chat: route AI customization list through item sources

[joshspicer]

Summary

Route the AI Customizations list widget through a unified item-source abstraction, eliminating the two separate code paths that branched on whether the active harness had a promptsService path vs an extension-contributed provider.

All three customization item producers — core promptsService (local), extension API providers, and AHP remote servers — now implement a single ICustomizationItemProvider interface and produce ICustomizationItem objects. A consolidated pipeline normalizes these into IAICustomizationListItem for the widget.

Resolves #309627

Design

promptsService ──→ PromptsServiceCustomizationItemProvider ──→ ICustomizationItem[]
                                                                       │
Extension API ────────────────────────────────────────────→ ICustomizationItem[]
                                                                       │
AHP Remote ───────────────────────────────────────────────→ ICustomizationItem[]
                                                                       │
                                                                       ▼
                                                  ProviderCustomizationItemSource
                                                                       │
                                                                       ▼
                                                    AICustomizationItemNormalizer
                                                                       │
                                                                       ▼
                                                    IAICustomizationListItem[] → Widget

Key interfaces (common layer)

• ICustomizationItem — universal shape all 3 producers emit. Includes optional storage?: PromptsStorage so providers that know the origin can set it directly.
• ICustomizationItemProvider — single method provideChatSessionCustomizations() that all sources implement.

What changed architecturally

• No more lossy round-trip: Previously an adapter stripped storage via toProviderItems(), then the normalizer re-inferred it from URI heuristics. Now storage flows through end-to-end; the normalizer only infers from URI as a fallback.
• No duck-typed interfaces: Removed the provideCustomizations? optional method pattern. All providers implement provideChatSessionCustomizations — the one established API.
• Consolidated pipeline file: aiCustomizationItemSource.ts (~400 lines) contains interfaces, utilities, normalizer, and item source — following the Testing framework precedent of bundling a strict dependency chain.
• PromptsServiceCustomizationItemProvider stays permanently — it's how core VS Code's "Local" harness feeds items from promptsService into the unified pipeline.

Files

New files

File	Purpose
aiCustomizationItemSource.ts	Consolidated pipeline: IAICustomizationListItem, IAICustomizationItemSource, utils, AICustomizationItemNormalizer, ProviderCustomizationItemSource
promptsServiceCustomizationItemProvider.ts	Adapts IPromptsService → ICustomizationItemProvider (local/static path)

Modified files

File	Change
customizationHarnessService.ts	Renamed IExternalCustomizationItem → ICustomizationItem, IExternalCustomizationItemProvider → ICustomizationItemProvider, added storage field
aiCustomizationListWidget.ts	Removed ~800 lines of dual-path fetch/normalize/group logic, now consumes IAICustomizationItemSource
aiCustomizationIcons.ts	storageToIcon() with PromptsStorage enum type safety
mainThreadChatAgents2.ts	Interface renames
remoteAgentHostCustomizationHarness.ts	Interface renames
aiCustomizationDebugPanel.ts	Interface renames
customizationHarnessService.test.ts	Interface renames
AI_CUSTOMIZATIONS.md	Design doc updated to reflect new architecture

Commits

1. chat: extract AI customization item sources — initial pipeline extraction
2. chat: clean up AI customization item source extraction — council-review fixes (dedup utils, cache source, O(n) hook lookup, .filter() chains)
3. chat: consolidate item source files into single module — merge 4 files → 1, unify ICustomizationItem/ICustomizationItemProvider interfaces, eliminate internal DTO

Validation

• npm run compile-check-ts-native: clean (pre-existing copilotAgent.ts errors only)
• Unit tests passing

[github-actions]

Screenshot Changes

Base: d4ff4fe5 Current: 2cb9a5fa

Changed (6)

chat/aiCustomizations/aiCustomizationListWidget/InstructionsTabWithItems/Dark

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chat/aiCustomizations/aiCustomizationListWidget/InstructionsTabWithItems/Light

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chat/aiCustomizations/aiCustomizationManagementEditor/HooksTab/Dark

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chat/aiCustomizations/aiCustomizationManagementEditor/HooksTab/Light

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chat/aiCustomizations/aiCustomizationManagementEditor/McpBrowseMode/Light

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editor/inlineCompletions/other/JumpToHint/Light

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[Copilot]

Pull request overview

Refactors the AI Customization management list to fetch items through a unified, browser-internal “item source” abstraction, converging both promptsService-backed discovery and extension-contributed providers onto the same normalized list-item model.

Changes:

• Introduces IAICustomizationItemSource + supporting utilities/normalizer to unify discovery and normalization into IAICustomizationListItem.
• Adds a promptsService adapter (PromptsServiceCustomizationItemProvider) so local/static harnesses keep the rich promptsService pipeline while still producing provider-shaped items.
• Updates the list widget to select/cache an item source per active harness and remove direct branching between “core” vs “provider” paths.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/browser/aiCustomization/providerCustomizationItemSource.ts	New unified item source that merges provider items + optional local sync overlays and emits a composed onDidChange.
src/vs/workbench/contrib/chat/browser/aiCustomization/promptsServiceCustomizationItemProvider.ts	Adapts IPromptsService to IExternalCustomizationItemProvider, including hook expansion and harness filtering.
src/vs/workbench/contrib/chat/browser/aiCustomization/aiCustomizationListWidget.ts	Switches the widget to consume an IAICustomizationItemSource and cache it per harness descriptor.
src/vs/workbench/contrib/chat/browser/aiCustomization/aiCustomizationListItem.ts	Extracts the widget list item model + item source contract into a shared browser file.
src/vs/workbench/contrib/chat/browser/aiCustomization/aiCustomizationItemSourceUtils.ts	Shared utilities for friendly naming, hook expansion, and built-in chat extension detection.
src/vs/workbench/contrib/chat/browser/aiCustomization/aiCustomizationItemNormalizer.ts	Normalizes provider-shaped items into rich UI list items, inferring source/grouping details.
src/vs/workbench/contrib/chat/browser/aiCustomization/aiCustomizationIcons.ts	Moves storageToIcon into the icons module.
src/vs/sessions/AI_CUSTOMIZATIONS.md	Updates sessions documentation to describe the new management editor item pipeline.

Copilot's findings

• Files reviewed: 8/8 changed files
• Comments generated: 2