---
id: PLN-0093
ticket: vm-render-parallel-execution-boundary
title: Add Render Telemetry Counters and Events
status: open
created: 2026-06-05
ref_decisions: [DEC-0031]
tags: [runtime, renderer, telemetry, diagnostics]
---

## Briefing

`DEC-0031` requires render drops, repeats, stale discards, render errors, and present errors to be observable without becoming VM semantics.

## Objective

Add the minimum render telemetry surface required for asynchronous render diagnostics and certification.

## Dependencies

- Source decision: `DEC-0031`.
- `PLN-0089` and `PLN-0092` provide main event sources.

## Scope

- Add minimum counters and last-frame IDs from `DEC-0031`.
- Add event recording hooks for handoff, consume, present, repeat, stale discard, errors, and shutdown discard.
- Expose telemetry through existing runtime/host diagnostics patterns.
- Ensure VM program behavior cannot observe telemetry as render ACK.

## Non-Goals

- Do not build a UI profiler.
- Do not add VM syscalls for present ACK.
- Do not define host-specific logging formats beyond necessary hooks.

## Execution Method

1. Locate current telemetry facilities and atomic counter patterns.
2. Add render telemetry structure with counters and last IDs.
3. Wire replacement-before-consume from handoff.
4. Wire consumed/presented/repeated from consumer path.
5. Wire stale epoch and shutdown discards.
6. Wire render/present error reporting.
7. Add read-only diagnostics access for host/debug tooling.

## Acceptance Criteria

- All minimum counters and IDs from `DEC-0031` exist.
- Latest-wins replacement is measurable.
- Repeated presents and stale epoch discards are measurable.
- Telemetry is not a blocking ACK path for the VM.

## Tests

- Unit tests for counter increments.
- Handoff replacement telemetry test.
- Stale epoch discard telemetry test.
- Error path telemetry test where render/present errors can be simulated.

## Affected Artifacts

- Runtime telemetry modules.
- `RenderManager`.
- Render handoff and publication paths.
- Host/debug telemetry readers.