Function try_target_kernel 

pub fn try_target_kernel(
    gpu: &dyn GpuBackend,
    module: &str,
    func: &str,
) -> KernelHandle

Probe a kernel that only SOME targets compile — a Hopper-owned twin, a tensor-core tier the gb10 tree does not carry — without issuing a lookup on a target that never built the module. The boot audit records every failed lookup as a dispatch site on a silent fallback path and refuses to serve; a target that does not carry the source has no fallback to be silent about, it has its only path. Stack 1089308’s first campaign found 17 such lookups on GB10 and could not boot. On a target that DOES carry the module this is exactly try_kernel, audit included.