Backend Selection

Wist currently exposes two canonical backend IDs:

• interpreter
• cil

Backend selection is part of the LanguageDefinition translated from WistEngineOptions or .wistdialect input. LanguageCompiler resolves exactly one backend route into LanguagePlan; LanguageRuntime executes that already-planned route without rediscovery.

Public facade

using UniversalToolchain.Wist;

using var interpreter = WistEngine.Create(new WistEngineOptions
{
    DialectSource = WistDialectSource.FromShippedPreset("pricing-restricted"),
    BackendId = "interpreter"
});

using var cil = WistEngine.Create(new WistEngineOptions
{
    DialectSource = WistDialectSource.FromShippedPreset("pricing-restricted"),
    BackendId = "cil"
});

A dialect file must explicitly enable the requested backend; otherwise planning fails closed.

Choosing a backend

Use interpreter when startup simplicity and inspectable execution matter more than repeated-call throughput. Use cil when the same approved formula will be invoked repeatedly and typed compiled delegates are useful.

Do not infer backend availability from loaded assemblies, reflection metadata or DI registrations. A backend is first-class only when its typed package contribution can be selected into a deterministic LanguagePlan and executed through the generic LanguageRuntime route.

Parity contract

When both backends are enabled, tests should compile both routes from the same semantic definition/plan basis and compare observable results. Backend-specific lowering may differ; language semantics must not.