deterministic-hybrid-proof

name	deterministic-hybrid-proof
description	Prove hybrid-search behavior without letting vector quality hide the real seam under test.

Deterministic Hybrid Proof

Use this when a hybrid search/query path changed but the regression claim belongs to one arm, not the merge in general.

Pattern

1. Force the target arm to matter

   • Build a corpus where the pre-change branch would miss (for example, FTS implicit AND returns zero on a compound query).

2. Zero the competing arm

   • For vector-search competition, do not write embeddings.
   • Assert search_vec* is empty before calling the hybrid entry point.

3. Prove the precondition explicitly

   • Assert the narrow helper still misses (search_fts empty, exact path empty, etc.).
   • Do not infer the miss from the later hybrid result.

4. Assert the hybrid result set exactly

   • Check the concrete slugs, not just !is_empty().
   • For CLI/canonical paths, assert <collection>::<slug> output.

Guardrails

• Do not rely on live model quality for deterministic regressions.
• If the surface canonicalizes page references, the proof must canonicalize its expectation too.
• Remove or downgrade smoke tests that only prove Ok when a reviewer is asking for behavioral proof.