# SDD Tasks: Multi-Session Terminal UX

## Review Workload Forecast

| Field | Value |
|-------|-------|
| Estimated changed lines | ~1,400–1,600 (new ~900, modified ~600–700) |
| 400-line budget risk | High |
| Chained PRs recommended | Yes |
| Suggested split | PR 1: DB + Backend Core → PR 2: Backend API + Tests → PR 3: Frontend + Tests |
| Delivery strategy | auto-chain |
| Chain strategy | stacked-to-main |

```text
Decision needed before apply: Yes
Chained PRs recommended: Yes
Chain strategy: stacked-to-main
400-line budget risk: High
```

---

## Task Overview

| # | Task | PR | Est. Lines | Dependencies |
|---|------|-----|------------|--------------|
| 1 | Database schema and Alembic migration | 1 | ~80 | None |
| 2 | TerminalManager multi-session core | 1 | ~250 | Task 1 |
| 3 | TerminalSession name and status fields | 1 | ~40 | Task 2 |
| 4 | WebSocket routing and backward-compat alias | 2 | ~200 | Task 2 |
| 5 | REST endpoints for session CRUD | 2 | ~180 | Task 2, 4 |
| 6 | Frontend API client and `useTerminalSessions` hook | 3 | ~180 | Task 5 |
| 7 | `TerminalComponent` `sessionId` support | 3 | ~100 | Task 4, 6 |
| 8 | `TerminalSessionTabs` UI component | 3 | ~220 | Task 6 |
| 9 | `TerminalPage` multi-session orchestration and fullscreen | 3 | ~200 | Task 7, 8 |
| 10 | Mobile terminal integration | 3 | ~100 | Task 8, 9 |
| 11 | Backend integration tests | 2 | ~250 | Task 4, 5 |
| 12 | Frontend component tests | 3 | ~150 | Task 8, 9, 10 |

---

## PR 1: Database + Backend Core

### Task 1: Database Schema and Alembic Migration

**Scope**: Create the `terminal_sessions` metadata table and corresponding Alembic migration.

**Files to create**:
- `apps/api/src/models/terminal_session.py`
- `apps/api/alembic/versions/XXXX_add_terminal_sessions_table.py`

**Files to modify**:
- `apps/api/src/main.py` — import new model so Alembic autogenerate discovers it

**Acceptance Criteria**:
- `TerminalSessionModel` extends `Base`, `UUIDPrimaryKeyMixin`, `TimestampMixin`
- Columns: `instance_id` (UUID, FK `tool_instances.id` ON DELETE CASCADE, indexed), `name` (String 255, nullable), `status` (String 50, default `"active"`), `created_at` (DateTime TZ, non-nullable), `last_activity_at` (DateTime TZ, nullable), `closed_at` (DateTime TZ, nullable)
- Migration is reversible (`downgrade` drops table + index)
- `make migrate` applies successfully in local dev

**Testing (TDD)**:
- RED: Write a migration metadata test asserting the new table exists in `Base.metadata` and has expected columns
- GREEN: Create model and migration
- Run `pytest tests/integration/test_models.py` or equivalent to verify table registration

---

### Task 2: TerminalManager Multi-Session Core

**Scope**: Refactor `TerminalManager` to support up to 5 concurrent sessions per instance using composite keys.

**Files to modify**:
- `apps/api/src/services/terminal_manager.py`

**Acceptance Criteria**:
- `self._sessions` keyed by `(instance_id: str, session_id: str)`
- `create_session(instance_id, container_id, startup_command=None, name=None)`:
  - Generates UUID `session_id`
  - Enforces max 5 active sessions per instance (raise `MaxSessionsExceededError` / HTTP 409)
  - Inserts `TerminalSessionModel` DB row (fire-and-forget async task acceptable)
  - Returns `TerminalSession`
- `get_or_create_session(instance_id, container_id, ...)` preserved for backward compatibility; uses `"default"` session_id
- `get_session(instance_id, session_id)` returns session or `None`
- `get_sessions_for_instance(instance_id)` returns list of in-memory sessions
- `close_session(instance_id, session_id)`: kills PTY, removes from `_sessions`, updates DB `status=closed`, `closed_at=now()`
- `reset_session(instance_id, container_id, session_id=None)`: if `session_id` omitted, resets `"default"` session
- `attach_websocket` only closes existing WebSockets **within the same `(instance_id, session_id)`**
- `_cleanup_idle_sessions` uses composite keys and updates DB status on cleanup
- Idle timeout (30 min) and buffer replay behavior preserved

