---
id: PLN-0066
ticket: prometeu-hub-ui-direction
title: Hub UI Slice Validation and Lesson
status: open
created: 2026-05-15
ref_decisions: [DEC-0028]
tags: [hub, ui, shell, system-apps, lifecycle, design-system]
---

## Briefing

Validate the completed `DEC-0028` implementation family, collect evidence, and prepare the post-execution lesson required by the repository workflow.

Source decision: `DEC-0028`.

## Objective

Prove that the initial Hub retro Shell UI slice satisfies the accepted decision and leave the discussion workflow ready for housekeeping after implementation.

## Dependencies

- `PLN-0062` must be implemented.
- `PLN-0063` must be implemented or explicitly documented as unnecessary because mouse/click was already available.
- `PLN-0064` must be implemented.
- `PLN-0065` must be implemented or explicitly deferred with evidence.

## Scope

- Run relevant crate tests.
- Perform manual desktop verification of the end-to-end flow.
- Check that no forbidden scope leaked into implementation.
- Record evidence in plan execution notes or final implementation summary.
- Draft an English lesson after execution is complete.

## Non-Goals

- No new UI implementation work except small fixes required to satisfy acceptance criteria.
- No new architecture decisions.
- No lesson before code/spec state is published.
- No housekeeping until plans are done.

## Execution Method

1. Run automated tests.
   - What changes: execute the crates affected by plans `PLN-0062` through `PLN-0065`.
   - How: run targeted cargo tests for firmware/system/host crates.
   - Files: test output only; no source changes unless failures expose implementation bugs.

2. Verify end-to-end desktop behavior.
   - What changes: manually exercise Hub -> ShellA -> close -> Hub -> ShellB -> close -> Hub.
   - How: run the desktop host or project runner used for Hub boot, click the buttons, and observe lifecycle return.
   - Files: none, unless bugs are found.

3. Check decision compliance.
   - What changes: inspect implementation against `DEC-0028` invariants.
   - How: verify no toolkit, no catalog, no Tabs/List/Footer, no direct task/process manager mutation from visual components, and task-owned Shell windows.
   - Files: implementation files from the prior plans.

4. Record validation evidence.
   - What changes: update the relevant plans or implementation summary with commands run, manual checks, failures, and fixes.
   - How: keep evidence concise and tied to acceptance criteria.
   - Files: plan artifacts if the workflow records execution notes there.

5. Prepare post-execution lesson.
   - What changes: create an English lesson only after implementation is complete and published.
   - How: use `discussion-housekeep` when all plans are done; lesson should explain how to think about Hub visual slices without making lessons normative.
   - Files: `discussion/lessons/DSC-0036-prometeu-hub-ui-direction/...`.

## Acceptance Criteria

- [ ] Automated tests for affected crates pass or failures are documented as unrelated.
- [ ] Manual flow passes: Hub -> ShellA -> close -> Hub.
- [ ] Manual flow passes: Hub -> ShellB -> close -> Hub.
- [ ] Shell windows are task-owned.
- [ ] App close uses lifecycle close.
- [ ] No complete UI toolkit or catalog was introduced.
- [ ] Pixel font integration outcome is recorded.
- [ ] A post-execution lesson is ready for housekeeping after plans are marked done.

## Tests

- `cargo test -p prometeu-system`
- `cargo test -p prometeu-firmware`
- `cargo test -p prometeu-host-desktop-winit` if host/input code changed
- Manual desktop host verification
- `discussion validate` after marking plans and housekeeping artifacts

## Affected Artifacts

- Implementation files touched by `PLN-0062` through `PLN-0065`
- `discussion/workflow/plans/PLN-0062-native-shell-launch-and-lifecycle-wiring.md`
- `discussion/workflow/plans/PLN-0063-hub-mouse-input-and-click-routing.md`
- `discussion/workflow/plans/PLN-0064-retro-hub-home-and-fake-shell-ui.md`
- `discussion/workflow/plans/PLN-0065-pixel-operator-font-integration.md`
- Future lesson under `discussion/lessons/DSC-0036-prometeu-hub-ui-direction/`