Skills
skills/microsoft/vscode/sessions

sessions

SKILL.md

When working on the Agent Sessions window (src/vs/sessions/), always follow these guidelines:

1. Read the Specification Documents First

The src/vs/sessions/ directory contains authoritative specification documents. Always read the relevant spec before making changes.

Document Path Covers
Layer spec src/vs/sessions/README.md Layering rules, dependency constraints, folder conventions
Layout spec src/vs/sessions/LAYOUT.md Grid structure, part positions, sizing, CSS classes, API reference
AI Customizations src/vs/sessions/AI_CUSTOMIZATIONS.md AI customization editor and tree view design
Chat Widget src/vs/sessions/browser/widget/AGENTS_CHAT_WIDGET.md Chat widget wrapper architecture, deferred session creation, option delivery

If you modify the implementation, you must update the corresponding spec to keep it in sync. Update the Revision History table at the bottom of LAYOUT.md with a dated entry.

2. Architecture Overview

2.1 Layering

vs/base          ← Foundation utilities
vs/platform      ← Platform services
vs/editor        ← Text editor core
vs/workbench     ← Standard VS Code workbench
vs/sessions      ← Agent Sessions window (this layer)

Key constraint: vs/sessions may import from vs/workbench and all layers below it. vs/workbench must never import from vs/sessions.

2.2 Dependency Rules

  • ✅ Import from vs/base, vs/platform, vs/editor, vs/workbench
  • ✅ Import within vs/sessions (internal)
  • ❌ Never import vs/sessions from vs/workbench
  • Run npm run valid-layers-check to verify layering

2.3 How It Differs from VS Code

Aspect VS Code Workbench Agent Sessions Window
Layout Configurable part positions Fixed layout, no settings customization
Chrome Activity bar, status bar, banner Simplified — none of these
Primary UX Editor-centric Chat-first (Chat Bar is a primary part)
Editors In the grid layout Modal overlay above the workbench
Titlebar Menubar, editor actions, layout controls Session picker, run script, toggle sidebar/panel
Navigation Activity bar with viewlets Sidebar (views) + sidebar footer (account)
Entry point vs/workbench workbench class vs/sessions/browser/workbench.ts Workbench class

3. Folder Structure

src/vs/sessions/
├── README.md                               # Layer specification (read first)
├── LAYOUT.md                               # Authoritative layout specification
├── AI_CUSTOMIZATIONS.md                    # AI customization design document
├── sessions.common.main.ts                 # Common (browser + desktop) entry point
├── sessions.desktop.main.ts                # Desktop entry point (imports all contributions)
├── common/                                 # Shared types, context keys, and theme
│   ├── categories.ts                       # Command categories
│   ├── contextkeys.ts                      # ChatBar and welcome context keys
│   └── theme.ts                            # Theme contributions
├── browser/                                # Core workbench implementation
│   ├── workbench.ts                        # Main Workbench class (implements IWorkbenchLayoutService)
│   ├── menus.ts                            # Agent sessions menu IDs (Menus export)
│   ├── layoutActions.ts                    # Layout toggle actions (sidebar, panel, auxiliary bar)
│   ├── paneCompositePartService.ts         # AgenticPaneCompositePartService
│   ├── widget/                             # Agent sessions chat widget
│   │   └── AGENTS_CHAT_WIDGET.md           # Chat widget architecture doc
│   ├── parts/                              # Workbench part implementations
│   │   ├── parts.ts                        # AgenticParts enum
│   │   ├── titlebarPart.ts                 # Titlebar (3-section toolbar layout)
│   │   ├── sidebarPart.ts                  # Sidebar (with footer for account widget)
│   │   ├── chatBarPart.ts                  # Chat Bar (primary chat surface)
│   │   ├── auxiliaryBarPart.ts             # Auxiliary Bar
│   │   ├── panelPart.ts                    # Panel (terminal, output, etc.)
│   │   ├── projectBarPart.ts               # Project bar (folder entries)
│   │   └── media/                          # Part CSS files
│   └── media/                              # Layout-specific styles
├── electron-browser/                       # Desktop-specific entry points
│   ├── sessions.main.ts                    # Desktop main bootstrap
│   ├── sessions.ts                         # Electron process entry
│   ├── sessions.html                       # Production HTML shell
│   ├── sessions-dev.html                   # Development HTML shell
│   ├── titleService.ts                     # Desktop title service override
│   └── parts/
│       └── titlebarPart.ts                 # Desktop titlebar part
├── services/                               # Service overrides
│   ├── configuration/browser/              # Configuration service overrides
│   └── workspace/browser/                  # Workspace service overrides
├── test/                                   # Unit tests
│   └── browser/
│       └── layoutActions.test.ts
└── contrib/                                # Feature contributions
    ├── accountMenu/browser/                # Account widget for sidebar footer
    ├── agentFeedback/browser/              # Agent feedback attachments, overlays, hover
    ├── aiCustomizationTreeView/browser/    # AI customization tree view sidebar
    ├── applyToParentRepo/browser/          # Apply changes to parent repo
    ├── changesView/browser/                # File changes view
    ├── chat/browser/                       # Chat actions (run script, branch, prompts)
    ├── configuration/browser/              # Configuration overrides
    ├── files/browser/                      # File-related contributions
    ├── fileTreeView/browser/               # File tree view (filesystem provider)
    ├── gitSync/browser/                    # Git sync contributions
    ├── logs/browser/                       # Log contributions
    ├── sessions/browser/                   # Sessions view, title bar widget, active session service
    ├── terminal/browser/                   # Terminal contributions
    ├── welcome/browser/                    # Welcome view contribution
    └── workspace/browser/                  # Workspace contributions

