sessions: align experimental composer controls

[Megan Rogge (meganrogge)]

Summary

• add keyboard commands for focusing the Agents Window workspace and harness pickers, including shortcut-aware hovers, context-menu keybinding configuration, and accessibility help
• add an opt-in new-session footer that groups the folder, branch, New Worktree, and harness controls
• align desktop running-session mode, approval, model, and context-usage controls with the experimental composer layout while preserving the existing phone layout
• keep the context-usage control clear of editor text at rest and while expanded
• preserve the existing layouts unless both the experimental composer layout and unified workspace picker settings are enabled

Enablement

The experimental layouts are enabled only when both of these application settings are true:

• sessions.chat.experimental.newSessionComposerLayout (experimental, defaults to false)
• sessions.chat.unifiedWorkspacePicker.enabled

The picker focus commands, shortcut-aware hovers, context-menu keybinding configuration, and accessibility help require the unified workspace picker but do not require the experimental layout setting.

Screenshots

New session composer

Fixes #337144
Fixes #337145
Fixes #337150

[Copilot]

Copilot review overview

🟡 Changes recommended

Repository ordering escapes the experimental gate, while accessible guidance and dynamic presentation coverage remain incomplete.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1 · 2

Open (3)

• Gate toolbar reordering on both experimental settings · New
• Add tests for dynamic keybinding and context-menu updates · New
• Document keyboard and screen-reader access to context menus · New

What changed in this PR

Adds experimental Agents Window composer alignment and keyboard-accessible workspace/harness picker controls.

Changes:

• Adds picker-focus commands, dynamic keybinding hovers, context menus, and accessibility help.
• Introduces opt-in new/active session composer layouts.
• Reorders and relocates repository, permission, model, and harness controls.

File	Description
agentHostSessionConfigPicker.test.ts	Updates repository and running-session menu expectations.
agentHostSessionConfigPicker.ts	Repositions Agent Host controls and repository actions.
sessionsChatAccessibilityHelp.test.ts	Tests conditional picker help.
newSessionComposerLayout.test.ts	Tests layout enablement and control relocation.
newChatWidget.test.ts	Updates the workspace-picker harness.
newChatPickerKeybinding.test.ts	Tests chords and enablement contexts.
constants.ts	Defines the experimental setting key.
webWorkspacePicker.ts	Forwards keybinding and context-menu services.
sessionWorkspacePicker.ts	Adds keybinding-aware workspace triggers.
sessionTypePicker.ts	Adds keybinding-aware harness triggers.
sessionsChatAccessibilityHelp.ts	Documents picker commands.
newChatWidget.ts	Applies layout changes and exposes picker focus methods.
newChatPickerKeybinding.ts	Implements commands’ presentation and context menus.
newChatInput.ts	Relocates controls and updates responsive layout.
mobileSessionTypePicker.ts	Forwards new picker dependencies.
chatWidget.css	Styles the experimental footer.
chatInput.css	Aligns composer toolbar controls.
chatView.ts	Applies active-session layout state and focus routing.
chat.contribution.ts	Registers commands, keybindings, and setting.
sessionCommands.ts	Defines picker command IDs.
sessionView.ts	Forwards picker focus requests.
parts/​chatView.ts	Adds default picker-focus hooks.

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[vs-code-engineering]

📬 CODENOTIFY

The following users are being notified based on files changed in this PR:

Kyle Cutler (@kycutler)

Matched files:

• extensions/vscode-api-tests/src/singlefolder-tests/browser.tools.test.ts

Joaquín Ruales (@jruales)

Matched files:

• extensions/vscode-api-tests/src/singlefolder-tests/browser.tools.test.ts

Benjamin Christopher Simmonds (@benibenj)

Matched files:

• src/vs/sessions/browser/parts/chatView.ts
• src/vs/sessions/browser/parts/sessionView.ts

[Justin Chen (justschen)]

i can't pull this branch quickly because it's from a fork - can we ensure a couple of things and test:

1. no change when the exp is off
2. no change in editor window chat panel and aux window chats
3. long chat requests don't overlap with the context widget
4. the branch codicon is too big and the gaps between icons for folder + vscode and the branch + branchname are not aligned

5. same with the spacing here for model picker vs. harness picker - just a few pixels too much for the harness picker

[Megan Rogge (meganrogge)]

Addressed the four concerns from the review in 4c60ad8:

1. Added regression coverage for all experiment-setting combinations so disabled settings preserve the existing layout.
2. Scoped the running-session toolbar move to isSessionsWindow, with coverage showing editor/auxiliary windows and phone layouts keep the legacy secondary toolbar.
3. Kept the 72px input-editor reservation and added coverage that it accommodates the expanded context-usage widget, so long requests wrap before it.
4. Reduced the experimental repository/branch codicons to the compact codicon size.

Validation: ESLint, npm run transpile-client, 36 Agent Host picker tests, 6 composer-layout tests, and 60 Sessions chat-view tests.

[Justin Chen (justschen)]

just one small nit! thanks

addressed