pub const MAX_FALLBACK_DEPTH: usize = 3;Expand description
Hard ceiling on providers.models.<alias>.fallback chain depth. The cycle
guard only bounds chains that loop; a long acyclic chain would otherwise
recurse one stack frame per alias at config-load and build time, turning a
pathological config into a startup stack overflow. Both the validation walk
and the runtime build walk stop descending past this depth and prune the
rest of the branch.