Function prefill_codispatch_enabled 

pub fn prefill_codispatch_enabled() -> bool

Cross-request co-dispatch of fresh prompts enabled? (--prefill-codispatch, legacy AVAROK_PREFILL_CODISPATCH=1; default OFF).

SSOT for all five readers. They must agree: the scheduler defers chunk-0 on this decision and the model layer then decides whether the batched path is eligible, so a disagreement strands streams mid-admission.