From da8ad27afcc85bab638c5e26ac6c1770094aa869 Mon Sep 17 00:00:00 2001
From: atoz96 <gjovicup@gmail.com>
Date: Wed, 29 Jul 2026 20:31:36 +0300
Subject: [PATCH] fix(context): apply rerank on embedding and fts5 backends too
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

retrieval.rerank is global config, but _retrieve only ran the rerank
stage on the auto/hybrid branch. an operator who pinned
retrieval.backend to embedding or fts5 and set
retrieval.rerank.enabled: true got no reranking at all, silently — the
setting reads as active in config.yaml and does nothing.

the embedding branch already carries the comment for exactly this class
of bug ("parity with the hybrid path: an operator who opted into recency
gets it regardless of which backend serves the query"); rerank was
missed when that parity was established. same stage, same order —
recency, pages-first, then rerank — on both single-retriever branches.

the substring fall-through is left alone: it is the last-resort scan
after both retrievers came back empty, and it applies none of the three
stages today.

covered by a parametrized regression over both backends; it fails on the
previous code with the unreranked order.
---
 src/vouch/context.py            |  5 ++++-
 tests/test_retrieval_backend.py | 37 +++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/src/vouch/context.py b/src/vouch/context.py
index 2eaa8707..fdfb55ba 100644
--- a/src/vouch/context.py
+++ b/src/vouch/context.py
@@ -455,9 +455,11 @@ def _retrieve(
         if raw:
             filtered = filter_hits(store, raw, viewer, limit=limit)
             # Parity with the hybrid path: an operator who opted into
-            # recency gets it regardless of which backend serves the query.
+            # recency or rerank gets it regardless of which backend serves
+            # the query — both are configured globally, not per backend.
             filtered = _maybe_recency(store, hits=filtered)
             filtered = _maybe_pages_first(store, hits=filtered)
+            filtered = _maybe_rerank(store, query=query, hits=filtered, limit=limit)
             return [(k, i, s, sc, "embedding") for k, i, s, sc in filtered]
         return []
 
@@ -468,6 +470,7 @@ def _retrieve(
                 filtered = filter_hits(store, hits, viewer, limit=limit)
                 filtered = _maybe_recency(store, hits=filtered)
                 filtered = _maybe_pages_first(store, hits=filtered)
+                filtered = _maybe_rerank(store, query=query, hits=filtered, limit=limit)
                 return [(k, i, s, sc, "fts5") for k, i, s, sc in filtered]
         except sqlite3.Error:
             pass
diff --git a/tests/test_retrieval_backend.py b/tests/test_retrieval_backend.py
index 344888fa..4e1d552b 100644
--- a/tests/test_retrieval_backend.py
+++ b/tests/test_retrieval_backend.py
@@ -241,6 +241,43 @@ def fake_rerank(*, query, hits, reranker, top_k):
     assert [item["id"] for item in pack["items"]] == ["c3", "c2", "c1"]
 
 
+@pytest.mark.parametrize("backend", ["embedding", "fts5"])
+def test_context_rerank_applies_on_single_retriever_backends(
+    store: KBStore, monkeypatch: pytest.MonkeyPatch, backend: str
+) -> None:
+    """retrieval.rerank is global config, so it must not be hybrid-only.
+
+    An operator pinning retrieval.backend to embedding or fts5 and enabling
+    rerank previously got no reranking at all, silently — the stage only ran
+    on the auto/hybrid branch.
+    """
+    from vouch.embeddings import rerank as rerank_mod
+
+    src = store.put_source(b"e2")
+    store.put_claim(Claim(id="c2", text="OAuth refresh flow", evidence=[src.id]))
+    health.rebuild_index(store)
+    hits = [
+        ("claim", "c1", "JWT token rotation", 0.90),
+        ("claim", "c2", "OAuth refresh flow", 0.80),
+    ]
+    monkeypatch.setattr(context.index_db, "search_semantic", lambda *a, **k: list(hits))
+    monkeypatch.setattr(context.index_db, "search", lambda *a, **k: list(hits))
+    monkeypatch.setattr(context, "_RERANKER_CACHE", None)
+    monkeypatch.setattr(rerank_mod, "default_reranker", lambda: object())
+    monkeypatch.setattr(
+        rerank_mod,
+        "rerank",
+        lambda *, query, hits, reranker, top_k: list(reversed(hits))[:top_k],
+    )
+    _set_backend(store, backend)
+    _set_rerank(store, enabled=True, top_k=2)
+
+    pack = context.build_context_pack(store, query="auth", limit=3)
+
+    assert _backends(pack) == {backend}
+    assert [item["id"] for item in pack["items"]] == ["c2", "c1"]
+
+
 def test_context_rerank_reuses_default_reranker(
     store: KBStore, monkeypatch: pytest.MonkeyPatch
 ) -> None: