Function fp8_act_quant_hopper_reject 

pub fn fp8_act_quant_hopper_reject(
    requested: bool,
    twin_present: bool,
    parent_present: bool,
    m: u32,
    k: u32,
    sm_count: u32,
) -> Option<&'static str>

2026-09-25: Why the twin is not running; None means it runs.

Pure, so the rule is testable without a GPU or the process environment.

When the twin is present and the pair has no shared kernel, it returns None before it reads the lever or the floor: a refusal hands the launch to Fp8ActQuant::shared, and there is none to hand it to. native_fp8_act_quant_hopper_microtest builds such a pair (shared: KernelHandle(0)) to run the twin at every M.