Function select_declared_body 

pub fn select_declared_body(
    contracts: &[DeployedWorkerContract],
    action: &str,
    run_version: Option<&ContentHash>,
) -> DeclaredBodyLookup

Resolve the body action runs, given every retained contract on the queue and — when it could be named — the package version the dispatching run is pinned to.

With run_version known, that version’s contract is the SOLE authority: if it declares a body, that body runs; if it does not, the action belongs to an out-of-band worker and the dispatch is delegated. Reading a body off any other version would run a command the run’s own package never declared.