Function vm_outcome_tiered 

pub fn vm_outcome_tiered(
    source: &str,
    program_args: &[String],
    tier: Tier,
    native_tier: Option<&dyn NativeTier>,
) -> RunOutcome

vm_outcome_with_args, but the statements pass through the run-path optimizer at an explicit hotness tier (HOTSWAP §4) before reaching the VM — the seam the tier_invariance gate drives at every tier T0..T3 to assert byte-identical output. tier = Tier::T3 reproduces today’s optimized run path.