kandev/docs/plans/threads-multi-session-windowing/task-04-prove-threads-resource-budget.md

id, title, status, wave, depends_on, plan, requirements, acceptance_criteria, system_design

id	title	status	wave	depends_on	plan	requirements	acceptance_criteria	system_design
04-prove-threads-resource-budget	Prove the Threads resource budget	completed	4	03-add-threads-session-switcher	plan.md	REQ-UI-THREADS-DECK-001 REQ-UI-THREADS-DECK-002 REQ-UI-THREADS-DECK-003 REQ-PLATFORM-VIEWPORT-SESSION-DELIVERY-001 REQ-PLATFORM-VIEWPORT-SESSION-DELIVERY-002	AC-UI-THREADS-DECK-001.1 AC-UI-THREADS-DECK-001.3 AC-UI-THREADS-DECK-001.4 AC-UI-THREADS-DECK-001.7 AC-UI-THREADS-DECK-002.3 AC-UI-THREADS-DECK-002.4 AC-UI-THREADS-DECK-002.6 AC-UI-THREADS-DECK-003.1 AC-UI-THREADS-DECK-003.3 AC-UI-THREADS-DECK-003.4 AC-UI-THREADS-DECK-003.5 AC-UI-THREADS-DECK-003.6 AC-PLATFORM-VIEWPORT-SESSION-DELIVERY-001.3 AC-PLATFORM-VIEWPORT-SESSION-DELIVERY-001.4 AC-PLATFORM-VIEWPORT-SESSION-DELIVERY-001.5 AC-PLATFORM-VIEWPORT-SESSION-DELIVERY-001.6 AC-PLATFORM-VIEWPORT-SESSION-DELIVERY-002.3	../../specs/ui/system-design/threads-conversation-deck.md ../../specs/platform/system-design/viewport-bounded-session-delivery.md

Task 04: Prove the Threads resource budget

Summary

Add browser-level desktop and mobile proof for multi-session switching, attention semantics, viewport activation, and full-session subscription limits. Run the complete focused package checks against rebuilt web assets.

In scope

• Extend desktop Threads E2E with a real primary session and sibling sessions.
• Record outgoing session subscribe/unsubscribe actions during initial load, tab switching, and horizontal scrolling.
• Verify same-row switch-only tabs, task/session deep links, inactive-tab status updates, review-ready status, and stable column positions.
• Extend mobile Threads E2E with the picker sheet, one detail owner, 44-pixel rows, safe-area containment, and zero document overflow.
• Run all targeted backend, frontend, i18n, typecheck, production-build, and E2E commands for the package.

Out of scope

• Broad repository verification, unrelated PR checks, screenshot publication, or GitHub review/comment operations.

Acceptance

• Initial browser subscriptions contain only selected sessions from the detail window and no unselected sibling.
• Tab switching replaces only that column's session membership; scrolling releases departed details and activates the newly visible selected session.
• Desktop and phone controls meet the interaction, status, containment, and deep-link criteria without regressing existing Threads tests.

Verification

Run the production build and the focused package checks:

(cd apps/backend && rtk go test ./internal/task/service ./internal/gateway/websocket ./pkg/websocket -run 'PendingAction|TaskEventBroadcaster|SessionPending' -race)
(cd apps && pnpm --filter @kandev/web test -- --run lib/ws/handlers/session-pending-action.test.ts lib/state/slices/session/update-session-read-cursor.test.ts lib/threads/active-threads.test.ts lib/threads/thread-session-selection.test.ts lib/threads/thread-session-status.test.ts components/threads/threads-board.test.tsx components/threads/thread-column-activation.test.tsx components/threads/thread-session-switcher.test.tsx lib/links.test.ts)
(cd apps/web && pnpm run typecheck)
(cd apps/web && pnpm run i18n:check)
(make build-web)
(cd apps/web && pnpm e2e:run --project chromium tests/task/threads-view.spec.ts)
(cd apps/web && pnpm e2e:run --project mobile-chrome tests/task/mobile-threads-view.spec.ts)

Files likely touched

• apps/web/e2e/tests/task/threads-view.spec.ts
• apps/web/e2e/tests/task/mobile-threads-view.spec.ts
• apps/web/e2e/helpers/ws-traffic.ts if the existing helper needs a Threads action filter
• Files from Tasks 01 through 03 only when an E2E finding exposes a scoped bug

Dependencies

• Tasks 01 through 03 must be green before browser resource-budget assertions can represent the final design.

Risks

• Use stable action and session IDs as the traffic oracle, not timing or byte counts.
• Wait for the settled observer/subscription state after scroll or tab changes before asserting membership.
• Test-harness sibling sessions must belong to a task with one real primary session so the contributor's production eligibility path remains exercised.

Parallelism

sequential

Results

Implemented and verified. Desktop and mobile E2E coverage records session subscriptions during deep-link load, tab switching, and viewport scrolling. The browser checks prove one selected conversation per active detail owner, inactive sibling status updates, review-ready status, stable column order, mobile picker geometry, safe-area containment, and zero horizontal overflow.

The review fix-up adds long-label desktop geometry coverage. The complete focused package passes 33 backend race tests, 127 frontend tests, strict web lint, typecheck, i18n validation, production web build, desktop Threads E2E (9 tests), and mobile Threads E2E (2 tests).