4. Layout

Use the agent-sessions-layout skill for detailed guidance on the layout. Key points:

4.1 Visual Layout

┌─────────┬───────────────────────────────────────────────────────┐
│         │                    Titlebar                           │
│         ├────────────────────────────────────┬──────────────────┤
│ Sidebar │              Chat Bar              │  Auxiliary Bar   │
│         ├────────────────────────────────────┴──────────────────┤
│         │                      Panel                            │
└─────────┴───────────────────────────────────────────────────────┘
  • Sidebar spans full window height (root grid level)
  • Titlebar is inside the right section
  • Chat Bar is the primary interaction surface
  • Panel is hidden by default (terminal, output, etc.)
  • Editor appears as a modal overlay, not in the grid

4.2 Parts

Part Default Visibility Notes
Titlebar Always visible 3-section toolbar (left/center/right)
Sidebar Visible Sessions view, AI customization tree
Chat Bar Visible Primary chat widget
Auxiliary Bar Visible Changes view, etc.
Panel Hidden Terminal, output
Editor Hidden Main part hidden; editors open via MODAL_GROUP into ModalEditorPart

Not included: Activity Bar, Status Bar, Banner.

4.3 Editor Modal

The main editor part is hidden (display:none). All editors open via MODAL_GROUP into the standard ModalEditorPart overlay (created on-demand by EditorParts.createModalEditorPart). The sessions configuration sets workbench.editor.useModal to 'all', which causes findGroup() to redirect all editor opens to the modal. Click backdrop or press Escape to dismiss.

5. Chat Widget

The Agent Sessions chat experience is built around AgentSessionsChatWidget — a wrapper around the core ChatWidget that adds:

  • Deferred session creation — the UI is interactive before any session resource exists; sessions are created on first message send
  • Target configuration — observable state tracking which agent provider (Local, Cloud) is selected
  • Welcome view — branded empty state with mascot, target buttons, option pickers, and input slot
  • Initial session options — option selections travel atomically with the first request
  • Configurable picker placement — pickers can appear in welcome view, input toolbar, or both

Read browser/widget/AGENTS_CHAT_WIDGET.md for the full architecture.

Key classes:

  • AgentSessionsChatWidget (browser/widget/agentSessionsChatWidget.ts) — main wrapper
  • AgentSessionsChatTargetConfig (browser/widget/agentSessionsChatTargetConfig.ts) — reactive target state
  • AgentSessionsChatWelcomePart (browser/parts/agentSessionsChatWelcomePart.ts) — welcome view
  • AgentSessionsChatInputPart (browser/parts/agentSessionsChatInputPart.ts) — standalone input adapter

6. Menus

The agent sessions window uses its own menu IDs defined in browser/menus.ts via the Menus export. Never use shared MenuId.* constants from vs/platform/actions for agent sessions UI — use the Menus.* equivalents instead.

Menu ID Purpose
Menus.ChatBarTitle Chat bar title actions
Menus.CommandCenter Center toolbar with session picker widget
Menus.CommandCenterCenter Center section of command center
Menus.TitleBarContext Titlebar context menu
Menus.TitleBarLeftLayout Left layout toolbar
Menus.TitleBarSessionTitle Session title in titlebar
Menus.TitleBarSessionMenu Session menu in titlebar
Menus.TitleBarRightLayout Right layout toolbar
Menus.PanelTitle Panel title bar actions
Menus.SidebarTitle Sidebar title bar actions
Menus.SidebarFooter Sidebar footer (account widget)
Menus.SidebarCustomizations Sidebar customizations menu
Menus.AuxiliaryBarTitle Auxiliary bar title actions
Menus.AuxiliaryBarTitleLeft Auxiliary bar left title actions
Menus.AgentFeedbackEditorContent Agent feedback editor content menu

7. Context Keys

Defined in common/contextkeys.ts:

Context Key Type Purpose
activeChatBar string ID of the active chat bar panel
chatBarFocus boolean Whether chat bar has keyboard focus
chatBarVisible boolean Whether chat bar is visible
sessionsWelcomeVisible boolean Whether the sessions welcome overlay is visible

8. Contributions

Feature contributions live under contrib/<featureName>/browser/ and are registered via imports in sessions.desktop.main.ts (desktop) or sessions.common.main.ts (browser-compatible).

