Function without_fp4_kernel 

pub fn without_fp4_kernel(
    c: &Circuit,
    rules: &[Rule],
    families: &Families,
    kernel: &dyn Fn(&KernelId) -> Option<bool>,
) -> BTreeSet<NodeIdx>

2026-10-01: The nodes of c that multiply an NVFP4 activation (nvfp4_mma) and that no compiled FP4 block-scale kernel of the class runs: no rule with a pattern element that fits the node has every kernel available and one that needs the FP4 block-scale MMA, and no family that implements the node has such a kernel available. kernel answers for one kernel: None when the device cannot run it, else whether its source guard needs the FP4 block-scale MMA. Row ranges and policy conditions are not consulted: they choose among the kernels a class compiles, not which kernels it compiles.