**Testing (TDD)**:
- RED: Create `apps/api/tests/services/test_terminal_manager_multi.py` with tests:
  - `test_create_session_increases_count`
  - `test_create_session_enforces_max_5`
  - `test_get_sessions_for_instance_filters_by_instance`
  - `test_close_session_removes_from_dict_and_updates_db`
  - `test_attach_websocket_only_closes_same_session`
  - `test_default_session_keyed_separately`
  - `test_idle_cleanup_updates_db_status`
- GREEN: Implement `TerminalManager` changes
- Run `make test-unit`

---

### Task 3: TerminalSession Name and Status Fields

**Scope**: Add runtime `name` and `status` tracking to `TerminalSession`.

**Files to modify**:
- `apps/api/src/services/terminal_session.py`

**Acceptance Criteria**:
- `__init__` accepts optional `name`; auto-generates `"Session N"` if omitted (N = per-instance counter)
- `self.name` stored as runtime attribute
- `self.status` enum-like string: `"active"`, `"resetting"`, `"closed"`
- `reset()` sets `status="resetting"` during transition, `"active"` after restart
- `close()` sets `status="closed"`
- No breaking changes to existing `TerminalSession` behavior

**Testing (TDD)**:
- RED: Extend `test_terminal_manager_multi.py` or add `test_terminal_session_name_and_status.py` covering auto-naming, status transitions, and reset/close side effects
- GREEN: Implement fields and transitions
- Run `make test-unit`

---

## PR 2: Backend API + Tests

### Task 4: WebSocket Routing and Backward-Compat Alias

**Scope**: Add session-scoped WebSocket route, extract shared handler, preserve legacy alias.

**Files to modify**:
- `apps/api/src/api/terminal.py`

**Files to create**:
- `apps/api/tests/api/test_terminal_ws_multi.py`

**Acceptance Criteria**:
- New route: `@router.websocket("/ws/tool-instances/{instance_id}/terminal/{session_id}")`
- Existing route `@router.websocket("/ws/tool-instances/{instance_id}/terminal")` preserved; calls `get_or_create_session(...)` for `"default"` session
- Extract `async def _handle_terminal_websocket(websocket, instance_id, session_id, db_session)` containing shared auth/validation/I/O loop logic
- Both routes call `_handle_terminal_websocket`
- Auth/validation logic unchanged (cookie-based, ownership check, running status)
- `reset` control message scoped to the current session only (via `SessionRef` update)
- On unknown `session_id`, close WS with code `4004` "Session not found"

**Testing (TDD)**:
- RED: Write `test_terminal_ws_multi.py`:
  - `test_specific_session_websocket_connects`
  - `test_default_session_alias_creates_default`
  - `test_concurrent_sessions_isolated_output`
  - `test_reset_control_message_scoped_to_session`
  - `test_unknown_session_id_returns_4004`
- GREEN: Implement routes and shared handler
- Run `pytest tests/api/test_terminal_ws_multi.py`

---

### Task 5: REST Endpoints for Session CRUD

**Scope**: Add REST endpoints for listing, creating, closing, resetting, and renaming sessions.

**Files to modify**:
- `apps/api/src/api/terminal.py`

**Acceptance Criteria**:
- `GET /projects/{pid}/repositories/{rid}/instances/{iid}/terminal/sessions`
  - Returns `{ sessions: [...] }` with `id`, `name`, `status`, `has_websockets`, `created_at`, `last_activity_at`
  - `has_websockets` queried live from `TerminalManager`
- `POST .../terminal/sessions` — body `{ name?: string }`
  - Returns `201` with `{ id, name, status, created_at }`
  - Returns `409` if max 5 reached
- `DELETE .../terminal/sessions/{sid}` — returns `{ status: "closed", session_id }`
- `POST .../terminal/sessions/{sid}/reset` — returns `{ id, name, status }`
- `POST .../terminal/sessions/{sid}/rename` — body `{ name: string }`, returns `{ id, name }`
- Existing `POST .../terminal/reset` preserved as alias for default session reset
- All endpoints validate auth, ownership, and running instance status

**Testing (TDD)**:
- RED: Add integration tests in `test_terminal_ws_multi.py` or new `test_terminal_rest.py`:
  - `test_list_sessions_returns_db_and_live_state`
  - `test_create_session_201`
  - `test_create_session_409_at_max`
  - `test_close_session_200`
  - `test_reset_session_200`
  - `test_rename_session_200`
  - `test_legacy_reset_alias_still_works`
- GREEN: Implement endpoints
- Run `make test-integration`

---

### Task 6: Frontend API Client and `useTerminalSessions` Hook

**Scope**: Add frontend REST client functions and the central session state hook.

**Files to create**:
- `apps/web/src/api/terminal.ts` (new file for terminal-specific API calls)
- `apps/web/src/hooks/use-terminal-sessions.ts`

