# Design: Tool Session Progress and Live Updates

## Goals / Non-Goals

**Goals:**
- Provide structured, real-time progress feedback for every tool lifecycle action.
- Ensure all session lists (nav, dashboard, sessions page) update immediately after create/delete.
- Remove blocking and card-dimming overlays that hide context and provide no step detail.
- Keep the change frontend-only, reusing existing SSE and session APIs.

**Non-Goals:**
- No new backend endpoints or event types.
- No changes to the actual Docker/container orchestration logic.
- No redesign of the session card layout beyond action/progress affordances.

## Decisions

### Decision: Global progress panel in the corner
A fixed panel (bottom-right desktop, bottom sheet style on mobile) lists in-flight operations. Each operation shows:
- Action icon + session display name
- Current step label derived from the latest SSE event
- A compact stepper: Created → Building → Starting → Probing → Ready/Error
- Dismiss button once settled

This is non-blocking, works across pages, and does not interfere with the modal create flow.

### Decision: SSE event-driven updates
The panel subscribes to `useEvents`. When an operation is started we record `instanceId` + `action`. Incoming events that match a tracked instance update the operation's message, status, and step. Events handled:
- `instance.created`, `instance.started`, `instance.restarted` → advance
- `instance.health_changed` with `status=running` → complete success
- `instance.error` → complete error
- `instance.stopped` → complete for stop action
- `instance.deleted` → complete for delete action

### Decision: Shared session state
`SessionsContext` is promoted from a nav-only data holder to the authoritative session list:
- Holds `sessions`, `isLoading`, `error`, `refreshSessions()`.
- Provides `addOrUpdateSession`, `removeSession` for optimistic updates.
- `AppShell`, `DashboardPage`, and `SessionsPage` read from this context instead of fetching independently.

### Decision: Optimistic create/delete updates
- **Create**: after the API returns a pending instance, add it to shared state and start tracking. Subsequent SSE events update its status.
- **Delete**: remove from shared state as soon as the API succeeds; the progress panel tracks the action until the `instance.deleted` event confirms it.
- **Other actions**: keep the existing per-action busy flag on the card for button disabled states, but the panel provides the detailed progress.

### Decision: Remove legacy overlays
- Delete `loading-overlay` and workflow step markup from `CreateSessionForm`.
- Remove `session-busy-overlay` and `instance-busy-overlay` (the dimming overlays), but keep button disabled states and small inline spinners.

## Risks / Trade-offs

**Risk: Shared context causes extra re-renders**
→ Mitigation: context value is memoized; lists use the same data they already fetched.

**Risk: SSE events arriving before operation is tracked**
→ Mitigation: start tracking before calling the create/start API; for deletes the removal is optimistic and the panel reconciles on the event.

**Risk: Duplicate feedback between panel and toasts**
→ Mitigation: panel shows in-flight steps; toasts remain for terminal success/error only. Existing `EventToastBridge` logic is left largely unchanged.

## Migration Plan

1. Extend `SessionsContext` with loading/error/refresh/update helpers.
2. Create `SessionOperationsContext` + `SessionProgressPanel` and render it in `AppShell`.
3. Update `useInstanceActions` to use shared state and start/stop tracking operations.
4. Update `ToolStarter`/`StartToolFAB` to add pending sessions and start tracking.
5. Update `CreateSessionForm` to remove overlay and report status to parent.
6. Update `InstanceList` to refresh shared state after create/delete.
7. Update `SessionsPage` and `DashboardPage` to consume shared context.
8. Remove legacy overlay styles.
9. Run typecheck, lint, and tests.
