Task 02: Wire Active-Session Editor Availability

Acceptance

The desktop task topbar filters internal_vscode with the active session's backend capability; missing capability data fails closed without hiding unrelated editors.
Saved-default fallback and active-session changes use the filtered editor set without mutating the stored preference or leaking the previous session's value.
The obsolete boot runtime.hostOS field, parser/accessor, tests, and Playwright helper are removed with no remaining consumer.

Verification

Use TDD: update the availability and prop-flow tests to describe the capability contract, observe the failures, wire the active-session value, and remove host metadata only after the new path is green. From apps/ run:

pnpm --filter @kandev/web test -- src/boot-payload.test.ts components/task/editors-menu-availability.test.ts components/task/task-top-bar.test.tsx
pnpm --filter @kandev/web typecheck
pnpm --filter @kandev/web lint

From apps/backend/ run the affected boot package tests:

go test ./internal/backendapp ./internal/webapp

Finally search from the repository root:

rg -n "readBackendHostOS|hostOS|rewriteBackendHostOS" apps

The search must return no obsolete editor-availability or boot-contract references.

Files likely touched

apps/web/hooks/domains/session/use-session-resumption.ts
apps/web/components/task/task-page-inner.tsx
apps/web/components/task/task-top-bar.tsx
apps/web/components/task/task-top-bar.test.tsx
apps/web/components/task/editors-menu.tsx
apps/web/components/task/editors-menu-availability.ts
apps/web/components/task/editors-menu-availability.test.ts
apps/web/src/boot-payload.ts
apps/web/src/boot-payload.test.ts
apps/backend/internal/webapp/payload.go
apps/backend/internal/backendapp/helpers.go
apps/backend/internal/backendapp/helpers_test.go
apps/web/e2e/helpers/boot-payload.ts (remove)

Dependencies

Task 01 provides the session capability and enforcement contract.

Parallelism

Sequential. The frontend contract and metadata removal must land together before E2E coverage.

Inputs

Spec sections: What, API surface, Failure modes, and scenarios 1–6 and 8.
Plan sections: Consume active-session capability, Filter and fallback, Retire host-wide boot metadata, and Mobile design contract.
Existing active-session source: resumption.sessionStatus in apps/web/components/task/task-page-inner.tsx.

Risks

Reset capability to false when effectiveSessionId changes instead of retaining asynchronous status from the previous session.
Pass one capability value to both halves of the split editor control.
Keep custom, hosted, Remote SSH, and installed built-in editors governed by their current rules.

Output contract

Report the prop/data flow, removed host metadata, files changed, red and green results, and the repository-wide search result. Update this task to done and its plan checkbox/status.

Completion record

The current session's capabilities.embedded_vscode flows from session resumption through TaskPageInner, TaskTopBar, TopBarRight, TopbarToolsGroup, and EditorsMenu. Missing data is false, while the hook's ID-keyed state prevents a previous session's status leaking into the next session.
Availability filtering now accepts the capability boolean and retains existing enabled/installed checks. The filtered set continues to drive saved-default fallback without persisting a change.
Removed boot runtime.hostOS from Go serialization and TypeScript parsing, plus the old E2E HTML-rewrite helper.
Red: the updated availability test still used the old host-OS argument and failed before the filtering implementation changed. Green: focused Vitest tests passed (15 tests), pnpm run typecheck and pnpm run lint passed, and go test ./internal/backendapp ./internal/webapp passed.
rg -n "readBackendHostOS|rewriteBackendHostOS|hostOS" apps/web apps/backend/internal/webapp apps/backend/internal/backendapp -g '*.ts' -g '*.tsx' -g '*.go' returned no matches.

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