Function model_takes_effort 

pub(crate) fn model_takes_effort(model: &str) -> bool

Whether --effort is passed for model. Haiku takes none (the pinned CLI drops it; older CLIs forwarded it and the API answered HTTP 400 on every turn). Matches the model id as well as the alias, case-insensitively — this was model == "haiku", so a concrete Haiku id still got the flag. Mirrors modelTakesEffort in frontend/app/view/agent/runtime-capabilities.ts.