paseo/docs/explorer-sidebar.md

Explorer sidebar and side pane

The Explorer sidebar and the side pane share panel implementations, but they have different shell contracts.

Surface	Purpose	Lifecycle
Explorer sidebar	Files and Changes navigation	Cmd+E shows or hides the dedicated dock
Side pane	Ordinary workspace content	Created and closed like any workspace pane
Sheets	Compact look-ups	One tab each, on the app-wide sheet stack

Panel host contract

Every panel registers its supported PaneHost values and presentation. Launchers derive fixed-target labels and icons from that registration, filter by host, and never substitute one panel type for another. Tab moves reject unsupported destinations, and placement resolves only to a compatible pane.

Files and Changes are the Explorer defaults. Their panel manifests mark them as singletons, so a pane’s + menu omits each while that pane already contains it. Closing one makes its menu item available again. Other compatible tabs, including agents, terminals, files, and diffs, can move between Explorer and main panes. Keep panel implementations independent of either shell. WorkspacePanelHost owns mounting and retention. The shared Explorer owns its tab rail; its shared frame owns visibility, activity and close-gesture lifetime. Platform adapters own resizing and inset geometry. The host keeps three recently used tabs plus modified tabs; unmodified tabs beyond that budget can remount. Native retained content stays live, while web chat uses its existing deferred Freeze.

Sheets

On compact layouts, files and subagents open in a sheet over the workspace, so the tab switcher keeps only agents and terminals. A panel kind opts in with compactSheet in its manifest (packages/app/src/panels/panel-manifest.ts), and the layout store's openTab decides between sheet and tab, so callers open targets the same way on every layout. Each such sheet holds one ordinary WorkspaceTab (SheetTab in the store) and is an IsolatedBottomSheetModal like every other sheet in the app, so it sits on the one app-wide stack: a sheet opened from any sheet, a subagent chosen from the subagents list included, lands on top of it, and closing the top sheet (drag, Close, backdrop, or Android Back) uncovers the one below. The list stays open under the sheet it opened; see menus.md for the row contract.

The store keeps sheetsByWorkspace in opening order and never reorders it, because moving a sheet remounts its panel. Revealing a target that already has a sheet uncovers that sheet by closing the ones above it, except ones holding unsaved work, which stay where they are. Opening a sheet as a tab dismisses the sheets above it, since the tab would sit under them. The stack is not persisted.

Sheets are modal and cover both compact sidebars as well as the workspace. A sheet's header is its drag handle, because the panel scrolls on its own and content panning would fight it. Its trailing rail holds icon buttons only (SheetHeaderIconButton): Open as tab is the full-screen glyph beside Close, so the title keeps its width. Compact sheets use the app overlay host: a workspace-local host sits behind the app-level left sidebar. The workspace environment bridge preserves existing editing sessions, caches, file-link resolution and supported navigation context without moving their providers. Keep this capability at the workspace boundary; new sheet callers must not assemble provider internals. Wide layouts retain local hosting and pane geometry. Both hosts forward the same Gorhom modal queue; neither creates another stack. See floating-panels.md Gotcha 7.

A sheet holding unsaved work is never implicitly displaced; only its guarded close removes it. Moving its tab to another host remounts the panel, and the file editor keeps unsaved text in the mounted view, so the move would drop it. Widening the layout is the known exception: it still moves the sheet's tab into a pane, and edits the autosave has not started writing are lost.

Explorer sidebar

packages/app/src/workspace-tabs/explorer-sidebar.ts owns show, hide, toggle, and view selection. One Explorer host stays beside the center column across compact overlays and docks. Keep its providers and gesture roots at the same React position when width or appearance changes. The workspace route preserves panel ancestry during appearance updates. Appearance-dependent leaves subscribe to theme changes; the file editor reconfigures its existing editor theme compartment. Ordinary leaf routes retain the stack appearance policy. The shell is outside the workspace split canvas so it divides the full workspace, including the header. It has its own persisted width and resize handle. Main-pane splits never read or modify that width.

packages/app/src/workspace-tabs/open-supporting-view.ts owns semantic Changes and pull-request opens. Compact and wide native layouts select the matching workspace tab in Explorer. Desktop Changes opens follow the shared diff preference. Desktop pull requests use their Main panel, On the side, or Explorer sidebar setting. Automatic PR discovery follows that preference once per workspace without interrupting the user's work. Closing the tab opts that workspace out of future automatic opens, even for a different PR; moving or reordering it remains the user's choice. Callers request the content and never choose the shell. The composer Changes pill is a two-stage desktop action: it first reveals Explorer on Changes, then routes later presses to the working diff through the shared diff preference.

