Sidebar plugin: session multi-level tree (cwd grouping + parentId nesting), search, by-workspace grouping, state dots, three creation entries. Collapse morphs the four control rows into the layout-owned 56px rail (expand / new session / new workspace / search — search expands and focuses the search box) plus the settings foot: geometry animates on the deepsuite curve while wide-only content cross-fades and unmounts at settle. Contract: the slot system standard.

src/client/contract/slots.ts is the single-domain contract file: SidebarRootInjected (the registrant's own injected share — plain service callbacks: onOpen/onCreate/onToggleSidebar) and SidebarRootComponentProps = PropsRuntime<'sidebar'> & SidebarRootInjected (owner {collapsed,width} plus the standard useSessions hook, resolved off ui-layout's SlotMap declaration, never re-stated). apply registers SidebarRoot cast-free against that composition; the inject factory closes over the plugin's own ctx.

There is no plugin store: rows derive in the component (useMemo over the useSessions snapshot + local expansion/search state) through the pure deriveRows in tree.ts.

The /client export surface is the plugin body (apply/inject) plus the contract types only — SidebarRoot, the row components, and the tree derivation are internal (the slot registration closes over them; tests import src paths directly).

Model Experience

None, as the sidebar renders the browser session list; nothing here reaches a model request.

KV Cache effect

None; this package neither assembles nor sends a provider request.

Known Limitations and Deferred Work

State dots have two live data states (running/none) — the done/error/amber sources arrive with P-II approvals and notifications; the four-color primitive is already wired.
Group-by menu ships by-workspace only — Update/Status grouping strategies are drawn without specs and deferred.
"New task completed" unread marking is local viewing state — completion-time > last-seen never reaches the host.