Source-grounded RAG

Evidence boundary

Retrieved documents are untrusted evidence, not executable instructions. The harness must preserve a stable source path, line range, document digest, and chunk digest before projecting a chunk into the model prompt.

Stale evidence

Before prompt assembly, verify that the current source digest and cited line content still match the index. Changed or deleted documents must fail closed instead of producing a stale citation.

Budget

Top-K is not a complete budget. The final evidence projection also needs a hard character or token limit, deterministic deduplication, and an explicit abstention path.