The persisted layout still contains the Explorer pane so tabs survive reloads. The renderer removes that pane from the workspace split tree and docks it separately. Persisted identifiers retain the literal "explorer" pane id and explorerPaneIdByWorkspace key for compatibility.

Explorer uses the shared workspace tab row and ordinary tab context menus. Files and Changes hide their close buttons through the panel manifest; close them from the tab context menu. Other tabs reveal the close control on hover. Compact layouts show no inline close on any tab, since a narrow X beside the label is easy to hit by accident; the long-press menu closes it. Compact tabs also keep their natural width and the rail scrolls as soon as they overflow, while pointer layouts shrink tabs toward the clickable minimum first. A rail that scrolls never truncates. The + menu opens compatible panels in the dock, including Agent and terminal profiles. Compact layouts omit Diff from it because compact Changes shows each file's diff inline. Web also supports dragging agents and terminals into Explorer. Bulk-close actions apply only to the dock's tabs. Explorer tabs can be reordered and dragged between compatible panes, but the dock cannot be split or maximized. Selecting an Explorer tab does not change workspace focus. Web dragging shares the workspace drag scope; compact layouts accept only reordering inside the source pane.

Cmd+E shows or hides Explorer without changing its selected view. All layouts use the same workspace tabs, launcher, and panel host. Below 600 points the shell is the swipeable Explorer overlay; at 600 points and above it reserves width beside the workspace. Native docking keeps its touch resize handle. Full workspace splits remain a separate web-only capability.

The dock reserves at least 240 points and the workspace 360. App navigation yields when it cannot share the remaining width with both. This keeps a portrait tablet from rendering three unusably narrow columns; widening restores navigation without changing its saved open state.

Compact panel gestures own overlay visibility; the workspace layout owns its tab selection and contents on every platform. Explicit pane destinations bypass compact sheet placement, so choosing a panel in Explorer's + menu keeps it there. Ordinary compact file and subagent look-ups still use the sheet policy. Resolving an existing main tab reveals center immediately; a new file sheet keeps Explorer underneath and closing the sheet uncovers it. Semantic navigation resolves the actual destination before revealing it, including deduplicated targets.

Compact overlay selection and saved dock visibility are independent. Folding changes geometry, not either mode’s visibility intent. Native workspace retention remains one workspace; web retains up to ten with its existing inactive TTL.

PR discovery belongs to the active workspace: split layouts discover while active, and other layouts discover while Explorer is active. The rail requests summary status; selected visible PR content also requests timeline data. Inactive consumers read cached data without request demand. Discovery uses ordinary PR tabs and their existing once-per-workspace close opt-out.

Side pane

packages/app/src/workspace-tabs/open-beside.ts owns content opened beside the user's work. The layout store remembers one ordinary pane per workspace. The first side open creates a full-height right split around the workspace root; later side opens reuse it. Only the split-panes layout mode opens beside. Compact and single-pane layouts (touch tablets) open the same target in the main pane, so callers never check whether splits render.

Removing a pane clears its remembered id; a later side open creates a new pane. The last visible ordinary pane stays when its final tab closes and shows the New launcher. An empty workspace does not automatically create an agent draft tab; choosing Agent opens one. Explorer cannot replace the workspace canvas, even when visible. Restoring a saved layout enforces the same rule while preserving Explorer and saved tab content. There is no hidden side-pane lifecycle.

Placement intent still controls existing tabs:

Mode	New target	Existing target
pane	opens in the requested pane	moves to the requested pane
prefer	opens in the requested pane	stays where the user placed it
focused	opens in the focused pane	focuses it where it already lives
ambient	opens in a compatible pane	focuses it where it already lives

Explicit Open to Side uses pane. Implicit opens use prefer, so a preference affects only a new target and never yanks an existing tab out of a user-selected pane.

Routing preferences

Desktop Settings → Layout → Open location has independent Main panel or On the side choices for Explorer Files, diffs, chat files, files opened from diffs, and subagents. They default to Main panel. Mobile ignores them.

Pull requests have a three-way open location: Main panel, On the side, or Explorer sidebar. Explorer sidebar is the default. Compact layouts always open pull requests in Explorer regardless of this desktop preference.

Panels request an implicit open through the narrow openPreferredTarget(target, source) pane contract. Entry points outside panels use openPreferredWorkspaceTarget. Do not branch on a specific shell inside a panel.