headquarter/openspec/changes/multi-session-terminal-ux/tasks.md

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

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

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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

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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.