ -76,3 +78,16 @@ export const builtinIcon = registerIcon('ai-customization-builtin', Codicon.star
  * Icon for MCP servers.
  */
 export const mcpServerIcon = registerIcon('ai-customization-mcp-server', Codicon.server, localize('aiCustomizationMcpServerIcon', "Icon for MCP servers."));
+
+/**
+ * Returns the icon for a given storage type.
+ */
+export function storageToIcon(storage: PromptsStorage): ThemeIcon {
+	switch (storage) {
+		case PromptsStorage.local: return workspaceIcon;
+		case PromptsStorage.user: return userIcon;
+		case PromptsStorage.extension: return extensionIcon;
+		case PromptsStorage.plugin: return pluginIcon;
+		default: return instructionsIcon;
+	}
+}