Agents: Add experimental tabbed workspace picker

[mrleemurray]

This pull request introduces a new experimental "Tabbed Workspace Picker" feature for the chat session workspace picker, along with several extensibility and usability improvements to the action widget infrastructure. The main changes include support for rendering a custom header (such as a tab bar) above the action list, new options for constraining the action widget's width, and extensibility hooks in the workspace picker to support filtering and custom layouts. There are also related styling updates and configuration wiring for the new tabbed picker.

Screen.Recording.2026-04-27.at.14.41.36.mov

Tabbed Workspace Picker and Extensibility:

• Added a new experimental setting sessions.experimental.tabbedWorkspacePicker and implemented the TabbedWorkspacePicker class, enabling a tabbed interface for selecting workspaces in chat sessions. The picker is conditionally enabled based on the configuration setting. [1] [2] [3]
• Refactored WorkspacePicker to support subclassing, including extensibility hooks for filtering workspaces and browse actions, customizing the header, and controlling minimum/maximum width. [1] [2] [3] [4] [5]
• Enhanced the logic for collecting and displaying recent workspaces and browse actions to respect subclass-provided filters and layout options. [1] [2] [3] [4]

Action Widget Infrastructure Improvements:

• Added maxWidth to IActionListOptions, and updated the action list widget to clamp its width between minWidth and maxWidth, ensuring long items are truncated rather than expanding the popup. [1] [2] [3] [4] [5]
• Enhanced the action widget service to support rendering an optional header element above the action list, used by the tabbed picker to display its tab bar. [1] [2] [3]

Styling Updates:

• Added CSS for the tabbed workspace picker, including styles for the tab bar and inline browse actions, improving visual clarity and reducing repetition in the UI.

These changes collectively enable a more flexible and user-friendly workspace picker experience, laying the groundwork for further UI enhancements and customization.

[Copilot]

Pull request overview

Introduces an experimental tabbed workspace picker for the Sessions window’s “new session” flow, enabling users to choose workspaces via separate Local/GitHub/Remote tabs and related UI enhancements behind a new configuration setting.

Changes:

• Add sessions.experimental.tabbedWorkspacePicker setting and wire it into the Sessions window new chat view.
• Implement TabbedWorkspacePicker with tab UI, category-based filtering, and inline browse actions.
• Extend the action widget/action list to support an optional header element and a max-width cap used by the picker.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/vs/sessions/contrib/copilotChatSessions/browser/copilotChatSessionsProvider.ts	Assign browse action grouping/icon updates to support tab categorization (e.g. repositories).
src/vs/sessions/contrib/configuration/browser/configuration.contribution.ts	Register the new experimental setting for enabling the tabbed picker.
src/vs/sessions/contrib/chat/browser/tabbedWorkspacePicker.ts	New tabbed picker implementation (tabs + workspace/browse-action categorization).
src/vs/sessions/contrib/chat/browser/sessionWorkspacePicker.ts	Add extensibility hooks (header/min/max width) and filtering logic used by the tabbed picker.
src/vs/sessions/contrib/chat/browser/newChatViewPane.ts	Select the appropriate picker implementation based on platform and the new setting.
src/vs/sessions/contrib/chat/browser/media/chatWidget.css	Styles for the tab bar and inline browse-action rows.
src/vs/sessions/common/configuration.ts	Define the new setting ID constant.
src/vs/platform/actionWidget/browser/actionWidget.ts	Allow callers to pass an optional header element rendered above the action list/filter.
src/vs/platform/actionWidget/browser/actionList.ts	Add maxWidth option and clamp computed list width accordingly.

Comments suppressed due to low confidence (1)

src/vs/sessions/contrib/chat/browser/sessionWorkspacePicker.ts:564

• Ungrouped browse actions are now rendered without description: action.description, so ISessionWorkspaceBrowseAction.description is effectively ignored in this path despite being intended for display in the workspace picker. Consider restoring the description here (or only suppressing it in the specific tabbed/inline UI variant).

			items.push({
				kind: ActionListItemKind.Action,
				label: localize('workspacePicker.browseSelectAction', "Select {0}...", action.label),
				group: { title: '', icon: action.icon },
				disabled: isUnavailable,
				item: { browseActionIndex: index },
			});

[github-actions]

blocks-ci screenshots changed

Replace the contents of test/componentFixtures/blocks-ci-screenshots.md with:

Updated blocks-ci-screenshots.md

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#### editor/inlineChatZoneWidget/InlineChatZoneWidget/Dark
![screenshot](https://hediet-screenshots.azurewebsites.net/images/041fd8cf01bf03e44367c80186743d6b4eae3aa7b38a6a1551e8a0168cb8f8f7)

#### editor/inlineChatZoneWidget/InlineChatZoneWidget/Light
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#### editor/inlineChatZoneWidget/InlineChatZoneWidgetTerminated/Light
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[sandy081]

A few architecture concerns:

1. Avoid extending IActionWidgetService with a generic headerElement API

The tab bar UI is specific to the session workspace picker — actionWidget is a generic action-list popup and shouldn't need to know about arbitrary caller-owned DOM. Passing an HTMLElement in creates unclear lifecycle/ownership responsibilities for child widgets and event listeners. The group selection state should live in the workspace picker layer, not in the action widget service.

2. No need for a new setting

If grouped workspace picker is the right UX direction, it should just be the behavior — no need for sessions.experimental.tabbedWorkspacePicker.

3. Groups should be provider-contributable, not hardcoded

The Local / GitHub / Remote grouping is currently hardcoded in TabbedWorkspacePicker based on provider-specific details like remoteAddress, GITHUB_REMOTE_FILE_SCHEME, and group === 'repositories'. The picker shouldn't need to know about these internals.

Instead, the groups should come from the providers themselves. One approach: extend ISessionWorkspaceBrowseAction.group to carry one of the well-known group values (Local, GitHub, Remote), and let the picker render those groups and their data dynamically. Providers contribute browse actions under a group; the picker just renders whatever groups are contributed.

[mrleemurray]

@sandy081 I've made some updates - please review