---
id: PLN-0090
ticket: vm-render-parallel-execution-boundary
title: Add Render Frame Pacing Contract
status: done
created: 2026-06-05
ref_decisions: [DEC-0031]
tags: [runtime, frame-clock, scheduler, vm]
---

## Briefing

`DEC-0031` separates Game logical frame pacing from render worker ACK. Game frames are paced by a frame clock/scheduler and still end at `FRAME_SYNC`.

## Objective

Define and implement the runtime contract that authorizes Game logical frames without using render present completion as ACK.

## Dependencies

- Source decision: `DEC-0031`.
- `PLN-0091` should define which AppModes consume this policy.

## Scope

- Introduce or formalize a `FrameClock`/`FrameScheduler` authority for Game workloads.
- Ensure Game VM runs at most one logical frame per authorized frame tick.
- Preserve `FRAME_SYNC` as logical frame end.
- Record overrun/repeat conditions through telemetry hooks.

## Non-Goals

- Do not make Shell UI run a game loop.
- Do not implement catch-up frames or logical frame skipping.
- Do not tie VM progress to render ACK.

## Execution Method

1. Inspect current tick/budget/`FRAME_SYNC` handling.
2. Identify where a frame tick should authorize Game VM execution.
3. Introduce a narrow scheduling API consumed by Game lifecycle code.
4. Preserve budget/cycle/time accounting only for watchdog, certification, and diagnostics.
5. Add telemetry points for logical-frame-overrun and no-new-frame/repeat.
6. Document the distinction between logical frame ID, produced submission ID, and presented frame ID.

## Acceptance Criteria

- Game VM cannot run unlimited logical frames ahead of the frame clock.
- Render worker or render consumer ACK is not required to start the next logical frame.
- Slow logical frames remain sequential and produce overrun/stutter telemetry.
- Shell lifecycle remains unaffected.

## Tests

- Unit tests for scheduler permitting one Game frame per tick.
- Test that no catch-up `N+k` logical frame is produced after overrun.
- Regression tests around `FRAME_SYNC` behavior.

## Affected Artifacts

- VM runtime scheduling modules.
- Firmware/Game running step.
- Telemetry interfaces touched by pacing.