Why: The old source index repeated most of a three-document input and its test fixture depended on that duplicate layout.
Evidence: Source prefix, ID scope, parser revision, table, truncation and mechanism tests failed before the change and pass after; full runmgr tests pass.
Impact: Compact the material prompt without widening quote authority, and version the recipe so old results are not reused.
Refs: Agent-System-Backend#193; Agent-System-Dev#512