---
id: PLN-0118
ticket: real-render-worker-establishment
title: Add Stale Epoch and Repeat Frame Behavior
status: open
created: 2026-06-15
completed:
ref_decisions: [DEC-0033]
tags: [runtime, renderer, worker, ownership, telemetry]
---

## Briefing

`DEC-0033` requires the worker to discard stale in-flight frames before publication and repeat the last published `OwnedRgba8888Frame` rather than recomposing.

## Decisions de Origem

- `DEC-0033`: Real Render Worker Contract.

## Alvo

Complete ownership/epoch checks and repeat-last-published-frame behavior for the worker path.

## Escopo

- Add shared active ownership/epoch observation for worker publication checks.
- Discard stale in-flight frames before publication.
- Store and expose the latest published `OwnedRgba8888Frame`.
- Implement repeat-last-frame behavior and telemetry.

## Fora de Escopo

- No desktop upload/present.
- No new AppMode policy.
- No native window invalidation changes.

## Plano de Execucao

### Step 1 - Expose ownership/epoch to worker

**What:** Let worker validate in-flight submissions before publishing.
**How:** Add a thread-safe snapshot or handle that the worker can read without mutating runtime state.
**File(s):** `render_manager.rs`, worker modules.

### Step 2 - Implement stale discard

**What:** Prevent stale pixels from publication.
**How:** Before publishing frame output, compare submission ownership/epoch with active ownership/epoch; discard on mismatch and increment telemetry.
**File(s):** worker controller module.

### Step 3 - Store latest published frame

**What:** Make the latest valid frame available to host/fallback tests.
**How:** Add a published-frame slot distinct from pending submission and in-flight work.
**File(s):** worker controller or published frame module.

### Step 4 - Implement repeat behavior

**What:** Repeat last valid frame without recomposition.
**How:** Add API to fetch/reuse the latest published `OwnedRgba8888Frame`; increment repeat telemetry when cadence requests reuse.
**File(s):** worker modules, tests.

### Step 5 - Add tests

**What:** Prove stale discard and repeat.
**How:** Use harness to hold in-flight work, change owner/epoch, release backend, and assert no publication; separately assert repeat returns last frame.
**File(s):** worker tests.

## Criterios de Aceite

- [ ] Worker checks active owner/epoch before publishing.
- [ ] Stale in-flight frames are discarded and counted.
- [ ] Latest published frame is an `OwnedRgba8888Frame`.
- [ ] Repeat uses the last published frame and does not recompose.
- [ ] Tests cover stale discard and repeat deterministically.

## Tests / Validacao

- `cargo test -p prometeu-system render_worker`
- `cargo test -p prometeu-system`

## Riscos

- Reading active ownership from the wrong layer may reintroduce mutable runtime coupling.
- Repeat behavior must not hide render failures unless telemetry records them.