Show Me Your Lineage: Query-Only Attribution of Evolving RAG Systems

RAG systems rely on evolving external knowledge, making curated knowledge bases valuable but vulnerable to theft, redeployment, and modification. Existing black-box ownership methods verify protected snapshots but do not address attribution after a stolen RAG evolves. We take three steps to bridge this gap. First, we formalize this problem by defining provenance laundering (PL) and its corresponding Provenance Laundering Attack (PLA) game, in which an attacker seeks to evade attribution while preserving task utility and inherited knowledge. We then introduce Update-Equivariant Lineage Coding (UELC). It distributes and refreshes coded epoch evidence across fact preserving carriers, recovers a matching epoch from black-box answers, and uses an authenticated commitment chain to extend the match to its predecessors. Finally, extensive experiments show that UELC retains more attribution evidence than the evaluated baselines under laundering attacks and maintains high true-positive rates throughout authorized evolution. Our work provides a new evolution-aware approach to tracing RAG lineages after theft and subsequent evolution using only black-box access.