8.1 Key Contributions

Contribution Location Purpose
Sessions View contrib/sessions/browser/ Sessions list in sidebar, session picker, active session service
Title Bar Widget contrib/sessions/browser/sessionsTitleBarWidget.ts Session picker in titlebar center
Account Widget contrib/accountMenu/browser/ Account button in sidebar footer
Chat Actions contrib/chat/browser/ Chat actions (run script, branch, prompts, customizations debug log)
Changes View contrib/changesView/browser/ File changes in auxiliary bar
Agent Feedback contrib/agentFeedback/browser/ Agent feedback attachments, editor overlays, hover
AI Customization Tree contrib/aiCustomizationTreeView/browser/ Sidebar tree for AI customizations
Apply to Parent Repo contrib/applyToParentRepo/browser/ Apply changes to parent repo
Files contrib/files/browser/ File-related contributions
File Tree View contrib/fileTreeView/browser/ File tree view (filesystem provider)
Git Sync contrib/gitSync/browser/ Git sync contributions
Logs contrib/logs/browser/ Log contributions
Terminal contrib/terminal/browser/ Terminal contributions
Welcome contrib/welcome/browser/ Welcome view contribution
Workspace contrib/workspace/browser/ Workspace contributions
Configuration contrib/configuration/browser/ Configuration overrides

8.2 Service Overrides

The agent sessions window registers its own implementations for:

  • IPaneCompositePartService → AgenticPaneCompositePartService (creates agent-specific parts)
  • IPromptsService → AgenticPromptsService (scopes prompt discovery to active session worktree)
  • IActiveSessionService → ActiveSessionService (tracks active session)

Service overrides also live under services/:

  • services/configuration/browser/ - configuration service overrides
  • services/workspace/browser/ - workspace service overrides

8.3 WindowVisibility.Sessions

Views and contributions that should only appear in the agent sessions window (not in regular VS Code) use WindowVisibility.Sessions in their registration.

9. Entry Points

File Purpose
sessions.common.main.ts Common entry; imports browser-compatible services, workbench contributions
sessions.desktop.main.ts Desktop entry; imports desktop services, electron contributions, all contrib/ modules
electron-browser/sessions.main.ts Desktop bootstrap
electron-browser/sessions.ts Electron process entry
electron-browser/sessions.html Production HTML shell
electron-browser/sessions-dev.html Development HTML shell
electron-browser/titleService.ts Desktop title service override
electron-browser/parts/titlebarPart.ts Desktop titlebar part

10. Development Guidelines

10.1 Adding New Features

  1. Core workbench code (layout, parts, services) → browser/
  2. Feature contributions (views, actions, editors) → contrib/<featureName>/browser/
  3. Register by importing in sessions.desktop.main.ts (or sessions.common.main.ts for browser-compatible)
  4. Use Menus.* from browser/menus.ts for menu registrations — never shared MenuId.*
  5. Use separate storage keys prefixed with workbench.agentsession.* or workbench.chatbar.*
  6. Use agent session part classes, not standard workbench parts
  7. Mark views with WindowVisibility.Sessions so they only appear in this window

10.2 Validating Changes

  1. Run npm run compile-check-ts-native to run a repo-wide TypeScript compilation check (including src/vs/sessions/). This is a fast way to catch TypeScript errors introduced by your changes.
  2. Run npm run valid-layers-check to verify layering rules are not violated.
  3. Use scripts/test.sh (or scripts\test.bat on Windows) for unit tests (add --grep <pattern> to filter tests)

Important do not run tsc to check for TypeScript errors always use above methods to validate TypeScript changes in src/vs/**.

10.3 Layout Changes

  1. Read LAYOUT.md first — it's the authoritative spec
  2. Use the agent-sessions-layout skill for detailed implementation guidance
  3. Maintain fixed positions — no settings-based customization
  4. Update LAYOUT.md and its Revision History after any changes
  5. Preserve no-op methods for unsupported features (zen mode, centered layout, etc.)
  6. Handle pane composite lifecycle when hiding/showing parts

10.3 Chat Widget Changes

  1. Read browser/widget/AGENTS_CHAT_WIDGET.md first
  2. Prefer composition over modifying core ChatWidget — add behavior in the wrapper
  3. Use IAgentChatTargetConfig observable for target state, not direct session creation
  4. Ensure initialSessionOptions travel atomically with the first request
  5. Test both first-load (extension not yet activated) and new-session flows

10.4 AI Customization Changes

  1. Read AI_CUSTOMIZATIONS.md first — it covers the management editor and tree view design
  2. Lean on existing VS Code services (IPromptsService, IMcpService, IChatService)
  3. Browser compatibility required — no Node.js APIs
  4. Active worktree comes from IActiveSessionService

10.5 Validation

  1. Check VS Code - Build task output for compilation errors before declaring work complete
  2. Run npm run valid-layers-check for layering violations
  3. Verify part visibility toggling (show/hide/maximize)
  4. Test editor modal open/close behavior
  5. Test sidebar footer renders with account widget
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