Reflex marker association across a Low Latency Off→On transition

Gaming and Visualization Technologies Engines Others
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Hello NVIDIA Reflex team,

I am seeking normative API clarification while implementing an NVAPI-compatible Reflex pacing path in vkd3d-proton. This concerns marker and frame-ID contract semantics, rather than latency debugging or game/platform support.

Reviewed NVIDIA guidance expects Reflex markers to continue while Low Latency is Off and exposes Off/On mode selection. However, I have not found a normative rule covering activation between marker calls.

The observed sequence is:

  1. SIMULATION_START(X) completes while Low Latency is Off.
  2. Activation occurs.
  3. The caller later submits RENDERSUBMIT_START(X) carrying the same external Reflex ID.

Does the API define those calls as associated?

The current implementation returns from the inactive SIMULATION_START before creating an authoritative SimulationLedger mapping. The later active RENDERSUBMIT_START carrying that external ID therefore finds no active-epoch authoritative mapping.

The render-start encounters MAPPING_ABSENT, producing INVALID_RENDER_START; that failure won internal vkd3d accounting epoch 5’s first successful false→true pacing-bypass transition. The bypass is sticky within that active epoch and may be reset by activateEpoch() for a later epoch.

This explains why the contract distinction matters, but it does not establish that either the caller or runtime is wrong.

Depending on the applicable contract:

  • Must the caller issue SIMULATION_START again after activation?
  • Must the runtime preserve or associate the pre-activation marker?
  • Is this transition undefined or unsupported?
  • Or does another marker-order or frame-ID lifetime rule govern the case?

Also, is equality of the external Reflex frame ID authoritative frame identity across this Off→On transition?

We need a normative rule precise enough to serve as an implementation invariant and regression-test oracle. In particular, we do not want to infer association merely from equal external IDs or implement retention/replay behavior without contractual authority.

Thank you.