**Files to modify**:
- `apps/web/src/api/sessions.ts` — optional, or keep terminal API separate

**Acceptance Criteria**:
- API functions: `listTerminalSessions`, `createTerminalSession`, `closeTerminalSession`, `resetTerminalSession`, `renameTerminalSession`
- `useTerminalSessions(instanceId: string)` hook:
  - Loads sessions on mount; auto-creates one if list is empty
  - Exposes `sessions`, `activeSessionId`, `setActiveSessionId`
  - Exposes `createSession`, `closeSession`, `renameSession`, `resetSession` with optimistic UI updates
  - Handles 409 errors (max sessions) gracefully
  - Refetches after reset/rename to stay in sync

**Testing (TDD)**:
- RED: Write hook unit tests mocking API client:
  - `test_loads_sessions_on_mount`
  - `test_auto_creates_session_if_empty`
  - `test_close_session_removes_from_state`
  - `test_create_session_enforces_max_5_error`
- GREEN: Implement hook and API client
- Run `cd apps/web && npm test`

---

## PR 3: Frontend + Tests

### Task 7: `TerminalComponent` `sessionId` Support

**Scope**: Update `TerminalComponent` to accept an optional `sessionId` and route WS accordingly.

**Files to modify**:
- `apps/web/src/components/terminal.tsx`

**Acceptance Criteria**:
- New optional prop `sessionId?: string`
- WS URL constructed as:
  - `/ws/tool-instances/{instanceId}/terminal/{sessionId}` if `sessionId` provided
  - `/ws/tool-instances/{instanceId}/terminal` if omitted (backward compat)
- Reset button sends `{"type": "reset"}` to the correct session's WS
- Component still supports all existing props and mobile behavior
- `onTerminalReady` callback still works; parent can differentiate sessions by key

**Testing (TDD)**:
- RED: Add/update `terminal.test.tsx` (or similar) to assert WS URL includes `sessionId` when provided
- GREEN: Implement prop and URL logic
- Run `cd apps/web && npm test`

---

### Task 8: `TerminalSessionTabs` UI Component

**Scope**: Build the tab bar for desktop and mobile.

**Files to create**:
- `apps/web/src/components/terminal-session-tabs.tsx`
- `apps/web/src/components/terminal-session-tabs.test.tsx`

**Acceptance Criteria**:
- Props interface: `sessions`, `activeSessionId`, `onSelect`, `onClose`, `onCreate`, `onRename`, `isMobile?`
- Desktop: horizontal tab strip above terminal, overflow scroll with fade indicator
- Mobile: compact tabs integrated into auto-hide chrome, horizontal swipe scroll
- Each tab shows: name, status dot (connecting/connected/disconnected/error), close button (×) on hover/active
- Double-click to rename: inline `<input>`, `Enter` to confirm, `Escape` to cancel, blur confirms
- New session button (+) at right end; disabled when 5 sessions exist
- Close confirmation: lightweight inline confirm tooltip (not modal)
- Accessible: `role="tablist"`, `role="tab"`, keyboard navigation

**Testing (TDD)**:
- RED: Write `terminal-session-tabs.test.tsx`:
  - `test_renders_all_tabs`
  - `test_click_tab_calls_onSelect`
  - `test_close_button_calls_onClose`
  - `test_double_click_enables_rename`
  - `test_plus_disabled_at_max_sessions`
  - `test_status_dot_reflects_connection_state`
- GREEN: Implement component
- Run `cd apps/web && npm test`

---

### Task 9: `TerminalPage` Multi-Session Orchestration, Fullscreen, and Shortcuts

**Scope**: Rewrite `TerminalPage` to manage multiple mounted terminals, fullscreen mode, and keyboard shortcuts.

**Files to modify**:
- `apps/web/src/pages/terminal.tsx`

**Acceptance Criteria**:
- Uses `useTerminalSessions` hook
- Renders `<TerminalSessionTabs />` above terminal area
- Renders one `<TerminalComponent />` per session; inactive sessions hidden via `display: none` (preserves scrollback and WS)
- On tab switch, active terminal calls `fitAddon.fit()` via ref + `useEffect` on visibility
- Fullscreen toggle:
  - `Ctrl+Shift+F` toggles `.fullscreen` class
  - Desktop: hides page header; tab strip becomes minimal overlay (auto-hides after 3s, reappears on mouse move)
  - Mobile: hides header, tab strip, special keys; floating handle reveals chrome
  - Exit via `Esc` or UI button
- Keyboard shortcuts (registered in `useEffect` on `keydown`):
  - `Alt+Shift+N` — new session
  - `Alt+Shift+W` — close current session
  - `Alt+Shift+←` / `Alt+Shift+→` — prev/next session
  - `Alt+Shift+R` — reset current session
  - All use `preventDefault()` only for the exact combo; no browser overrides
- Closing last session auto-creates a new default session

