Completes FIX #12: the hint reached optimize_merge but not auto_tune's _normalize_stack, so inline autotuner-mode candidate scoring + the community arch bucket used key-based detection (mis-tagging e.g. attention-only Qwen as ACE-Step). File-based stacks have no virtual items → hint unreachable → unchanged. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>