**Testing (TDD)**:
- RED: Add `terminal-page.test.tsx`:
  - `test_creates_default_session_on_empty_load`
  - `test_switching_tabs_hides_inactive_terminals`
  - `test_fullscreen_toggle_adds_class`
  - `test_keyboard_shortcut_creates_session`
  - `test_close_last_session_auto_creates_default`
- GREEN: Implement page orchestration
- Run `cd apps/web && npm test`

---

### Task 10: Mobile Terminal Integration

**Scope**: Integrate session tabs into mobile terminal wrapper and update header.

**Files to modify**:
- `apps/web/src/components/mobile-terminal-wrapper.tsx`
- `apps/web/src/components/mobile-terminal-header.tsx`

**Acceptance Criteria**:
- `MobileTerminalWrapper` accepts session-related props from `TerminalPage` and passes them to `TerminalSessionTabs`
- `MobileTerminalHeader` displays `activeSession.name` instead of generic `"Terminal"`
- Tab strip shares `useAutoHide` behavior with header (tapping terminal toggles visibility)
- Special keys strip remains functional; no z-index conflicts with tabs
- Fullscreen on mobile correctly hides/shows all chrome layers

**Testing (TDD)**:
- RED: Add/update mobile wrapper tests:
  - `test_renders_session_tabs`
  - `test_header_shows_session_name`
  - `test_auto_hide_applies_to_tabs`
- GREEN: Implement mobile integration
- Run `cd apps/web && npm test`

---

### Task 11: Backend Integration Tests

**Scope**: Complete backend test coverage for multi-session WebSocket and REST behavior.

**Files to create / modify**:
- `apps/api/tests/services/test_terminal_manager_multi.py` (finalize)
- `apps/api/tests/api/test_terminal_ws_multi.py` (finalize)

**Acceptance Criteria**:
- All tests from Tasks 2, 4, 5 pass
- Additional integration tests:
  - `test_list_sessions_after_api_restart_shows_db_metadata` (simulates restart by clearing in-memory dict)
  - `test_two_websockets_on_same_session_receive_same_output`
  - `test_idle_cleanup_per_session_not_global`
- `make test` passes (unit + integration)

**Testing (TDD)**:
- These are the GREEN/TRIANGULATE phases for earlier backend tasks; ensure coverage is comprehensive

---

### Task 12: Frontend Component Tests

**Scope**: Finalize frontend test coverage for tabs, page, and hook.

**Files to create / modify**:
- `apps/web/src/components/terminal-session-tabs.test.tsx` (finalize)
- `apps/web/src/hooks/use-terminal-sessions.test.ts` (new, if not created earlier)
- `apps/web/src/pages/terminal.test.tsx` (new)

**Acceptance Criteria**:
- Tab component tests cover rendering, selection, close, rename, and max-session disable
- Hook tests cover load, create, close, error handling
- Page tests cover session lifecycle, fullscreen, and keyboard shortcuts
- `cd apps/web && npm test` passes

**Testing (TDD)**:
- Finalize RED→GREEN→TRIANGULATE for all frontend tasks

---

## Risks and Mitigations

| Risk | Likelihood | Impact | Mitigation |
|------|------------|--------|------------|
| Resource exhaustion (5× docker exec per instance) | Medium | High | Max 5 enforced in `create_session`. Idle timeout (30 min) applies per session. |
| Mobile UX degraded by tab bar + special keys strip | Medium | Medium | Auto-hide shared between tabs and header. Compact tab design. Overflow scroll. |
| Concurrent WS policy closes wrong session's sockets | Medium | High | Explicit unit test: `attach_websocket` must only affect same `(instance_id, session_id)`. |
| DB writes on hot path (activity tracking) | Low | Medium | `last_activity_at` updates are fire-and-forget async tasks; do not block I/O loop. |
| Frontend performance with 5 mounted xterm.js instances | Low | Medium | Max 5 sessions. Inactive terminals use `display: none` (not unmounted). xterm.js GPU acceleration handles this. |
| Default session alias ambiguity | Low | Low | Document that `/terminal` maps to `"default"`. Future deprecation can migrate to explicit IDs. |
| Browser shortcut conflicts | Low | Medium | Use `Alt+Shift+*` instead of `Ctrl+Shift+W/N`. Only `preventDefault()` on exact matching combos. |

---

## Rollback Plan

- **PR 1 rollback**: Alembic downgrade removes `terminal_sessions` table. Old `TerminalManager` code is fully replaced, so reverting PR 1 requires reverting all subsequent PRs.
- **PR 2 rollback**: Revert API changes. Legacy `/terminal` WS route and `POST .../terminal/reset` continue to work; new `/terminal/{session_id}` returns 404 but no clients call it until PR 3 is deployed.
- **PR 3 rollback**: Revert frontend. Users see old single-session UI. Backend `/terminal` alias continues to serve them.

Because PRs are stacked, rolling back PR 2 or PR 1 requires rolling back all dependent PRs above it.